Control of differentiation in aggregates of embryonic skin cells: Suppression of feather morphogenesis by cells from other tissues

Abstract

Aggregates of dissociated skin cells from 8-day chick embryos grafted to the chorioallantoic membrane reconstructed typical integumental tissues with feathers that developed to advanced stages. Similarly, aggregates of dissociated mouse skin cells from 15-day embryos grafted to the chorioallantois gave rise to skin, hair follicles, and sebaceous glands primordia. A complete suppression of feather formation was obtained consistently when the dissociated chick skin cells were commingled and coaggregated with mouse skin cells prior to grafting; hair formation was not markedly suppressed in such composite aggregates. A similarly complete and consistent suppression of feather morphogenesis was obtained in coaggregates of skin cells with cells from several other tissues of chick embryos, as well as of mouse embryos. Some aspects of the causality of feather suppression in aggregates were examined: (1) interspersion of skin cells and suppressor cells was essential for the effect, under the conditions employed; (2) by varying the relative concentration of suppressor cells it was found that a minority of suppressor cells caused a complete suppression of feather development; in the cases examined, only when the proportion of suppressor cells to skin cells was reduced to 1:24 did feathers develop. Additional changes took place in the developmental pattern of skin cells coaggregated with cells from other tissues and were related to the kind of admixed cells.