Anatomie et physiologie : recherches en cours
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Distribution and Extracellular Matrix Environment of Premelanoblasts during Skin Development in Xiphophorus Hybrids

John Ku and Ahmed HK El-Hashash

Neural crest cells give rise to melanoblasts that invade the dermis and epidermis to differentiate into melanocytes that can develop melanoma, which is one of the most aggressive forms of human cancer. Identification of mechanisms important for the initial development of melanoma is hampered because of the difficulty in studying them in transgenic mice with melanoma. In addition, there is only fragmentary knowledge about the histochemical and biochemical changes that accompany the very early stages of neural crest/premelanoblast invasion into the skin, which may later develop melanoma, in the naturally occurring melanoma models such as Xiphophorus fish hybrids. Herein, we used Xiphophorus hybrid fish to investigate the distribution and extracellular matrix (ECM) environment of premelanoblasts during early stages of skin development, and to test the hypothesis that there are parallels between neural crest/premelanoblast invasion and ECM changes in the early developing skin. To test this hypothesis, we investigated neural crest/premelanoblast cell distribution through development and characterize their ECM environment. We found several histochemical evidences for the correlation between this pattern of developing skin invasion by neural crest cells/premelanoblasts and the spatiotemporal relationship of extracellular matrix components that stimulate cell migration/invasion such as collagen, and others such as non-sulfated glycosaminoglycan that may facilitate cell invasion by enhancing the intercellular spaces and inhibition of extensive intercellular interactions by physically separating cells. These findings help to uncover some histochemical and biochemical changes that accompany the early stages of skin formation in Xiphophorus fish hybrids, and can also provide a conceptual framework for future mechanistic studies in this area, and for studies that use this fish hybrid as a naturally occurring melanoma model.