Project description:Background: The vertebrate retina consists of six major classes of neuronal cells. During development, these cells are generated from a pool of multipotent retinal progenitor cells (RPCs) that express the gene Vsx2. Fate-restricted RPCs have recently been identified, with limited mitotic potential and cell fate possibilities compared to multipotent RPCs. One population of fate-restricted RPCs, marked by activity of the regulatory element ThrbCRM1, gives rise to both cone photoreceptors and horizontal cells. These cells do not express Vsx2, but co-express the transcription factors (TFs) Onecut1 and Otx2, which bind to ThrbCRM1. The components of the gene regulatory networks that control the transition from multipotent to fate-restricted gene expression are not known. This work aims to identify and evaluate cis-regulatory elements proximal to Onecut1 to identify the gene regulatory networks involved in RPC fate-restriction. Method: We identified regulatory elements through ATAC-seq and conservation, followed by reporter assays to screen for activity based on temporal and spatial criteria. The regulatory elements of interest were subject to deletion and mutation analysis to identify functional sequences and evaluated by quantitative flow cytometry assays. Finally, we combined the enhancer::reporter assays with candidate TF overexpression to evaluate the relationship between the TFs, the enhancers, and early vertebrate retinal development. Statistical tests included ANOVA, Kruskal-Wallis, or unpaired t-tests.Results: Two regulatory elements, ECR9 and ECR65, were identified to be active in ThrbCRM1(+) restricted RPCs. Candidate bHLH binding sites were identified as critical sequences in both elements. Overexpression of candidate bHLH TFs revealed specific enhancer-bHLH interactions. Nhlh1 overexpression expanded ECR65 activity into the Vsx2(+) RPC population, and overexpression of NeuroD1/NeuroG2/NeuroD4 had a similar effect on ECR9. Furthermore, bHLHs that were able to activate ectopic ECR9 reporter were able to induce endogenous Otx2 expression. Conclusions: This work reports a large-scale screen to identify spatiotemporally specific regulatory elements near the Onecut1 locus. These elements were used to identify distinct populations in the developing retina. In addition, fate-restricted regulatory elements responded differentially to bHLH factors, and suggest a role for retinal bHLHs upstream of the Otx2 and Onecut1 genes during the formation of restricted RPCs from multipotent RPCs.
Project description:Here we report a transcriptomic analysis of fate-restricted progenitor cells biased to produce cone photoreceptors and horizontal cells, marked by the THRB cis-regulatory element ThrbCRM1. Comparison to a control population enriched in multipotent progenitor cells identified several genes considered to be pan-progenitor, such as VSX2, LHX2, and PAX6, as downregulated in these fate-restricted retinal progenitor cells
Project description:Genes involved in distinct diabetes types suggest shared disease mechanisms. We show that rare ONECUT1 coding variants cause monogenic recessive diabetes (neonatal or very early-onset, syndromic) in two unrelated patients, and monogenic dominant diabetes (early adult-onset) in heterozygous relatives of these and 13 additional unrelated cases. Patients heterozygous for rare ONECUT1 coding variants define a subgroup of T2D with early-onset diabetes and other features. In addition, common regulatory ONECUT1 variants are associated with multifactorial T2D. Directed differentiation of human pluripotent stem cells to the pancreatic lineage revealed that loss of ONECUT1 impairs pancreatic progenitor formation and a subsequent endocrine program. We uncovered that ONECUT1 activates the pro-endocrine genes NKX6.1 and NKX2.2 through binding to their cis-regulatory elements. Globally, ONECUT1-directed gene transcription occurs in association with major islet transcription factors, at clusters of pancreas- and endocrine-specific enhancers within open chromatin. ONECUT1 regulates a transcriptional and epigenetic machinery critical for proper endocrine pancreatic development, involved in a spectrum of diabetes, monogenic recessive and dominant, and multifactorial.
Project description:In this study, we examine the consequences of the loss of two related factors, Onecut1 and Onecut2, during mouse retinal development.
Project description:The integrity of the epithelium is maintained by a complex but regulated interplay of processes that allow seamless orchestration of a proliferative state into a stably differentiated state. In this study, using stem cell derived Retinal Pigment Epithelium (RPE) cells as a model; we have investigated the molecular mechanisms that affect attainment of the epithelial phenotype. We identify a novel role for the proto-oncogene FOXM1 in determining epithelial fate of RPE by directly regulating cell proliferation and by indirectly regulating expression of signalling factors BMP7 and Wnt5B; both of which are intimately required for eventual acquisition of the epithelial phenotype. This study uncovers the role of FOXM1 in a non-oncogenic, native-like setting and shows that human ES derived RPE can serve as a useful model system to address biological questions not restricted to visual function.
Project description:The aim of this project is to locate the precise binding of the ONECUT1 transcription factor. NOTE: This study was updated on 7th May 2014. All samples, experiments, runs and files were replaced. This was due to an incorrect reagent being used in the earlier version.
Project description:The development of the retina into a highly organized structure occurs via the production of over 100 cell types from a pool of retinal progenitor cells (RPCs). While some RPCs are capable of making many types of retinal cell types, some terminally dividing RPCs are restricted to the production of specific types of daughter cells. Notably, although such restrictions can be limited to the production of a very specific single cell type, in other cases, production of two very different cell types, such as a photoreceptor and an interneuron, occurs. How specific types of RPCs make specific types of neuron is not fully understood. Combining RNA-seq and ATAC-seq, we compared the transcriptome and chromatin profiles between one type of biased RPC and other types of RPCs. The biased RPC that was studied is one that we previously defined by its expression of a cis-regulatory module (CRM) for the thyroid hormone receptor beta gene (Thrb), the earliest known marker of cone photoreceptors. In this earlier study, we found that Otx2 and Onecut1 drove expression of this Thrb CRM, as well as regulated expression of the Thrb gene. Here we explored the roles of these Otx2 and Oc1 further. We discovered that their roles extend well beyond regulating Thrb. They collaborate to regulate multiple genes important in cone development and/or function, including Rxrg, a known partner of Thrb. We also identified several new enhancers of genes active in developing cones. These data expand our understanding of the gene regulatory network (GRN) for cone development and contribute new CRMs for vectors that are expressed only in cones, as well as enable the genesis of cones from stem cells, for their use in retinal disease cell and gene therapies.