Date of Award

12-2020

Document Type

Thesis

Department

Biology

First Advisor

Jorge A. Cantu, Ph.D.

Abstract

Neurofibromatosis Type 2 (NF2) is a rare genetic disorder, classified as a neurocutaneous syndrome inherited through an autosomal dominant genetic mutation or deletion of the NF2 gene in humans. The tumor suppressor gene NF2 encodes the cytoskeletal protein MERLIN to promote apoptosis and inhibit abnormal cellular proliferation. Mutations in NF2 lead to a deficiency of functional MERLIN in humans and can result in hearing loss, disability, and premature death. These symptoms are due to uncontrollable growth of schwann cells generating bilateral benign tumors (schwannomas) within the nerve sheath of cranial nerve VIII. Here we seek to understand the function of MERLIN by studying homologous proteins in zebrafish (D. rerio). To begin our analysis of MERLIN function, we determined that NF2 has been duplicated in the zebrafish genome to yield two paralogs, NF2a and NF2b. Compared to human MERLIN, the proteins encoded by NF2a and NF2b have retained 79% and 72% amino acid identity, respectively, including high conservation of the signaling “blue box” motif. Our data also shows that NF2a and NF2b are expressed at different times during embryonic development, suggesting non-redundant functions. Lastly, we used a catalytically inactive variant of Cas9 to knock down transcription of nf2a and/or nf2b in zebrafish. Following knockdown, zebrafish displayed evidence of cellular over proliferation in hematopoietic cells. Using immunofluorescence, we also observed fewer apoptotic cells in the brain of knockdown zebrafish when compared to wildtype siblings. Thus, our data suggests that nf2a and nf2b promotes cell survival in the brain and the blood island.

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