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Abstract
Embryonic development is the remarkable and complex process whereby one cell gives rise to all of the cells, tissues, structures, and organs that make up a metazoan. Through the processes of morphogenesis individual cells and tissues are rearranged to give form and structure to the embryo. Within this thesis I examine multiple developmental stages of C. elegans embryonic morphogenesis with a primary focus on the roles of SRGP-1/srGAP and HMP-1/⍺-catenin in these processes. First, I examine an interaction between SRGP-1 and HMP-1 during elongation, demonstrating that the SRGP-1 C-terminus can only interact with a closed conformation of HMP-1. Mutations in key residues in the HMP-1 M domain destabilize salt bridges between the MII and MIII domains and prevent recruitment of the SRGP-1 C-terminus. In addition, my results suggest that SRGP-1 and HMP-1 may also engage in additional interactions dependent on multiple binding interfaces. Second, I examine the nature of the hmp-1 salt bridge mutations and how they interact with srgp-1 loss of function. Interestingly, the hmp-1 salt bridge mutations can suppress cleft closure defects observed in embryos homozygous for a nonsense allele of srgp-1. The salt bridge mutations can suppress defects when the C-terminus of SRGP-1 is deleted but not when the F-BAR domain is deleted. This suppression is partially abrogated by loss of afd-1/afadin, suggesting that HMP-1 salt bridge mutants bypass a function of the SRGP-1 C- terminus in a manner that is at least partially dependent on AFD-1. Lastly, I examined the role of several candidate genes in dorsal intercalate on. Here I show that neither mig-10/Lamellipodin nor srgp-1 are necessary for dorsal intercalation, but that prkl-1/Prickle is a strong regulator of dorsal intercalation. I also detail my efforts to generate fluorescent knock-in and domain deletion alleles for known dorsal intercalation regulator, crml-1/CARMIL. These studies document novel morphogenetic roles for several phylogenetically conserved proteins in a living embryo.
