Date of Award

5-2024

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Kellee Siegfried

Second Advisor

Linda Huang

Third Advisor

Labib Rouhana

Abstract

The dmrt1 gene is common amongst most animals and functions to determine or maintain male sex during development. Similarly, in zebrafish dmrt1 is important for male sex determination and maintaining proper testis morphology. This gene is expressed in two different cell types of the testis in zebrafish, germ cells and Sertoli cells. While we know where this gene is expressed and what its role is, it is not known if it is sufficient to drive male fate. If so, then in which cells is it sufficient to drive male fate in the testis? I aimed to answer this question by analyzing two different dmrt1 transgenic lines that express dmrt1 specifically in either the germ cells or the Sertoli cells. We then analyzed sex ratios of the transgenic fish compared to the wild-type siblings. We found that dmrt1 overexpression in both cell types leads to an overwhelming male bias in the population as compared to wild type fish. We also found that dmrt1 overexpression exclusively in the germ cells led to a higher frequency of males in comparison to the wild type fish. Meanwhile, dmrt1 overexpression exclusively in the Sertoli cell led to no change in the number of males compared to wild type fish. I then wanted to see if the dmrt1 gene was sufficient to rescue male fate in dmrt1 mutant zebrafish. After testing out the individual transgenic lines against mutant dmrt1 fish, we found that neither transgene by themselves could rescue the male sex determination defects in the progeny of mutant fish. Combining all of these data together, we see that dmrt1 overexpression in the germ cells is sufficient to drive male sex determination. However, dmrt1 expression from each of our transgenic lines is not sufficient to drive male sex determination, under dmrt1 mutated conditions in the zebrafish testis.

Comments

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