Project description:The niche controls stem cell self-renewal and progenitor differentiation for maintaining adult tissue homeostasis in various organisms. However, it remains unclear if the niche is compartmentalized to control stem cell self-renewal and stepwise progeny differentiation. In the Drosophila ovary, inner germarial sheath (IGS) cells form a niche for controlling germline stem cell (GSC) progeny differentiation. In this study, we have identified four IGS subpopulations, which form linearly arranged niche compartments for controlling GSC maintenance and multi-step progeny differentiation. Single-cell analysis of the adult ovary has identified four IGS subpopulations (IGS1-4), which identities and cellular locations have been further confirmed by fluorescent in situ hybridization. IGS1 and IGS2 physically interact with GSCs and mitotic cysts to control GSC maintenance and cyst formation, respectively, whereas IGS3 and IGS4 physically interact with 16-cell cysts to regulate meiosis and oocyte development. Finally, one follicle cell progenitor population has also been transcriptionally defined for facilitating future studies on follicle stem cell regulation. Therefore, this study has structurally revealed that the niche is organized into multiple compartments for orchestrating stepwise adult stem cell development, and has also provided useful resources and tools for further functional characterization of the niche in the future.
Project description:Purpose: Piwi family protein Aubergine (Aub) maintains genome integrity in late germ cells of the Drosophila ovary through piRNA-mediated repression of transposon activities. Although it is highly expressed in germline stem cells (GSCs) and early progeny, it remains unclear if it plays any roles in early GSC lineage development. Results: The study reveals a novel function of Aub in GSCs and their progeny, which promotes translation of self-renewal and differentiation factors by directly binding to its target mRNAs and interacting with translational initiation factors.
Project description:In homeostasis of adult vertebrate tissues, stem cells are thought to self-renew by infrequent and asymmetric divisions that generate another stem cell daughter and a progenitor daughter cell committed to differentiate. This model is based largely on in vivo invertebrate or in vitro mammal studies. Here we examine the dynamic behaviour of adult hair follicle stem cells in their normal setting by employing mice with repressible H2B-GFP expression to track cell divisions and Cre inducible mice to perform long-term single cell lineage tracing. We provide direct evidence for the infrequent stem cell division model in intact tissue. Moreover, we find that differentiation of progenitor cells occurs at different times and tissue locations than self-renewal of stem cells. Distinct fates of differentiation or self-renewal are assigned to individual cells in a temporal-spatial manner. We propose that large clusters of tissue stem cells behave as populations, whose maintenance involves unidirectional daughter-cell fate decisions. We used microarrays to expression profile the stem cell progeny generated at distinct differentiation and self-renewal stages.
Project description:Male and female germline stem cells are critical for passing genetic information from generation to generation. Accumulating evidences indicate that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) play important roles in self-renewal and differentiation of germline stem cells. However, the mechanisms remain largely unknown. In this study, we explored the mRNAs, lncRNAs and circRNAs expression profiles of male and female germline stem cells through high-throughput sequencing.
Project description:Differentiated macrophages can self-renew in tissues and expand long-term in culture, but the gene regulatory mechanisms that accomplish self-renewal in the differentiated state have remained unknown. Here we show that in mice, the transcription factors MafB and c-Maf repress a macrophage-specific enhancer repertoire associated with a gene network controlling self-renewal. Single cell analysis revealed that, in vivo, proliferating resident macrophages can access this network by transient down-regulation of Maf transcription factors. The network also controls embryonic stem cell self-renewal but is associated with distinct embryonic stem cell-specific enhancers. This indicates that distinct lineage-specific enhancer platforms regulate a shared network of genes that control self-renewal potential in both stem and mature cells.
Project description:Stem cells (SC) exhibit a unique capacity for self-renewal in an undifferentiated state. It is unclear whether the self-renewal of pluripotent embryonic SC (ESC) and of tissue-specific adult SC such as hematopoietic SC (HSC) is controlled by common mechanisms. The deletion of transcription factor Zfx impaired the self-renewal but not the differentiation capacity of murine ESC; conversely, Zfx overexpression facilitated ESC self-renewal by opposing differentiation. Furthermore, Zfx deletion abolished the maintenance of adult bone marrow HSC, but did not affect erythromyeloid progenitors or fetal HSC. In both ESC and HSC, Zfx activated a common set of direct target genes. In addition, the loss of Zfx resulted in the induction of immediate-early and/or stress-inducible genes in both SC types but not in their differentiated progeny. These studies identify the first shared transcriptional regulator of ESC and HSC, suggesting a common molecular basis of self-renewal in embryonic and adult SC. Keywords: Global gene expression data analysis in Zfx-deficient murine ESC and HSC
Project description:Hematopoietic stem cells (HSCs) constitute a rare cell population in bone-marrow and are capable of live-long self-renewal and production of all mature blood cell types. Cell differentiation processes are governed by epigenetic mechanisms whose study during early differentiation steps will provide insights into stem cell function and differentiation. We performed whole-genome bisulfite sequencing on HSCs and their immediate progeny, namely three different multipotent progenitor subpopulations (MPP1, MPP2, and MPP). Whole-genome bisulfite sequencing of hematopoietic stem cells (HSCs) and 3 different multipotent progenitor subpopulations (MPP). Three independent biological replicates each were analyzed.
Project description:Hematopoietic stem cells (HSCs) constitute a rare cell population in bone-marrow and are capable of live-long self-renewal and production of all mature blood cell types. Cell differentiation processes are governed by epigenetic mechanisms whose study during early differentiation steps will provide insights into stem cell function and differentiation. We performed whole-genome bisulfite sequencing on HSCs and their immediate progeny, namely three different multipotent progenitor subpopulations (MPP1, MPP2, and MPP).
Project description:Nodal and Activin are morphogens of the TGFbeta superfamily of signaling molecules that direct differential cell fate decisions in a dose- and distance-dependent manner. During early embryonic development the Nodal/Activin pathway is responsible for the specification of mesoderm, endoderm, node and mesendoderm. In contradiction to this drive towards cellular differentiation, the pathway also plays important roles in the maintenance of self-renewal and pluripotency in embryonic and epiblast stem cells. The molecular basis behind stem cell interpretation of Nodal/Activin signaling gradients and the undertaking of disparate cell fate decisions remains poorly understood. Here, we show that any perturbation of endogenous signaling levels in mouse ES cells leads to their exit from self renewal towards divergent differentiation programs. Increasing Nodal signals above basal levels by direct stimulation with Activin promotes differentiation towards the mesendodermal lineages while repression of signaling with the specific Nodal/Activin receptor inhibitor SB431542 induces trophectodermal differentiation. To address how quantitative Nodal/Activin signals are translated qualitatively into distinct cell fates decisions, we performed chromatin immunoprecipitation of phospho-Smad2 the primary downstream transcriptional factor of the Nodal/Activin pathway followed by massively parallel sequencing and show that phospho-Smad2 binds to and regulates distinct subsets of target genes in a dose-dependent manner. Crucially, Nodal/Activin signaling directly controls the Oct4 master regulator of pluripotency by graded phospho-Smad2 binding in the promoter region. Hence stem cells interpret and carry out differential Nodal/Activin signaling instructions via a corresponding gradient of Smad2 phosphorylation that selectively titrates self-renewal against alternative differentiation programs by direct regulation of distinct target gene subsets and Oct4 expression. Four biological replicates consisting of 4 different passages of E14TG2a ES cells at P20, P21, P23 and P24