Elsevier

Developmental Biology

Volume 8, Issue 1, August 1963, Pages 99-127
Developmental Biology

Changes in melanogenesis during the dedifferentiation of chick retinal pigment cells in cell culture

https://doi.org/10.1016/0012-1606(63)90028-9Get rights and content

Abstract

The gradual loss of melanin pigment (dedifferentiation) has been demonstrated in monolayer cultures of proliferating retinal pigment cells of the chick embryo. Pigment was resynthesized when depigmented cells were subsequently cultured as pellets in an organ culture technique.

Culture experiments have demonstrated a correlation between diminished growth (cell division) and resynthesis of pigment when a certain minimal nutritional level was maintained in the culture medium. Crowding of depigmented cells could also induce melanin synthesis, apparently by inhibiting cell division.

Three chemical characteristics of the melanin-synthesizing system in retinal pigment cells were investigated during the first 14 days in monolayer culture: (1) melanin concentration, (2) the activity of DOPA oxidase, and (3) the rate of the tyrosinase-dependent incorporation of C14-labeled tyrosine. All three characteristics declined rapidly during the first 4 days in culture.

When melanin concentration and the levels of DOPA oxidase activity were correlated with the available cell division data, it appeared that changes in the rate of melanogenesis occurred prior to cell division. It was tentatively concluded that progressive dilution caused by a difference between the rates of cell division and melanogenesis is not the sole mechanism involved in retinal pigment cell dedifferentiation.

Data from experiments with the incorporation of C14-labeled tyrosine and leucine into the acid-insoluble fraction of cultured cells suggested an inverse correlation between the rate of general protein synthesis and the rate of melanin synthesis. Nevertheless, general protein synthesis and melanin synthesis may be basically similar processes, since both were equally affected by puromycin, an inhibitor of protein synthesis. The possibility of dedifferentiation being regulated at the level of protein synthesis was considered.

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    Supported by Scholarships from the Ontario Research Foundation and a Yale University Sterling Predoctoral Fellowship. This paper is based on a dissertation presented to the Graduate School of Yale University for the degree of Doctor of Philosophy, August, 1962.

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    Present address: Department of Zoology, University of California, Los Angeles, California.

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