PU.1 is required to restrain myelopoiesis during chronic inflammatory stress

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 represses cell cycle genes in T cell progenitors.

“PU.1 similarly represses cell cycle genes in T cell progenitors”

• cites Kueh et al., 2013 sourcePartly supported

  The gene-expression passage (indexed under Abstract; page unavailable) reports that PU.1 transduction reduced the cell-cycle-promoting factors Cyclin D2 and Cdc25a. But the paper describes experiments in progenitors cultured for macrophage and B-cell differentiation, not T-cell progenitors, so it does not establish the claimed T-cell setting. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Staber et al., 2013 sourcePartly supported

  The Results section reports that PU.1 represses cell-cycle activators including Cdk1, E2f1, and Cdc25a. The paper identifies the cells studied as hematopoietic stem cells, not T-cell progenitors, so it does not support the claimed cell population. Page numbers are unavailable in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites Champhekar et al., 2015 sourceDisputed

  The Results section on DN progression reports that PU.1-deficient DN2 cells proliferated significantly less than controls; PU.1 was needed for optimal proliferation. The genome-wide Results section also says the PU.1 repressor construct had little, if any, impact on major cell-cycle regulators. These passages do not support the claim that PU.1 represses cell-cycle genes in T-cell progenitors. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 can engage in competitive interactions with transcriptional regulators such as GATA1 to promote myeloid differentiation.

“PU.1 can also engage in competitive interactions with transcriptional regulators such as GATA1 to promote myeloid differentiation (Strasser et al., 2018; Wheat et al., 2020; Raghav and Gangenahalli, 2021).”

• cites Strasser et al., 2018 sourcePartly supported

  The Results section describes PU.1 and GATA1 as mutually binding and cross-antagonistic, and says PU.1 is important in executing the granulocyte-macrophage lineage program. But it rejects the idea that their competitive toggle initiates lineage choice: PU.1 is described as an effector that locks down an already chosen lineage, not the driver of that choice. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites Wheat et al., 2020 sourceSupported
• cites Raghav and Gangenahalli, 2021 sourceDisputed

  The Introduction (page unavailable) says GATA-1 binds PU.1, displaces c-Jun, and represses PU.1 function, promoting erythropoiesis—not myeloid differentiation. It attributes myelopoiesis to c-Jun binding with PU.1 instead. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

May combine two claims.

PU.1 deficiency leads to increased proliferation in HSCLT following IL-1β stimulation, thereby driving expansion of these cells in vivo.

“We previously showed that PU.1 deficiency leads to increased proliferation in HSCLT following IL-1β stimulation, thereby driving expansion of these cells in vivo (Chavez et al., 2021).”

• cites Chavez et al., 2021 sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

IL-1β promotes hematopoietic regeneration and is capable of briefly driving HSPC into the cell cycle, in large part via activation of the PI3K-AKT pathway.

“Indeed, we and others have shown that IL-1β promotes hematopoietic regeneration and is capable of briefly driving HSPC into the cell cycle, in large part via activation of the PI3K-AKT pathway (Hemmati et al., 2019).”

• cites Hemmati et al., 2019 sourceCould not verify

  The available indexed passages contain the article title, author affiliations, and publication details, but no findings about IL-1β. Searches for hematopoietic regeneration, HSPC cell-cycle entry, and PI3K-AKT activation returned no relevant passage, so the claim cannot be checked against our copy. (LLM, conf=0.68)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Several other transcriptional regulators interact with PU.1, including AP-1 family transcription factors.

“Moreover, several other transcriptional regulators interact with PU.1, including AP-1 family transcription factors (Steidl et al., 2006; Boasman et al., 2019; Zhao et al., 2022).”

• cites Steidl et al., 2006 sourceNot checked — no full text of the source
• cites Boasman et al., 2019 sourceNot checked — no full text of the source
• cites Zhao et al., 2022 sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

NF-κB is crucial for PU.1 induction in HSC.

“which we and others previously showed to be crucial for PU.1 induction in HSC.”

• cites Pietras et al., 2016 sourceSupported
• cites Etzrodt et al., 2019 sourcePartly supported

  The Results and discussion report that inhibiting NF-κB decreased PU.1 induction in HSCs in response to TNF. Figure 2A likewise calls NF-κB signaling essential for PU.1 induction by TNF. The source supports the claim for TNF-driven induction, but does not establish that NF-κB is crucial for PU.1 induction in HSCs generally. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites Yamashita and Passegue, 2019 sourcePartly supported

  The Discussion reports that TNFα activates PU.1 in HSCs and drives p65/NF-κB activation during inflammation. The Results establish that NF-κB is crucial for HSC survival after TNFα exposure, but the passages do not establish that NF-κB is crucial for PU.1 induction. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

May combine two claims.

