Maternal immune activation by LPS selectively alters specific gene expression profiles of interneuron migration and oxidative stress in the fetus without triggering a fetal immune response

“In addition, the placenta itself reacts strongly to MIA both morphologically and immunologically and likely contributes to fetal distress (Abrahams and Geschwind, 2008; Carpentier et al., 2011; Fatemi et al., 2011; Girard et al., 2010; Hauguel-de Mouzon and Guerre-Millo, 2006; Hsiao and Patterson,…”

“…perturb brain development remain unknown, but blocking the actions of the specific cytokines such as IL-6 or IL-1βprevents MIA-induced behavioral and physiological consequences in mouse offspring, offering further support for the cytokine hypothesis (Girard et al., 2010; Smith et al., 2007).”

“Bnip3 is a prominent and early responding hypoxia-induced cell death gene (Chinnadurai et al., 2008), and silencing of the gene using an siRNA suppresses hypoxia-induced autophagy (Bellot et al., 2009).”

“Tangential migration from the ganglionic eminences to the cortex and hippocampus is virtually absent in double Dlx1/2 knock-out mice (Anderson et al., 1997; Cobos et al., 2005), whereas migration is fairly intact in single Dlx1 or Dlx2 knock-outs, but the mutants have fewer total numbers of…”

“Already evidence is surfacing to show that improper cortical interneuron development and function may play a role in maladaptive social behaviors associated with autism and schizophrenia (Belforte et al., 2009; Geschwind and Levitt, 2007; Levitt, 2005).”

“The resulting activation of the transcription factor NF-κB induces pro-inflammatory cytokine expression (Palsson-McDermott and O'Neill, 2004).”

“Members of the heat shock family of proteins, which respond to cellular stress signals including oxidative stress and hypoxia (Chi and Karliner, 2004; Tucker et al., 2011; Welch, 1992) were also significantly up-regulated in fetal brain further suggestive of intermittent fetal hypoxia.”

“, 2010; Ciaranello and Ciaranello, 1995) and schizophrenia (Brown et al., 2004).”

“, 2007), influenza (Shi et al., 2003), or Borna disease virus (Pletnikov et al.”

“Cytokines are a class of secreted polypeptides that have diverse functions (Benveniste, 1998; Patterson and Nawa, 1993; Rothwell and Hopkins, 1995).”

“Maternal infections of both viral and bacterial origin have been linked with later development in the offspring of psychiatric disorders including autism (Atladottir et al., 2010; Ciaranello and Ciaranello, 1995) and schizophrenia (Brown et al.”

“…of the inflammatory immune response, there is evidence, primarily from in vitro studies, that they modulate normal developmental processes such as glial and neuronal commitment, proliferation, differentiation and survival, neurite outgrowth, and synaptogenesis (Deverman and Patterson, 2009).”

“, polyI:C (Meyer et al., 2006; Meyer et al., 2008; Smith et al., 2007), influenza (Shi et al., 2003), or Borna disease virus (Pletnikov et al., 1999).”

“…disorders has its roots in the prenatal environment such that insults to the fetus during critical times of development may alter fetal brain structure and function thereby acting as risk factors for disorders later in life (Bilbo and Schwarz, 2009; Patterson, 2002; Schlotz and Phillips, 2009).”

“Thus, although it has been demonstrated that MIA alters behavioral and biological outcomes in juvenile and adult offspring, the mechanisms by which this immune reaction ultimately disrupt brain and behavioral development remain unclear (Boksa, 2010).”

“Olfaction—Basic olfactory skills (the ability to recover a hidden piece of food) were assessed on postnatal day 40 following the Hidden Cookie Task established by (Yang and Crawley, 2009).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“…Cobos et al., 2005), whereas migration is fairly intact in single Dlx1 or Dlx2 knock-outs, but the mutants have fewer total numbers of cortical and hippocampal interneurons, abnormal neurite morphology, and increased seizure susceptibility (Cobos et al., 2007; Cobos et al., 2005; Mao et al., 2009).”

“The MIA model was established to test the hypothesis that activation of the maternal immune system, specifically the pro-inflammatory cytokines, permanently alters fetal brain development and increases risk for neurodevelopmental disorders (Jarskog et al., 1997; Meyer et al., 2005).”

“, polyI:C (Meyer et al., 2006; Meyer et al., 2008; Smith et al., 2007), influenza (Shi et al., 2003), or Borna disease virus (Pletnikov et al., 1999).”

