Project description:To rigorously examine the role of b-catenin dependent transcription, we created mice deficient for the transcriptional output of beta-catenin in skeletal mesenchyme (bcat-dTF-Dermo1-cKO) and compare the transcriptional profiles to that of the beta-catenin conditional KO mice in skeletal mesenchyme (bcat-Dermo1-cKO).
Project description:Stem cells undergo differentiation in complex and dynamic environments wherein instructive signals fluctuate on various timescales. Thus, cells must be equipped to properly respond to the timing of signals, for example to distinguish sustained signaling from transient noise. However, how stem cells respond to dynamic variations in differentiation cues is not well characterized. Here, we use optogenetic activation of b-catenin signaling to probe the dynamic responses of differentiating adult neural stem cells (NSCs). We discover that while elevated, sustained b-catenin activation sequentially promotes proliferation and differentiation, transient b-catenin induces apoptosis. Genetic perturbations revealed that the neurogenic/apoptotic fate-switch was mediated through cell cycle regulation by Growth Arrest and DNA Damage 45 gamma (Gadd45g). Our results thus reveal a role for b-catenin dynamics in NSC fate decisions and may suggest a novel role for signal timing to minimize cell fate errors, analogous to kinetic proofreading of stem cell differentiation.
Project description:: Sex determination triggers the differentiation of the bi-potential gonad into either an ovary or testis. In non-mammalian vertebrates, the presence or absence of oestrogen dictates gonad differ-entiation, while in mammals, this mechanism has been supplanted by the testis determining SRY gene. Exogenous oestrogen can override this genetic trigger to shift somatic cell fate in the gonad towards ovarian developmental pathways by limiting the bioavailability of the key testis factor SOX9 within somatic cells. Our previous work has implicated the MAPK pathway in mediating the rapid cellular response to oestrogen. We performed proteomic and phosphoproteomic anal-yses to investigate the precise mechanism through which oestrogen impacts these pathways to ac-tivate -catenin—a factor essential for ovarian development. We show that oestrogen can activate -catenin within 30 minutes, concomitant with the cytoplasmic retention of SOX9. This occurs through changes to the MAP3K1 cascade, suggesting this pathway is a mechanism through which oestrogen influences gonad somatic cell fate. We demonstrate that oestrogen can promote the shift from SOX9 pro-testis activity to -catenin pro-ovary activity through activation of MAP3K1. Our findings define a previously unknown mechanism through which oestrogen can promote a switch in gonad somatic cell fate and provided novel insights into the impacts of exogenous oestrogen exposure on the testis.
Project description:Metabolic characteristics of adult stem cells are distinct from their differentiated progeny, and cellular metabolism is emerging as a potential driver of cell fate conversions. However, how metabolism influences fate determination remains unclear. Here, we identified inherited metabolism imposed by functionally distinct mitochondrial age-classes as a fate determinant in asymmetric division of epithelial stem-like cells. While chronologically old mitochondria support oxidative respiration, new organelles are immature and metabolically less active. Upon cell division, selectively segregated mitochondrial age-classes elicit a metabolic bias in progeny cells, with old mitochondria imposing oxidative energy metabolism inducing differentiation. High pentose phosphate pathway flux, promoting redox maintenance, is favoured in cells receiving newly synthesised mitochondria, and is required to maintain stemness during early fate determination after division. Our results demonstrate that fate decisions are susceptible to intrinsic metabolic bias imposed by selectively inherited mitochondria.
Project description:Metazoan development depends on accurate execution of differentiation programs that allow pluripotent stem cells to adopt specific fates. Differentiation is brought about by global changes to chromatin architecture and transcriptional networks, yet whether other regulatory events support cell fate determination is less well understood. Using human embryonic stem cell and Xenopus models, we identified the vertebrate-specific ubiquitin ligase Cul3KBTBD8 as an essential regulator of neural crest specification. Cul3KBTBD8 monoubiquitylates NOLC1 and its paralog TCOF1, whose mutation underlies the craniofacial disorder Treacher Collins Syndrome that is characterized by a loss of cranial neural crest cells. Ubiquitylation of NOLC1 and TCOF1 drives formation of a platform that connects RNA polymerase I with ribosome modification enzymes, thereby altering the translational program of differentiating cells to support the generation of neural crest cells. We conclude that the dynamic regulation of ribosome function is an important feature of cell fate determination. Ribosome profiling and mRNA-Seq
Project description:Metazoan development depends on accurate execution of differentiation programs that allow pluripotent stem cells to adopt specific fates. Differentiation is brought about by global changes to chromatin architecture and transcriptional networks, yet whether other regulatory events support cell fate determination is less well understood. Using a human embryonic stem cell model, we identified the vertebrate-specific ubiquitin ligase Cul3KBTBD8 as an essential regulator of neural crest cell formation. Cul3KBTBD8 monoubiquitylates NOLC1 and its paralog TCOF1, whose mutation underlies the developmental disease Treacher Collins Syndrome that is characterized by a loss of cranial neural crest cells. Ubiquitylation of NOLC1 and TCOF1 drives formation of a platform that connects RNA polymerase I with ribosome modification enzymes, thereby altering the translational program of differentiating cells to support the generation of neural crest cells. We conclude that the dynamic regulation of ribosome function is an important feature of cell fate determination. Affymetrix assays were performed according to the manufacturer's directions on total RNA isolated from three independent samples of human embryonic stem cells (hESC) H1 cells or cells that had been differentiated into embryoid bodies for 6 days. Where indicated, hESC cells were transduced with control shRNA or shRNA targeting KBTBD8 prior to mRNA isolation. HUMAN GENE 1.0 ST ARRAY chips were used.