PU.1's braking mechanism allows sufficient myeloid expansion for host defense while preventing aberrant expansion of progenitor pools.

“allowing for sufficient myeloid expansion for host defense while preventing aberrant expansion of progenitor pools (Caiado et al., 2021).”

• cites Caiado et al., 2021 sourcePartly supported

  The IL-1 section (page unavailable) describes PU.1 activation as a proliferation-limiting mechanism: PU.1-deficient HSCs instead show aberrant proliferation and pool expansion. It also says PU.1 facilitates myeloid differentiation, and the Introduction links myeloid cells to host defense. The paper does not establish that PU.1’s braking mechanism permits sufficient myeloid expansion for host defense. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Emergency myelopoiesis is a critical response to physiological insults that supplies the host with enough innate immune cells to fight infections and/or contribute to repair and immunosurveillance of damaged tissues.

““Emergency” myelopoiesis is a critical response to physiological insults that supplies the host with enough innate immune cells to fight infections and/or contribute to the repair and immunosurveillance of damaged tissues (Caiado et al., 2021; Collins et al., 2021).”

• cites Caiado et al., 2021 sourcePartly supported

  The Introduction describes emergency hematopoiesis as increased blood-cell production in response to stress such as infection, and identifies leukocytes as serving host defense. It does not say that emergency myelopoiesis supplies cells for the repair or immunosurveillance of damaged tissues; its separate discussion of immune surveillance concerns elimination of mutated cell clones. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites Collins et al., 2021 sourcePartly supported

  The Introduction says inflammation stimulates hematopoietic progenitors to replenish depleted lineages and that blood cells provide innate immunity and contribute to tissue repair. The section on adult hematopoiesis describes increased myeloid production to meet organismal needs. Our copy does not specifically connect emergency myelopoiesis to immunosurveillance of damaged tissues. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 binds to and represses key genes in glycolysis and lipid biosynthesis pathways used for production of energy and anabolic factors that support cell proliferation.

“These observations are broadly consistent with prior work showing that PU.1 binds to and represses key genes in glycolysis and lipid biosynthesis pathways used for production of energy and anabolic factors that support cell proliferation (Solomon et al., 2017).”

• cites Solomon et al., 2017 sourcePartly supported

  The Results and Discussion (page numbers unavailable) report that PU.1 binding is associated with reduced expression of lipid-anabolism genes and reduced cell-cycle progression. They do not establish repression of glycolysis genes. The Discussion also distinguishes binding from direct transcriptional repression: it suggests that PU.1 activates some bound genes transcriptionally while induced microRNAs reduce their steady-state expression. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Mechanisms regulating emergency myelopoiesis are likely multifactorial, and transcriptional regulators such as C/EBPβ have also been implicated as drivers of hematopoietic responses to injury and infection.

“The mechanisms regulating “emergency” myelopoiesis are likely multifactorial, and transcriptional regulators such as C/EBPβ have also been implicated as drivers of hematopoietic responses to injury and infection (Hirai et al., 2006; Hirai et al., 2015).”

• cites Hirai et al., 2006 sourceNot checked — no full text of the source
• cites Hirai et al., 2015 sourcePartly supported

  The Emergency Granulopoiesis section says C/EBPβ is required for infection- or cytokine-induced granulocyte production. The Modes of Hematopoiesis section describes emergency responses to bleeding, but the passages do not establish C/EBPβ as a driver of responses specifically to injury. No page numbers were available in our copy. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Early stages of myeloid oncogenesis are typically characterized by graded reductions in PU.1 activity due to oncogenic mutations, rather than complete ablation of expression.

“early stages of myeloid oncogenesis are typically characterized by graded reductions in PU.1 activity due to the action of oncogenic mutations, rather than complete ablation of expression (Will et al., 2015).”

• cites Will et al., 2015 sourcePartly supported

  The Introduction says modest PU.1 impairment is common in human AML and that homozygous PU.1 mutations or deletions have not been observed; the Discussion says minimal inhibition can be a founding event in leukemogenesis. The paper does not establish that early stages are typically characterized by PU.1 reductions specifically caused by oncogenic mutations: it also describes epigenetic mechanisms and frames a minimal reduction as a possible founding event. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

The mechanism of IL-1β-driven upregulation of Spi1 may be driven by pathways such as NF-κB.

