Cerebral Cortex Of Adult Mice Research Articles

MTG8 interacts with LHX6 to specify cortical interneuron subtype identity

Cortical interneurons originating in the embryonic medial ganglionic eminence (MGE) diverge into a range of different subtypes found in the adult mouse cerebral cortex. The mechanisms underlying this divergence and the timing when subtype identity is set up remain unclear. We identify the highly conserved transcriptional co-factor MTG8 as being pivotal in the development of a large subset of MGE cortical interneurons that co-expresses Somatostatin (SST) and Neuropeptide Y (NPY). MTG8 interacts with the pan-MGE transcription factor LHX6 and together the two factors are sufficient to promote expression of critical cortical interneuron subtype identity genes. The SST-NPY cortical interneuron fate is initiated early, well before interneurons migrate into the cortex, demonstrating an early onset specification program. Our findings suggest that transcriptional co-factors and modifiers of generic lineage specification programs may hold the key to the emergence of cortical interneuron heterogeneity from the embryonic telencephalic germinal zones.

Neuron-specific chromosomal megadomain organization is adaptive to recent retrotransposon expansions

Regulatory mechanisms associated with repeat-rich sequences and chromosomal conformations in mature neurons remain unexplored. Here, we map cell-type specific chromatin domain organization in adult mouse cerebral cortex and report strong enrichment of Endogenous Retrovirus 2 (ERV2) repeat sequences in the neuron-specific heterochromatic B2NeuN+ megabase-scaling subcompartment. Single molecule long-read sequencing and comparative Hi-C chromosomal contact mapping in wild-derived SPRET/EiJ (Mus spretus) and laboratory inbred C57BL/6J (Mus musculus) reveal neuronal reconfigurations tracking recent ERV2 expansions in the murine germline, with significantly higher B2NeuN+ contact frequencies at sites with ongoing insertions in Mus musculus. Neuronal ablation of the retrotransposon silencer Kmt1e/Setdb1 triggers B2NeuN+ disintegration and rewiring with open chromatin domains enriched for cellular stress response genes, along with severe neuroinflammation and proviral assembly with infiltration of dendrites . We conclude that neuronal megabase-scale chromosomal architectures include an evolutionarily adaptive heterochromatic organization which, upon perturbation, results in transcriptional dysregulation and unleashes ERV2 proviruses with strong neuronal tropism.

Lipopolysaccharide induces neuroglia activation and NF-\u03baB activation in cerebral cortex of adult mice

Lipopolysaccharide (LPS) acts as an endotoxin, releases inflammatory cytokines, and promotes an inflammatory response in various tissues. This study investigated whether LPS modulates neuroglia activation and nuclear factor kappa B (NF-κB)-mediated inflammatory factors in the cerebral cortex. Adult male mice were divided into control animals and LPS-treated animals. The mice received LPS (250 μg/kg) or vehicle via an intraperitoneal injection for 5 days. We confirmed a reduction of body weight in LPS-treated animals and observed severe histopathological changes in the cerebral cortex. Moreover, we elucidated increases of reactive oxygen species and oxidative stress levels in LPS-treated animals. LPS administration led to increases of ionized calcium-binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) expression. Iba-1 and GFAP are well accepted as markers of activated microglia and astrocytes, respectively. Moreover, LPS exposure induced increases of NF-κB and pro-inflammatory factors, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Increases of these inflammatory mediators by LPS exposure indicate that LPS leads to inflammatory responses and tissue damage. These results demonstrated that LPS activates neuroglial cells and increases NF-κB-mediated inflammatory factors in the cerebral cortex. Thus, these findings suggest that LPS induces neurotoxicity by increasing oxidative stress and activating neuroglia and inflammatory factors in the cerebral cortex.

Inhibition of Piezo1 attenuates demyelination in the central nervous system.

