Sex differences in response of the bovine embryo to colony-stimulating factor 2.

Luiz G B Siqueira,Peter J Hansen

doi:10.1530/rep-16-0336

Abstract

We tested whether gene expression of the bovine morula is modified by CSF2 in a sex-dependent manner and if sex determines the effect of CSF2 on competence of embryos to become blastocysts. Embryos were produced in vitro using X- or Y-sorted semen and treated at Day 5 of culture with 10 ng/mL bovine CSF2 or control. In experiment 1, morulae were collected at Day 6 and biological replicates (n = 8) were evaluated for transcript abundance of 90 genes by RT-qPCR using the Fluidigm Delta Gene assay. Expression of more than one-third (33 of 90) of genes examined was affected by sex. The effect of CSF2 on gene expression was modified by sex (P < 0.05) for five genes (DDX3Y/DDX3X-like, NANOG, MYF6, POU5F1 and RIPK3) and tended (P < 0.10) to be modified by sex for five other genes (DAPK1, HOXA5, PPP2R3A, PTEN and TNFSF8). In experiment 2, embryos were treated at Day 5 with control or CSF2 and blastocysts were collected at Day 7 for immunolabeling to determine the number of inner cell mass (ICM) and trophectoderm (TE) cells. CSF2 increased the percent of putative zygotes that became blastocysts for females, but did not affect the development of males. There was no effect of CSF2 or interaction of CSF2 with sex on the total number of blastomeres in blastocysts or in the number of inner cell mass or trophectoderm cells. In conclusion, CSF2 exerted divergent responses on gene expression and development of female and male embryos. These results are evidence of sexually dimorphic responses of the preimplantation embryo to this embryokine.

Highlights

Optimal development of the preimplantation embryo depends upon signals from the maternal reproductive tract
One possible explanation for differences in responses of female and male embryos to changes in maternal environment is that maternal embryokines that undergo a change in secretion in response to environmental stimuli act on female embryos differently than on male embryos
colony-stimulating factor 2 (CSF2) exerts a variety of actions on embryonic development (Sjöblom et al 1999, 2005, Loureiro et al 2009, 2011, Kwak et al 2012) that result in increased competence to establish pregnancy after transfer into female recipients (Loureiro et al 2009, Ziebe et al 2013, Denicol et al 2014)

Summary

Introduction

Optimal development of the preimplantation embryo depends upon signals from the maternal reproductive tract. One of the characteristics of developmental programming of postnatal function by maternal inputs during the preimplantation period is that alterations in phenotype often are different for male offspring than female offspring (Hansen et al 2016). Restriction of vitamin B and methionine supply in the maternal diet during the periconceptional period led to changes in the phenotype of adult male offspring, which were heavier, fatter and insulin-resistant, and had elevated blood pressure. These effects were not observed in the female offspring (Sinclair et al 2007)

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