Project description:The transcription factor Pax6 acts as a key developmental regulator in various organs. In the developing brain Pax6 regulates patterning, neurogenesis and proliferation, but how these diverse effects are mediated at the molecular level is not well understood. As Pax6 regulates forebrain development including neurogenesis, proliferation and patterning, almost exclusively by one of its DNA-binding domains, the bipartite paired domain, we examined the role of its respective DNA-binding subdomains (PAI and RED). Using mice with point mutations in the PAI (Pax6Leca4, N50K) and RED (Pax6Leca2, R128C) subdomains we unravelled opposing roles of mutations in these subdomains in regulating genes that control proliferation in the developing cerebral cortex. Mutation of the PAI domain reduced proliferation of both apical and basal progenitors, while the RED domain mutation significantly increased proliferation. Conversely, neurogenesis was affected only by the PAI domain mutation phenocopying the neurogenic defects observed in full Pax6 mutants. Genome-wide expression analysis supported the molecularly distinct signature upon mutation of these subdomains unravelling the key neurogenic signature mediated by the PAI domain. The altered expression of genes identified as direct Pax6 targets by chromatin immunoprecipitation allowed to further identify regulatory elements whose function was impaired by each individual Pax6 mutated protein. Thus, Pax6 achieves its key roles in the developing forebrain by utilizing distinct subdomains to regulate neurogenesis and exert opposing effects on proliferation, while Pax6-target genes involved in patterning tolerate either subdomain mutation. We performed gene expression microarray analysis of Pax6 mutant mice (Leca2, Leca4, Sey) and control mice
Project description:The transcription factor Pax6 acts as a key developmental regulator in various organs. In the developing brain Pax6 regulates patterning, neurogenesis and proliferation, but how these diverse effects are mediated at the molecular level is not well understood. As Pax6 regulates forebrain development including neurogenesis, proliferation and patterning, almost exclusively by one of its DNA-binding domains, the bipartite paired domain, we examined the role of its respective DNA-binding subdomains (PAI and RED). Using mice with point mutations in the PAI (Pax6Leca4, N50K) and RED (Pax6Leca2, R128C) subdomains we unravelled opposing roles of mutations in these subdomains in regulating genes that control proliferation in the developing cerebral cortex. Mutation of the PAI domain reduced proliferation of both apical and basal progenitors, while the RED domain mutation significantly increased proliferation. Conversely, neurogenesis was affected only by the PAI domain mutation phenocopying the neurogenic defects observed in full Pax6 mutants. Genome-wide expression analysis supported the molecularly distinct signature upon mutation of these subdomains unravelling the key neurogenic signature mediated by the PAI domain. The altered expression of genes identified as direct Pax6 targets by chromatin immunoprecipitation allowed to further identify regulatory elements whose function was impaired by each individual Pax6 mutated protein. Thus, Pax6 achieves its key roles in the developing forebrain by utilizing distinct subdomains to regulate neurogenesis and exert opposing effects on proliferation, while Pax6-target genes involved in patterning tolerate either subdomain mutation.
Project description:The transcription factor Pax6 is comprised of the paired domain (PD) and homeodomain (HD). In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific subpopulations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification. Pax6 also regulates the entire lens developmental program. To reconstruct Pax6-dependent gene regulatory networks (GRNs), ChIP-seq studies were performed using lens and forebrain chromatin from mice. A total of 3,723 (forebrain) and 3,514 (lens) Pax6-containing peaks were identified, with ~70% of them found in both tissues and thereafter called “common” peaks. Analysis of Pax6-bound peaks identified motifs that closely resemble Pax6-PD, -PD/HD and -HD established binding sequences. Mapping of H3K4me1, H3K4me3, H3K27ac, H3K27me3 and RNA polymerase II revealed distinct types of tissue-specific enhancers bound by Pax6. Pax6 directly regulates cortical neurogenesis through activation (e.g. Dmrta1 and Ngn2) and repression (e.g. Ascl1, Fezf2, and Gsx2) of transcription factors. In lens, Pax6 directly regulates cell cycle exit control via components of FGF (Fgfr2, Ccnd1, and Prox1) and Wnt (Dkk3, Wnt7a, Lrp6, Bcl9l, and Ccnd1) signaling pathways. Collectively, these studies provide genome-wide analysis of Pax6-dependent GRNs in lens and forebrain and establish novel roles of Pax6 in organogenesis. Examination of Pax6 in mouse embryonic forebrain and newborn lens. We performed ChIP-seq on mouse E12.5 embryonic forebrain and newborn lens. Genome-wide binding sites of Pax6, H3K4me1, H3K4me3, H3K27ac, H3K27me3, and Pol2 were generated. We also performed RNA-seq on mouse E12.5 embryonic forebrain and newborn lens epithelial cells and fibers.
Project description:The transcription factor Pax6 is comprised of the paired domain (PD) and homeodomain (HD). In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific subpopulations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification. Pax6 also regulates the entire lens developmental program. To reconstruct Pax6-dependent gene regulatory networks (GRNs), ChIP-seq studies were performed using lens and forebrain chromatin from mice. A total of 3,723 (forebrain) and 3,514 (lens) Pax6-containing peaks were identified, with ~70% of them found in both tissues and thereafter called “common” peaks. Analysis of Pax6-bound peaks identified motifs that closely resemble Pax6-PD, -PD/HD and -HD established binding sequences. Mapping of H3K4me1, H3K4me3, H3K27ac, H3K27me3 and RNA polymerase II revealed distinct types of tissue-specific enhancers bound by Pax6. Pax6 directly regulates cortical neurogenesis through activation (e.g. Dmrta1 and Ngn2) and repression (e.g. Ascl1, Fezf2, and Gsx2) of transcription factors. In lens, Pax6 directly regulates cell cycle exit control via components of FGF (Fgfr2, Ccnd1, and Prox1) and Wnt (Dkk3, Wnt7a, Lrp6, Bcl9l, and Ccnd1) signaling pathways. Collectively, these studies provide genome-wide analysis of Pax6-dependent GRNs in lens and forebrain and establish novel roles of Pax6 in organogenesis.
