Sex-dependent insulin like growth factor-1 expression in preattachment equine embryos.

The research explored the difference in expression of insulin-like growth factor (IGF)-1, a key growth factor, in male and female preattachment equine embryos and found that female embryos show higher IGF-1 expression. This potentially contributes to the observed preferential survival of certain sexed embryos under different environmental conditions.

Research Methodology

• The researchers analyzed IGF-1 mRNA expression in equine embryos produced naturally at different stages of pregnancy (Days 8, 10, and 12). This was achieved using the technique of reverse transcription quantitative polymerase chain reaction.
• The gender of the embryos was identified by detecting the X-inactivation specific transcript (Xist) RNA and the equine sex determining region of the Y chromosome DNA. Embryos with positive Xist expression were classified as females and those that were Xist-negative and had presence of equine sex determining Y chromosome were classified as males.

Results

• Out of 28 embryos studied, 15, about 54%, were identified as female because they displayed positive expression of Xist.
• The research found a significant effect of the embryo’s sex on the expression of IGF-1 mRNA. Females displayed higher expression levels of IGF-1 throughout all the examined pregnancy stages (Day 8: male 5.1 ± 2.1, female 11.4; Day 10: male 5.2 ± 1.6, female 17.4 ± 6.7; Day 12: male 2.6 ± 0.3, female 11.6 ± 2.4).
• However, the time of pregnancy at which the evaluation was conducted did not significantly impact the expression of IGF-1.

Conclusions

• The findings demonstrate a heightened expression of IGF-1 in female equine embryos when compared with males.
• The researchers concluded that the sex-related influence on IGF expression is likely connected to a gradual X chromosome inactivation. This has implications for understanding how embryos of different sexes may have varying survival rates under certain environments due to their dissimilar growth factor expression.