“the mechanism of IL-1β-driven upregulation of Spi1 may be driven by pathways such as NF-κB (Pietras et al., 2016; Etzrodt et al., 2019; Yamashita and Passegue, 2019; Ahmed et al., 2022)”

• cites Pietras et al., 2016 sourceSupported
• cites Etzrodt et al., 2019 sourcePartly supported

  The Results and discussion report that IL-1β upregulates PU.1 protein in HSCs. They also find that NF-κB inhibition reduces TNF-induced PU.1, but do not test whether NF-κB mediates the IL-1β response. The proposed IL-1β–NF-κB mechanism is therefore not established by this paper. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites Yamashita and Passegue, 2019 sourcePartly supported

  The Discussion says PU.1 activation has been observed with IL-1, and the Results describe IL-1 signaling as a known NF-κB inducer. But the paper does not link NF-κB to IL-1-driven PU.1/Spi1 upregulation; in its pIC inflammation experiments, it identifies TNFα rather than IL-1 as the main driver of NF-κB activation. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

• AssumptionRests on an assumption: PU.1 KI/KI mice lack the PU.1 autoregulatory binding site at the −14 kb enhancer.

May combine two claims.

In phenotypically defined long-term HSC, increased PU.1 levels drive activation of myeloid differentiation gene programs and repression of cell proliferation, thereby limiting expansion of the HSC pool.

“In phenotypically defined long-term HSC, increased PU.1 levels drive 1) activation of myeloid differentiation gene programs and 2) repression of cell proliferation (Chavez et al., 2021), thereby limiting the expansion of the HSC pool.”

• cites Chavez et al., 2021 sourcePartly supported

  The Discussion reports that increased PU.1 activity in long-term HSCs restricts proliferation while myeloid determinant genes are upregulated in IL-1–exposed cells. The Results also show that PU.1 restricts expansion of the phenotypic long-term HSC pool during chronic IL-1 challenge. The citing sentence omits that inflammatory-stress condition, extending the expansion finding beyond the setting demonstrated here. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

Classified as probably not a substantial claim. May combine two claims.

PU.1 restricts the cell cycle activity of myeloid-committed progenitors, thereby facilitating homeostatic myeloid differentiation via accumulation of sufficient myeloid lineage determinants prior to cell division.

“Previous work has shown that PU.1 restricts the cell cycle activity of myeloid-committed progenitors (Kueh et al., 2013), thereby facilitating homeostatic myeloid differentiation via accumulation of sufficient myeloid lineage determinants prior to cell division.”

• cites Kueh et al., 2013 sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

Activation of mitogenic pathways such as PI3K-AKT by inflammatory signals induces post-translational modifications of cell cycle regulatory proteins to potentiate cell cycle progression.

“it is well known that the activation of mitogenic pathways such as PI3K-AKT by inflammatory signals induces the necessary post-translational modifications (e.g., phosphorylation) of cell cycle regulatory proteins to potentiate cell cycle progression (Chang et al., 2003; Pietras et al., 2011; Warr et al., 2011; Pietras et al., 2014).”

• cites Chang et al., 2003 sourceNot checked — no full text of the source
• cites Pietras et al., 2011 sourcePartly supported

  The PI3K signaling pathway section says PI3K/Akt promotes HSC proliferation, and the cell-extrinsic mechanisms section suggests inflammatory interferons may induce HSC cell-cycle entry partly through Akt. The Rb Family section describes phosphorylation of cell-cycle regulators during progression, but the paper does not establish that inflammatory activation of PI3K-Akt induces those post-translational modifications; its interferon–Akt link is also hedged. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Warr et al., 2011 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Cell cycle restriction may play a similar role in lymphoid development.

“and thus cell cycle restriction may play a similar role in lymphoid development (Kueh et al., 2013; Staber et al., 2013; Champhekar et al., 2015).”