Project description:Pax6 is a transcription factor that is expressed in neuroepithelial cells from the initial stage of brain development. Region specific expression of Pax6 plays pivotal roles in the developing CNS, including brain patterning, neuronal specification, neuronal migration, and axonal projection. Regarding neurogenesis, Pax6 multiply works either as to promote neuronal differentiation or cell proliferation in a highly context-dependent manner. However, no Pax6 target gene is identified as to promote proliferation and/or inhibit differentiation of neuroepithelial cells. Here, we performed comparative analysis using the Affymetrix U34A array to identify genes that are differentially expressed in the early stage of wild-type and Pax6 homozygous mutant rat (rSey2/rSey2) brains.
Project description:Pax6 is a transcription factor that is expressed in neuroepithelial cells from the initial stage of brain development. Region specific expression of Pax6 plays pivotal roles in the developing CNS, including brain patterning, neuronal specification, neuronal migration, and axonal projection. Regarding neurogenesis, Pax6 multiply works either as to promote neuronal differentiation or cell proliferation in a highly context-dependent manner. However, no Pax6 target gene is identified as to promote proliferation and/or inhibit differentiation of neuroepithelial cells. Here, we performed comparative analysis using the Affymetrix U34A array to identify genes that are differentially expressed in the early stage of wild-type and Pax6 homozygous mutant rat (rSey2/rSey2) brains. Keywords = Pax6 transcription factor Keywords = rat Keywords = forebrain and hindbrain regions of the wild-type or Pax6 homozygous embryos Keywords = up-or down-regulated genes Keywords: ordered
Project description:The molecular mechanisms of neurogenic fate determination are of particular importance in light of the need to regenerate neurons. However the molecular logic of neurogenic fate determination is still ill understood, even though some key transcription factors have been implicated. Here we describe how one of these, the transcription factor Pax6, regulates adult neurogenesis by initiating a cross-regulatory network of 3 transcription factors executing neuronal fate and regulating genes required for neuronal differentiation. This network is initiated and driven to sufficiently high expression levels by the transcription factor Pax6 in close interaction with Brg1-containing SWI/SNF chromatin remodeling factors. Genetic deletion of either Pax6 or Brg1, the ATPase unit of the SWI/SNF complex, in neural stem cells of the adult mouse subependymal zone results in a fate conversion to distinct glial subtypes most pronounced when neuroblasts leave the neurogenic niche. Consistent with the phenocopy in vivo virtually all genes down-regulated by Brg1 deletion have Pax6-binding motifs. Amongst the few down-stream transcription factors are Sox11, Nfib and Brn4 that crossregulate each other and rescue neurogenesis also in direct reprogramming in the absence of Brg1 (or Pax6). Thus the function of Pax6-SWI/SNF is necessary and sufficient for neuronal fate maintenance and initiates a cross-regulatory effector network required for neuronal fate execution and maintenance to counteract glial differentiation in the adult brain. This identifies a novel role highly specific role of a chromatin-remodelling complex in stabilizing fate decisions in normal and forced neurogenesis. We performed gene expression microarray analysis on tissue derived from the SEZ or from the core region of the olfactory bulb from Brg1 cKO and control mice
Project description:Pax6 is a transcription factor with key functional roles in embryonic development. In order to identify downstream effectors of Pax6 in the developing cerebral cortex we performed microarray analysis. We compared gene expression profiles of cortical tissues isolated from wild type and Pax6-/- mouse embryos.
Project description:Nonsense and missense mutations in the transcription factor PAX6 cause a wide range of eye development defects, including aniridia, microphthalmia and coloboma. To understand how changes of PAX6:DNA binding cause these phenotypes, we combined saturation mutagenesis of the paired domain of PAX6 with a yeast one-hybrid (Y1H) assay in which expression of a PAX6-GAL4 fusion gene drives antibiotic resistance. We quantified binding of more than 2,700 single amino-acid variants to two DNA sequence elements. Mutations in DNA-facing residues of the N-terminal subdomain and linker region were most detrimental, as were mutations to prolines and to negatively charged residues. Many variants caused sequence-specific molecular gain-of-function effects, including variants in position Ile71 that increased binding to the LE9 enhancer but decreased binding to a SELEX-derived binding site. In the absence of antibiotic selection, variants that retained DNA binding slowed yeast growth, likely because such variants perturbed the yeast transcriptome. Benchmarking against known patient variants and applying ACMG/AMP guidelines to variant classification, we obtained supporting to moderate evidence to suggest that 1,306 variants are likely benign, and 977, likely pathogenic. Our analysis shows that most pathogenic mutations in the paired domain of PAX6 can be explained simply by the effects of these mutations on PAX6:DNA association, and establishes Y1H as a generalisable assay for the interpretation of variant effects in transcription factors.
Project description:Pax6 is a transcription factor with key functional roles in embryonic development. In order to identify downstream effectors of Pax6 in the developing cerebral cortex we performed microarray analysis. We compared gene expression profiles of cortical tissues isolated from wild type and Pax6-/- mouse embryos. In order to identify Pax6 downstream targets we carried out microarray analysis of Pax6-/- mutant mice. Pax6 is highly expressed in the mouse cerebral cortex at embryonic day E14.5, therefore we selected this tissue in order to compare gene expression profiles between wild type and Pax6-/- homozygous cortici. RNA samples were isolated from three mutant and three wild type embryos.