The evolutionarily conserved COMPASS family of methyltransferases implements histone H3 lysine 4 (H3K4) methylation, an epigenetic mark associated with transcriptional activation. Given the high mutational prevalence of COMPASS subunits across cancers and neurodevelopmental disorders, understanding COMPASS function would lend important insights into disease pathogenesis to facilitate development of effective therapies. The H3K4 methylase Set1A is one of six COMPASS members identified in mammals, and possesses an enzymatic SET domain responsible for genome-wide H3K4 di- and tri-methylation (H3K4me2 and H3K4me3 respectively). Previous studies demonstrated that loss of full-length Set1A resulted in embryonic lethality and embryonic stem cell (ESC) viability defects; however, the dependency of ESC pluripotency on H3K4 methylation by Set1A was not investigated. As shown in this dissertation, the SET domain of Set1A was dispensable for ESC viability and self-renewal, although necessary for proper differentiation. In addition, deleting the Set1A SET domain did not perturb bulk H3K4me3, implicating possible compensatory roles played by other COMPASS methyltransferases. By investigating a series of ESC lines harboring compounding mutations of the COMPASS enzymes, an elaborate relationship was unveiled: despite the differential regulation of H3K4me3 deposition and peak breadth by Set1A-B vs. Mll2, Mll2 could still help preserve global H3K4me3 level and breadth in the absence of Set1A-B. These findings illustrate the biological flexibility of such enzymes in transcriptional regulation to ensure cell viability. Finally, ongoing efforts to elucidate the critical role of Set1A in ESC pluripotency include leveraging a CRISPR/Cas9 dropout screen to identify targets that functionally interact with Set1ASET. These efforts point to an uncharacterized interplay between COMPASS and another family of chromatin modifiers in regulating ESC viability. Taken together, this dissertation provides novel insights into the epigenetic complexities in regulating stem cell pluripotency and development, which will ultimately facilitate effective treatment development.

Creator

• Sze, Christie C.

DOI

• https://doi.org/10.21985/n2-zb28-s184

Subject

• Molecular biology

Language

• en

Alternate Identifier

• etdadmin_upload_744273
• http://dissertations.umi.com/northwestern:15142

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright