Alzheimer's Protection by PLCγ2 Compacts Plaques, Redistributes Microglia, and Protects Synapses in App NL ‐G‐F Mice

A rare protective protein-coding missense variant in PLCG2 (rs72824905, P522R) decreases the risk of developing late-onset Alzheimer's disease.

“A rare protective protein‐coding missense variant in the PLCG2 gene (rs72824905, P522R) decreases the risk of developing late‐onset Alzheimer's disease (AD) (Sims et al. 2017).”

• cites Sims et al. 2017 sourceSupported

In the 5xFAD model, the R522 variant's reduction in plaque load was associated with improved downstream measures of behavior and synaptic function.

“In a study of the 5xFAD model, the R522 variant reduced plaque load, and this was associated with improved downstream measures of behavior and synaptic function (Tsai et al. 2023).”

• cites Tsai et al. 2023 sourceSupported

Human studies confirmed the relevance of the R522 variant with other dementias.

“Human studies confirmed the relevance of the R522 variant with other dementias and associated it with increased longevity in centenarian cohorts (Bellenguez et al. 2022; Conway et al. 2018; van der Lee et al. 2019).”

• cites Bellenguez et al. 2022 sourceCould not verify

  The GWAS meta-analysis lists an association for a PLCG2 variant with Alzheimer’s disease and related dementias, but does not identify it as R522 or establish an association with other dementias. The ‘Genetic overlap with other neurodegenerative diseases’ section discusses other loci, not R522; searches for R522 and P522R found no passage establishing the claimed link. No page numbers were available in our copy. (LLM, conf=0.73)

  Experimental — accuracy not yet measured
• cites Conway et al. 2018 sourcePartly supported

  The Results section reports a suggestive association between the PLCG2 R522 variant and dementia with Lewy bodies (p = 0.124), but says no other disease cohort showed a significant association concordant with Alzheimer’s disease. The Discussion likewise describes a shared genetic component as a possibility, not a confirmed finding. Page numbers are unavailable in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites van der Lee et al. 2019 sourceSupported

The P522R PLCG2 coding variant (rs72824905) is downstream of TREM2.

“The Alzheimer's disease protective P522R PLCG2 coding variant (rs72824905) is downstream of TREM2, but how it confers disease protection is poorly understood.”

• cites Andreone et al. 2020 sourceNot checked — no full text of the source
• cites Jonsson et al. 2013 sourceCould not verify

  The Discussion describes TREM2 signaling through DAP12, but does not identify PLCG2 or place the P522R variant downstream of TREM2. Searches for PLCG2, P522R, rs72824905, and the proposed pathway relationship found no passage addressing that claim in our copy. (LLM, conf=0.76)

  Experimental — accuracy not yet measured

Human studies associated the R522 variant with increased longevity in centenarian cohorts.

“Human studies confirmed the relevance of the R522 variant with other dementias and associated it with increased longevity in centenarian cohorts (Bellenguez et al. 2022; Conway et al. 2018; van der Lee et al. 2019).”

• cites Bellenguez et al. 2022 sourceCould not verify

  The GWAS meta-analysis table reports an association between a PLCG2 variant and Alzheimer’s disease, but it does not identify the variant as R522 or report longevity outcomes. Searches for R522, P522R, longevity, and centenarian cohorts found no passage in our copy supporting the attributed longevity association; page numbers were unavailable. (LLM, conf=0.74)

  Experimental — accuracy not yet measured
• cites Conway et al. 2018 sourceCould not verify

  The Methods > Subjects section describes Alzheimer’s disease and other neurodegenerative-disease cohorts, not centenarian cohorts. The Discussion identifies PLCG2 p.Pro522Arg, but the passages retrieved for longevity and centenarians do not report an association with increased longevity. No page numbers are available in our copy. (LLM, conf=0.76)

  Experimental — accuracy not yet measured
• cites van der Lee et al. 2019 sourceSupported

Monoclonal antibody interventions promoting amyloid removal are associated with risk of side effects, including brain swelling and microhemorrhages.

“These interventions have demonstrated a modest capacity to reduce cognitive decline in select patient subgroups, but are associated with the risk of side effects, including brain swelling and microhemorrhages.”

• cites Sims et al. 2023 sourceSupported
• cites Mintun et al. 2021 sourceNot checked — no full text of the source
• cites Van Dyck et al. 2023 sourceSupported

Monoclonal antibodies promoting removal of amyloid have demonstrated a modest capacity to reduce cognitive decline in select patient subgroups.

“These interventions have demonstrated a modest capacity to reduce cognitive decline in select patient subgroups, but are associated with the risk of side effects, including brain swelling and microhemorrhages.”

• cites Sims et al. 2023 sourceSupported
• cites Mintun et al. 2021 sourceNot checked — no full text of the source
• cites Van Dyck et al. 2023 sourceSupported

In the brain, PLCG2 is predominantly microglial expressed.

“In the brain, PLCG2 is predominantly microglial expressed, positioning PLCγ2 within the same interaction network as TREM2—a notable AD risk gene (Andreone et al. 2020; Jonsson et al. 2013).”

• cites Andreone et al. 2020 sourceNot checked — no full text of the source
• cites Jonsson et al. 2013 sourcePartly supported

  The Discussion (page unavailable) says TREM2, not PLCG2, is primarily expressed on microglia in the brain. The Results identify a TREM2 variant associated with Alzheimer’s disease risk, supporting that part of the citing sentence. Our copy does not establish predominant microglial expression of PLCG2 or an interaction network linking PLCγ2 to TREM2. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

PLCγ2 is positioned within the same interaction network as TREM2, a notable AD risk gene.

