Utrastructural observations on melanosome aggregation in genetically defective melanocytes of the mouse

Abstract

Cultivated mouse melanocytes with the genotype of D/‐ and d/d obtained from dorsal skin of infants, and the variant melanoma cells (subline agm) in which melanosomes were aggregated around the nucleus were characterized by means of electron microscopy. In D/‐ melanocytes, dendrites contained a number of microtubules and 10‐nm filaments, mitochondria, endoplasmic reticulum, and peripherally distributed melanosomes. On the other hand, in d/d melanocytes and agm cells, melanosomes were aggregated in the perinuclear region of the cell body. Their fibrous dendrites contained numerous microtubules and 10‐nm filaments, mitochondria, and endoplasmic reticulm. It is suggested that the interactive process of melanosomes with cytoskeletal elements is defective in d/d melanocytes, and that a similar defect is present in agm cells.