I. Embryonic Gene Expression: what controls timing?
We aim to expand understanding of the Dorsal-Ventral (DV) patterning gene-regulatory network (GRN) acting in the early Drosophila embryo: a developmental system, which uses morphogens to support patterning and undergoes rapid development. Our goal is to integrate spatiotemporal information into the DV patterning GRN with the objective of obtaining additional insights into the roles of transcription factor and target gene dynamics (see Reeves, Trisnadi et al. Dev Cell 2012). Recently, we have determined that broadly expressed repressors can influence when genes are allowed to turn on in embryos (see Koromila & Stathopoulos, Cell Rep 2019). In particular, they are important at the maternal-to-zygotic (MZT) transition. In addition, there are a number of pioneer activators that help to move nucleosomes, making the chromatin accessible to transcription factors including the pivotal activator Dorsal. We are interested in late-acting pioneers that regulate the MZT including regulating expression of genes pivotal for the onset of gastrulation and segmentation (see Koromila et al. eLife 2020). Many studies of patterning in the Drosophila embryo have focused on regulation of spatial outputs of gene expression. However, our studies are currently focused on how timing of expression is controlled, as this is certainly an equally important variable that embryos must regulate for proper development.