Project description:Maternal-to-zygotic transition (MZT) is a conserved and fundamental process during which the maternal environment of oocyte transits to the zygotic genome driven expression program, and terminally differentiated oocyte and sperm are reprogrammed to totipotency. It is initiated by maternal mRNAs and proteins during the period of zygotic genome quiescence after fertilization, followed by a gradual switch to zygotic genome activation and accompanied by clearance of maternal RNAs and proteins. A key question for embryonic development is how MZT process is regulated. Here we used a low-input proteomic analysis to measure the proteomic dynamics during early development of mouse maternal-to-zygotic transition.
Project description:Maternal-to-zygotic transition (MZT) is a conserved and fundamental process during which the maternal environment of oocyte transits to the zygotic genome driven expression program, and terminally differentiated oocyte and sperm are reprogrammed to totipotency. Metaphase II (MII) oocytes and zygotes (one-cell embryo) serve as the mature oocyte and the initiation of pre-implantation embryo development respectively, and characterizing their molecular landscapes at protein levels plays an important role in uncovering MZT and zygotic genome activation (ZGA )in mammals. Here we used an ultrasensitive proteomic approach to depict an in-depth landscape for the very early stage of mouse MZT.
Project description:Mammalian embryogenesis involves intricate epigenetic reprogramming and chromatin remodeling. In this study, we investigated the role of Brg1, a catalytic ATPase subunit of the SWI/SNF complex, in early embryonic development and mouse embryonic stem cell (mESC) pluripotency. By generating Smarca4 flox/flox Gdf9-Cre female mice to knockout Brg1 in MII oocytes and using CRISPR-Cas9 to knockout Brg1 in mESCs, we found that Brg1 deficiency led to multiple defects. In mouse embryos, maternal knockout of Brg1 caused reduced blastocyst formation, delayed development, elevated nucleosome occupancy at gene promoters, and dysregulation of zygotic genome activation (ZGA) genes, potentially due to disrupted binding of totipotency-related transcription factors (TFs). In mESCs, Brg1 knockout resulted in abnormal clone morphology, decreased pluripotency marker expression, and reduced cell proliferation. Brg1 affected pluripotency mainly by influencing the binding of pluripotency-related TFs such as Oct4 through enhancer accessibility. We identified those TFs as totipotency/pluripotency Brg1-dependent TFs. Overall, this study demonstrates the crucial role of Brg1 in ZGA and mESC identity maintenance in affecting specific TF binding on proximal and distal regulatory elements.
Project description:Mammalian embryogenesis involves intricate epigenetic reprogramming and chromatin remodeling. In this study, we investigated the role of Brg1, a catalytic ATPase subunit of the SWI/SNF complex, in early embryonic development and mouse embryonic stem cell (mESC) pluripotency. By generating Smarca4 flox/flox Gdf9-Cre female mice to knockout Brg1 in MII oocytes and using CRISPR-Cas9 to knockout Brg1 in mESCs, we found that Brg1 deficiency led to multiple defects. In mouse embryos, maternal knockout of Brg1 caused reduced blastocyst formation, delayed development, elevated nucleosome occupancy at gene promoters, and dysregulation of zygotic genome activation (ZGA) genes, potentially due to disrupted binding of totipotency-related transcription factors (TFs). In mESCs, Brg1 knockout resulted in abnormal clone morphology, decreased pluripotency marker expression, and reduced cell proliferation. Brg1 affected pluripotency mainly by influencing the binding of pluripotency-related TFs such as Oct4 through enhancer accessibility. We identified those TFs as totipotency/pluripotency Brg1-dependent TFs. Overall, this study demonstrates the crucial role of Brg1 in ZGA and mESC identity maintenance in affecting specific TF binding on proximal and distal regulatory elements.
Project description:We generated maternal and paternal mouse models with Yap1-deletion, and elucidated the function of maternal YAP in zygotic genome activation.
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:Zygotic genome activation (ZGA) is essential for early embryonic development. However, the regulation of ZGA remains elusive in mammals. Here we report that a maternal factor TDP-43, a nuclear transactive response DNA-binding protein, regulates ZGA through RNA Pol II and is essential for mouse early embryogenesis. Maternal TDP-43 translocates from the cytoplasm into the nucleus at the early two-cell stage when minor to major ZGA transition occurs. Genetic deletion of maternal TDP-43 results in mouse early embryos arrested at late two-cell stage and female infertile. TDP-43 co-occupies with RNA Pol II as large foci in the nucleus and also at the promoters of ZGA genes at the late two-cell stage. Biochemical evidence indicates that TDP-43 binds Polr2a and Cyclin T1. Depletion of maternal TDP-43 caused the loss of Pol II foci and reduced Pol II binding on chromatin at major ZGA genes, accompanied by defective ZGA. Collectively, our results suggest that maternal TDP-43 is critical for mouse early embryonic development, in part through facilitating the correct RNA Pol II configuration and zygotic genome activation.