Researchers uncover news clues about the cause of craniofacial birth defects

Cleft lip and palate are the most common craniofacial birth defects in humans, affecting more than 175,000 newborns around the world each year. Yet despite decades of research, it's still not known fully what causes most cases or what can be done to prevent them.

A recent study has uncovered new information about orofacial development in mice that researchers think  could one day help reduce the risk of these birth defects in humans.

Published in the Proceedings of the National Academy of Sciences (PNAS) the study provides the first direct evidence of a mechanism called DNA methylation being required for craniofacial development. DNA methylation is a process where a group of molecules are added to DNA that change the expression of genes without actually altering the DNA sequence. It's also affected by various environmental factors. The researchers discovered that disruption to DNA methylation interferes with the development of the lip and palate and causes these birth defects in mice.

The research is an important step toward developing preventive strategies that could one day lessen the risk of cleft lip and palate, known collectively as orofacial clefts (OFCs), in both animals and humans.

Past research has shown that genetics and the environment interact to cause these types of birth defects, but our understanding of the environmental component lagged far behind that of genetics.

Unlike genetics, we don't have a permanent record of the prenatal environment that can be examined retrospectively, but connecting OFCs to DNA methylation helps narrow our focus on the particular environmental influences that modify the risk for these types of birth defects.

This new work confirmed the essential role of DNA methylation in regulating orofacial development during embryonic development and demonstrates how disruptions to that process alter the ability of stem cells to form the connective tissue of craniofacial bone and cartilage, resulting in OFCs.

The researchers arrived at these results by first genetically manipulating DNA methylation in two separate groups of mouse embryos. The experiments resulted in seemingly contradictory results, with OFCs developing in one group of mice, but not the other.

To understand why there was a difference between the groups, the team conducted another round of experiments in which they inhibited DNA methylation in mouse embryos at different stages of development. The timing of when DNA methylation occurs, was critical to the development of orofacial clefts.

They found that exposure on the 10th gestational day resulted in OFCs but administering the same inhibitor just 48 hours later resulted in normal orofacial development.

Identifying this narrow window of gestational sensitivity is important,  because it not only helps narrow the focus of the next stage of his team's research but it will also help design future public education initiatives once more is known about the modifiable environmental and behavioral risk factors that impact OFC risk in humans.

 Caden M. Ulschmid et al, Disruption of DNA methylation–mediated cranial neural crest proliferation and differentiation causes orofacial clefts in mice, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2317668121