Piezo1 is a mechanosensitive ion channel that facilitates the translation of extracellular mechanical cues to intracellular molecular signaling cascades through a process termed, mechanotransduction. In the central nervous system (CNS), mechanically gated ion channels are important regulators of neurodevelopmental processes such as axon guidance, neural stem cell differentiation, and myelination of axons by oligodendrocytes. Here, we present evidence that pharmacologically mediated overactivation of Piezo1 channels negatively regulates CNS myelination. Moreover, we found that the peptide GsMTx4, an antagonist of mechanosensitive cation channels such as Piezo1, is neuroprotective and prevents chemically induced demyelination. In contrast, the positive modulator of Piezo1 channel opening, Yoda-1, induces demyelination and neuronal damage. Using an ex vivo murine-derived organotypic cerebellar slice culture model, we demonstrate that GsMTx4 attenuates demyelination induced by the cytotoxic lipid, psychosine. Importantly, we confirmed the potential therapeutic effects of GsMTx4 peptide in vivo by co-administering it with lysophosphatidylcholine (LPC), via stereotactic injection, into the cerebral cortex of adult mice. GsMTx4 prevented both demyelination and neuronal damage usually caused by the intracortical injection of LPC in vivo; a well-characterized model of focal demyelination. GsMTx4 also attenuated both LPC-induced astrocyte toxicity and microglial reactivity within the lesion core. Overall, our data suggest that pharmacological activation of Piezo1 channels induces demyelination and that inhibition of mechanosensitive channels, using GsMTx4, may alleviate the secondary progressive neurodegeneration often present in the latter stages of demyelinating diseases.

Fragile X mental retardation protein modulates the stability of its m6A-marked messenger RNA targets.

N6-methyladenosine (m6A) is the most prevalent internal modification of mammalian messenger RNAs (mRNAs) and long non-coding RNAs. The biological functions of this reversible RNA modification can be interpreted by cytoplasmic and nuclear 'm6A reader' proteins to fine-tune gene expression, such as mRNA degradation and translation initiation. Here we profiled transcriptome-wide m6A sites in adult mouse cerebral cortex, underscoring that m6A is a widespread epitranscriptomic modification in brain. Interestingly, the mRNA targets of fragile X mental retardation protein (FMRP), a selective RNA-binding protein, are enriched for m6A marks. Loss of functional FMRP leads to Fragile X syndrome (FXS), the most common inherited form of intellectual disability. Transcriptome-wide gene expression profiling identified 2035 genes differentially expressed in the absence of FMRP in cortex, and 92.5% of 174 downregulated FMRP targets are marked by m6A. Biochemical analyses indicate that FMRP binds to the m6A sites of its mRNA targets and interacts with m6A reader YTHDF2 in an RNA-independent manner. FMRP maintains the stability of its mRNA targets while YTHDF2 promotes the degradation of these mRNAs. These data together suggest that FMRP regulates the stability of its m6A-marked mRNA targets through YTHDF2, which could potentially contribute to the molecular pathogenesis of FXS.

A review of functional heterogeneity among astrocytes and the CS56-specific antibody-mediated detection of a subpopulation of astrocytes in adult brains.

Astrocytes comprise the largest class of glial cells in the mammalian central nerve system (CNS). Although astrocytes were long considered to be a homogeneous population of neuron-supporting cells, recent decades have seen a shift toward the recognition that astrocytes exhibit morphological and functional heterogeneities and serve as essential modulators of brain functions. However, the mechanism underlying astrocyte diversity remains unclear, and the different subpopulations are difficult to identify due to a lack of specific cell markers. In this review, I discuss current knowledge regarding astrocyte heterogeneity and introduce a subpopulation that can be detected via labeling with a chondroitin sulfate-specific antibody (CS56). These CS56-positive astrocytes were found to selectively express tenascin-R (TNR) in the adult mouse cerebral cortex. Further research demonstrated significantly lower levels of glutamate uptake activity and glutamate aspartate transporter expression in TNR-knockdown astrocytes relative to controls, suggesting that the expression and secretion of Tnr by a subpopulation of astrocytes may contribute to region-specific neuron-astrocyte interactions. In summary, these results suggest that CS56-specific antibody and Tnr could be used as novel markers to detect an astrocyte subpopulation in the adult CNS.

