Sex determination of porcine embryos using a new developed duplex polymerase chain reaction procedure based on the amplification of repetitive sequences

Polymerase chain reaction (PCR)-based assays have become increasingly prevalent for sexing embryos. The aim of the present study was to develop a suitable duplex PCR procedure based on the amplification of porcine repetitive sequences for sexing porcine tissues, embryos and single cells. Primers were designed targeting the X12696 Y chromosome-specific repeat sequence (SUSYa and SUSYb; sex-related primer sets), the multicopy porcine-specific mitochondrial 12S rRNA gene (SUS12S; control primer set) and the X51555 1 chromosome repeat sequence (SUS1; control primer set). The specificity of the primer sets was established and the technique was optimised by testing combinations of two specific primer sets (SUSYa/SUS12S; SUSYb/SUS12S), different primer concentrations, two sources of DNA polymerase, different melting temperatures and different numbers of amplification cycles using genomic DNA from porcine ovarian and testicular tissue. The optimised SUSYa/SUS12S- and SUSYb/SUS12S-based duplex PCR procedures were applied to porcine in vitro-produced (IVP) blastocysts, cell-stage embryos and oocytes. The SUSYb/SUS12S primer-based procedure successfully sexed porcine single cells and IVP cell-stage embryos (100% efficiency), as well as blastocysts (96.6% accuracy; 96.7% efficiency). This is the first report to demonstrate the applicability of these repetitive sequences for this purpose. In conclusion, the SUSYb/SUS12S primer-based duplex PCR procedure is highly reliable and sensitive for sexing porcine IVP embryos.

Characterization of bovine transcripts preferentially expressed in testis and with a putative role in spermatogenesis

Although the number of genes known to be associated with bovine spermatogenesis has increased in the past few years, regulation of this biological process remains poorly understood. Therefore, discovery of new male fertility genetic markers is of great value for assisted selection in commercially important cattle breeds, e.g., Nelore, that have delayed reproductive maturation and low fertility rates. The objective of the present study was to identify sequences associated with spermatogenesis that could be used as fertility markers. With RT-PCR, the following five transcripts preferentially expressed in adult testis were detected: TET(656) detected only in adult testis; TET(868) and TET(515) expressed preferentially in adult testis but also detected in fetal gonads of both sexes; and TET(456) and TET(262,) expressed primarily in the testis, but also present in very low amounts in somatic tissues. Based on their homologies and expression profiles, we inferred that they had putative roles in spermatogenesis. Detection of sequences differentially expressed in testis, ovary, or both, was a useful approach for identifying new genes related to bovine spermatogenesis. The data reported here contributed to discovery of gene pathways involved in bovine spermatogenesis, with potential for prediction of fertility.