“In the brain, PLCG2 is predominantly microglial expressed, positioning PLCγ2 within the same interaction network as TREM2—a notable AD risk gene (Andreone et al. 2020; Jonsson et al. 2013).”

• cites Andreone et al. 2020 sourceNot checked — no full text of the source
• cites Jonsson et al. 2013 sourceSupported

Genetic study of AD identified the rare protective coding variant of PLCG2 (P522R) associated with reduced risk of late-onset AD.

“Genetic study of AD identified the rare protective coding variant of PLCG2 (P522R) associated with reduced risk of late‐onset AD (Sims et al. 2017).”

• cites Sims et al. 2017 sourceSupported

Altered amyloid clearance is unlikely to be the dominant mechanism of protection in the App NL-G-F model.

“the largely unchanged total amyloid burden observed here suggests that altered amyloid clearance is unlikely to be the dominant mechanism of protection in the App NL‐G‐F model.”

• cites Maguire et al. 2021 sourceCould not verify

  The Discussion reports increased uptake of soluble amyloid oligomers by cells expressing the protective R522 variant and suggests this could contribute to protection. It does not assess total amyloid burden in the App NL-G-F model or whether altered amyloid clearance is a dominant mechanism there. The citing sentence’s 'observed here' appears to refer to the citing authors’ own finding. (LLM, conf=0.76)

  Experimental — accuracy not yet measured

PLCγ2 has a role in Alzheimer's disease.

“Given the role for PLCγ2 in AD, we investigated how Plcg2 R522 expressing microglia altered amyloid‐driven pathology (Sims et al. 2017; Bellenguez et al. 2022; van der Lee et al. 2019).”

• cites Sims et al. 2017 sourceSupported
• cites Bellenguez et al. 2022 sourceSupported
• cites van der Lee et al. 2019 sourceSupported

Significant numbers of aged cognitively normal individuals exhibit some level of amyloid deposition.

“and significant numbers of aged cognitively normal individuals exhibit some level of amyloid deposition”

• cites Bourgeat et al. 2010 sourceNot checked — no full text of the source
• cites Aizenstein et al. 2008 sourceSupported
• cites Sturchio et al. 2022 sourcePartly supported

  The Introduction and Discussion describe people with normal cognition despite PET-detected brain amyloid, supporting the coexistence of amyloid deposition and normal cognition. They do not establish that significant numbers of aged cognitively normal people have amyloid deposition; the Results describe a selected mutation-carrier cohort with a mean age of about 38, not an aged population. Page numbers are unavailable in our copy. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Cognitive decline itself is poorly correlated with changes in amyloid burden.

“Furthermore, cognitive decline itself is poorly correlated with changes in amyloid burden”

• cites Bourgeat et al. 2010 sourceNot checked — no full text of the source
• cites Aizenstein et al. 2008 sourcePartly supported

  The Results and COMMENT report that amyloid-positive, clinically unimpaired elderly participants did not perform significantly worse than amyloid-negative participants. But the claim concerns cognitive decline correlated with changes in amyloid burden over time; the Conclusions say longitudinal follow-up is still required, so this study does not establish that relationship. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Sturchio et al. 2022 sourceSupported

Plcg2 R522 mice have significantly higher Iba1+ microglial density in the dorsal hippocampal CA1 region than Plcg2 P522 mice.

“Mice expressing Plcg2 R522 exhibited a modest, but significantly higher density and tiling of Iba1+ microglia within the dorsal hippocampal CA1 region (Figure 1a–c) and the overlying cortices (Figure 1d–f) than Plcg2 P522 expressing mice.”

In the absence of Alzheimer's disease-like pathology, the R522 variant was associated with reduced ramification complexity.

“In the absence of Alzheimer's disease‐like pathology, the R522 variant increased microglial coverage and was associated with reduced ramification complexity, fewer terminal points, and elevated lysosomal CD68 expression.”

The protective R522 variant was associated with decreased engulfment of synaptic material by microglia.

“The protective R522 variant was also associated with: enhanced microglial engagement with less compact amyloid plaques; reduced microglial localisation around highly compacted plaques; protection from amyloid‐induced synapse loss; and decreased engulfment of synaptic material by microglia.”

On the App NL-G-F background, expression of the R522 variant led to increased plaque compaction compared to the P522 common variant.

“On the App NL‐G‐F background, total amyloid burden was unaffected, but expression of the R522 variant led to increased plaque compaction compared to the P522 common variant.”

In the absence of Alzheimer's disease-like pathology, the R522 variant increased microglial coverage.

“In the absence of Alzheimer's disease‐like pathology, the R522 variant increased microglial coverage and was associated with reduced ramification complexity, fewer terminal points, and elevated lysosomal CD68 expression.”

The protective R522 variant was associated with reduced microglial localisation around highly compacted plaques.

“The protective R522 variant was also associated with: enhanced microglial engagement with less compact amyloid plaques; reduced microglial localisation around highly compacted plaques; protection from amyloid‐induced synapse loss; and decreased engulfment of synaptic material by microglia.”

Plcg2 R522 mice have significantly higher Iba1+ microglial tiling in the dorsal hippocampal CA1 region than Plcg2 P522 mice.

“Mice expressing Plcg2 R522 exhibited a modest, but significantly higher density and tiling of Iba1+ microglia within the dorsal hippocampal CA1 region (Figure 1a–c) and the overlying cortices (Figure 1d–f) than Plcg2 P522 expressing mice.”