“…disorders has its roots in the prenatal environment such that insults to the fetus during critical times of development may alter fetal brain structure and function thereby acting as risk factors for disorders later in life (Bilbo and Schwarz, 2009; Patterson, 2002; Schlotz and Phillips, 2009).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“…the placenta itself reacts strongly to MIA both morphologically and immunologically and likely contributes to fetal distress (Abrahams and Geschwind, 2008; Carpentier et al., 2011; Fatemi et al., 2011; Girard et al., 2010; Hauguel-de Mouzon and Guerre-Millo, 2006; Hsiao and Patterson, 2011).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“Additional roles include the regulation of dendritic branching, synaptogenesis, and synaptic pruning (Mann et al., 2007; Tran et al., 2007).”

“…et al., 2009b) is used to study how an insult directed at the maternal host can have adverse effects on the fetus leading to behavioral changes later in life, specifically within the domains of sensorimotor function, exploration, and social behaviors (Meyer et al., 2009a; Nouel et al., 2011).”

“…E1B 19KDa interacting protein 3 (Bnip3) code for BH3-only proteins that respond to hypoxic and inflammatory signals to induce programmed cell death via apoptotic and autophagic processes (Azad et al., 2008; Guo et al., 2001; Kothari et al., 2003; Wan et al., 2008; Zhaorigetu et al., 2008).”

“…E1B 19KDa interacting protein 3 (Bnip3) code for BH3-only proteins that respond to hypoxic and inflammatory signals to induce programmed cell death via apoptotic and autophagic processes (Azad et al., 2008; Guo et al., 2001; Kothari et al., 2003; Wan et al., 2008; Zhaorigetu et al., 2008).”

“Their inhibitory outputs are responsible for maintaining a balance between excitation and inhibition, and a loss of GABAergic activity is responsible for unchecked excitatory neuronal firing that causes seizure activity (Cossart et al., 2005).”

“…et al., 2009b) is used to study how an insult directed at the maternal host can have adverse effects on the fetus leading to behavioral changes later in life, specifically within the domains of sensorimotor function, exploration, and social behaviors (Meyer et al., 2009a; Nouel et al., 2011).”

“…affect CNS developmental processes, the presence of inflammatory molecules in the fetal brain may adversely affect the survival of neuronal subpopulations (Araujo and Cotman, 1995; Jarskog et al., 1997; Keohane et al.; Marx et al., 2001; Neumann et al., 2002; Qiu et al., 1998; Zhao et al., 2001).”

“…the placenta itself reacts strongly to MIA both morphologically and immunologically and likely contributes to fetal distress (Abrahams and Geschwind, 2008; Carpentier et al., 2011; Fatemi et al., 2011; Girard et al., 2010; Hauguel-de Mouzon and Guerre-Millo, 2006; Hsiao and Patterson, 2011).”

“Cytokines are a class of secreted polypeptides that have diverse functions (Benveniste, 1998; Patterson and Nawa, 1993; Rothwell and Hopkins, 1995).”

“…are believed to result at least partially from an excitation/inhibition imbalance caused by a loss of GABAergic interneurons, supported by the clinical evidence for reduced protein and gene markers for GABAergic interneurons (Curley et al., 2011; Fatemi et al., 2002; Thompson Ray et al., 2011).”

“The class III POU domain transcription factors, all of whose members had reduced expression following maternal LPS, are important for radial migration of pyramidal neurons destined for the neocortex and hippocampus (Alvarez-Bolado et al., 1995; McEvilly et al., 2002; Sugitani et al., 2002).”

“…disorders has its roots in the prenatal environment such that insults to the fetus during critical times of development may alter fetal brain structure and function thereby acting as risk factors for disorders later in life (Bilbo and Schwarz, 2009; Patterson, 2002; Schlotz and Phillips, 2009).”

“The class III POU domain transcription factors, all of whose members had reduced expression following maternal LPS, are important for radial migration of pyramidal neurons destined for the neocortex and hippocampus (Alvarez-Bolado et al., 1995; McEvilly et al., 2002; Sugitani et al., 2002).”

“Celsr3 mutant mice have a number of brain malformations such as a loss of several major axonal fiber tracts (Tissir et al., 2005; Zhou et al., 2008), stunted tangential migration evidenced by misguided cortical interneurons, and accumulation of interneurons at the corticostriatal boundary (Ying et…”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“…arise from germinal zones within the ventral telencephalon, specifically the medial, lateral, and caudal ganglionic eminences, and they migrate in a tangential direction across the network of radial glial fibers to enter the cortex before differentiating into mature neurons (Cobos et al., 2007).”

