Publication Date

2016-08-04

Availability

Embargoed

Embargo Period

2018-08-04

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biology (Arts and Sciences)

Date of Defense

2016-04-01

First Committee Member

Athula H Wikramanayake

Second Committee Member

Mary Lou King

Third Committee Member

Julia Dallman

Fourth Committee Member

James Baker

Abstract

How the embryonic body axis emerges from a seemingly symmetrical egg and is subsequently patterned during embryogenesis is one of the most fundamental questions in developmental biology. It is now clear that localized activation of the Wnt/β-catenin signaling pathway plays a conserved role in primary body axis formation and/or endoderm/endomesoderm specification during embryo development of phylogenetically diverse animal species. In sea urchin embryos, recent experimental evidence has shown that Dishevelled (Dsh), a central hub protein in the Wnt/β-catenin pathway, is asymmetrically enriched and differentially modified in a vegetal cortical domain (VCD) of the unfertilized egg. Experimental evidence has also shown that during embryonic development the VCD-enriched Dsh plays a critical role in locally activating Wnt/β-catenin to specify the primary body axis and to activate the endomesodermal gene regulatory network. Hence, elucidating the molecular mechanisms that regulate the accumulation of Dsh in the VCD, mediate its activity in the Wnt/β-catenin pathway will provide key insight into how the sea urchin egg becomes an embryo. In this dissertation, I successfully used two complementary approaches, RNA-seq and protein co-immunoprecipitation, to identify key candidate molecules that may participate in regulating the spatiotemporal activity of Dsh and the Wnt/β-catenin pathway. Functional analysis of one particular candidate, DIXDC1, has shown that it may play an important role in regulating nuclear β-catenin and endomesoderm formation; two other candidate proteins were shown to be co-localized with Dsh, suggesting that they may have potentially novel functions in interacting with and regulating Dsh in sea urchin embryos. This dissertation has provided a valuable resource of candidate RNAs and proteins to study the regulation of Wnt/β-catenin pathway in early embryo development in sea urchins. Studies on these candidates in other phylogenetically important species will further provide useful insight into the regulation and evolution of the Wnt/β-catenin pathway in metazoans.

Keywords

Wnt pathway; Dishevelled; Development; sea urchin; Animal-vegetal axis; Vegetal cortical domain

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