On the App NL-G-F background, total amyloid burden was unaffected by the R522 variant.

“On the App NL‐G‐F background, total amyloid burden was unaffected, but expression of the R522 variant led to increased plaque compaction compared to the P522 common variant.”

In the absence of Alzheimer's disease-like pathology, the R522 variant was associated with fewer terminal points.

“In the absence of Alzheimer's disease‐like pathology, the R522 variant increased microglial coverage and was associated with reduced ramification complexity, fewer terminal points, and elevated lysosomal CD68 expression.”

In the absence of Alzheimer's disease-like pathology, the R522 variant was associated with elevated lysosomal CD68 expression.

“In the absence of Alzheimer's disease‐like pathology, the R522 variant increased microglial coverage and was associated with reduced ramification complexity, fewer terminal points, and elevated lysosomal CD68 expression.”

The protective R522 variant was associated with protection from amyloid-induced synapse loss.

“The protective R522 variant was also associated with: enhanced microglial engagement with less compact amyloid plaques; reduced microglial localisation around highly compacted plaques; protection from amyloid‐induced synapse loss; and decreased engulfment of synaptic material by microglia.”

Tmem119 expression per microglia remained similar between the two Plcg2 genotypes.

“Tmem119 expression per microglia remained similar between the two genotypes (Figure 4e,i–iv).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Plcg2 R522-expressing mice exhibited fewer 5-10 μm plaques than Plcg2 P522-expressing mice.

“However, when stratified by diameter (Figure 3e), Plcg2 R522 ‐expressing mice exhibited fewer 5–10 μm plaques than Plcg2 P522 ‐expressing mice but an increased number in the 20–40 μm plaques, with no differences observed with the 10–20 or > 40 μm sizes.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In the hippocampus, Plcg2 R522 increases ThioS area of coverage.

“In the hippocampus, ThioS staining revealed an increased area of coverage”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

Plcg2 R522 increases plaque core coverage in the cortex compared to Plcg2 P522.

“the protective Plcg2 R522 variant increased the coverage of plaque cores in both the hippocampus and cortex compared to the common risk variant”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's, and the Plcg2 P522 variant is a common risk variant.

Plcg2 R522-expressing mice exhibited an increased plaque load in the 10-20 μm range compared with common risk variant-expressing mice.

“Plcg2 R522 ‐expressing mice exhibited a reduced plaque load in the 5–10 μm range but an increased load in the 10–20 and 20–40 μm groups, with no differences observed in plaques > 40 μm.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In female Plcg2 R522 mice, plaques are more densely compacted than in P522 carriers.

“these plaques were more densely compacted than those in P522 carriers”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

In Plcg2 R522-expressing mice, a reduction in Tmem119+ expression per microglia was associated with 20-40 μm plaques at compactness Level 2.

“However, in the Plcg2 R522 ‐expressing mice, a reduction in Tmem119+ expression per microglia was associated with the most compact 5–10 μm (Figure 4e,i) and 10–20 μm (Figure 4e,ii) plaques, as well as in 20–40 μm plaques at compactness Level 2 (Figure 4e,iii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

In the largest plaques (> 40 μm), there was a reduction in microgliosis at the lowest compactness level (Level 1) in R522 variant-expressing mice.

“However, in the largest plaques (> 40 μm), we observed a reduction in microgliosis at the lowest compactness level, an increase at compactness Level 2, and no changes in the most compact plaques (Figure 4d,iv).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Total X34 plaque count did not differ significantly between Plcg2 R522-expressing and common risk variant-expressing mice.

“Similarly, total X34 plaque count did not differ significantly between genotypes (Figure 3d).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.

In App NL-G-F mice at 6 months, 6E10 labels the majority of amyloid, including diffuse deposits.

“In App NL‐G‐F mice at 6 months of age, 6E10 labeled the majority of amyloid, including diffuse deposits”

Plcg2 R522 is associated with fewer terminal points in CA1 microglia.

“Microglial morphological analysis (CA1 region) revealed association of the Plcg2 R522 variant with lower ramification complexity (Figure 1g,h) and fewer terminal points (Figure 1i), consistent with a less arborized microglial phenotype.”

For plaques > 40 μm, the protective Plcg2 R522 variant increased plaque load for compactness Level 3.

“For plaques > 40 μm, the protective variant decreased both measures for compactness Level 1 but increased them for plaques scored at compactness Level 3 (Figure 3i,n).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

Six-month-old App NL-G-F mice expressing Plcg2 R522 exhibited significantly increased Tnf expression.

“Six‐month‐old App NL‐G‐F mice expressing Plcg2 R522 exhibited significantly increased Tnf expression.”

The most compact plaques within the 5-10 and 10-20 μm size ranges showed a strong reduction in microglial association in R522 variant-expressing mice.

“Notably, the most compact plaques within these size ranges showed a strong reduction in microglial association (Figure 4d,i,ii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Plcg2 R522 reduces the number of diffuse plaques.

“we observed a reduction in diffuse plaques in Plcg2 R522 ‐expressing mice”

Total Clec7a expression changes around smaller, lower-compactness plaques reflected microglial density, similar to total Tmem119 expression.

“When assessed as total Clec7a expression, we observed changes, particularly, around smaller, lower‐compactness plaques, that reflected microglial density (Figure 4h,i,ii), similar to the pattern seen with total Tmem119 expression.”

For 10-20 μm plaques, the Plcg2 R522 variant increased the count of the most compact plaques (Level 3).

