Scientists Hone In On Genetic Culprit in Heart Birth Defects
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.
She notes that the syndrome can also include problems with the immune system, abnormalities in the urinary tract and genitals, and even behavioral and psychiatric problems. "This seems to be a syndrome that affects a number of organ systems," Pearson tells WebMD. The recent genetic findings may "shed a lot of light on how one or more genetic defects can lead to this complex constellation of problems."
And she echoes Epstein in stating that the Tbx1 gene may hold the key to heart defects beyond DiGeorge syndrome. In particular, the family of genes related to Tbx1 appears to be implicated in Holt-Oram syndrome, which involves a defect in the upper chambers of the heart, Pearson says.