GROWTH OF NEURAL CREST CELLS IN-VITRO IS ENHANCED BY EXTRACTS FROM SILKY FOWL EMBRYONIC-TISSUES

In the Silky Fowl (SF) breed of chicken, most of the internal organs a re infiltrated with melanocytes. Previous studies have shown that this generalized mesodermal pigmentation is not due to a cell autonomous a bnormality of the melanocytes but to environmental factors able to pro mote both the homing of pigment cell precursors in abnormal embryonic sites and their proliferation and differentiation. To analyse the mode of these environmental cues, we tested the effect of SF embryo extrac t (SFEE) on cultured quail neural crest cells as compared with that of EE from normal chickens of the JA57 strain (JA57EE). We found that SF EE enhances crest cell proliferation as judged by H-3-TdR incorporatio n and cell counting. In contrast, no effect of SFEE was observed eithe r on the proportion of cultured cells that are engaged into the melano cytic differentiation pathway or on the amount of melanin produced by each differentiated pigment cell. The simple observation, however, rev eals that SFEE has a significant effect on pigmentation of the culture d quail neural crest cells. This effect has therefore to be accounted for by the general increase in cell number induced by SFEE. The questi on is raised as to whether the in vivo SF phenotype is generated exclu sively by this mechanism.