Differential neuronal and glial expression of nuclear factor I proteins in the cerebral cortex of adult mice

AbstractThe nuclear factor I (NFI) family of transcription factors plays an important role in the development of the cerebral cortex in humans and mice. Disruption of nuclear factor IA (NFIA), nuclear factor IB (NFIB), or nuclear factor IX (NFIX) results in abnormal development of the corpus callosum, lateral ventricles, and hippocampus. However, the expression or function of these genes has not been examined in detail in the adult brain, and the cell type‐specific expression of NFIA, NFIB, and NFIX is currently unknown. Here, we demonstrate that the expression of each NFI protein shows a distinct laminar pattern in the adult mouse neocortex and that their cell type‐specific expression differs depending on the family member. NFIA expression was more frequently observed in astrocytes and oligodendroglia, whereas NFIB expression was predominantly localized to astrocytes and neurons. NFIX expression was most commonly observed in neurons. The NFI proteins were equally distributed within microglia, and the ependymal cells lining the ventricles of the brain expressed all three proteins. In the hippocampus, the NFI proteins were expressed during all stages of neural stem cell differentiation in the dentate gyrus, with higher expression intensity in neuroblast cells as compared to quiescent stem cells and mature granule neurons. These findings suggest that the NFI proteins may play distinct roles in cell lineage specification or maintenance, and establish the basis for further investigation of their function in the adult brain and their emerging role in disease.

Neuronal tetraploidization in the cerebral cortex correlates with reduced cognition in mice and precedes and recapitulates Alzheimer's-associated neuropathology

A controversy exists as to whether de novo-generated neuronal tetraploidy (dnNT) occurs in Alzheimer's disease. In addition, the presence of age-associated dnNT in the normal brain remains unexplored. Here we show that age-associated dnNT occurs in both superficial and deep layers of the cerebral cortex of adult mice, a process that is blocked in the absence of E2F1, a known regulator of cell cycle progression. This blockage correlates with improved cognition despite compromised neurogenesis in the adult hippocampus was confirmed in mice lacking the E2f1 gene. We also show that the human cerebral cortex contains tetraploid neurons. In normal humans, age-associated dnNT specifically occurs in the entorhinal cortex whereas, in Alzheimer, dnNT also affects association cortices prior to neurofibrillary tangle formation. Alzheimer-associated dnNT is likely potentiated by altered amyloid precursor protein (APP) processing as it is enhanced in the cerebral cortex of young APPswe/PS1deltaE9 mice, long before the first amyloid plaques are visible in their brains. In contrast to age-associated dnNT, enhanced dnNT in APPswe/PS1deltaE9 mice mostly affects the superficial cortical layers. The correlation of dnNT with reduced cognition in mice and its spatiotemporal course, preceding and recapitulating Alzheimer-associated neuropathology, makes this process a potential target for intervention in Alzheimer's disease.

Differential neuronal and glial expression of nuclear factor I proteins in the cerebral cortex of adult mice.

The nuclear factor I (NFI) family of transcription factors plays an important role in the development of the cerebral cortex in humans and mice. Disruption of nuclear factor IA (NFIA), nuclear factor IB (NFIB), or nuclear factor IX (NFIX) results in abnormal development of the corpus callosum, lateral ventricles, and hippocampus. However, the expression or function of these genes has not been examined in detail in the adult brain, and the cell type-specific expression of NFIA, NFIB, and NFIX is currently unknown. Here, we demonstrate that the expression of each NFI protein shows a distinct laminar pattern in the adult mouse neocortex and that their cell type-specific expression differs depending on the family member. NFIA expression was more frequently observed in astrocytes and oligodendroglia, whereas NFIB expression was predominantly localized to astrocytes and neurons. NFIX expression was most commonly observed in neurons. The NFI proteins were equally distributed within microglia, and the ependymal cells lining the ventricles of the brain expressed all three proteins. In the hippocampus, the NFI proteins were expressed during all stages of neural stem cell differentiation in the dentate gyrus, with higher expression intensity in neuroblast cells as compared to quiescent stem cells and mature granule neurons. These findings suggest that the NFI proteins may play distinct roles in cell lineage specification or maintenance, and establish the basis for further investigation of their function in the adult brain and their emerging role in disease.

