364 QUANTIFICATION OF DEVELOPMENTALLY IMPORTANT GENE TRANSCRIPTS EXPRESSED IN EMBRYOS PRODUCED IN VIVO AND IN VITRO USING SEX-SORTED AND NON-SORTED RAM SPERMATOZOA

Abstract

The AI of sex-sorted spermatozoa results in decreased levels of fertility in most species. This is not the case in sheep, where low-doseAI of sex-sorted ram spermatozoa produces similar, if not superior levels of fertility to non-sorted controls (Beilby et al. 2009 Theriogenology, 71, 829-835). In an effort to provide insight into the molecular basis for this difference in fertility between species, the aim of the present study was to examine the impact of sex-sorting technology on ovine embryo gene expression. After semen collection, ejaculates (n = 8) were split and either sex-sorted by flow cytometry and frozen, or diluted and frozen (non-sorted control). Embryos were produced in vivo by inseminating superovulated ewes with either X- or Y-chromosome enriched spermatozoa, or non-sorted control spermatozoa, and collected by flushing uterine horns on Day 6 after AI. Embryos were produced in vitro by using established oocyte in vitro maturation and in vitro fertilization procedures (using X, Y or non-sorted spermatozoa), and cultured in vitro for 6 days. The relative abundance of Glut-3, G6PD, SUV39H1, DnMT3a, and HSP70 was measured in high grade blastocysts (in vivo Day 6: n = 23; in vitro Day 6: n = 21) using quantitative, real-time PCR (iCycler5TM, BioRad, Hercules, CA, USA). Blastocyst cell numbers were quantified to ensure embryos were at a similar stage of development. The sex of all embryos was identified by PCR to allow comparison between treatments. Fold differences in gene expression, acquired through the A ACt method, were calculated and compared by an ANOVA. The expression of HSP70 was up-regulated in in vitro embryos derived from sex-sorted spermatozoa compared to those produced in vivo (P < 0.05). For all other genes examined, there was no effect of sex or sperm treatment on gene expression. Glut-3, G6PD, SUV39H1, andDnMT3a were all up-regulated in in vitro embryos compared with in vivo embryos (P < 0.05). These results suggest that fertilization with sex-sorted ram spermatozoa does not result in aberrant patterns of gene expression in embryos produced in vivo. The data from the present study provide further evidence that in vitro culture induces epigenetic modification within the embryonic genome, when compared to the in vivo physiological standard. It would be of interest to conduct a similar in vivo study in cattle, where sex-sorting technology has not been as biologically successful. The altered expression of HSP70, which is associated with cellular stress, may demonstrate a cumulative impact of in vitro reproductive technologies on the preimplantation embryo.

Research supported by XY, Inc.