ABSTRACT
The study of the variations in expression of chaperones during development, and the role of these variations, is at the same time trivial and difficult. Trivial because it is well known that the expression of chaperones differs widely from one adult tissue to another (Tanguay et al., 1993) and that these differences are established during development. Moreover, it has been extensively documented that the synthesis of chaperones is dependent upon metabolic conditions (Lanks, 1986) and is not uniform during the different phases of the cell cycle (Wu and Morimoto, 1985; Milarski and Morimoto, 1985; Jérome et al., 1993). Since the embryo is submitted during development to dramatic variations in metabolism, and given that the duration of the different cell cycle phases varies widely in embryonic cells, it can be expected that the expression of chaperones will vary during development. If one considers the functions of chaperones in protein folding (Hartl, 1996), translocation across membranes but also protein degradation (Hayes and Dice, 1996), it is also obvious that the concentrations of chaperones and heat shock proteins (HSPs) will vary during development, in parallel with protein synthesis, cell remodeling or secretion (as during the formation of the extracellular matrix).