• cites Kueh et al., 2013 sourcePartly supported

  The discussion (page unavailable) suggests that cell-cycle-linked mechanisms may operate in other differentiation systems, supporting the cautious possibility in the claim. It does not specifically propose this role in lymphoid development: its B-cell observations instead show similar cell-cycle lengths to progenitors and reduced PU.1 transcription, unlike the cell-cycle lengthening seen in macrophages. (LLM, conf=0.78)

  Experimental — accuracy not yet measured
• cites Staber et al., 2013 sourcePartly supported

  The Discussion reports that PU.1 restrains the cell cycle to maintain adult hematopoietic stem-cell function. This supports the proposed analogy, but the paper does not establish a similar role for cell-cycle restriction in lymphoid development; its mention of lymphoid cells concerns a different regulatory comparison. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites Champhekar et al., 2015 sourcePartly supported

  The Results (page unavailable) show that PU.1-deficient early T cells proliferated less yet differentiated faster, supporting a possible link between reduced proliferation and lymphoid development. The paper does not establish that cell-cycle restriction itself drives that progression; both changes followed PU.1 deletion. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

Classified as probably not a substantial claim. May combine two claims.

Loss of PU.1 activity is closely associated with myeloid leukemia, and the PU.1 network is commonly disrupted in myeloid hematological malignancies, though PU.1 itself is rarely mutated.

“Notably, loss of PU.1 activity is closely associated with myeloid leukemia, and the PU.1 network is commonly disrupted in myeloid hematological malignancies, though PU.1 itself is rarely mutated (Will et al., 2015; Aivalioti et al., 2022).”

• cites Will et al., 2015 sourceSupported
• cites Aivalioti et al., 2022 sourcePartly supported

  The Introduction links impaired PU.1 regulation to leukemogenesis, and the Discussion describes PU.1 inhibition in most patients with AML and a perturbed PU.1 network as a proposed common feature of myeloid leukemia. The paper does not establish that PU.1 itself is rarely mutated; the searched passages discuss mutations that affect PU.1 regulation or function, not the frequency of mutations in PU.1. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 functions to prevent spurious HSC proliferation and expansion of the HSC pool during chronic inflammatory stress by repressing induction of cell proliferation gene programs during chronic IL-1β treatment.

“We recently showed that PU.1 also functions to prevent spurious HSC proliferation and expansion of the HSC pool during chronic inflammatory stress by repressing induction of cell proliferation gene programs during chronic IL-1β treatment (Chavez et al., 2021).”

• cites Chavez et al., 2021 sourceSupported

May combine two claims.

The PU.1 KI/KI mouse model has a deactivating point mutation knocked into the PU.1 autoregulatory binding site within the −14 kb upstream regulatory element, leading to graded loss of PU.1 function without the development of overt leukemia-like disease.

“we employed the PU.1 knock-in (KI) mouse model, in which a deactivating point mutation was knocked into the PU.1 autoregulatory binding site within the −14 kb upstream regulatory element (URE), leading to graded loss of PU.1 function without the development of overt leukemia-like disease (Staber et al., 2013).”

• cites Staber et al., 2013 sourcePartly supported

  Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

May combine two claims.

PU.1 deficiency leads to overproduction of mature myeloid cells and aberrant expansion of MPPGM following chronic IL-1β treatment.

“We find that PU.1 deficiency leads to overproduction of mature myeloid cells and aberrant expansion of MPPGM, a progenitor population that serves as an “emergency” reservoir for myeloid cell production (Pietras et al., 2015), following chronic IL-1β treatment.”

• cites Pietras et al., 2015 sourceSupported

Classified as probably not a substantial claim. May combine two claims.

IL-1 signaling is closely linked to chronic inflammatory diseases and plays a critical role in the activation of inflammatory myelopoiesis.

“IL-1β is produced in response to a wide range of physiological insults, and IL-1 signaling is closely linked to a wide variety of chronic inflammatory diseases, where it plays a critical role in the activation of inflammatory myelopoiesis (Ueda et al., 2009; Dinarello, 2011; Mirantes et al., 2014; Pietras, 2017).”

• cites Ueda et al., 2009 sourcePartly supported

  The Discussion reports that IL-1RI is indispensable for alum-induced emergency granulopoiesis in mice, supporting a critical role for IL-1 signaling in that inflammatory response. It does not establish the claim’s broader link to a wide variety of chronic inflammatory diseases or show that IL-1 activates myelopoiesis in those diseases. No page number is available in our copy. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Dinarello, 2011 sourcePartly supported

  The Abstract links the IL-1 family to acute and chronic inflammation and lists several inflammatory diseases responsive to IL-1β blockade. The passages on bone marrow and myeloid cells do not establish that IL-1 signaling plays a critical role in activating inflammatory myelopoiesis, so that part of the attributed claim is unsupported. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites Mirantes et al., 2014 sourcePartly supported

  The IL-6 section says IL-1 activates myelopoiesis in response to infection and inflammatory disease. It does not establish that IL-1 signaling is linked to a wide variety of chronic inflammatory diseases or that its role is critical; the passage specifically describing a critical activator in chronic inflammatory disorders concerns IL-6, not IL-1. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Cebpa-deficient MPPGM retained high expression levels of stem cell genes including Foxo3, Mycn, Bmi1 and Bcl2 following chronic exposure to IL-1β.