“For 10–20 μm plaques, the Plcg2 R522 protective variant increased both load and count of the most compact plaques (Level 3) (Figure 3g,l).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

There was no significant difference in overall X34 plaque load between mice expressing the protective Plcg2 R522 variant and those expressing the common risk variant.

“There was no significant difference in overall X34 plaque load between mice expressing the protective Plcg2 R522 variant and those expressing the common risk variant (Figure 3b).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.

In the 20-40 μm range, Plcg2 R522-expressing mice exhibited elevated plaque load for compactness Levels 2 and 3.

“In the 20–40 μm range, Plcg2 R522 ‐expressing mice exhibited elevated plaque load and number for compactness Levels 2 and 3 (Figure 3h,m).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In wildtype mice, Plcg2 R522 was associated with increased Clec7a expression.

“However, in wildtype mice, Plcg2 R522 was associated with increased Clec7a expression, highlighting the need for spatially resolved analyses to detect microglial differences in the amyloid models when looking at changes likely to have milder phenotypic effects (Figure S3a).”

Sex had no detectable effect on the Plcg2 variant-related differences in microglial density and tiling.

“Sex had no detectable effect on these Plcg2 variant‐related differences.”

Plcg2 R522 significantly reduces diffuse amyloid load in the cortex compared to Plcg2 P522.

“Quantification indicated a significant reduction in diffuse amyloid load in both the hippocampus and cortex of mice expressing the protective Plcg2 R522 variant compared to the common risk variant”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's, and the Plcg2 P522 variant is a common risk variant.

The Plcg2 R522 variant decreased the load of 5-10 μm plaques with low compactness (Levels 1 and 2).

“The Plcg2 R522 variant decreased both the load and number of 5–10 μm plaques with low compactness (Levels 1 and 2) (Figure 3f,k).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In the cortex, the reduction in diffuse plaques is primarily observed in male mice.

“In the cortex, this reduction was primarily observed in male mice.”

Mean Clec7a expression was similar between the protective and common risk variants across all plaque types.

“In contrast, mean Clec7a expression was similar between the protective and common risk variants across all plaque types (Figure 4g,i–iv).”

In male App NL-G-F mice, Plcg2 R522 is associated with an increase of ThioS+ plaques in the cortex.

“Notably, in male App NL‐G‐F mice, the R522 variant was associated with an increase of ThioS+ plaques in the cortex”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

Plcg2 R522 increases plaque core coverage in the hippocampus compared to Plcg2 P522.

“the protective Plcg2 R522 variant increased the coverage of plaque cores in both the hippocampus and cortex compared to the common risk variant”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's, and the Plcg2 P522 variant is a common risk variant.

Plcg2 R522 mice have significantly increased microglial density in overlying cortex compared to Plcg2 P522.

“Mice expressing the Plcg2 R522 variant exhibited a significantly increased microglial density in both the hippocampal CA1 region and the overlying cortex compared to the Plcg2 P522 mice”

In the hippocampus, Plcg2 R522 increases the number of individual plaques.

“associated with a greater number of individual plaques”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

The Plcg2 R522 variant decreased the number of 5-10 μm plaques with low compactness (Levels 1 and 2).

“The Plcg2 R522 variant decreased both the load and number of 5–10 μm plaques with low compactness (Levels 1 and 2) (Figure 3f,k).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In Plcg2 R522-expressing mice, a reduction in Tmem119+ expression per microglia was associated with the most compact 10-20 μm plaques.

“However, in the Plcg2 R522 ‐expressing mice, a reduction in Tmem119+ expression per microglia was associated with the most compact 5–10 μm (Figure 4e,i) and 10–20 μm (Figure 4e,ii) plaques, as well as in 20–40 μm plaques at compactness Level 2 (Figure 4e,iii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Plcg2 R522-expressing mice exhibited an increased plaque load in the 20-40 μm range compared with common risk variant-expressing mice.

“Plcg2 R522 ‐expressing mice exhibited a reduced plaque load in the 5–10 μm range but an increased load in the 10–20 and 20–40 μm groups, with no differences observed in plaques > 40 μm.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In App NL-G-F mice at 6 months, 4G8 primarily marks plaque cores.

“whereas 4G8 primarily marked the plaque cores”

Relative to Plcg2 P522-expressing mice, a pattern toward elevated Clec7a expression in Plcg2 R522-expressing mice in response to smaller, lower-compactness plaques, significantly reduced in the largest, most compacted plaques.

“When visualized relative to the Plcg2 P522 ‐expressing mice (Figure 4h,v), a pattern toward elevated Clec7a expression in the Plcg2 R522 ‐expressing mice in response to smaller, lower‐compactness plaques, which was significantly reduced in the largest, most compacted plaques was observed.”

PC1 was driven by global diffuse plaque burden.

“with PC1 driven by global diffuse plaque burden”

Females have a higher number of cored plaques in both brain regions.

“with an overall sex effect reflecting a higher number of cored plaques in females in both brain regions”

Peri-plaque microgliosis, measured as Iba1 area within 5 μm of plaque borders, showed significant increases in microglia associated with 10-20 μm plaques in R522 variant-expressing mice, but only those with lower compactness (Levels 1 and 2).

“Assessment of peri‐plaque microgliosis, measured as Iba1 area within 5 μm of plaque borders, indicated significant increases in microglia associated with 5–10 μm (Figure 4d,i) and 10–20 μm (Figure 4d,ii) plaques in the R522 variant‐expressing mice, but only those with lower compactness (Levels 1 and 2).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

In the hippocampus, Plcg2 R522 increases plaque size.

