Developmental kinetics and gene expression in male and female bovine embryos produced in vitro with sex-sorted spermatozoa

Using bovine embryos generated in vitro from IVF with X-sorted, Y-sorted and unsorted sperm, we compared the kinetics of male and female embryo development and gene expression between male and female blastocysts. Bovine in vitro matured oocytes (n=8858) were fertilized with semen from each of 3 different bulls (X-sorted, Y-sorted or unsorted, depending on the experiment). Cleavage rate was assessed at 24, 27, 30, 33, 36, 40, 44 and 48 hpi and blastocyst development was recorded on Days 6 to 9. Relative mRNA abundance of 9 genes was analyzed in male and female Day 7 blastocysts produced with sorted and unsorted semen from one bull. Cumulative cleavage rate and blastocyst yield were significantly higher in the unsorted group compared with the X- or Y-sorted group from the same bull (p?0.05). While differences existed between bulls in cleavage rate, no differences were observed in cleavage rate between X- and Y-sorted sperm within a bull; blastocyst yield was significantly higher only for Bull 3 (Y-: 27.1.8 vs X-: 19.1.4, P<0.05) when Y-sorted semen was used. No differences in mRNA abundance of the 9 genes analyzed (GSTM3, DNTM3A, PGRMC1, TP53, BAX, COX2, IGF2R, AKR1B1 and PLAC8) were found between embryos of the same sex produced with sorted or unsorted semen. However, significant differences between male and female blastocysts were observed for three genes (GSTM3, DNMT3A and PGRMC1) (p?0.05). In conclusion, the use of sorted semen in IVF significantly delayed the onset of first cleavage compared with unsorted; differences between bulls but not between X- and Y-sorted semen were noted; and no differences in mRNA abundance were found between sorted and unsorted semen, but sex-related differences appeared in three genes.