Project description:ChIP-seq provides a genome-wide view of the binding sites of Alx1, a pivotal transcription factor in a gene regulatory network that controls skeletogenesis in sea urchins and other echinoderms.
Project description:Thyroid hormones are crucial regulators of metamorphosis and development in bilaterians, particularly in chordate deuterostomes. Recent evidence suggests a role for thyroid hormone signaling, principally via 3,5,3',5'-Tetraiodo-L-thyronine (T4), in the regulation of metamorphosis, programmed cell death and skeletogenesis in echinoids (sea urchins and sand dollars) and sea stars. Here, we test whether TH signaling in skeletogenesis is a shared trait of Echinozoa (Echinoida and Holothouroida) and Asterozoa (Ophiourida and Asteroida). We demonstrate dramatic acceleration of skeletogenesis after TH treatment in three classes of echinoderms: sea urchins, sea stars, and brittle stars (echinoids, asteroids, and ophiuroids). Fluorescently labeled thyroid hormone analogues reveal thyroid hormone binding to cells proximal to regions of skeletogenesis in the gut and juvenile rudiment. We also identify, for the first time, a potential source of thyroxine during gastrulation in sea urchin embryos. Thyroxine-positive cells are present in tip of the archenteron. In addition, we detect thyroid hormone binding to the cell membrane and nucleus during metamorphic development in echinoderms. Immunohistochemistry of phosphorylated MAPK in the presence and absence of TH-binding inhibitors suggests that THs may act via phosphorylation of MAPK (ERK1/2) to accelerate initiation of skeletogenesis in the three echinoderm groups. Together, these results indicate that TH regulation of mesenchyme cell activity via integrin-mediated MAPK signaling may be a conserved mechanism for the regulation of skeletogenesis in echinoderm development. In addition, TH action via a nuclear thyroid hormone receptor may regulate metamorphic development. Our findings shed light on potentially ancient pathways of thyroid hormone activity in echinoids, ophiuroids, and asteroids, or on a signaling system that has been repeatedly co-opted to coordinate metamorphic development in bilaterians.
Project description:We identified cis-regulatory elements based on their dynamic chromatin accessibility during the gastrula-larva stages of sea urchin and sea star and studied their evolution in these echinoderm species
Project description:Osteoarthritis (OA) is a polygenic disease of older people resulting in the breakdown of cartilage within articular joints. Although a leading cause of disability, there are no disease-modifying therapies. Evidence is emerging to support the origins of OA in skeletogenesis. Whilst methylation QTLs (mQTLs) co-localizing with OA GWAS signals have been identified in aged human cartilage and used to identify effector genes and variants, such analyses have never been conducted during human development. Here, for the first time, we have investigated the developmental origins of OA genetic risk at seven well-characterized OA risk loci, comprising 39 OA-mQTL CpGs, in human fetal limb (FL) and cartilage (FC) tissues using a range of molecular genetic techniques. We compared our results to aged cartilage samples (AC) and identified significant OA-mQTLs at 14 CpGs and 29 CpGs in FL and FC tissues, respectively. Differential methylation was observed at 26 sites between fetal and aged cartilage, with the majority becoming actively hypermethylated in old age. Notably, 6/9 OA effector genes showed allelic expression imbalances during fetal development. Finally, we conducted ATAC-sequencing in cartilage from the developing and aged hip and knee to identify accessible chromatin regions, and found enrichment for transcription factor-binding motifs including SOX9 and FOS/JUN. For the first time, we have demonstrated the activity of OA-mQTLs and expression imbalance of OA effector genes during skeletogenesis. We show striking differences in the spatiotemporal function of these loci, contributing to our understanding of OA aetiology, with implications for the timing and strategy of pharmacological interventions.