Poster abstracts
Poster number 77 submitted by Rinku Dhungana
Dynamic upregulation of CHD3 and CHD5 following CHD4 depletion in mouse embryonic stem cells
Rinku Dhungana (Department of Biological Sciences, University of Pittsburgh ), Sarah J Hainer (Department of Biological Sciences, University of Pittsburgh )
Abstract:
CHD3, CHD4, and CHD5 are paralogous members of the CHD family of nucleosome remodelers. CHD4 is highly expressed in mouse embryonic stem cells (mESCs), while CHD3 and CHD5 are not expressed highly until mESCs differentiate into neuronal cell types. Strikingly, upon rapid depletion of CHD4 in mESCs, I observed increased transcription of Chd3 and Chd5 within three hours of CHD4 depletion and increased CHD3 protein abundance within four hours of CHD4 depletion. Despite CHD4 loss, the cells retained their stem cell identity, suggesting redundancy among these remodelers. However, whether this upregulation is functional and what mechanisms govern possible compensation remains unknown.
CHD3, CHD4, and CHD5 are mutually exclusive ATPase subunits of the Nucleosome Remodeling and Deacetylase (NuRD) complex, which plays a crucial role in development. CHD4 is also the remodeling subunit of the ChAHP complex, which ensures proper lineage specification. Independent of the multi-protein complex, CHD4 plays a role in cell cycle progression. Given such diverse functions of CHD4, I aim to determine whether CHD3 and CHD5 functionally compensate for CHD4 loss in mESCs by maintaining nucleosome positioning, gene expression, and/or cell cycle progression.
To explore the mechanisms underlying this possible compensation, I am testing two complementary hypotheses. First, I hypothesize that CHD3 and/or CHD5 are incorporated into the NuRD and/or ChAHP complex following CHD4 loss. Second, I hypothesize that CHD3 and/or CHD5 bind to genomic loci normally occupied by CHD4 in CHD4-depleted cells, thereby partially compensating for its function. My preliminary data show a time-dependent increase in CHD3 occupancy at CHD4 loci upon CHD4 depletion. Understanding the interplay among CHD3, CHD4, and CHD5 will reveal how stem cells adapt to the loss of a key remodeler, with implications for understanding developmental robustness and resilience to disease-causing mutations.
Keywords: Molecular compensation, Chromatin, Nucleosome remodeler