“larger plaques”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

For the most compact (Level 3) 20-40 μm plaques, an increase in Tmem119+ microgliosis was detected in Plcg2 R522-expressing mice.

“For the most compact (Level 3) 20–40 μm plaques, an increase was detected in the Plcg2 R522 ‐expressing mice (Figure 4f,iii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

There is no significant difference in total 6E10+ plaque burden in hippocampal CA1 and overlying cortex between Plcg2 R522 and Plcg2 P522 mice.

“Quantification of the total 6E10+ plaque burden in the hippocampal CA1 region and the overlying cortex revealed no significant differences in amyloid pathology between mice expressing either Plcg2 variant”

Plcg2 R522 mice have significantly higher Iba1+ microglial tiling in the overlying cortex than Plcg2 P522 mice.

“Mice expressing Plcg2 R522 exhibited a modest, but significantly higher density and tiling of Iba1+ microglia within the dorsal hippocampal CA1 region (Figure 1a–c) and the overlying cortices (Figure 1d–f) than Plcg2 P522 expressing mice.”

In the hippocampus, Plcg2 R522 increases plaque compaction.

“and more densely compacted plaques”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

Plcg2 R522 is associated with increased prevalence of CD68 in microglia compared to Plcg2 P522.

“These morphological changes accompanied a significant reduction in microglial volume and increased prevalence of the lysosomal protein CD68, an indicator of phagocytic activity, in Plcg2 R522 ‐expressing microglia compared to those expressing Plcg2 P522 (Figure 1j–l).”

• AssumptionRests on an assumption: CD68 is an indicator of phagocytic activity.

In the 20-40 μm range, Plcg2 R522-expressing mice exhibited elevated plaque number for compactness Levels 2 and 3.

“In the 20–40 μm range, Plcg2 R522 ‐expressing mice exhibited elevated plaque load and number for compactness Levels 2 and 3 (Figure 3h,m).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

For plaques > 40 μm, the protective Plcg2 R522 variant increased plaque number for compactness Level 3.

“For plaques > 40 μm, the protective variant decreased both measures for compactness Level 1 but increased them for plaques scored at compactness Level 3 (Figure 3i,n).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

Plcg2 R522 is associated with lower ramification complexity in CA1 microglia.

“Microglial morphological analysis (CA1 region) revealed association of the Plcg2 R522 variant with lower ramification complexity (Figure 1g,h) and fewer terminal points (Figure 1i), consistent with a less arborized microglial phenotype.”

In the hippocampus, males exhibit a higher diffuse plaque burden than females.

“A sex effect was also observed, with males exhibiting a higher diffuse plaque burden in the hippocampus than females.”

PCA revealed a clear distinction between Plcg2 P522 and Plcg2 R522 genotypes based on plaque load, number, and core status.

“PCA revealed a clear distinction between Plcg2 P522 and Plcg2 R522 genotypes based on these parameters”

Plcg2 R522 is associated with a significant reduction in microglial volume compared to Plcg2 P522.

“These morphological changes accompanied a significant reduction in microglial volume and increased prevalence of the lysosomal protein CD68, an indicator of phagocytic activity, in Plcg2 R522 ‐expressing microglia compared to those expressing Plcg2 P522 (Figure 1j–l).”

In the cortex, females have a higher plaque core burden than males.

“with a sex effect in the cortex associated with a higher plaque core burden in females than males”

For plaques > 40 μm, the protective Plcg2 R522 variant decreased plaque number for compactness Level 1.

“For plaques > 40 μm, the protective variant decreased both measures for compactness Level 1 but increased them for plaques scored at compactness Level 3 (Figure 3i,n).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

Plcg2 R522-expressing mice exhibited an increased number of 20-40 μm plaques compared with Plcg2 P522-expressing mice.

“However, when stratified by diameter (Figure 3e), Plcg2 R522 ‐expressing mice exhibited fewer 5–10 μm plaques than Plcg2 P522 ‐expressing mice but an increased number in the 20–40 μm plaques, with no differences observed with the 10–20 or > 40 μm sizes.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

No significant differences between the Plcg2 variants were observed for larger plaques in total Tmem119 peri-plaque expression.

“No significant differences between the variants were observed for larger plaques (Figure 4f,iv).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

A significant drop in Clec7a association was evident in the largest most compact plaques.

“This significant drop in Clec7a association was also evident in the largest most compact plaques (Figure 4h,iv).”

For 10-20 μm plaques, the Plcg2 R522 variant increased the load of the most compact plaques (Level 3).

“For 10–20 μm plaques, the Plcg2 R522 protective variant increased both load and count of the most compact plaques (Level 3) (Figure 3g,l).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

Plcg2 R522 significantly increases the number of cored plaques.

“quantification of the number of cored plaques showed a significant increase in Plcg2 R522 ‐expressing mice”

There were no differences in plaque load for plaques > 40 μm between Plcg2 R522-expressing and common risk variant-expressing mice.

“Plcg2 R522 ‐expressing mice exhibited a reduced plaque load in the 5–10 μm range but an increased load in the 10–20 and 20–40 μm groups, with no differences observed in plaques > 40 μm.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

No significant changes in microgliosis were detected for any 20-40 μm plaques.

“No significant changes in microgliosis were detected for any 20–40 μm plaques (Figure 4d,iii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Total Tmem119 peri-plaque expression for the smaller plaques was broadly consistent with the general microglial distribution data.

“Total Tmem119 peri‐plaque expression for the smaller plaques (Figure 4f,i,ii) was broadly consistent with the general microglial distribution data (Figure 4d,v).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

In Plcg2 R522-expressing mice, a reduction in Tmem119+ expression per microglia was associated with the most compact 5-10 μm plaques.

“However, in the Plcg2 R522 ‐expressing mice, a reduction in Tmem119+ expression per microglia was associated with the most compact 5–10 μm (Figure 4e,i) and 10–20 μm (Figure 4e,ii) plaques, as well as in 20–40 μm plaques at compactness Level 2 (Figure 4e,iii).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

Plcg2 R522 mice have significantly increased microglial density in hippocampal CA1 compared to Plcg2 P522.

“Mice expressing the Plcg2 R522 variant exhibited a significantly increased microglial density in both the hippocampal CA1 region and the overlying cortex compared to the Plcg2 P522 mice”

Plcg2 R522 significantly reduces diffuse amyloid load in the hippocampus compared to Plcg2 P522.

“Quantification indicated a significant reduction in diffuse amyloid load in both the hippocampus and cortex of mice expressing the protective Plcg2 R522 variant compared to the common risk variant”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's, and the Plcg2 P522 variant is a common risk variant.

In the largest plaques (> 40 μm), there were no changes in microgliosis in the most compact plaques (Level 3) in R522 variant-expressing mice.

“However, in the largest plaques (> 40 μm), we observed a reduction in microgliosis at the lowest compactness level, an increase at compactness Level 2, and no changes in the most compact plaques (Figure 4d,iv).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

For plaques > 40 μm, the protective Plcg2 R522 variant decreased plaque load for compactness Level 1.

“For plaques > 40 μm, the protective variant decreased both measures for compactness Level 1 but increased them for plaques scored at compactness Level 3 (Figure 3i,n).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In the largest plaques (> 40 μm), there was an increase in microgliosis at compactness Level 2 in R522 variant-expressing mice.

“However, in the largest plaques (> 40 μm), we observed a reduction in microgliosis at the lowest compactness level, an increase at compactness Level 2, and no changes in the most compact plaques (Figure 4d,iv).”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

In female Plcg2 R522 mice, overall ThioS plaque load remains unchanged.

“Although overall ThioS plaque load in female Plcg2 R522 mice remained unchanged”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

Plcg2 R522-expressing mice exhibited a reduced plaque load in the 5-10 μm range compared with common risk variant-expressing mice.

“Plcg2 R522 ‐expressing mice exhibited a reduced plaque load in the 5–10 μm range but an increased load in the 10–20 and 20–40 μm groups, with no differences observed in plaques > 40 μm.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: X34 labeling specifically identifies amyloid plaques.
• AssumptionRests on an assumption: Plaque compactness categorization (diffuse, cored with surrounding diffuse amyloid, cored compact) is a valid measure of plaque compactness.

In the cortex, female App NL-G-F mice have a higher ThioS-labeled plaque burden than males.

“In the cortex, female App NL‐G‐F mice exhibited a higher ThioS‐labeled plaque burden than males”

• AssumptionRests on an assumption: Thioflavin S labels fibrillar amyloid.

Plcg2 R522 mice have significantly higher Iba1+ microglial density in the overlying cortex than Plcg2 P522 mice.

“Mice expressing Plcg2 R522 exhibited a modest, but significantly higher density and tiling of Iba1+ microglia within the dorsal hippocampal CA1 region (Figure 1a–c) and the overlying cortices (Figure 1d–f) than Plcg2 P522 expressing mice.”

In Plcg2 R522-expressing mice, Iba1+ microglia exhibited a stronger peri-plaque response around smaller, lower-compactness plaques.

“In Plcg2 R522 ‐expressing mice, Iba1+ microglia exhibited a stronger peri‐plaque response around smaller, lower‐compactness plaques”

In Plcg2 R522-expressing mice, microglial engagement was reduced in compacted plaques.

“while microglial engagement was reduced in compacted plaques.”

Plcg2 R522-expressing mice exhibited fewer small, diffuse plaques.

“Plcg2 R522 ‐expressing mice exhibited fewer small, diffuse plaques”

Plcg2 R522 mice have increased microglial network coverage compared to Plcg2 P522 mice, in both dorsal hippocampus (CA1) and cortex.

“Plcg2 R522 mice have increased microglial network coverage compared to Plcg2 P522 mice, in both dorsal hippocampus (CA1) and cortex.”

A sex-specific effect of the PLCγ2 variants was observed in the cortex of males distal from the plaques.

“Interestingly, a sex‐specific effect of the PLCγ2 variants was observed in the cortex of males distal from the plaques (Figure S4d).”

Diffuse plaque pathology was reduced in Plcg2 R522 mice compared to Plcg2 P522 mice.

“while diffuse plaque pathology was reduced in the same mice when compared to Plcg2 P522 mice.”

The presence of the AD-protective R522 variant did not reduce overall amyloid load; total amyloid deposition (6E10 staining) was comparable between Plcg2 R522- and Plcg2 P522-expressing mice.

“Somewhat unexpectedly, the presence of the AD‐protective R522 variant did not reduce overall amyloid load, as total amyloid deposition (6E10 staining) was comparable between Plcg2 R522 ‐ and Plcg2 P522 ‐expressing mice.”

• Also stated in: § Discussion · boosted

  “confirmed that overall amyloid burden was similar between the Plcg2 genotypes, consistent with 6E10‐staining.”