Partial Loss of Presenilin Impairs Age-Dependent Neuronal Survival in the Cerebral Cortex

Mutations in the presenilin (PSEN1 and PSEN2) genes are linked to familial Alzheimer's disease (AD) and cause loss of its essential function. Complete inactivation of presenilins in excitatory neurons of the adult mouse cerebral cortex results in progressive memory impairment and age-dependent neurodegeneration, recapitulating key features of AD. In this study, we examine the effects of varying presenilin dosage on cortical neuron survival by generating presenilin-1 conditional knock-out (PS1 cKO) mice carrying two, one, or zero copies of the PS2 gene. We found that PS1 cKO;PS2(+/-) mice at 16 months exhibit marked neurodegeneration in the cerebral cortex with ∼17% reduction of cortical volume and neuron number, as well as astrogliosis and microgliosis compared with ∼50% reduction of cortical volume and neuron number in PS1 cKO;PS2(-/-) mice. Moreover, there are more apoptotic neurons labeled by activated caspase-3 immunoreactivity and TUNEL assay in PS1 cKO;PS2(+/-) mice at 16 months, whereas apoptotic neurons are increased in the PS1 cKO;PS2(-/-) cerebral cortex at 4 months. The accumulation of the C-terminal fragments of the amyloid precursor protein is inversely correlated with PS dosage. Interestingly, levels of PS2 are higher in the cerebral cortex of PS1 cKO mice, suggesting a compensatory upregulation that may provide protection against neurodegeneration in these mice. Together, our findings show that partial to complete loss of presenilin activity causes progressively more severe neurodegeneration in the mouse cerebral cortex during aging, suggesting that impaired presenilin function by PSEN mutations may lead to neurodegeneration and dementia in AD.

Sox2-Mediated Conversion of NG2 Glia into Induced Neurons in the Injured Adult Cerebral Cortex

SummaryThe adult cerebral cortex lacks the capacity to replace degenerated neurons following traumatic injury. Conversion of nonneuronal cells into induced neurons has been proposed as an innovative strategy toward brain repair. Here, we show that retrovirus-mediated expression of the transcription factors Sox2 and Ascl1, but strikingly also Sox2 alone, can induce the conversion of genetically fate-mapped NG2 glia into induced doublecortin (DCX)+ neurons in the adult mouse cerebral cortex following stab wound injury in vivo. In contrast, lentiviral expression of Sox2 in the unlesioned cortex failed to convert oligodendroglial and astroglial cells into DCX+ cells. Neurons induced following injury mature morphologically and some acquire NeuN while losing DCX. Patch-clamp recording of slices containing Sox2- and/or Ascl1-transduced cells revealed that a substantial fraction of these cells receive synaptic inputs from neurons neighboring the injury site. Thus, NG2 glia represent a potential target for reprogramming strategies toward cortical repair.

A subconvulsive dose of kainate selectively compromises astrocytic metabolism in the mouse brain in vivo.

Despite the well-established use of kainate as a model for seizure activity and temporal lobe epilepsy, most studies have been performed at doses giving rise to general limbic seizures and have mainly focused on neuronal function. Little is known about the effect of lower doses of kainate on cerebral metabolism and particularly that associated with astrocytes. We investigated astrocytic and neuronal metabolism in the cerebral cortex of adult mice after treatment with saline (controls), a subconvulsive or a mildly convulsive dose of kainate. A combination of [1,2-(13)C]acetate and [1-(13)C]glucose was injected and subsequent nuclear magnetic resonance spectroscopy of cortical extracts was employed to distinctively map astrocytic and neuronal metabolism. The subconvulsive dose of kainate led to an instantaneous increase in the cortical lactate content, a subsequent reduction in the amount of [4,5-(13)C]glutamine and an increase in the calculated astrocytic TCA cycle activity. In contrast, the convulsive dose led to decrements in the cortical content and (13)C labeling of glutamate, glutamine, GABA, and aspartate. Evidence is provided that astrocytic metabolism is affected by a subconvulsive dose of kainate, whereas a higher dose is required to affect neuronal metabolism. The cerebral glycogen content was dose-dependently reduced by kainate supporting a role for glycogen during seizure activity.

OASIS regulates chondroitin 6‐O‐sulfotransferase 1 gene transcription in the injured adult mouse cerebral cortex