“These data are strongly reminiscent of Cebpa-deficient MPPGM, which likewise retained high expression levels of stem cell genes including Foxo3, Mycn, Bmi1 and Bcl2 following chronic exposure to IL-1β (Higa et al., 2021).”

• cites Higa et al., 2021 sourcePartly supported

  The Results section, “Chronic IL-1β triggers a self-renewal gene program in Cebpa-knockout MPP3s” (page unavailable), reports elevated Bmi1, Foxo3, and Mycn in Cebpa-deficient MPP3s after chronic IL-1β exposure. It names Mpl as the fourth gene, not Bcl2; our copy does not support the claim about Bcl2. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Therapeutic modalities targeting pathogenic cytokines such as IL-1 and TNF are already in widespread clinical use.

“Therapeutic modalities targeting pathogenic cytokines such as IL-1 and TNF are already in widespread clinical use (Davignon et al., 2013).”

• cites Davignon et al., 2013 sourcePartly supported

  The Introduction describes TNF-blocking therapies as a major tool in rheumatoid arthritis treatment, and the Discussion lists therapies targeting both TNF and IL-1. The paper does not establish that IL-1-targeting therapies, specifically, are in widespread clinical use. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

May combine two claims.

Tet2-deficient HSPC exhibit similar characteristics to PU.1-deficient HSPC, namely the capacity to undergo accelerated expansion in the context of chronic inflammation, coupled with altered cell cycle activity.

“Indeed, Tet2-deficient HSPC exhibit similar characteristics to PU.1-deficient HSPC, namely the capacity to undergo accelerated expansion in the context of chronic inflammation, coupled with altered cell cycle activity (Consortium et al., 2007; Caiado et al., 2022).”

• cites Consortium et al., 2007 sourceCould not verify

  The passages from “Regulation of transcription” concern genomic regulatory elements and transcription-factor binding, not Tet2- or PU.1-deficient HSPC. Searches for those cells, chronic inflammation, accelerated expansion, and altered cell-cycle activity found no passage addressing the claim. Page numbers were not available in our copy. (LLM, conf=0.76)

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

May combine two claims.

IL-1R blockade could reduce the expression of PU.1 target genes in HSC closer to homeostatic levels, with concurrent reductions in myeloid output.

“Along these lines, we recently showed that IL-1R blockade could reduce the expression of PU.1 target genes in HSC closer to homeostatic levels, with concurrent reductions in myeloid output (Hernandez et al., 2020).”

• cites Hernandez et al., 2020 sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

Dysregulation of the PU.1 transcriptional network is a common phenotype associated with hematological malignancy, particularly diseases of the myeloid lineage.

“Dysregulation of the PU.1 transcriptional network is a common phenotype associated with hematological malignancy, particularly diseases of the myeloid lineage (Cook et al., 2004; Dakic et al., 2005; Koschmieder et al., 2005; Will et al., 2015; Sive et al., 2016; Aivalioti et al., 2022).”

• cites Cook et al., 2004 sourcePartly supported

  The Discussion reports impaired PU.1 function in the mouse myeloid leukemias studied. In “Relevance to human AML” (page unavailable), the authors suggest that several common oncogenic alterations in human AML likely reduce PU.1 expression or compromise its function, but present this as a prediction rather than an established common phenotype across hematological malignancies. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites Dakic et al., 2005 sourcePartly supported

  The Abstract describes PU.1 as a possible tumor suppressor in AML. The Discussion reports that PU.1-deficient mice developed myeloid leukemia at high frequency, but it does not establish that PU.1-network dysregulation is a common phenotype across hematological malignancies generally. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Koschmieder et al., 2005 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Pathogenic myeloid cell activity in the context of autoimmunity and chronic inflammatory disease has been attributed to PU.1-dependent gene programs.