“…autism and epilepsy suggest a common underlying pathophysiological mechanism, such as disruptions in the functions and properties of GABAergic interneurons, as well as local cortical circuit formation that accounts for the cooccurrence (Di Cristo, 2007; Rubenstein, 2010; Sgado et al., 2011).”

“Additional transcription factors, Arx1, which is directly regulated by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et…”

“…E1B 19KDa interacting protein 3 (Bnip3) code for BH3-only proteins that respond to hypoxic and inflammatory signals to induce programmed cell death via apoptotic and autophagic processes (Azad et al., 2008; Guo et al., 2001; Kothari et al., 2003; Wan et al., 2008; Zhaorigetu et al., 2008).”

“Bnip3 is a prominent and early responding hypoxia-induced cell death gene (Chinnadurai et al., 2008), and silencing of the gene using an siRNA suppresses hypoxia-induced autophagy (Bellot et al., 2009).”

“…E1B 19KDa interacting protein 3 (Bnip3) code for BH3-only proteins that respond to hypoxic and inflammatory signals to induce programmed cell death via apoptotic and autophagic processes (Azad et al., 2008; Guo et al., 2001; Kothari et al., 2003; Wan et al., 2008; Zhaorigetu et al., 2008).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript fluid, and placenta (Ashdown et al., 2006; Cai et al., 2000; Gayle et al., 2004; Girard et al., 2010; Golan et al., 2005; Liverman et al., 2006; Ning et al., 2008; Urakubo et al., 2001).”

“The protocadherin genes Celsr3 and Pcdhγb6 are enriched within growth cones and synapses, and they are known to regulate synapse formation and maintenance (Kallenbach et al., 2003; Morishita and Yagi, 2007; Zhou et al., 2008).”

“The class III POU domain transcription factors, all of whose members had reduced expression following maternal LPS, are important for radial migration of pyramidal neurons destined for the neocortex and hippocampus (Alvarez-Bolado et al., 1995; McEvilly et al., 2002; Sugitani et al., 2002).”

“In vivo and in vitro models show that cerebral ischemia induced either by artery occlusion or oxygen-glucose deprivation significantly upregulates hemoglobin mRNA expression (He et al., 2009), and that excessive hemoglobin is toxic to cerebral cortical neurons (Wang et al., 2002).”

“The developing fetus relies on placental transfer of maternal nutrients including oxygen and glucose across the transporting epithelial membrane into the fetal capillary circulation (Desforges and Sibley, 2009).”

“…for the basis for how maternal LPS can affect selective aspects of behavior in the adult offspring and has broader implications for the pathogenesis of schizophrenia and autism, both of which are characterized by GABA dysfunction (for review: (Rossignol, 2011; Rubenstein, 2010; Sgado et al., 2011).”

“All GABAergic interneurons require proper expression and function of Dlx1 and 2 for intact migration, and Dlx5 and 6 preferentially regulate the MGE-derived parvalbumin-expressing cortical interneurons (Wang et al., 2010b).”

“In the MIA model, maternally generated cytokines are thought to penetrate the placental barrier to gain access to the fetus (Dahlgren et al., 2006; Nawa and Takei, 2006).”

“The protocadherin genes Celsr3 and Pcdhγb6 are enriched within growth cones and synapses, and they are known to regulate synapse formation and maintenance (Kallenbach et al., 2003; Morishita and Yagi, 2007; Zhou et al., 2008).”

“…by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et al., 2010; Huang, 2009; Metin et al., 2006).”

“…affect CNS developmental processes, the presence of inflammatory molecules in the fetal brain may adversely affect the survival of neuronal subpopulations (Araujo and Cotman, 1995; Jarskog et al., 1997; Keohane et al.; Marx et al., 2001; Neumann et al., 2002; Qiu et al., 1998; Zhao et al., 2001).”

“…affect CNS developmental processes, the presence of inflammatory molecules in the fetal brain may adversely affect the survival of neuronal subpopulations (Araujo and Cotman, 1995; Jarskog et al., 1997; Keohane et al.; Marx et al., 2001; Neumann et al., 2002; Qiu et al., 1998; Zhao et al., 2001).”

“Cortical and hippocampal interneuron loss has been reported following maternal polyI:C (Meyer and Feldon, 2009), neonatal LPS (Feleder et al.”

“Alpha-hemoglobin stabilizing protein, also called erythroid associated factor (Eraf) the second-most up-regulated gene, serves to protect against the production of reactive oxygen species by excessive levels of free α-hemoglobin (Feng et al., 2004; Weiss et al., 2005).”

“…E1B 19KDa interacting protein 3 (Bnip3) code for BH3-only proteins that respond to hypoxic and inflammatory signals to induce programmed cell death via apoptotic and autophagic processes (Azad et al., 2008; Guo et al., 2001; Kothari et al., 2003; Wan et al., 2008; Zhaorigetu et al., 2008).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript and exploration of an open field maze in offspring born to dams exposed to LPS (Hava et al., 2006; Kirsten et al., 2010a; Kirsten et al., 2010b; Wang et al.)”

“…behavioral changes remain unclear, it is believed that the induction of the maternal cytokine response and the cascade of downstream cellular and molecular events are responsible for the altered brain development and increased risk for atypical developmental outcomes (Jonakait, 2007).”

“Additional transcription factors, Arx1, which is directly regulated by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et…”

“…autism and epilepsy suggest a common underlying pathophysiological mechanism, such as disruptions in the functions and properties of GABAergic interneurons, as well as local cortical circuit formation that accounts for the cooccurrence (Di Cristo, 2007; Rubenstein, 2010; Sgado et al., 2011).”

“…affect CNS developmental processes, the presence of inflammatory molecules in the fetal brain may adversely affect the survival of neuronal subpopulations (Araujo and Cotman, 1995; Jarskog et al., 1997; Keohane et al.; Marx et al., 2001; Neumann et al., 2002; Qiu et al., 1998; Zhao et al., 2001).”

“, polyI:C (Meyer et al., 2006; Meyer et al., 2008; Smith et al., 2007), influenza (Shi et al., 2003), or Borna disease virus (Pletnikov et al., 1999).”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript and exploration of an open field maze in offspring born to dams exposed to LPS (Hava et al., 2006; Kirsten et al., 2010a; Kirsten et al., 2010b; Wang et al.)”

“Already evidence is surfacing to show that improper cortical interneuron development and function may play a role in maladaptive social behaviors associated with autism and schizophrenia (Belforte et al., 2009; Geschwind and Levitt, 2007; Levitt, 2005).”

“…the placenta itself reacts strongly to MIA both morphologically and immunologically and likely contributes to fetal distress (Abrahams and Geschwind, 2008; Carpentier et al., 2011; Fatemi et al., 2011; Girard et al., 2010; Hauguel-de Mouzon and Guerre-Millo, 2006; Hsiao and Patterson, 2011).”

“…are believed to result at least partially from an excitation/inhibition imbalance caused by a loss of GABAergic interneurons, supported by the clinical evidence for reduced protein and gene markers for GABAergic interneurons (Curley et al., 2011; Fatemi et al., 2002; Thompson Ray et al., 2011).”

“Members of the heat shock family of proteins, which respond to cellular stress signals including oxidative stress and hypoxia (Chi and Karliner, 2004; Tucker et al., 2011; Welch, 1992) were also significantly up-regulated in fetal brain further suggestive of intermittent fetal hypoxia.”

“Microglia populate the embryonic brain during a surge of infiltration from external sources such as the yolk sac at about the time of the LPS injection in our study (Rigato et al., 2011).”

“There have also been reports of semaphorin mutations in individuals with autism (Melin et al., 2006).”

“Point mutations of Dlx1, 2, and 6 have been detected in patients diagnosed with autism (Liu et al., 2009; Nakashima et al., 2010), which provides a genetic basis for GABAerigc dysfunction.”

“N IH -PA Author M anuscript N IH -PA Author M anuscript N IH -PA Author M anuscript regulates apoptosis (Gargalovic and Dory, 2003).”

“Additional transcription factors, Arx1, which is directly regulated by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et…”

“Additional transcription factors, Arx1, which is directly regulated by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et…”

“…the placenta itself reacts strongly to MIA both morphologically and immunologically and likely contributes to fetal distress (Abrahams and Geschwind, 2008; Carpentier et al., 2011; Fatemi et al., 2011; Girard et al., 2010; Hauguel-de Mouzon and Guerre-Millo, 2006; Hsiao and Patterson, 2011).”

“Additional roles include the regulation of dendritic branching, synaptogenesis, and synaptic pruning (Mann et al., 2007; Tran et al., 2007).”

“Neuron navigator 1 (Nav1) and glypican 2 (Gpc2) are developmentally-regulated genes, both of whose expression is restricted to the axonal growth cones of postmitotic, migrating neurons (Ivins et al., 1997; Martinez-Lopez et al., 2005).”

“Some evidence exists supporting a selective vulnerability of cortical interneurons to perinatal hypoxia (Fagel et al., 2009).”