Old astrocyte specifically induced substance (OASIS), a basic leucine zipper transcription factor of the cAMP response element binding/Activating transcription factor family, is induced in reactive astrocytes in vivo and has important roles in quality control of protein synthesis at the endoplasmic reticulum. Reactive astrocytes produce a non-permissive environment for regenerating axons by up-regulating chondroitin sulfate proteoglycans (CSPGs). In this study, we focus on the potential role of OASIS in CSPG production in the adult mouse cerebral cortex. CS-C immunoreactivity, which represents chondroitin sulfate moieties, was significantly attenuated in the stab-injured cortices of OASIS knockout mice compared to those of wild-type mice. We next examined expression of the CSPG-synthesizing enzymes and core proteins of CSPGs in the stab-injured cortices of OASIS knockout and wild-type mice. The levels of chondroitin 6-O-sulfotransferase 1 (C6ST1, one of the major enzymes involved in sulfation of CSPGs) mRNA and protein increased after cortical stab injury of wild-type, but not of OASIS knockout, mice. A C-terminal deletion mutant OASIS over-expressed in rat C6 glioma cells increased C6ST1 transcription by interacting with the first intron region. Neurite outgrowth of cultured hippocampal neurons was inhibited on culture dishes coated with membrane fractions of epidermal growth factor-treated astrocytes derived from wild type but not from OASIS knockout mice. These results suggest that OASIS regulates the transcription of C6ST1 and thereby promotes CSPG sulfation in astrocytes. Through these mechanisms, OASIS may modulate axonal regeneration in the injured cerebral cortex. OASIS, an ER stress-responsive CREB/ATF family member, is up-regulated in the reactive astrocytes of the injured brain. We found that the up-regulated OASIS is involved in the transcriptional regulation of C6ST1 gene, which promotes chondroitin sulfate proteoglycan (CSPG) sulfation. We conclude that OASIS functions as an anti-regenerative transcription factor by establishing a non-permissive microenvironment to regenerating axons.

Chondroitin Sulfate Proteoglycan Tenascin-R Regulates Glutamate Uptake by Adult Brain Astrocytes

In our previous study, the CS-56 antibody, which recognizes a chondroitin sulfate moiety, labeled a subset of adult brain astrocytes, yielding a patchy extracellular matrix pattern. To explore the molecular nature of CS-56-labeled glycoproteins, we purified glycoproteins of the adult mouse cerebral cortex using a combination of anion-exchange, charge-transfer, and size-exclusion chromatographies. One of the purified proteins was identified as tenascin-R (TNR) by mass spectrometric analysis. When we compared TNR mRNA expression patterns with the distribution patterns of CS-56-positive cells, TNR mRNA was detected in CS-56-positive astrocytes. To examine the functions of TNR in astrocytes, we first confirmed that cultured astrocytes also expressed TNR protein. TNR knockdown by siRNA expression significantly reduced glutamate uptake in cultured astrocytes. Furthermore, expression of mRNA and protein of excitatory amino acid transporter 1 (GLAST), which is a major component of astrocytic glutamate transporters, was reduced by TNR knockdown. Our results suggest that TNR is expressed in a subset of astrocytes and contributes to glutamate homeostasis by regulating astrocytic GLAST expression.

Protocol to Isolate a Large Amount of Functional Oligodendrocyte Precursor Cells from the Cerebral Cortex of Adult Mice and Humans

During development, oligodendrocytes are generated from oligodendrocyte precursor cells (OPCs), a cell type that is a significant proportion of the total cells (3-8%) in the adult central nervous system (CNS) of both rodents and humans. Adult OPCs are responsible for the spontaneous remyelination that occurs in demyelinating diseases like Multiple Sclerosis (MS) and they constitute an interesting source of cells for regenerative therapy in such conditions. However, there is little data regarding the neurobiology of adult OPCs isolated from mice since an efficient method to isolate them has yet to be established. We have designed a protocol to obtain viable adult OPCs from the cerebral cortex of different mouse strains and we have compared its efficiency with other well-known methods. In addition, we show that this protocol is also useful to isolate functional OPCs from human brain biopsies. Using this method we can isolate primary cortical OPCs in sufficient quantities so as to be able to study their survival, maturation and function, and to facilitate an evaluation of their utility in myelin repair.

Transplantation reveals regional differences in oligodendrocyte differentiation in the adult brain

To examine the role of gray and white matter niches for oligodendrocyte differentiation, we used homo- and heterotopic transplantations into the adult mouse cerebral cortex. White matter-derived cells differentiated into mature oligodendrocytes in both niches with equal efficiency, whereas gray matter-derived cells did not. Thus, white matter promotes oligodendrocyte differentiation, and cells from this niche differentiate more easily, even in the less supportive gray matter environment.