“Of note, pathogenic myeloid cell activity in the context of autoimmunity and chronic inflammatory disease has been attributed to PU.1-dependent gene programs (Fang et al., 2022)”

• cites Fang et al., 2022 sourceSupported

May combine two claims.

Loss-of-function mutations in TET2 lead to hypermethylation at PU.1 binding sites throughout the genome, disrupting the PU.1 transcriptional network.

“Of note, recent work has shown that loss-of-function mutations in TET2, leads to hypermethylation at PU.1 binding sites throughout the genome, disrupting the PU.1 transcriptional network (Aivalioti et al., 2022).”

• cites Aivalioti et al., 2022 sourcePartly supported

  The Results (page not available) report hypermethylation at a subset of methylation-sensitive PU.1-binding motifs and reduced expression of associated genes in leukemic HSPCs. They do not show hypermethylation at PU.1 sites throughout the genome as a consequence of TET2 loss alone: the finding concerns leukemic compound-mutant cells, while healthy aged compound-mutant cells retained expression of those genes. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

MPPGM appears to be a nexus of myeloid expansion under both inflammatory conditions and in animal models of myeloid malignancy.

“It is noteworthy that MPPGM (also commonly referred to as MPP3) (Challen et al., 2021) appears to be a nexus of myeloid expansion under both inflammatory conditions and in animal models of myeloid malignancy (Schepers et al., 2013; Pietras et al., 2015; Shih et al., 2015; Pietras et al., 2016; Herault et al., 2017; Hernandez et al., 2020; Kang et al., 2020; Rabe et al., 2020).”

• cites Schepers et al., 2013 sourcePartly supported

  The Results section on MPN development reports severe granulocytic expansion in a mouse model of CML, supporting the broad myeloid-expansion context. But the paper does not identify MPPGM/MPP3 as the nexus of that expansion; its Discussion says the MPN myeloid cells were not characterized beyond broad Mac-1 expression. Its discussion of inflammation concerns niche remodeling, not MPPGM expansion under inflammatory conditions. Page numbers are unavailable in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites Pietras et al., 2015 sourcePartly supported

  The Results (Contribution to blood regeneration; page unavailable) identify MPP2 and MPP3 as a rapidly emerging compartment of myeloid amplification after transplantation, supporting a role for MPP3 in myeloid expansion. The paper does not establish that MPP3 has this role under inflammatory conditions or in animal models of myeloid malignancy; its discussion of increased IL-6 concerns MPP4. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Shih et al., 2015 sourcePartly supported

  The Results section reports selective expansion of MPPs in a Tet2/Flt3ITD mouse model of AML and shows that sorted MPPs can propagate leukemia after transplantation. It does not identify those cells specifically as MPPGM/MPP3 or examine their role under inflammatory conditions. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The AP-1 factors c-Jun and JunB are critical interacting partners with PU.1 that also regulate myeloid differentiation, including PU.1 expression.

“Indeed, the AP-1 factors c-Jun and JunB are also critical interacting partners with PU.1 that also regulate myeloid differentiation (including PU.1 expression) (Steidl et al., 2006; Raghav et al., 2018; Zhao et al., 2022).”

• cites Steidl et al., 2006 sourceNot checked — no full text of the source
• cites Raghav et al., 2018 sourceNot checked — no full text of the source
• cites Zhao et al., 2022 sourcePartly supported

  The Discussion identifies c-Jun as a direct PU.1 interaction partner, and the Results report that their physical interaction is crucial for early myeloid differentiation (page not provided). The Introduction names JunB as an AP-1 family member, but our copy does not establish JunB as a PU.1 interaction partner or show that either factor regulates PU.1 expression. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 regulates numerous gene programs associated with host defense and immune function, including expression of MHC and costimulatory genes, as well as immune checkpoints and immune effector genes.

“PU.1 regulates numerous gene programs associated with host defense and immune function, including expression of MHC and costimulatory genes, as well as immune checkpoints and immune effector genes (Fisher et al., 1998; Karpurapu et al., 2011; Kitamura et al., 2012; Keightley et al., 2017).”

• cites Fisher et al., 1998 sourcePartly supported

  The Abstract and the section on PU.1 functional domains describe PU.1 promoting lymphoid and myeloid gene expression, including immunoglobulin-enhancer activity. They do not establish the claim’s specific regulation of MHC, costimulatory, immune-checkpoint, or immune-effector genes. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Karpurapu et al., 2011 sourceNot checked — no full text of the source
• cites Kitamura et al., 2012 sourcePartly supported

  The paper’s Abstract (page not provided) reports that PU.1 regulates CIITA pI and subsequent MHC class II expression in dendritic cells. It also describes prior work identifying PU.1 as a regulator of the costimulatory genes CD80 and CD86. Our copy does not support attributing regulation of immune checkpoint or immune effector genes to this paper. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

May combine two claims.

