EXPRESSION OF PATERNAL AND MATERNAL MITOCHONDRIAL HSP70 FAMILY, HSC74, IN PREIMPLANTATION MOUSE EMBRYOS

We have investigated the regulation of gene expression of a novel mito chondrial HSP70 family, hsc74 in preimplantation mouse embryos. We use d a monoclonal antibody, anti-CSA, which reacts with only one of strai n variants of the hsc74. By immunostaining with anti-CSA antibody, the hsc74 protein was constitutively detected in C3H embryos from 1-cell to blastocyst stage, but no signals were detectable in C57BL/6 embryos , To know the timing of paternal genome expression, we examined the ex pression of hsc74 in (C57BL/6 X C3H)F1 embryos. No positive signals we re detectable in embryos before 8-cell stage. In early 8-cell stage we akly positive signals appeared in the peripheral region of the blastom eres. From late 8-cell stage, the protein was intensively detectable a nd was persistently expressed in all types of cells. We have also appl ied a sensitive methodology to distinguish genetic variants of hsc74 f rom C3H and C57BL/6 by reverse transcription polymerase chain reaction followed by single strand conformation polymorphism analysis. In (C57 BL/6 X C3H)F1 embryos, the paternal transcripts were first detected in 4-cell embryos, while the maternal transcripts were constantly detect able. These results indicate that the transcripts and proteins of hsc7 4 were derived only from the maternal gene from 1-cell to 4-cell stage s, and that from 4-cell stage the paternal gene is also transcribed, a nd the significant increase of the paternally derived protein occurred around late 8-cell stage.