Melanosomes are highly specialized organelles that produce and store the pigment melanin, thereby fulfilling essential functions within their host organism. Besides having obvious cosmetic consequences--determining the color of skin, hair and the iris--they contribute to photochemical protection from ultraviolet radiation, as well as to vision (by defining how much light enters the eye). Though...

Avian plumage colours are model traits in understanding the evolution of sexually selected ornamental traits. Paradoxically, iridescent structural colours, probably the most dazzling of these traits, remain the most poorly understood. Though some data suggest that expression of bright iridescent plumage colours produced by highly ordered arrays of melanosomes and keratin is condition-dependent,...

BACKGROUND Age-related macular degeneration (AMD) is associated with lipofuscin accumulation whereas the content of melanosomes decreases. Melanosomes are the main storage of zinc in the pigmented tissues. Since the elderly population, as the most affected group for AMD, is prone to zinc deficit, we investigated the chemical and ultrastructural effects of zinc deficiency in pigmented rat eyes a...

Mice with mutations at the dilute locus exhibit a 'washed out' or 'diluted' coat color. The pigments that are responsible for the coloration of mammalian hair are produced by melanocytes within a specialized organelle, the melanosome. Each melanocyte is responsible for delivering melanosomes via its extensive dendritic arbor to numerous keratinocytes, which go on to form the pigmented hair shaf...

Melanosome transport in melanocytes is a model system for the study of cytoskeletal regulation of intracellular transport. Melanophilin (Mlph) is a Rab27a- and myosin Va (MyoVa)-binding protein that regulates this process. Using yeast two-hybrid screening, we identified MT plus-end binding protein (EB1) as a melanocyte-expressed Mlph-interacting protein. To address the role of EB1 versus Rab27a...

Microtubules and F-actin, and associated motor proteins, are considered to play complementary roles in longand short-range organelle transport. However, there is growing appreciation that myosin/F-actin networks can drive long-range transport. In melanocytes myosin-Va and kinesin-1 have both been proposed as long-range centrifugal melanosome transporters. Here we investigated the role of kinesi...

Southern right whales (SRWs, Eubalena australis) are polymorphic for an X-linked pigmentation pattern known as grey morphism. Most SRWs have completely black skin with white patches on their bellies and occasionally on their backs; these patches remain white as the whale ages. Grey morphs (previously referred to as partial albinos) appear mostly white at birth, with a splattering of rounded bla...

Cytoplasmic microtubules (MTs) continuously grow and shorten at their free plus ends, a behavior that allows them to capture membrane organelles destined for MT minus end-directed transport. In Xenopus melanophores, the capture of pigment granules (melanosomes) involves the +TIP CLIP-170, which is enriched at growing MT plus ends. Here we used Xenopus melanophores to test whether signals that s...

Melanophores offer an outstanding system for the study of intracellular motility. These cells aggregate their pigment-filled melanosomes to the cell center or disperse them throughout the cytoplasm in response to hormonal modulation of intracellular cyclic AMP levels in order to effect color changes in lower vertebrates [1]. Previous work from our laboratory demonstrated a role for microtubule-...

Whereas resistance to chemotherapy has long impeded effective treatment of metastatic melanoma, the mechanistic basis of this resistance remains unknown. One possible mechanism of drug resistance is alteration of intracellular drug distribution either by drug efflux or sequestration into intracellular organelles. Melanomas, as well as primary melanocytes from which they arise, have intracellula...