Tight Junction Messenger RNA Expression Levels in Bovine Embryos are Dependent upon the Ability to Compact and In Vitro Culture Methods1

Abstract

We have established a transcription map of individual bovine embryos using semiquantitative reverse transcriptase-polymerase chain reaction to detect the levels of six marker genes involved in early embryo differentiation. The critical step of compaction during preimplantation development is often not accomplished or it takes place for only a short period in in vitro generated embryos, which may result in reduced viability. Compaction is accompanied by the assembly of intercellular tight junctions (TJs) as a barrier against the extraembryonic environment and as a prerequisite for blastocele formation. In the present study, we have related the expression of TJ gene mRNA in individual bovine embryos to their developmental stage, their competence to undergo a clear period of compaction before blastocyst formation, and their in vitro or in vivo origin. Our results indicate that embryos that showed a detectable and well-formed compaction period in vitro are of similar quality to their in vivo counterparts. Starting from the same amount of maternal message, in vivo and in vitro development differ most during the critical period of the major switch from maternal to embryonic genomic control before a dramatic increase of TJ mRNAs occurs upon blastocyst formation. Failure to compact in vitro results in significant reduction of specific transcript levels, in a manner that depends on culture conditions, which may contribute to reduced viability. We conclude that TJ mRNA expression levels are sensitive to environmental conditions that may influence the developmental potential of bovine blastocysts.

Contribution of JAM-1 to epithelial differentiation and tight-junction biogenesis in the mouse preimplantation embryo

“…We recently examined JAM-1 expression in bovine eggs and embryos using poly(A) + RNA and found a similar temporal pattern, with JAM-1-encoding transcripts detectable in only a small minority of germinal vesicle and in-vitro-matured metaphase-II oocytes and, when present, barely detectable using semiquantitative methods (Miller et al, 2003). Likewise, we have found that only a minority of cultured human embryos before the eight-cell stage (presumed maternal genome) (Braude et al, 1988) exhibit JAM-1-encoding mRNA within poly(A) + RNA compared with later cleavage when the transcript is readily detectable (Ghassemifar et al, 2003).…”

Different Culture Media Requirements of IVF and Nuclear Transfer Bovine Embryos

“…2003). Failure in compact in vitro resulted in a significant decrease in specific transcript levels pertaining to tight junction proteins, which may contribute to poor viability (Miller et al. 2003).…”

Embryotropic actions of follistatin: paracrine and autocrine mediators of oocyte competence and embryo developmental progression

“…The cells in cleavage stage embryos are known as blastomeres which start to form tight junctions with one another after 8- or 16-cell stage (depending upon the species) and results in development of a mulberry shaped structure called a morula (Sheth et al . 1997; Miller et al . 2003) and subsequent cavitation and blastocyst formation.…”