Differentiation of Pigment Cells in Tissue Cultures of Chick Neural Crest

Abstract

The experiments of DuShane 1 , 2 have proved conclusively that the dermal melanophores of the amphibia originate in the neural crest, as suggested by Harrison, 3 and later by Weidenreich 4 and Holtfreter. 5 The differentiation of large numbers of typical pigment cells in tissue cultures of neural crest taken from embryos of pigmented fowls indicates the probability of a similar source of origin in the chick.

Embryos of various breeds have been used, ranging in stage between 6 and 10 somites. Thin strips of the rising folds anterior to the first somites were removed with fine scissors and explanted in a medium consisting of equal parts of plasma and embryonic extract. For controls, whole embryos minus the neural crest were cut into small pieces and explanted on a single slide; or specific areas, such as the eye, the brain floor with underlying endoderm, and the ectoderm and mesoderm lateral to the crest region, were explanted separately. Control cultures never contained more than one or 2 isolated pigment cells, and were for the most part totally negative.

The cells appear at the border of the explant during the first day in vitro. They are extremely variable in shape, ranging from bipolar to stellate forms, but are frequently found with long, thin, branching processes. They are filled with colorless, refractile granules, which gradually acquire pigment, developing from a pale yellow to deep brown or black, and reaching full intensity in many cells by the third day in vitro. The cells are actively amœboid, and show no tendency to form sheets or tissues, a trait which distinguishes them sharply from the pigmented epithelium of the eye, and from the nervous tissue and epithelium which frequently make up the remainder of such explants.