Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Collaborative Specialization

Developmental Biology

Supervisor

Kelly, Gregory M.

2nd Supervisor

Bulakbasi Balci, Tugce

Co-Supervisor

Abstract

Pathogenic variants in the human PRR12 (Proline Rich 12) gene are associated with PRR12-related Neuroocular Syndrome. However, little is known about the gene/protein function. The zebrafish was utilized to address this, as its attributes place it as a premier model to study genes involved in human development and disease. In situ hybridization and RT-PCR of embryos and larvae, and qRT-PCR of adult tissues revealed the spatial and temporal distributions of the prr12 paralogues: prr12a and prr12b. Both paralogues were detected from the maternal and zygotic transcriptomes in a global and diffuse expression pattern, and there was enrichment of prr12a in the ovary and prr12b in the male mesencephalon of adult zebrafish. Overall, research into the PRR12 zebrafish orthologues, provides new information to help elucidate its function in humans; and more importantly, it sets the stage for using zebrafish as a model to study this and other rare human disorders.

Summary for Lay Audience

Rare diseases are individually rare but collectively common, and they impact the life of approximately 1 in 12 Canadians. Majority of rare diseases are seen in children, who face debilitating disorders that affect many organ systems. Almost all individuals will wait on average 5 years to receive a diagnosis. Getting a diagnosis opens the way for treatment options, which is paramount for the wellbeing of patients and their families. However, a genetic diagnosis is only possible based on the available knowledge connecting genes to diseases.

Animal systems may be used to investigate gene function and model human genetic disorders. In this thesis, the human gene Proline Rich 12 (PRR12) was the target of interest. Disease causing changes in the PRR12 gene have been recently associated with the PRR12-related Neuroocular Syndrome. Individuals with this syndrome present primarily with developmental impairment and eye abnormalities. Currently, there is little known about the PRR12 gene or protein it encodes in normal or abnormal development. Therefore, I sought to investigate its expression in zebrafish, an established developmental and disease animal system. Zebrafish have two gene copies of PRR12, known as prr12a and prr12b (paralogues). I hypothesized the prr12 paralogues would act similarly in zebrafish development like those in humans. Furthermore, when turned off using a genetic approach, the zebrafish would present phenotypes reminiscent of patients with Neuroocular Syndrome. In a first step, I found that both prr12a and prr12b are expressed throughout early zebrafish development and in various embryonic and larval tissues. In adults, prr12a is predominately expressed in the ovary and prr12b is expressed in specific neural structures in the brain and eyes.

These patterns suggest prr12a and prr12b are required in early development, similar to reports of human PRR12, and have more restricted roles in adult zebrafish. Taken together, these results provide a rationale for using zebrafish to investigate PRR12 and the PRR12-related Neuroocular Syndrome. The next steps, beyond the scope of my work, will be to study the effects of mutations of these paralogues, which may ultimately help to understand their functions and lead to the development of targeted therapies in humans.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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