Hsp70 expression and function during embryogenesis

This review focuses on the expression and function of 70-kDa heat shock pro teins (Hsp70s) during mammalian embryogenesis, though many features of embr yogenesis and the developmental expression of Hsp70s are conserved between mammals and other vertebrates. A variety of Hsp70s are expressed from the p oint of zygotic gene activation in cleavage-stage embryos, through blastula tion, implantation, gastrulation, neurulation, organogenesis, and on throug hout fetal maturation. The regulation and patterns of hsp70 gene expression and the known and putative Hsp70 protein functions vary from constitutive and metabolic housekeeping to stress-inducible and embryo-protective roles. Understanding the genetic regulation and molecular function of Hsp70s has been pursued by developmental biologists interested in the control of gene expression in early embryos as well as reproductive toxicologists and terat ologists interested in how Hsp70s protect embryos from the adverse effects of environmental exposures. These efforts have also been joined by those in terested in the chaperone functions of Hsp70s, and this confluence of effor t has yielded many advances in our understanding of Hsp70s during critical phases of embryonic development and cellular differentiation.