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Scientists Hone In On Genetic Culprit in Heart Birth Defects

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Next, the scientists replaced the genes in groups of four to determine whether resulting mice offspring would still have the DiGeorge syndrome symptoms. In this way, they were able to hone in on the culprit Tbx1, Epstein explains.

And he notes that Tbx1 is a member of a family of related genes implicated in other heart defects. "The importance of the finding goes beyond [DiGeorge syndrome]," he says.

Knowledge of the genetic component in heart birth defects can aid in understanding how those components work with other factors. "Diet and environment contribute to congenital heart disease, but we need to understand the genes that contribute and how they interact," he says.

As if to complicate matters, another report by researchers at the University of Chicago and Oregon Health Sciences University that appears in the journal Nature Genetics found another gene in the same region of chromosome 22 also implicated in symptoms of DiGeorge syndrome. That finding may reflect some difference between mice and humans, or it could indicate that DiGeorge syndrome requires a mutation in both genes, according to researchers.

However, the isolation of Tbx1 by three independent laboratories lends credence to its important association with DiGeorge syndrome in humans, says pediatric cardiologist Gail D. Pearson, MD, ScD.

"We won't know with certainty what the role of analogous genes in humans is until that human work is done," Pearson tells WebMD. "These findings are exciting and we hope they will shed some light on the gene or genes involved in the human condition."

Pearson is leader of the heart development, function and failure scientific research group in the division of heart and vascular diseases at the National Heart, Lung, and Blood Institute of the National Institutes of Health. The National Heart, Lung, and Blood Institute supported the work by Epstein as well as some others, she says.

Pearson notes that nearly three-fourths of all people with DiGeorge syndrome have "significant cardiovascular disease requiring one or more surgical interventions, in childhood and later on." And she adds that cardiovascular disease associated with the syndrome can be fatal.

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