Genetic control of cell differentiation in platyfish‐swordtail melanomas

Abstract

In certain fish hybrids, malignant transformation of skin pigment cells is due to the presence of a tumor gene (Tu), the action of which is controlled by several regulatory elements. Absence of these controlling genes causes rapid proliferation of the Tu-transformed cells and results in melanoma formation. One of these genes was identified as a differentiation gene (Diff), since it seems to control the differentiation of the transformed pigment cells. Light microscopy and EM of Tu-transformed cells of fish differing in the dosage of Diff, and the determination of tyrosinase activity in homogenates of the respective tissues, revealed that the degree of cellular differentiation depends on the dosage of Diff present in the genome. The gene Diff promotes the differentiation of malignant melanoma cells into benign melanophores.