In the last decade, the field of transcription has focused heavily on studying various types of clusters and condensates formed by components of transcriptional machinery. The main model systems used are yeast, mamalian cell culture, Drosophila embryo and to a lesser extent Zebrafish embryos. We have made the first steps in establishing C. elegans embryo as a powerfull system to study transcriptional condensates during normal development and in face of environmental stress. We have made progress in studying several types of nuclear condensates. First, we characterized the formation of condensates by a master regulator of heat shock response. Importantly, we identified the genomic locations of condensate formation within the non-coding, transposon-derived repetitive parts of the genome, which are believed to be non-functional. We began investigating their role in gene expression during stress and development. Second, we described and characterized dynamic nuclear clusters formed by RNA Polymerase II in early C. elegans embryos. We were able to pinpoint the genomic location of some of these clusters and observed cell-specific differences in clustering patterns. Lastly, we created transgenic lines to study a key muscle fate transcription factor's role in differentiation and investigated the effects of protein domain modifications on function and condensate formation. The team has also conducted screens to identify regulators of these condensates identifying putative regulators for all studied nuclear bodies. Lastly, we performed in vitro studies to investigate the phase separation properties of purified proteins identifying the domain regions which promote phase transition.
