An improved method for specific-target preamplification PCR analysis of single blastocysts useful for embryo sexing and high-throughput gene expression analysis

Presence of KREMEN receptors for DKK1 in the preimplantation bovine embryo

The WNT inhibitory protein DKK1 has been shown to regulate development of the preimplantation embryo to the blastocyst stage. In cattle, DKK1 increases the number of trophectoderm cells that are the precursor of the placenta. DKK1 can affect cells by blocking WNT signaling through its receptors KREMEN1 and KREMEN2. Here it was shown that the mRNA for KREMEN1 and KREMEN2 decline as the embryo advances in development. Nonetheless, immunoreactive KREMEN1 was identified in blastocysts using Western blotting. DKK1 also decreased amount of immunoreactive CTNNB1 in blastocysts, as would be expected if DKK1 was signaling through a KREMEN-mediated pathway. Thus, it is likely that KREMEN1 functions as a receptor for DKK1 in the preimplantation bovine embryo.

Male Embryos Produced in vitro Deviate From Their in vivo Counterparts in Placental Gene Expression on Day 32 of Pregnancy

This study compared the gene expression of extraembryonic membranes (EEM) from in vitro produced (IVP) and in vivo (AI) derived pregnancies. A piece of conceptus (day 18) or chorioallantois (day 32) was used for DNA and RNA isolation and sex determination. Male and female ratios were analyzed by Chi-square. A total of three samples per sex and group (AI and IVP, days 18 and 32) were used for transcriptome analysis. Differentially expressed genes (DEGs) were determined using edgeR-robust. A false discovery rate (FDR) <0.05 was used for statistical significance. Sex ratio was similar on day 18 for AI and IVP groups. On day 32, the IVP group had a greater number of females than males (75 vs. 25%, P = 0.004). When comparing AI and IVP males vs. females, in both groups, genes upregulated in females on day 18 were related to placental function such as PAGs and TKDPs. On males on day 18, IFNT-related genes were upregulated. Comparing the techniques within sex, on day 18 female conceptuses, 50 genes were upregulated in IVP, and 21 in AI. IGF2, which is involved in placenta development, and APOA2, APOB, and APOE, involved in lipid metabolism, were upregulated in IVP conceptuses. On day 18, males had 15 upregulated genes in AI and 7 in IVP. On day 32, females had 21 upregulated genes in AI and 53 in IVP. Genes involved in lipid synthesis and metabolism were increased in the IVP group. Males on day 32 presented 899 DEGs, 564 upregulated in AI and 335 in IVP. Embryos from IVP had decreased expression of genes related to lipid and carbohydrate metabolism. Interestingly, pregnancy-associated glycoproteins (PAG) 7, 9, 10, and 19, were downregulated in IVP male. In conclusion, IVP-derived male embryos were more susceptible to alterations in gene expression and these effects extend to the peri-implantation period including genes associated with placental development and markers of placental function.

Regulation of gene expression in the bovine blastocyst by colony-stimulating factor 2 is disrupted by CRISPR/Cas9-mediated deletion of CSF2RA

Colony-stimulating factor 2 (CSF2) functions in the reproductive tract to modulate the function of the preimplantation embryo. The β subunit of the CSF2 receptor (CSF2RB) is not expressed in the embryo, and signal transduction is therefore different than for myeloid cells where the receptor is composed of α (CSF2RA) and β subunits. Here, we produced embryos in which exons 5 and 6 of CSF2RA were disrupted using the CRISPR/Cas 9 system to test whether CSF2RA signaling was essential for actions of CSF2 in the bovine embryo. Wild-type and CSF2RA knockout embryos were treated with 10 ng/mL CSF2 or vehicle at day 5 of development. Blastocysts were harvested at day 8 to determine transcript abundance of 90 genes by real-time polymerase chain reaction (PCR). Responses in female blastocysts were examined separately from male blastocysts because actions of CSF2 are sex-dependent. For wild-type embryos, CSF2 altered expression of 10 genes in females and 20 in males. Only three genes were affected by CSF2 in a similar manner for both sexes. Disruption of CSF2RA prevented the effect of CSF2 on expression for 9 of 10 CSF2-regulated genes in females and 19 of 20 genes in males. The results confirm the importance of CSF2RA for regulation of gene expression by CSF2 in the blastocyst.