Fgd5, Ctnnal1, Egr1, Bmi1 and Hoxa9 are downregulated following IL-1β exposure in PU.1 KI/KI MPPGM, but only to levels found at steady state in PU.1 +/+ MPPGM.

“These genes were nonetheless downregulated following IL-1β exposure, but only to levels found at steady state in PU.1 +/+ MPPGM (Figure 4B).”

Probably not a substantial claim: may not pass S3 (load-bearing).

There are no overt defects in Il1r1 expression levels in PU.1 KI/KI MPPGM.

“Furthermore, we did not notice overt defects in Il1r1 expression levels in PU.1 KI/KI MPPGM (Supplementary Figure S3A).”

May combine two claims.

IL-1β-induced alterations in blood are confined to the myeloid lineage, with no significant changes in lymphoid cell numbers.

“These alterations appeared confined to the myeloid lineage, as we observed no significant changes in lymphoid cell numbers and a similar degree of inflammation-induced anemia in these animals (Supplementary Figure S1A).”

May combine two claims.

MPPGM samples are clearly distinguished by principal component analysis, with PC1 appearing to discriminate samples based on relative PU.1 activity and PC2 distinguishing PU.1 +/+ controls from all other samples.

“MPPGM samples likewise were clearly distinguished by principal component analysis (PCA), with PC1 appearing to discriminate samples based on relative PU.1 activity and PC2 distinguishing PU.1 +/+ controls from all other samples (Supplementary Figure S3C)”

May combine two claims.

In bone marrow, myeloid cell numbers in IL-1β-treated PU.1 KI/KI mice are expanded with IL-1β treatment but not significantly different from wild-type counterparts.

“In the bone marrow (BM), myeloid cell numbers in the BM of IL-1β-treated PU.1 KI/KI mice were expanded with IL-1β treatment but not to an extent significantly different than their wild-type counterparts (Figure 1E)”

May combine two claims.

PU.1 KI/KI MPPGM exhibit aberrant cell cycle activity, retain high levels of self-renewal gene expression and exhibit delayed myeloid differentiation in response to IL-1β signaling.

“Further, we show that PU.1 KI/KI MPPGM exhibit aberrant cell cycle activity, retain high levels of self-renewal gene expression and exhibit delayed myeloid differentiation in response to IL-1β signaling.”

May combine two claims.

The impaired differentiation of PU.1 KI/KI MPPGM in response to IL-1β is characterized by high levels of self-renewal gene expression and delayed expression of key myeloid surface markers.

“characterized by high levels of self-renewal gene expression and delayed expression of key myeloid surface markers.”

May combine two claims.

IL-1β exposure downregulates Foxo3, Hif1a, Nrf2, and Mycn in PU.1 KI/KI MPPGM, but expression is only reduced to levels found in PU.1 +/+ MPPGM at steady state.

“While IL-1β exposure likewise downregulated their expression in PU.1 KI/KI MPPGM, expression was again only reduced to levels found in PU.1 +/+ MPPGM at steady state (Figure 4C).”

May combine two claims.

There is a lower proportion and number of myeloid-committed PU.1 KI/KI MPPGM during the culture period.

“Conversely, we observed a lower proportion and number of myeloid-committed PU.1 KI/KI MPPGM during the culture period (Figures 5E–G)”

May combine two claims.

IL-1β triggers increased cell cycle activity in PU.1 KI/KI MPPGM, thereby contributing to the aberrant expansion of this population.

“Taken together, these data indicate that IL-1β triggers increased cell cycle activity in PU.1 KI/KI MPPGM, thereby contributing to the aberrant expansion of this population.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Complete genetic ablation of PU.1 can yield a profound differentiation block that graduates to an AML-like phenotype.

“While complete genetic ablation of PU.1 can yield a profound differentiation block that graduates to an AML-like phenotype (Steidl et al., 2006)”

• cites Steidl et al., 2006 sourceNot checked — no full text of the source

May combine two claims.

PU.1 plays a critical role in regulating inflammation-driven HSPC expansion and myelopoiesis by ensuring appropriate regulation of self-renewal and differentiation genes in addition to restraining cell cycle activity.

