The Expression of Growth Factors and Growth Factor Receptors During Mouse Embryogenesis

Abstract

Elucidation of molecular mechanisms underlying embryonic growth control is a key step to understanding embryonic development, as well as the regulation of cellular proliferation and its impairment in malignancy. Since extensive proliferation and differentiation take place during development, it seems likely that growth factors have a major role in embryogenesis. Identification of specific growth factors involved in embryonic development and their characterization is a difficult task because the events that occur at each developmental step are complex and the quantities of embryonic material available are limited. In the mouse, for example, the first 3 days after fertilization are devoted primarily to continuous multiplication. During the next 2 days, the first two differentiation steps take place to form the layers which will give rise to the fetus and to extra-embryonic structures (see Fig. 1). After implantation, at about day 7 of gestation, gastrulation begins, followed by major morphogenetic and organogenetic processes during the next 5 days. The remainder of the 20-day gestational period is devoted primarily to terminal differentiation and enlargement of the fetus. Therefore, elucidation of the key developmental processes requires investigation of the embryo during the peri-implantation period-stages in which small numbers of cells undergo extensive differentiation.