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UBC Theses and Dissertations

The role of Adamts9 in melanoblast migration and modification of the skin proteome Tharmarajah, Grace T.


The glabrous skin, which includes, the tail, the footpads, the nose and the ears, of the mouse retain melanocytes in the dermis, the hair follicles of the epidermis and the interfollicular regions of the epidermis. Given that melanocytes in humans are exclusively found in the epidermis and hair follicles, the epidermis of the glabrous skin of the mouse can be a functional model in the study of melanocytes. A dominant N-ethyl-N-nitrosourea (ENU) mutagenesis screen of C3HeB/FeJ mice at the National Research Center for Environment and Health (GSF) in Germany recovered two mutants, Und3 and Und4. These mice are characterized by a reduction in pigmentation that is localized to the middle regions of the tail, with the base and tip retaining pigmentation. Mapping and sequencing revealed single base pair changes in Adamts9. The mutations in Adamts9 create null alleles and Adamts9, expressed in the epidermis, is required for melanoblast migration in the tail at 18.5 dpc. A conditional knockout of Adamts9 suggests that the hypopigmentation is due to the loss of Adamts9 in melanocytes, but not keratinocytes. Terminal amine isotopic labeling of substrates (TAILS) was used to identify changes in potential cleavage processes between Adamts9Und4/+ and wildtype mice. Several candidates, associated with the stratum basale, were found to be significantly different between the wildtype and the mutant proteomes. These candidates are involved in the regulation of cytoplasmic cell structure (Filamin-A, Filamin-B, beta-tubulin 4A and alpha-tubulin 1C), maintaining the structural organization of cells within the extracellular matrix (Plectin, Desmoplakin, Perisotin and Vimentin) and communication between cells (Type XII collagen, Type VII collagen, Fibrillin-1, Fibronectin, Tenascin and Biglycan). These findings suggest that Adamts9 is essential for the appropriate migration of melanoblasts in the developing embryo and immediately after birth. Additionally, this protease is likely involved in mouse pigmentation by maintaining an environment in the stratum basale that supports the migration of melanoblasts in the epidermis through the activation of proliferation pathways during development.

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