Abstract
BackgroundAlterations in maternal environment can sometimes affect embryonic development in a sexually-dimorphic manner. The objective was to determine whether preimplantation bovine embryos respond to three maternally-derived cell signaling molecules in a sex-dependent manner.ResultsActions of three embryokines known to increase competence of bovine embryos to develop to the blastocyst stage, insulin-like growth factor 1 (IGF1), activin A, and WNT member 7A (WNT7A), were evaluated for actions on embryos produced in vitro with X- or Y- sorted semen from the same bull. Each embryokine was tested in embryos produced by in vitro fertilization of groups of oocytes with either pooled sperm from two bulls or with sperm from individual bulls. Embryos were treated with IGF1, activin A, or WNT7A on day 5 of culture. All three embryokines increased the proportion of cleaved zygotes that developed to the blastocyst stage and the effect was similar for female and male embryos. As an additional test of sexual dimorphism, effects of IGF1 on blastocyst expression of a total of 127 genes were determined by RT-qPCR using the Fluidigm Delta Gene assay. Expression of 18 genes was affected by sex, expression of 4 genes was affected by IGF1 and expression of 3 genes was affected by the IGF1 by sex interaction.ConclusionSex did not alter how IGF1, activin A or WNT7A altered developmental competence to the blastocyst stage. Thus, sex-dependent differences in regulation of developmental competence of embryos by maternal regulatory signals is not a general phenomenon. The fact that sex altered how IGF1 regulates gene expression is indicative that there could be sexual dimorphism in embryokine regulation of some aspects of embryonic function other than developmental potential to become a blastocyst.
Highlights
Alterations in maternal environment can sometimes affect embryonic development in a sexuallydimorphic manner
This was the case for insulin-like growth factor 1 (IGF1), activin A and WNT member 7A (WNT7A)
The exception was for experiment 3 in which effects of activin A were tested for embryos produced using pooled spermatozoa
Summary
Alterations in maternal environment can sometimes affect embryonic development in a sexuallydimorphic manner. Its importance for the fate of the embryo can be observed by examination of the consequences of embryo production in vitro, i.e., in the absence of maternal signals Such embryos differ from their in vivo counterparts in terms of gene expression [1], metabolism [2], lipid content [3, 4], ultrastructure [5], freezability [6], DNA methylation [7], competence to establish pregnancy [8] and postnatal phenotype [9,10,11,12]. Sexual dimorphism in response to altered maternal function could be mediated by changes in secretion of embryokines which act on female embryos differently than male embryos. CSF2 treatment decreased trophoblast elongation and secretion of the maternal recognition of pregnancy protein, interferon-τ, but opposite effects occurred in male embryos
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