Project description:During myogenesis, myocyte fusion leads to the formation of multinucleated muscle fibers but how exactly this process is initiated remains poorly understood. Here, we performed single-cell RNA sequencing on mouse somites from E9.5-11.5 embryos, revealing multiple differentiation states during primary myogenesis. Among these, we identified two unexpected myocyte populations: one expressing both Myomaker (Mymk) and Myomixer (Mymx) (termed Mc1) and another expressing only Mymk (termed Mc2). Fluorescent in situ hybridization demonstrated that both populations are mononucleated and co-exist within the same somites, with only Mc1 persisting during secondary myogenesis. Lineage tracing using Mymx:Cre; RosaTdT mice demonstrated that the Mc2 cells arise from the Mc1. Mechanistically, we show that Mef2 and Rxr factors positively and negatively regulate Mymx expression, respectively. Additionally, RXRG interacts with MYOD1 and MYOG, modulating their transcriptional activity in luciferase assays. Collectively, our findings uncover two populations among the myocytes that drive primary and secondary fiber formation, challenging the traditional view of vertebrate muscle precursor homogeneity.
Project description:We performed the whole transcriptome analysis in Zscan4 positive ES cells (Em+) and Zscan4 negative ES cells (Em-) by using FACS-sorted MC1-ZE7 ES cells.
Project description:Transcription, the copying of genetic information into RNA, is accomplished by multi-subunit RNA polymerases (msRNAPs) in all living organisms. msRNAPs are highly conserved in evolution and invariantly share a ~400 kDa five-subunit catalytic core1,2. A group of hypothetical single-chain proteins of unknown function, present in various bacteria and bacteriophages, was predicted to be distantly related to msRNAPs, having diverged from them before the Last Universal Common Ancestor3. Here, we studied a ~100 kDa protein, YonO, from this group encoded by the bacteriophage SPβ of Bacillus subtilis. We show that despite homology to only several amino acids of msRNAP, and the absence of most of the conserved domains, YonO is a highly processive and fast DNA-dependent RNA polymerase. Unlike msRNAPs, YonO can start specific transcription on double-stranded DNA without additional factors. We show that YonO is a bona fide RNAP of SPβ bacteriophage that transcribes its late genes. This new class of RNAPs may represent an intermediate step in the evolution of an ancestor of all msRNAPs.
Project description:We analyzed the genome-wide chromatin states in Zscan4 positive ES cells (Em+) and Zscan4 negative ES cells (Em-) by using FACS-sorted MC1-ZE7 ES cells. H3K27 hyperacetylation and DNA demethylation were detected in heterochromatic regions of Em+ cells. These results suggested that the heterochromatin is activated in Zscan4 positive state.
Project description:By using FACS-sorted MC1-ZE7 ES cells, we analyzed the genome-wide distribution of H3K27ac and DNA methylation in Zscan4 positive ES cells (Em+) and Zscan4 negative ES cells (Em-). H3K27 hyperacetylation and DNA demethylation were detected in heterochromatic regions of Em+ cells, but not Em- cells. These results suggested that the Zscan4 state takes "open" chromatin conformation in ES cells.