In vitro and in vivo culture effects on mRNA expression of genes involved in metabolism and apoptosis in bovine embryos

Bovine blastocysts produced in vitro differ substantially from their in vivo- derived counterparts with regard to glucose metabolism, level of apoptosis and mRNA expression patterns. Maternal embryonic genomic transition is a critical period in which these changes could be induced. The goals of the present study were twofold: ( 1) to identify the critical period of culture during which the differences in expression of gene transcripts involved in glucose metabolism are induced; and ( 2) to identify gene transcripts involved in apoptosis that are differentially expressed in in vitro- and in vivo- produced blastocysts. Relative abundances of transcripts for the glucose transporters Glut- 1, Glut- 3, Glut- 4 and Glut- 8, and transcripts involved in the apoptotic cascade, including BAX, BCL-XL, XIAP and HSP 70.1, were analysed by a semiquantitative reverse transcription-polymerase chain reaction assay in single blastocysts produced in vitro or in vivo for specific time intervals, that is, before or after maternal embryonic transition. Whether the culture environment was in vitro or in vivo affected the expression of glucose transporter transcripts Glut-3, Glut-4 and Glut-8. However, the critical period during culture responsible for these changes, before or after maternal embryonic transition, could not be determined. With the exception of XIAP, no effects of culture system on the mRNA expression patterns of BAX, BCL- XL and HSP 70.1 could be observed. These data show that expression of XIAP transcripts in expanded blastocysts is affected by in vitro culture. These findings add to the list of bovine genes aberrantly expressed in culture conditions, but do not support the hypothesis that maternal embryonic transition is critical in inducing the aberrations in gene expression patterns studied here.