March, 2025. Biology of Sex Differences 16, Article #18. In this study led by Amy Inkster, we examine DNA methylation in the human placenta on the X chromosome in over 350 placental samples. We found that the placenta has unique DNA methylation patterns on the inactive X chromosome (the second X chromosome in females, which is typically silenced). Interestingly, we observed that genes on the X chromosome in placenta sometimes are silenced (have low gene expression) in the absence of the high levels of promoter DNA methylation that is typically seen in other tissues. This suggests that the rules of X chromosome inactivation may differ in the placenta as compared to other tissues. These differences may influence early development and sex differences before birth but there are more questions than answers!. Read more here: https://doi.org/10.1186/s13293-025-00696-6.
