UCSF Study Finds Molecular Timer in Early Pregnancy May Influence Birth Timing

A new study from UC San Francisco researchers has uncovered a potential molecular mechanism that influences the timing of birth in mice, offering insights that could have implications for understanding preterm birth in humans. The research, published in Cell, reveals a surprising early-pregnancy process that may act as a timer for gestation length.

The study focused on a protein called KDM6B, which regulates gene activity by removing methyl groups from histones. When researchers blocked KDM6B in mice, pregnancies lasted longer than usual. Contrary to initial expectations, the effects were linked to fibroblasts in the uterus rather than epithelial cells, and occurred during the first days of pregnancy.

"Our findings highlight a surprising role for uterine fibroblasts in regulating birth timing," said Tara McIntyre, who led the work. "This wasn't something we anticipated, and it completely reshaped our understanding of the cell types and processes driving labor onset."

The researchers discovered that shortly after conception, methyl groups accumulate on histones near certain genes in uterine fibroblasts, keeping these genes inactive. Throughout pregnancy, methylation levels gradually decrease, eventually allowing the activation of genes related to labor. This process appears to function as a molecular timer for pregnancy duration.

Adrian Erlebacher, senior author of the paper, explained, "Essentially what appears to happen is this timer gets wound up right at the beginning of pregnancy, and then progressively winds down. When histone methylation erodes enough, nearby genes flip on."

While the study was conducted in mice, the researchers hope these findings could lead to new avenues for understanding and potentially addressing preterm birth in humans. If similar mechanisms exist in human pregnancies, they could potentially be used to predict or control pregnancy length.

"The new findings raise the possibility that preterm birth is triggered by things that happen much earlier in pregnancy than we expected," Erlebacher noted.