Developmental Signalling and Chromatin Structure
The main focus of the laboratory is to understand how genes are activated and different cell types are formed in mammalian development. Mechanistic understanding of these issues is critical for rational approaches to maintain human health and to combat human disease. The issues are also fundamental to the science of biology, challenging, and interesting to study.
The laboratory has two general experimental strategies. First, we investigate the signalling pathways that commit an undifferentiated cell to a particular cell type fate, using the specification of embryonic endoderm to liver cells as a model. Second, we investigate the ways that transcriptional regulatory proteins control the packaging of genes, or chromatin structure, during cell type specification, using in vitro and in vivo model systems.
Both strategies stimulate one another in the laboratory, in that understanding regulatory signals in development provides critical biological contexts within which chromatin transitions should be investigated, and understanding the molecular transitions in chromatin structure helps identify targets for regulatory signals that control developmental processes.
To investigate the specification of liver cells from the endoderm in development, we use primary cultures of mouse embryo tissues, genetically modified mice, and cell line model systems to identify signalling pathways and transcription factors that control endoderm differentiation and early hepatic development. The relevant factors have been identified by their expression patterns, gene knockout studies, and by comparison with factors causing endoderm differentiation in model organisms such as flies and worms. We are currently employing gene array studies to identify new regulatory proteins in the endoderm.
To investigate how embryonic transcription factors open up silent chromatin during the developmental activation of genes, we employ in vivo footprinting to monitor factor occupancy and to map nucleosome positions in chromatin. We then employ in vitro chromatin and transcription reconstitution systems to understand the mechanism of factor binding to nucleosomes and chromatin remodeling. Ultimately, the biochemical mechanisms discovered from in vitro studies are tested in vivo.