How Dad Genes Determine the Way Moms Care for Babies

Infants may benefit most from fathers silencing one key gene, new research reveals.

A father’s genes may actually help determine how a mother cares for their baby before it even arrives, new research reveals. During pregnancy, hormonal signals are given off through the placenta that help a woman transition into motherhood biologically. The catch is these hormones are controlled by a gene that only gets turned off, typically for dads, as a result of epigenetic imprinting. While that may make it seem like dads are losing out of some level of cellular level, there’s evidence in mice that pups seem to benefit from dad genes being more of the strong and silent type.

“A new mother is primed during pregnancy,” study author Rosalind John, a professor at Cardiff University’s School of Biosciences, told Smithsonian Magazine. “It’s really important for the wellbeing of the pups.”

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The way this works is the hormones that prime women for parenthood during pregnancy are set off by placenta cells called spongiotrophoblasts. The way these cells multiply spread depends on a gene know as Phlda2, which influences the level of hormonal changes — the less active the Phlda2 gene is, the higher level of placental hormones there is. Unlike other genes where there’s a copy gene for the mother and the father, the Phlda2 gene is turned off for fathers as a result of epigenetic imprinting. In the past scientists believed that this is a result of conflict between maternal and paternal interests, mostly about whether to make more babies or invest resources in the one who just showed up.

To test this John and her colleagues compared genetically altered mice, with both copies of the Phlda2 gene activated (maternalized mice) and both copies silenced (paternalized mice). They found that when mothers had the highest Phlda2 activity (and lowest placental hormones) spent less time nursing, grooming, and caring for their pups, and more time on nest building. However, when both copies of the Phlda2 were turned off, spent more time nurturing and less time on housekeeping. Researchers then showed these how theses changes showed up differently in the hypothalamus and hippocampus of the mothers’ brains as well. While it’s often assumed that a father’s genes are at odds with a mother’s, these preliminary findings suggest that by being silent, dad genes play a critical role balancing the mother’s caretaking behaviors.

“We had to rethink what defines good mothering. There’s not a gold standard. It’s a sliding scale of priorities,” study co-author Hugo Creeth, a biologist working under John supervision at Cardiff University, told Smithsonian.

Creeth, John, and their team suspect that the findings are relevant to humans because levels of Phlda2 vary during pregnancy, and the lower the activity, the higher the level or hormones. Future research could be vital for developing better treatments and interventions to help families raise happy and healthy children.

“Our previous work has reported that a similar placental gene is linked to prenatal depression, and we are currently asking whether similar gene changes are associated with poor quality maternal care” John added in a statement. “More work must be done to further our understanding of how this works in humans.”

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