PhD Proposal Seminar – Tara McDonnell (Tropepe Lab)

Examining the role of Ehmt1/2-dependent gene regulation in zebrafish retinal progenitor cells

Abstract

During retinal development, retinal progenitor cells (RPCs) undergo a series of multiplication and differentiation events across a concise timeline to form the stratified retina. Epigenetic silencing is crucial when RPCs differentiate to coordinate the downregulation of progenitor genes. A key complex responsible for initiating the first repressive modifications is the Ehmt1/2 complex, which contains four known proteins: Ehmt1, Ehmt2, WIZ and ZNF644. The Ehmt1/2 complex is most well-known for depositing a repressive dimethylation mark at Histone 3 Lysine 9 (H3K9me2) at gene promotors to recruit other repressive complexes and promote gene silencing. However, research over the last decade indicates that in addition to gene silencing, Ehmt2 possesses a multifaceted role in neural tissues including direct and indirect transcriptional activation, and exon splicing, to encourage proper neural cell differentiation and survival. Despite significant research into the Ehmt1/2 complex across various species and tissues, many questions remain, particularly surrounding the discrete roles for different Ehmt1/2 components in its various functions.

Hence, my thesis research is focussed on delineating the distinct roles of different components of the Ehmt1/2 complex in RPC function, and ultimately, retinal development. Our lab generated a zebrafish Ehmt2 loss of function mutant (Ehmt2^∆4/∆4) which mimics Ehmt2 loss of function models in other species, however it is unique in that it is also adult viable and fertile. The first aim of my project involves characterising these Ehmt2^∆4/∆4 mutant embryos and determining the effects of Ehmt2 loss of function on RPC cell cycle regulation. The Ehmt2^∆4/∆4 mutant demonstrates a global loss of H3K9me2 in embryonic cells. Thus, the second aim will focus on understanding the genome wide impact of the loss of this repressive mark on global and RPC-specific gene expression. Finally, the third aim uses CRISPR gene targeting to generate four other Ehmt1/2 complex loss of function mutants. These mutants will then be compared with the Ehmt2^∆4/∆4 mutants, and with each other, to examine the distinct roles of different complex components and investigate potential forms of compensation between different Ehmt1/2 mutant alleles. Understanding the roles of different Ehmt1/2 complex components will provide insight for future research into tissue development, developmental disorders, illnesses with aberrant Ehmt1/2 function such as some cancers, and in developing drugs to target these illnesses.

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Join Zoom Meeting

https://utoronto.zoom.us/j/85249561868

Meeting ID: 852 4956 1868

Host: Vincent Tropepe (v.tropepe@utoronto.ca)

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