• Also stated in: § Discussion · hedged

  “staining of X34 and 6E10 detected no clear difference between the genotypes”

Plcg2 R522-expressing mice exhibited an increased incidence of larger, highly compacted plaques.

“and an increased incidence of larger, highly compacted plaques.”

Human iPSC-derived microglia with the Plcg2 R522 variant showed an enhanced TNF response to Aβ.

“and also an enhanced TNF response to Aβ, by the human cells with the same variant”

ThioS and 4G8 antibody staining showed a generalized increase in compacted plaque cores in Plcg2 R522 mice compared to Plcg2 P522 mice.

“ThioS and 4G8 antibody staining, which preferentially label compacted plaque cores, showed a generalized increase in Plcg2 R522 mice”

In vivo, there was an increase in TNF in App NL-G-F mice expressing the Plcg2 R522 variant.

“While we observed an in vivo increase in TNF in the App NL‐G‐F mice expressing the Plcg2 R522 variant”

The R522 variant has limited impact on total amyloid burden.

“Through study of the App NL‐G‐F mouse model, we have found that the R522 AD‐protective variant drives multiple pathological changes in the context of limited impact on the total amyloid burden.”

In Plcg2 R522-expressing App NL-G-F mice, microglia exhibited a significantly reduced CD68-to-Iba1 ratio at peri-plaque niches compared to those expressing Plcg2P522.

“In Plcg2 R522 ‐expressing App NL‐G‐F mice, microglia exhibited a significantly reduced CD68‐to‐Iba1 ratio at peri‐plaque niches compared to those expressing Plcg2P522 (Figure 6b), which contrasted with observations in the absence of App NL‐G‐F (Figure 1j–l).”

Higher peri-plaque density of VGLUT2+ excitatory synapses in Plcg2 R522-expressing App NL-G-F mice.

“Further analysis showed higher peri‐plaque density of VGLUT2+ excitatory synapses in Plcg2 R522 ‐expressing App NL‐G‐F mice (Figure S4i,j).”

Tmem119 was found to be further reduced in compact plaques in Plcg2 R522-expressing mice.

“Tmem119, a homeostatic marker that is generally downregulated within plaque niches, was found to be further reduced in compact plaques in Plcg2 R522 ‐expressing mice.”

In the absence of App NL-G-F, there was no significant alteration in synaptic puncta density associated with Plcg2 genotype.

“In the absence of App NL‐G‐F , there was no significant alteration in synaptic puncta density associated with Plcg2 genotype (Figure 5b).”

The R522 variant skews plaque morphology toward larger, more compact plaques and away from smaller, diffuse ones.

“Specifically, the R522 variant manifests: (i) a skewing of plaque morphology toward larger, more compact plaques and away from smaller, diffuse ones (Figures 2 and 3);”

Significantly reduced Clec7a expression was observed in the largest, most compacted plaques in Plcg2 R522-expressing mice.

“while significantly reduced Clec7a expression was observed in the largest, most compacted plaques.”

There were marked differences depending on the stimulus (Aβ versus LPS) in human iPSC-derived microglia.

“but notably also, marked differences depending on the stimulus (Aβ versus LPS).”

Total Tmem119 expression showed a similar pattern, aligning with Iba1+ microgliosis data.

“A similar pattern was observed for total Tmem119 expression, aligning with our Iba1+ microgliosis data”

Microglia in Plcg2 R522-expressing mice exhibited higher total Clec7a expression around smaller, diffuse plaques.

“Microglia in Plcg2 R522 ‐expressing mice exhibited higher total Clec7a expression around smaller, diffuse plaques”

There were clear differences between the PLCG2 variants in human iPSC-derived microglia.

“There were clear differences between the PLCG2 variants”

We observed increased diffuse plaque presence in the hippocampus of males.

“and increased diffuse plaque presence in the hippocampus of males (Figures 2 and S2).”

We observed increases in cortex plaque compaction associated with females.

“Broadly summarized, we observed increases in cortex plaque compaction associated with females”

The synaptic protection occurred in the context of similar plaque loads.

“occurred in the context of similar plaque loads”

The R522 AD protective variant of PLCγ2 promotes marked neuroprotection characterized by retention of essentially normal synaptic densities in App NL-G-F mice.

“the R522 AD protective variant of PLCγ2 promotes a marked neuroprotection characterized by retention of essentially normal synaptic densities in App NL‐G‐F mice.”

A protective effect of the R522 PLCγ2 variant distal from the plaques in the cortex was significantly demonstrated only in the male mice, which experience lower plaque compaction than females in this region.

“Interestingly, a protective effect of the R522 PLCγ2 variant distal from the plaques in the cortex was significantly demonstrated only in the male mice, which experience lower plaque compaction than females in this region.”

The synaptic protection in App NL-G-F mice expressing the R522 variant was associated with a notable reduction in phagocytic clearance of synaptic materials.

“This synaptic protection was associated with a notable reduction in phagocytic clearance of synaptic materials”

The synaptic protection was associated with changes in plaque structure and microglial involvement.

“was associated with changes in plaque structure and microglial involvement.”

PLCγ2 modulation is a neuropathology-protective strategy.

“In spite of substantial amyloid burden, expression of the R522 variant resulted in enhanced plaque compaction and a marked protection of synaptic integrity, reinforcing the concept of PLCγ2 modulation as a neuropathology‐protective strategy.”

PLCγ2 has a significant direct role in controlling microglial-plaque interactions and synaptic protection downstream of amyloid deposition.

