Date Approved

11-15-2023

Embargo Period

11-15-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biomedical Engineering

College

Rowan-Virtua School of Translational Biomedical Engineering & Sciences

Advisor

Ronald E. Ellis, Ph.D.

Committee Member 1

Sergei Borukhov, Ph.D.

Committee Member 2

Eric Moss, Ph.D.

Committee Member 3

Michael Anikin, Ph.D.

Committee Member 4

Sal Caradonna, Ph. D.

Keywords

auxin-inducible degron system;Caenorhabditis briggsae;Caenorhabditis elegans;evolutionary conservation;heterochronic genes

Subject(s)

Heterochronic genes; Cells--Development

Disciplines

Biochemistry, Biophysics, and Structural Biology | Biomedical Engineering and Bioengineering | Life Sciences | Molecular Biology

Abstract

The heterochronic pathway of C. elegans is the most well-characterized system to date for controlling the sequence and timing of developmental events. However, we still have critical unanswered questions to address. First, little is known about the evolution of the heterochronic pathway, and of developmental timing in general. To determine if the roles of major heterochronic genes are conserved, I made mutants in orthologs of these genes in C. briggsae, using CRISPR/Cas9. My studies revealed a significant drift in the roles of some of the genes, although all of them are still involved in the developmental timing regulation, and several important interactions between the genes are conserved. Second, previous studies showed that C. elegans lin-14, a transcription factor controlling L1 and L2 developmental events, has two activities separated in time during development. My goal was to learn if other heterochronic genes also had separate activities that worked at different points in development. Since there are no temperature-sensitive alleles for many of the key genes, I applied a system of targeted protein degradation – the auxin-inducible degron system – to study the times of action for the core heterochronic genes lin-28, hbl-1, and lin-41. My results revealed that each lin-28 and hbl-1 had two activities separated in time as well, and that all these genes act in a temporal sequence that reflects their positions in the epistasis pathway. Thus, I deepened our understanding of when the C. elegans heterochronic genes act. This will improve our understanding of how developmental timing mechanisms work.

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