Novel pathways in heterochromatin regulation

Project Summary: The eukaryotic genome is highly organized within the nucleus in ways that control many cellular processes. The genome is packaged into three major states: broadly accessible euchromatin, less accessible facultative heterochromatin, and inaccessible constitutive heterochromatin. My lab focuses on understanding how different chromatin regulators influence facultative heterochromatin balance and organization. We require a complete understanding of how these complexes differ in function and specificity and the contributions of the unique subunits to facultative heterochromatin regulation to improve human health. We will achieve this understanding through two distinct projects that test novel models of facultative heterochromatin regulation. The first project focuses on the mSWI/SNF family, which comprises three main complexes in stem cells: canonical BAF (cBAF), polybromo-associated BAF (pBAF), and GLITSCR-associated BAF (gBAF). The three forms share common subunits, but each also has distinct subunits. We will test a model where these complexes work in opposition to each other to regulate facultative heterochromatin. The second major project will focus on how proteins involved in homologous recombination-based DNA-double strand break repair act as facultative heterochromatin regulators in the absence of induced DNA damage. We will define the roles of these two classes of chromatin regulators using loss-of-function and gain-of-function studies. Biochemical and genomics approaches using degradable alleles and mutant histone lines will allow us to determine transcription and chromatin changes when these complexes are lost. Using an inducible dCas9-based recruitment strategy that I developed, we will evaluate transcription and chromatin changes mediated by these complexes when targeted at a new site in the genome. Since facultative heterochromatin dysregulation can lead to various human diseases, including developmental and neurological disorders and cancer, understanding normal and dysfunctional mechanisms of chromatin regulation is of great importance to human health.