BackgroundPreimplantation bovine development is emerging as an attractive experimental model, yet little is known about the mechanisms underlying trophoblast (TE)/inner cell mass (ICM) segregation in cattle. To gain an insight into these processes we have studied protein and mRNA distribution during the crucial stages of bovine development. Protein distribution of lineage specific markers OCT4, NANOG, CDX2 were analysed in 5-cell, 8–16 cell, morula and blastocyst stage embryos. ICM/TE mRNA levels were compared in hatched blastocysts and included: OCT4, NANOG, FN-1, KLF4, c-MYC, REX1, CDX2, KRT-18 and GATA6.ResultsAt the mRNA level the observed distribution patterns agree with the mouse model. CDX2 and OCT4 proteins were first detected in 5-cell stage embryos. NANOG appeared at the morula stage and was located in the cytoplasm forming characteristic rings around the nuclei. Changes in sub-cellular localisation of OCT4, NANOG and CDX2 were noted from the 8–16 cell onwards. CDX2 initially co-localised with OCT4, but at the blastocyst stage a clear lineage segregation could be observed. Interestingly, we have observed in a small proportion of embryos (2%) that CDX2 immunolabelling overlapped with mitotic chromosomes.ConclusionsCell fate specification in cattle become evident earlier than presently anticipated – around the time of bovine embryonic genome activation. There is an intriguing possibility that for proper lineage determination certain transcription factors (such as CDX2) may need to occupy specific regions of chromatin prior to its activation in the interphase nucleus. Our observation suggests a possible role of CDX2 in the process of epigenetic regulation of embryonic cell fate.

No abstract

No abstract

No abstract

An AI Ayrshire bull was subjected to cytogenetic examination due to lowered fertility. Preliminary Giemsa staining revealed a normal chromosome complement (60,XY) and G-banding did not allow us to draw a clear conclusion concerning an occurrence of chromosome rearrangement. Testicles were collected at slaughter and synaptonemal complex (SC) analysis revealed a large cross-shaped tetravalent configuration in pachytene spreads. No association between the tetravalent and XY bivalent was observed. Chromosome painting, with the use of bovine whole chromosome painting probes, conjugated with DAPI staining, facilitated a detailed description of the translocation rcp(2;4)(q45;q34). This study shows that post mortem analysis of synaptonemal complexes is a simple and useful tool for the preliminary detection of reciprocal translocation carriers.