CHARACTERISTIC EXPRESSION OF HIGH-MOLECULAR-MASS HEAT-SHOCK-PROTEIN HSP105 DURING MOUSE EMBRYO DEVELOPMENT

Expression of 105 k-Da heat shock protein (HSP105) during mouse embryo development was investigated. Although HSP105 was detected scarcely i n mouse embryos at gestational day (GD) 8, its level of HSP105 increas ed markedly in the embryos from GD 9 to 11, and then decreased gradual ly by Go 14. In contrast, 70 k-Da heat shock cognate protein (HSC70) w as detected at constantly high levels in embryo from GD 8 to 17 (befor e birth). The transient increase in level of HSP105 was observed in mo st embryonic tissues. Since the levels of HSP105 mRNA was detected at constantly high levels in the embryos between Go 8 and 12, the increas ed expression of HSP105 at Go 9 to II seemed to be regulated at posttr anscriptional level. Immunohistochemically, HSP105 as well as HSC70 we re localized in the cytoplasm and the nuclei of cells in various mouse embryonic tissues. After treatment of tissue sections with proteinase K, HSP105 but not HSC70 was also found to be localized in condensed c ells and condensed bodies which showed the typical characteristics of apoptotic cells and apoptotic bodies at the interdigital regions of li mbs. These findings suggest that HSP105 plays important roles during m ouse embryo development.