Spontaneous Mutation May Play a Vital Role in Congenital Heart Defects

Spontaneous mutations may be responsible for congential heart defects in newborns.

Genetic factors were thought to be a major contribution in causing congenital heart defects in newborns until now. However a new study suggests that it may also be caused as a result of spontaneous mutations.

"Until recently, we simply didn't have the technology to test for this possibility," Howard Hughes Medical Institute (HHMI) investigator Richard Lifton said.

Together with Christine Seidman and other colleagues, Hughes compared the protein-coding regions of genomes of children both with and without the congenital heart defects using sequencing technologies. This comparison revealed that new mutations led to the development of congenital heart defects in around 10 percent of severe cases.

The study took into account 362 families with no family history of heart problems and congenital heart defects. The comparison of genomes within these families revealed that mutations are actually responsible for the congenital heart defects, and that these mutations were present in the child's DNA, not his parents.

The mutations occurred in a variety of genes, but there was one particular cellular pathway that was starkly enriched in children suffering from this condition. "The mutations in patients with congenital heart disease were found much more frequently in genes that are highly expressed in the developing heart," Seidman says.

The human body contains DNA, which is wrapped around proteins called histones and chemical tags known as methyl groups which help control the turning on and turning off of the genes. Children suffering from congenital heart defects were found to have an excess number of mutations in genes that affect the histone methylation at sites that are very important for proper development.

De novo, or spontaneous, mutations were finally confirmed to be the cause of 10 percent of cases of severe congenital heart disease, and around one third of this contribution was accounted for by the histone-methylation pathways.

Though these mutations cannot be controlled, and the progression of this disease cannot be stopped, this revelation may be helpful in developing different treatments for the condition and may provide valuable insights for different developments in the near future. 

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