“Altogether, our data show that PU.1 plays a critical role in regulating inflammation driven HSPC expansion and myelopoiesis by ensuring appropriate regulation of self-renewal and differentiation genes in addition to restraining cell cycle activity.”

May combine two claims.

PU.1 negatively regulates expression of numerous self-renewal genes, with PU.1-deficient MPPGM consequently retaining high expression levels of these factors.

“Collectively, these data support a model in which PU.1 negatively regulates expression of numerous self-renewal genes, with PU.1-deficient MPPGM consequently retaining high expression levels of these factors.”

May combine two claims.

While PU.1 functions as a key driver of myeloid differentiation, it plays an equally critical role in tailoring hematopoietic responses to inflammatory stimuli while limiting expansion and self-renewal gene expression in MPPs.

“Our data show that while PU.1 functions as a key driver of myeloid differentiation, it plays an equally critical role in tailoring hematopoietic responses to inflammatory stimuli while limiting expansion and self-renewal gene expression in MPPs.”

May combine two claims.

PU.1 and CEBPA are critical for establishing the homeostatic 'set point' for numerous self-renewal and myeloid differentiation gene programs and jointly contribute to their regulation in response to IL-1β.

“Hence, our data support a model in which PU.1 and CEBPA are critical for establishing the homeostatic ‘set point’ for numerous self-renewal and myeloid differentiation gene programs and jointly contribute to their regulation in response to IL-1β.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Increased PU.1 expression may occur in PU.1 KI/KI MPPGM via CEBPA-mediated transduction.

“Increased PU.1 expression in may also occur in PU.1 KI/KI MPPGM via CEBPA-mediated transduction”

Probably not a substantial claim: may not pass S3 (load-bearing).

PI3K-AKT signaling can modulate the activity of PU.1 via phosphorylating it.

“As PI3K-AKT signaling can also modulate the activity of PU.1 via phosphorylating it (Rieske and Pongubala, 2001)”

• cites Rieske and Pongubala, 2001 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

CEBPA binds to and induces Spi1 expression in HSPC.

“as CEBPA binds to and induces Spi1 expression in HSPC (Kummalue and Friedman, 2003; Yeamans et al., 2007).”

• cites Kummalue and Friedman, 2003 sourceNot checked — no full text of the source
• cites Yeamans et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

Reduced PU.1 expression in PU.1 KI/KI MPPGM delays activation of myeloid differentiation programs, leading to retention of an immature phenotype following IL-1β stimulation.

“Hence, reduced PU.1 expression in PU.1 KI/KI MPPGM delays the activation of myeloid differentiation programs, leading to retention of an immature phenotype following IL-1β stimulation.”

May combine two claims.

Loss of PU.1 function broadly impacts the size and function of the myeloid hematopoietic hierarchy in addition to driving abnormal expansion of the long-term HSC pool.

“Thus, our data support a model in which loss of PU.1 function broadly impacts the size and function of the myeloid hematopoietic hierarchy in addition to driving abnormal expansion of the long-term HSC pool.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Oncogenic mutations in signaling pathway genes such as Ras and Flt3 that trigger downstream mitogenic activity could serve a similar function as inflammatory signaling in our model, triggering abnormal expansion of HSPC.

“In this setting, oncogenic mutations in signaling pathway genes such as Ras and Flt3 that trigger downstream mitogenic activity could serve a similar function as inflammatory signaling in our model, triggering abnormal expansion of HSPC.”

• AssumptionRests on an assumption: Oncogenic mutations in signaling pathway genes such as Ras and Flt3 trigger downstream mitogenic activity.

May combine two claims.

Loss of PU.1 expression is sufficient to support aberrant myelopoiesis and HSPC expansion in this setting.

“Hence, loss of PU.1 expression is sufficient to support aberrant myelopoiesis and HSPC expansion in this setting.”

Probably not a substantial claim: may not pass S3 (load-bearing).

PU.1 plays important roles in establishing the functional properties of mature myeloid cells.

“PU.1 also plays important roles in establishing the functional properties of mature myeloid cells (Singh et al., 1999).”

• cites Singh et al., 1999 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Loss of PU.1 in conjunction with IL-1β signaling could trigger aberrant expansion of HSC.

“We had previously shown that loss of PU.1 in conjunction with IL-1β signaling could trigger aberrant expansion of HSC.”