The origin of cell-type differences in early embryos.
Differences between cells first arise in embryonic development by two principal mechanisms. One is the asymmetric distribution of cytoplasmic substances at mitosis in eggs and early embryos. The other is cell interaction or embryonic induction. Certain aspects of these major mechanisms are considered, and emphasis is placed on the value of molecular markers. The effects of unequal cell division on the concentration of cytoplasmic determinants are discussed. In embryonic induction, the nature and timing of response is determined more by properties of the responding tissue than by those of the inducing molecules. Possible future directions of work are discussed in relation to experience with amphibian eggs and oocytes.
Gurdon
J B
JB
Department of Zoology, University of Cambridge, U.K.
D000818:Animals; D002454:Cell Differentiation; D003593:Cytoplasm / Q000502:physiology; D004627:Embryonic Induction; D005314:Embryonic and Fetal Development