Project description:The mechanisms by which the early spatiotemporal expression patterns of transcription factors such as Pax6 regulate the region-specific proliferation rates of neural progenitors are poorly understood. Pax6 is expressed in a gradient across the developing cortex and is essential for normal corticogenesis. We found that constitutive or conditional loss of Pax6 increases cortical progenitor proliferation by amounts that vary regionally with normal Pax6 levels. We compared the gene expression profiles of equivalent Pax6-expressing progenitors isolated from Pax6+/+ and Pax6-/- cortices and identified many negatively-regulated cell cycle genes including those encoding Cyclins and Cdks. Biochemical assays indicated that Pax6 directly represses Cdk6 expression. Cyclin/Cdk repression inhibits retinoblastoma protein (pRb) phosphorylation, thereby limiting the transcription of genes directly promoting mitosis, and we showed that Pax6 inhibits pRb phosphorylation and represses several genes involved in DNA replication. Our results indicate that Pax6M-bM-^@M-^Ys modulation of the cell cycles of cortical progenitors is regional and direct. Two condition experiment, Pax6sey/sey vs Pax6+/+ cortical progenitor cells from lateral cortex. 3 biological replicates. Each replicate contains RNA from cells pooled from 4 individual E12.5 embryos
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
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:We have generated transgenic mice with tetracycline-regulated conditional expression of a constitutively active allele of FoxO3 under the control of the forebrain-specific CaMKIIa promoter. In adult animals, there was a reduction of brain weight by 30% and an almost complete loss of the dorsal dentate gyrus with normal cortical layering. Interestingly, the adult mice showed motor hyperactivity and a selective loss of long-term memory with normal spatial learning. We observed enhanced apoptosis starting from day E10.5. Performing microarray expression analyses and Q-PCR validation with E12.5 forebrain RNA, we observed an over-representation of thalamic markers and an under-representation of cortical markers in transgenic as compared to control animals. Immunohistochemical data show a loss of progenitors in the lateral ventricles. Up-regulation of Pik3ip1 as a target gene of FoxO3 could be responsible for the observed increase in apoptosis. The obtained forebrain expression signature is reminiscent of a Pax6 knockdown phenotype showing that expression of this FoxO3 allele during development affected neural progenitor survival and overall brain development. Conclusion: Neural progenitors are vulnerable to constitutively active FoxO3-induced apoptosis. We sought to determine the transcriptional differences in forebrains from E12.5 mice expressing a constitutively active alleleof FoxO3 under the control of the forebrain-specific CaMKIIa promoter. To this end two time-pregnant dams were sacrificed 12 days after the vaginal plug was detected, and the embryos were prepared. Visual staging of the embryos confirmed their age. Genotyping and luciferase measurements were performed in order to assess presence and acitivity of the transgenes.
Project description:Increased cortical size is essential to the enhanced intellectual capacity of primates during mammalian evolution. The mechanisms that control cortical size are largely unknown. Here, we show that mammalian BAF170, a subunit of the chromatin remodeling complex mSWI/SNF, is an intrinsic factor that controls cortical size. We find that the conditional deletion of BAF170 promotes indirect neurogenesis by increasing the pool of intermediate progenitors (IPs) and results in an enlarged cortex, whereas cortex-specific BAF170 over-expression results an opposing phenotype. Mechanistically, BAF170 competes with BAF155 subunit in the BAF complex, affecting the euchromatin structure and thereby modulating the binding efficiency of Pax6/REST-corepressor complex to Pax6 target genes that regulate the generation of IPs and late cortical progenitors. Our findings reveal a molecular mechanism mediated by the mSWI/SNF chromatin-remodeling complex that controls cortical architecture. Cortical gene expression is compared between three E12.5 mouse embryos with cortex-specific loss of BAF170 function and three littermate control embryos.
Project description:We have generated transgenic mice with tetracycline-regulated conditional expression of a constitutively active allele of FoxO3 under the control of the forebrain-specific CaMKIIa promoter. In adult animals, there was a reduction of brain weight by 30% and an almost complete loss of the dorsal dentate gyrus with normal cortical layering. Interestingly, the adult mice showed motor hyperactivity and a selective loss of long-term memory with normal spatial learning. We observed enhanced apoptosis starting from day E10.5. Performing microarray expression analyses and Q-PCR validation with E12.5 forebrain RNA, we observed an over-representation of thalamic markers and an under-representation of cortical markers in transgenic as compared to control animals. Immunohistochemical data show a loss of progenitors in the lateral ventricles. Up-regulation of Pik3ip1 as a target gene of FoxO3 could be responsible for the observed increase in apoptosis. The obtained forebrain expression signature is reminiscent of a Pax6 knockdown phenotype showing that expression of this FoxO3 allele during development affected neural progenitor survival and overall brain development. Conclusion: Neural progenitors are vulnerable to constitutively active FoxO3-induced apoptosis.