Developmental change in morphogenetic properties: embryonic chick heart tissue and cells segregate from other tissues in age-dependent patterns.

Abstract

AbstractDuring animal development complex morphogenetic movements occur. If these movements are controlled by cell‐to‐cell adhesiveness, the latter should change during embryonic development. To test this possibility indirectly, heart cells or tissue fragments from chick embryos of one and one‐half to five days of incubation were paired in separate experiments with five‐day pigmented retina or neural retina or 36‐hour neural tube. The combinations were made either by fusing together intact tissue pieces or by aggregating mixed cell suspensions dissociated from tissue pairs. All fused pieces and aggregates were cultured for two and one‐half days. The heart cells and tissue fragments from young embryos (1.5–2 days of incubation) displayed a tendency to take up external positions when combined with neural tube. In contrast, heart cells and tissue fragments from older embryos (4–5 days of incubation) tended to take up internal positions when combined with neural tube. A similar result (young heart outside, old heart inside) was found when combinations of heart fragments were made with pigmented retina fragments. When heart fragments of varying developmental ages were fused with neural retina, the older heart pieces were completely covered by neural retina, whereas younger heart pieces were only partially, if at all, covered by neural retina. These results clearly indicate a change in morphogenetic properties of embryonic heart cells during these early developmental stages. The interpretation is that the heart cells are gradually increasing their cell‐to‐cell adhesiveness, passing from a less adhesive condition at one and one‐half days to a more adhesive condition at four days of incubation.