“Our data indicate a significant direct PLCγ2 role in controlling microglial‐plaque interactions and synaptic protection downstream of amyloid deposition, prioritizing it as a therapeutic target, potentially as an adjunct to other approaches, such as those targeting amyloid.”

App NL-G-F mice exhibit a substantial amyloid plaque burden in the brain by 6 months of age.

“By 6 months of age, App NL‐G‐F mice exhibit a substantial amyloid plaque burden in the brain”

• cites Saito et al. 2014 sourceNot checked — no full text of the source

Tmem119+ microgliosis in response to plaques generally mirrored the initial Iba1+ area response but displayed distinct differences.

“Tmem119+ microgliosis in response to plaques generally mirrored the initial Iba1+ area response but displayed distinct differences.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

The morphological changes are consistent with a less arborized microglial phenotype.

“consistent with a less arborized microglial phenotype.”

A pattern toward reduced Tmem119 expression in microglia associated with smaller, more compact plaques was seen with Plcg2 R522-expression.

“When represented as fold change between the Plcg2 genotypes (Figure 4e,v), a pattern toward reduced Tmem119 expression in microglia associated with smaller, more compact plaques was seen with Plcg2 R522 ‐expression.”

• AssumptionRests on an assumption: The Plcg2 R522 variant is protective against Alzheimer's disease, and the P522 variant is a common risk variant.
• AssumptionRests on an assumption: The App NL-G-F mouse model recapitulates Alzheimer's amyloid pathology.
• AssumptionRests on an assumption: Iba1 is a pan-microglial marker, Tmem119 is a homeostatic microglial marker, and Clec7a is a disease-associated microglia (DAM) marker.
• AssumptionRests on an assumption: Peri-plaque region within 5 μm of plaque borders is appropriate for assessing microgliosis.

The impact of the R522 variant on microglia may manifest through promotion of plaque compaction.

“These findings indicated that the impact of the R522 variant on microglia may manifest through promotion of plaque compaction.”

The R522 variant confers marked protection from synapse loss in spite of similar amyloid burdens.

“(iii) a marked protection from synapse loss in spite of similar amyloid burdens (Figure 5) and associated reduction in microglial‐mediated clearance of synaptic material (Figure 6).”

• AssumptionRests on an assumption: Dendritic spine density is a valid indicator of postsynaptic integrity.
• AssumptionRests on an assumption: Findings in App NL-G-F mice and iPSC-derived microglia are translatable to human AD.

The R522 variant is associated with a reduction in microglial-mediated clearance of synaptic material.

“and associated reduction in microglial‐mediated clearance of synaptic material (Figure 6).”

• AssumptionRests on an assumption: Findings in App NL-G-F mice and iPSC-derived microglia are translatable to human AD.

The protective variant influences plaque maturation rather than overall amyloid accumulation.

“This points toward the protective variant influencing plaque maturation rather than overall amyloid accumulation.”

The LPS response in human iPSC-derived microglia with the Plcg2 R522 variant was different from results previously reported with mouse cells in vitro.

“the LPS response was evidently different, and hence different to results previously reported with mouse cells in vitro.”

• AssumptionRests on an assumption: Results from in vivo mouse models of the PLCγ2 inflammatory cytokine response have not been consistent.

The observations underscore a potential neuroprotective role of microglia modulated by PLCγ2.

“These observations underscore a potential neuroprotective role of microglia modulated by PLCγ2.”

The reduced ramifications and increased CD68 expression indicate a more reactive microglial state in Plcg2 R522 mice.

“indicative of a more reactive state (Figure 1)”

The App NL-G-F knock-in model has physiological App expression levels, avoiding the overexpression artifacts found in other transgenic models.

“The App NL‐G‐F knock‐in model, however, has physiological App expression levels, avoiding the overexpression artifacts found in other transgenic models”

• cites Saito et al. 2014 sourceNot checked — no full text of the source

There is a potential shift in microglial function and plaque interaction dynamics.

“indicating a potential shift in microglial function and plaque interaction dynamics.”

The App NL-G-F mouse model is an AD-like model.

“These were bred to the App NL‐G‐F AD‐like model to determine responses in the context of amyloid‐driven pathology (Saito et al. 2014).”

• cites Saito et al. 2014 sourceNot checked — no full text of the source

The App NL-G-F knock-in model is strongly biased toward very high Aβ42:40 ratios (~10-100:1) because of the familial mutations.

“but is strongly biased toward very high Aβ42:40 ratios (~10–100:1) because of the familial mutations”

• cites Saito et al. 2014 sourceNot checked — no full text of the source

Our findings contrast with the results of others studying the P522R variant in the 5xFAD AD model.

“Our findings contrast with the results of others studying the P522R variant in the 5xFAD AD model.”

• AssumptionRests on an assumption: All mouse models of AD are confounded by different disease progression and hence level and nature of challenge.

Modulation of amyloid-associated microglial activation can directly regulate synaptic clearance, perhaps via alteration of plaque constitution.

“This novel insight suggests that modulation of amyloid‐associated microglial activation can directly regulate synaptic clearance, perhaps via alteration of plaque constitution.”

Our studies indicate an uncoupling of total amyloid burden and synaptic loss mediated by PLCγ2.

“Collectively, our studies indicate an uncoupling of total amyloid burden and synaptic loss mediated by PLCγ2.”

PLCγ2 can mediate dramatic protection of synapses from amyloid-driven synapse loss.

“our findings indicate that PLCγ2 can mediate dramatic protection of synapses from amyloid‐driven synapse loss.”

Other mechanisms drive symptom development.

“suggesting that other mechanisms drive symptom development”