Gcn5 Impacts Fgf Signaling At Multiple Levels And Activates C-Myc Target Genes During Early Differentiation Of Embryoid Bodies

Author

Li Wang, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical SciencesFollow

Author ORCID Identifier

0000-0003-0029-1920

Date of Graduation

8-2017

Document Type

Dissertation (PhD)

Program Affiliation

Epigenetics and Molecular Carcinogenesis

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Sharon Y. R. Dent, Ph.D.

Committee Member

Mark T. Bedford, Ph.D.

Committee Member

David G. Johnson, Ph.D.

Committee Member

Xiaobing Shi, Ph.D.

Committee Member

Pierre D. McCrea, Ph.D.

Abstract

Precise control of gene expression during development is orchestrated by transcription factors, signaling pathways and co-regulators, with complex cross-regulatory events often occurring. Growing evidence has identified chromatin modifiers as important regulators for development as well, yet how particular chromatin modifying enzymes affect specific developmental processes remains largely unclear. Embryonic stem cells (ESCs) are self-renewing, pluripotent, and have the abilities to generate almost all cell types in adult tissues. The dual capacity of ESCs to self-renew and differentiate offers unlimited potential for studying gene regulation events at specific developmental stages in vitro that parallel developmental events during embryogenesis in vivo.

In this dissertation project, we use a murine ESC aggregation assay (embryoid body formation, EB) to model the early development stages that proceed gastrulation, and report that GCN5, a histone acetyltransferase (HAT) essential for embryonic development, is required for proper expression of multiple genes encoding components of the FGF signaling pathway, and for normal activation of ERK and p38 downstream of FGF signaling at early stages of EB formation. Loss of Gcn5 is associated with disorganized cytoskeletal networks, and compromised capacity of ESCs to differentiate toward mesodermal and endodermal lineages. We identified 7 genes as putative direct targets of GCN5 during early differentiation by using RNAseq and H3K9ac ChIPseq. These genes are reportedly involved in signaling and metabolism, and most interestingly, 4 of them are c-MYC targets. These findings established a novel link between GCN5 and FGF signaling pathway, and highlighted the GCN5-MYC partnership in gene regulation during early differentiation.

Keywords

Gcn5, FGF signaling, Myc, Emrbyoid body, Chromatin, Histone H3, Acetylation