“There has been one other report of gestational day 18 maternal LPS reducing semaphorin (Sema 5b) mRNA expression in the mouse fetal brain 6 h post treatment (Liverman et al., 2006).”

“Neuron navigator 1 (Nav1) and glypican 2 (Gpc2) are developmentally-regulated genes, both of whose expression is restricted to the axonal growth cones of postmitotic, migrating neurons (Ivins et al., 1997; Martinez-Lopez et al., 2005).”

“The BH3 domain is present on upstream activators of cell death and facilitates death by binding pro-death effector molecules such as the Bcl-2 family members to initiate a pro-death signaling cascade (Ghiotto et al., 2009).”

“All GABAergic interneurons require proper expression and function of Dlx1 and 2 for intact migration, and Dlx5 and 6 preferentially regulate the MGE-derived parvalbumin-expressing cortical interneurons (Wang et al., 2010b).”

“Cortical and hippocampal interneuron loss has been reported following maternal polyI:C (Meyer and Feldon, 2009), neonatal LPS (Feleder et al., 2009), and maternal LPS treatment (Nouel et al.”

“In vivo and in vitro models show that cerebral ischemia induced either by artery occlusion or oxygen-glucose deprivation significantly upregulates hemoglobin mRNA expression (He et al., 2009), and that excessive hemoglobin is toxic to cerebral cortical neurons (Wang et al., 2002).”

“Alpha-hemoglobin stabilizing protein, also called erythroid associated factor (Eraf) the second-most up-regulated gene, serves to protect against the production of reactive oxygen species by excessive levels of free α-hemoglobin (Feng et al., 2004; Weiss et al., 2005).”

“Increased cytokine gene expression by fetal brain has not been shown in the maternal LPS model except in some studies that used a much higher dose of LPS than what was used in our study (Cai et al., 2000; Lasala and Zhou, 2007).”

“A recent report by Ghiani et al. (2011) showed that following maternal LPS administered twice, on gestational days 15 and 16 in rats, there was evidence of activated microglia and astrocytes in fetal cortex two days later.”

“, 2010) and oxidative stress activity (Paintlia et al., 2008) in the placenta following MIA can disrupt the maternal/placental transfer of nutrients to the fetus leading to transient fetal hypoxia.”

“…Capillary Electrophoresis Maternal serum, amniotic fluid, and fetal brain samples were analyzed using chip-based immunoaffinity capillary electrophoresis with laser-induced fluorescence detection, as previously described (Phillips and Wellner, 2006, 2007), to measure TNF-α, IL-6, and IL-1β.”

“Additional transcription factors, Arx1, which is directly regulated by Dlx1/2, Lhx6, and Mgat5B, all of whose expression was reduced in our study, play specific roles in interneuron fate determination and migration (Alifragis et al., 2004; Butt et al., 2007; Cobos et al., 2006; Faux et al., 2010; Hernandez-Miranda et…”

“…affect CNS developmental processes, the presence of inflammatory molecules in the fetal brain may adversely affect the survival of neuronal subpopulations (Araujo and Cotman, 1995; Jarskog et al., 1997; Keohane et al.; Marx et al., 2001; Neumann et al., 2002; Qiu et al., 1998; Zhao et al., 2001).”

“, 2008), stunted tangential migration evidenced by misguided cortical interneurons, and accumulation of interneurons at the corticostriatal boundary (Ying et al., 2009).”

“…Cobos et al., 2005), whereas migration is fairly intact in single Dlx1 or Dlx2 knock-outs, but the mutants have fewer total numbers of cortical and hippocampal interneurons, abnormal neurite morphology, and increased seizure susceptibility (Cobos et al., 2007; Cobos et al., 2005; Mao et al., 2009).”

“…Capillary Electrophoresis Maternal serum, amniotic fluid, and fetal brain samples were analyzed using chip-based immunoaffinity capillary electrophoresis with laser-induced fluorescence detection, as previously described (Phillips and Wellner, 2006, 2007), to measure TNF-α, IL-6, and IL-1β.”

“Point mutations of Dlx1, 2, and 6 have been detected in patients diagnosed with autism (Liu et al., 2009; Nakashima et al., 2010), which provides a genetic basis for GABAerigc dysfunction.”

“The protocadherin genes Celsr3 and Pcdhγb6 are enriched within growth cones and synapses, and they are known to regulate synapse formation and maintenance (Kallenbach et al., 2003; Morishita and Yagi, 2007; Zhou et al., 2008).”

“Exploration was operationally defined as the number of nose-hole pokes per minute of ambulation during a 10-min observation period (Walker et al., 2007).”