Live imaging of astrocyte responses to acute injury reveals selective juxtavascular proliferation

Astrocytes are thought to have important roles after brain injury, but their behavior has largely been inferred from postmortem analysis. To examine the mechanisms that recruit astrocytes to sites of injury, we used in vivo two-photon laser-scanning microscopy to follow the response of GFP-labeled astrocytes in the adult mouse cerebral cortex over several weeks after acute injury. Live imaging revealed a marked heterogeneity in the reaction of individual astrocytes, with one subset retaining their initial morphology, another directing their processes toward the lesion, and a distinct subset located at juxtavascular sites proliferating. Although no astrocytes actively migrated toward the injury site, selective proliferation of juxtavascular astrocytes was observed after the introduction of a lesion and was still the case, even though the extent was reduced, after astrocyte-specific deletion of the RhoGTPase Cdc42. Thus, astrocyte recruitment after injury relies solely on proliferation in a specific niche.

MRNA expression, splicing and editing in the embryonic and adult mouse cerebral cortex

The complexity of the adult brain is a result of both developmental processes and experience-dependent circuit formation. One way to look at the differences between embryonic and adult brain is to examine gene expression. Previous studies have used microarrays to address this in a global manner. However, the transcriptome is more complex than gene expression levels alone, as alternative splicing and RNA editing generate a diverse set of mature transcripts. Here, we developed a high-resolution transcriptome dataset of mouse cerebral cortex at embryonic and adult stages using RNA sequencing (RNA-Seq). We found many differences in gene expression, splicing and RNA editing between embryonic and adult cerebral cortex. Each dataset was validated technically and biologically, and in each case we found our RNA-Seq observations to have predictive validity. We propose this dataset and analysis to be a helpful resource for understanding gene expression in the embryonic and adult cerebral cortex.

Loss of GABAergic neurons in the hippocampus and cerebral cortex of Engrailed-2 null mutant mice: Implications for autism spectrum disorders

The homeobox-containing transcription factor Engrailed-2 (En2) is involved in patterning and neuronal differentiation of the midbrain/hindbrain region, where it is prominently expressed. En2 mRNA is also expressed in the adult mouse hippocampus and cerebral cortex, indicating that it might also function in these brain areas. Genome-wide association studies revealed that En2 is a candidate gene for autism spectrum disorders (ASD), and mice devoid of its expression (En2−/− mice) display anatomical, behavioral and clinical “autistic-like” features. Since reduced GABAergic inhibition has been proposed as a possible pathogenic mechanism of ASD, we hypothesized that the phenotype of En2−/− mice might include defective GABAergic innervation in the forebrain. Here we show that the Engrailed proteins are present in postnatal GABAergic neurons of the mouse hippocampus and cerebral cortex, and adult En2−/− mice show reduced expression of GABAergic marker mRNAs in these areas. In addition, reduction in parvalbumin (PV), somatostatin (SOM) and neuropeptide Y (NPY) expressing interneurons is detected in the hippocampus and cerebral cortex of adult En2−/− mice. Our results raise the possibility of a link between altered function of En2, anatomical deficits of GABAergic forebrain neurons and the pathogenesis of ASD.

Reverse engineering a mouse embryonic stem cell-specific transcriptional network reveals a new modulator of neuronal differentiation

Gene expression profiles can be used to infer previously unknown transcriptional regulatory interaction among thousands of genes, via systems biology ‘reverse engineering’ approaches. We ‘reverse engineered’ an embryonic stem (ES)-specific transcriptional network from 171 gene expression profiles, measured in ES cells, to identify master regulators of gene expression (‘hubs’). We discovered that E130012A19Rik (E13), highly expressed in mouse ES cells as compared with differentiated cells, was a central ‘hub’ of the network. We demonstrated that E13 is a protein-coding gene implicated in regulating the commitment towards the different neuronal subtypes and glia cells. The overexpression and knock-down of E13 in ES cell lines, undergoing differentiation into neurons and glia cells, caused a strong up-regulation of the glutamatergic neurons marker Vglut2 and a strong down-regulation of the GABAergic neurons marker GAD65 and of the radial glia marker Blbp. We confirmed E13 expression in the cerebral cortex of adult mice and during development. By immuno-based affinity purification, we characterized protein partners of E13, involved in the Polycomb complex. Our results suggest a role of E13 in regulating the division between glutamatergic projection neurons and GABAergic interneurons and glia cells possibly by epigenetic-mediated transcriptional regulation.