Melanization stimulating factor (MSF) and melanization inhibiting factor (MIF) in the integument of fish

Abstract

The present studies were directed to demonstrate that adult fish skin contains putative factors that affect chromatophore and/or chromatoblast function. This hypothesis is based upon the possibility that hypo and/or hyperpigmented areas of the skin are so pigmented because of the localized expression of intrinsic factors that are either stimulatory or inhibitory to the differentiation of specific pigment cell types. In all the morphological and biochemical experiments carried out, we used culture media conditioned by dorsal (DCM) or ventral (VCM) skin from different species of fish. Both DCM and VCM were capable of stimulating differentiation of melanophores in neural crest explants. While the stimulation of melanization is an activity present in both dorsal and ventral skin, an inhibitory activity is also present in ventral skin at such a concentration that it overrides the stimulatory activity afforded by DCM. With biochemical assays, we demonstrated that the three important sequential enzymatic steps in melanogenesis are all stimulated by the conditioned media in a dose-dependent manner and this results in an increase in the amount of melanin present in cultured cells. The results of our investigations provide strong evidence that there are intrinsic pigment cell regulatory factors in the integument of fish, the inhibitory activity being stronger in the ventrum, and that those factors strongly influence, perhaps even determine, the pigment patterns of fish.

Fish melanocortin system

“…Similar experiments in catfish demonstrated that conditioned medium from catfish ventral skin and semi-purified amphibian MIF inhibits melanoblast differentiation but stimulates or supports iridophore proliferation (Zuasti, 2002).…”

“…In teleosts, this countershading is achieved by a patterned distribution of the pigment cells, with the light-absorbing and light reflecting chromatophores mostly distributed in the dorsal and ventral areas, respectively (Fuji, 1993). Early experiments in amphibian and fish species suggested that the dorsal-ventral pigment pattern is achieved through a putative diffusible melanization inhibition factor (MIF), mainly produced by cells in the ventral skin, which inhibits melanoblast differentiation and stimulates or supports iridophore proliferation in the ventrum (Fukuzawa and Ide, 1988, Bagnara and Fukuzawa, 1990, Zuasti et al, 1992Zuasti, 2002). Amphibian MIF was reported to block stimulation of the melanization provoked by α-MSH in neural explants of Xenopus (Fukuzaga and Bagnara, 1989).…”

Hyperpigmentation in North Sea dab Limanda limanda. II. Macroscopic and microscopic characteristics and pathogen screening

“…Adult fish skin contains factors that affect the function of pigment cells, and therefore, hyperpigmented areas of the skin could be the result of a localized expression of intrinsic melanisation stimulatory (MSF) or inhibitory factors (Zuasti 2002). MSF were originally described for the integument of channel catfish Ictalurus punctatus and later were also found in marine species (Zuasti et al 1992(Zuasti et al , 1993(Zuasti et al , 2000.…”

“…As only young dab larvae are pelagic and live in the upper layers of the water column during the early spring and summer, they are likely to be impacted by UV-B radiation; however, after metamorphosis, young dab living in shallow waters such as the Wadden Sea will still be potentially exposed. If the influence of UV-B radiation at an early life stage, or a combination of light and nutritional factors, plays a role, then either the anomaly persists in a way that is enhanced with time/age, or abnormal pigmentation in larger fish also develops by other means, as discussed by Zuasti (2002) in relation to the influence of stimulatory or inhibitory molecules.…”

Flatfish (Pleuronectiformes) chromatic biology

“…Since variations between discrete areas within patterns are so important in flatfish, factors distributed locally in the skin may be more significant than circulating pituitary hormones in regulating their melanogenesis. Such putative factors may include a localised integumentary melanization inhibiting factor (MIF) and a melanization stimulating factor (MSF) (Bagnara et al 1992;Zuasti 2002) working together, or independently, in establishing pigmentation patterns in vertebrates. In the fish integument there is strong evidence (Zuasti 2002) for such an MSF in both dorsal and ventral skin, as well as MIF in the ventral skin with a capacity to override the MSF at an appropriate concentration.…”