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Date of Award

Spring 4-15-2019

Degree Type

Thesis

Degree Name

Bachelor of Science

Department

Biomedical Sciences

Abstract

Melanocytes are pigment-producing cells which are distributed throughout various regions of the body. Cutaneous melanocytes (CM) are found in the skin and hair follicles while non-cutaneous melanocytes (NCM) are found in such places as the leptomeninges, inner ears, and heart valves. Several differences have been identified between these two groups of melanocytes which support the hypothesis that melanocytes are a heterogeneous collection of cells with different ontogenies, as opposed to one identical cell type that is widespread through the body. The first differences appear during development, where CM and NCM precursors migrate along different paths in the developing embryo and depend on different signaling pathways. In the adult, CM interact extensively with keratinocytes in the skin, which are absent from the sites where NCM reside. Lastly, melanomas arising from each melanocyte type tend to differ in the mutations they commonly harbor. In this study, I investigated whether pigment regulation also differs between these two groups. The melanocortin-1 receptor (MC1R) has been studied as the main regulator of melanin synthesis. However, I did not observe any differences in eumelanin synthesis between wildtype mice and MC1Re/e and Ay mice at the heart valve leaflets, meninges, and inner ear, which contrasts cutaneous eumelanin synthesis. I attempted to quantify the level of eumelanin synthesis in the absence of MC1R activity through immunofluorescence staining of the enzyme Dct. As expected, there is less production of Dct in the hair follicles when MC1R signaling is silenced, but there are Dct-positive cells present on the leptomeninges regardless of MC1R status. Furthermore, I observed that the increase in melanin at the sites of NCM in transgenic mice which overexpress Edn3 does not differ between transgenic mice with and without functional MC1R. These preliminary results suggest that NCM do not depend on MC1R for eumelanin synthesis as do CM.

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