Date of Award

Summer 7-28-2017

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Major Professor

Martin Hudson

First Committee Member

Joel McNeal

Second Committee Member

Tsai-Tien Tseng

Third Committee Member

Michael Van Dyke

Abstract

X-linked Kallmann syndrome (KS) is a genetic disease that is caused by loss-of-function mutations in the human kal-1 gene. The disorder consists of a loss of sense-of-smell coupled with failure to undergo spontaneous puberty. At the cellular level, KS phenotypes are caused by olfactory neurons’ failure to properly migrate to the olfactory bulb. This also prevents gonadotropin-releasing hormone neuroendocrine cells from migrating to the pituitary, preventing the pulsatile release of sex hormones at puberty. While many kal-1 interacting proteins have been studied in model organisms, little is known about the regulatory mechanisms that control kal-1’s expression. Since a 5.27kb promoter is sufficient to rescue loss-of-function defects, we hypothesized that most of the kal-1 control elements are contained in this region. In order to address our hypothesis, a lineage of P-kal-1-GFP was produced to determine the cell-specific expression pattern. Using a promoter deletion assay the location of tissue-specific enhancers was determined. In addition, a transcription factor candidate gene screen was performed in which a single transcription factor, cnd-1, was found to regulate kal-1 with variable penetrance. From this we hypothesized that the regulation would be cell autonomous. As such, cnd-1 loss-of-function mutations may have similar embryonic phenotypes as kal-1 and could involve other, intermediate transcription factors. A co-expression assay found that the regulation of kal-1 by cnd-1 was cell autonomous. Using an embryonic lethality assay and timing gastrulation cleft duration, cnd-1 loss-of-function was found to have synergistic lethality with mutations in the efn-4 gene, similar to those seen in kal-1, although they did not obviously affect neuroblast migration and gastrulation cleft duration. To identify additional regulatory targets of cnd-1, we performed a comparative transcriptome of embryonic gene expression. No potential transcription factor intermediates or other nematode orthologs of Kallmann syndrome genes were found to be differentially expressed in the transcriptome with a q-value of less than 0.05. The transcriptome suggested that cnd-1 regulation covered a variety of pathways including ubiquitination and synaptic vesicle control. Finally, this thesis details the beginning of a new endeavor to determine if CND-1 interacts with the kal-1 regulatory region in a direct manner.

Available for download on Wednesday, July 20, 2022

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