Dissertations, Theses, and Capstone Projects

Date of Degree

6-2017

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Cathy Savage-Dunn

Committee Members

Daniel Weinstein

Paul Feinstein

Christine A. Rushlow

Chris Li

Subject Categories

Biology | Biomechanics | Cell and Developmental Biology | Genetics | Genomics | Molecular Genetics

Keywords

BMP, SMADS, CUTICLE COLLAGENS, SIGNAL TRANSDUCTION, C. ELEGANS

Abstract

The body size of an organism can be a crucial determinant of access to nutrition, reproductive success and overall survival in the wild. However, how body size of an individual is determined is incompletely understood. Body size is a complex trait determined by multiple pathways and genes, making it difficult to understand the role of individual genes and pathways in determining overall size. In Caenorhabditis elegans, a homolog of Bone Morphogenetic Proteins (BMP) is a major regulator of body size; functional loss of DBL-1 leads to a small body size. Due to a drastic change in body size in dbl-1 mutants, we have the advantage of studying body size as a monogenic trait and we are able to investigate the upstream and downstream factors involved in body size regulation. During the course of our investigation, we identified cuticle collagen genes as hypodermal transcriptional targets of DBL-1 signaling that act as effectors of body size regulation. We have identified positive (col-41), negative (col-141, co-142), and dose-sensitive regulators (rol-6) of body size. In Yin et al. (2014) we performed promoter dissection to define sequences necessary for col-41 expression, we further showed a GATA factor elt-1, regulates col-41 expression. Next, I have shown cuticle collagens are directly and indirectly regulated, using chromatin immunoprecipitation followed by high throughput sequencing (ChIP-Seq). Furthermore, I have shown Smad binding to v conserved Smad Binding Elements (SBE) in a common promoter region for col-141 and col-142 and demonstrated that SBE in this region are required for gene expression. Utilizing electrophoretic mobility shift assays (EMSA), I showed functional conservation of Smads in C. elegans via strong and specific SMA-4 binding to GTCT (Smad Binding Element) sites. I have discovered a stage specific requirement of Smads for expression of cuticle collagen genes. Based on our work we emphasize that cuticle collagens are the effectors of body size regulation via the DBL-1 pathway. Lastly, utilizing transcriptional and translation reporters we show that inhibition of col-41, rol-6, col-141, and col-142 affects DBL-1 transcription. Hence, we have provided first evidence of a feedback loop between the cuticle and DBL-1 signaling.

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