DALLAS - February 19, 1999 - Researchers at UT Southwestern Medical Center at Dallas have isolated the gene they believe is responsible for the most common genetic cause of heart and facial birth defects.
Scientists have suspected for many years that a gene on chromosome 22 is responsible for these birth defects, but the identification of a single gene that could be involved in cardiac and facial defects has been elusive. In the February 19 issue of Science, Dr. Deepak Srivastava, assistant professor of pediatrics and molecular biology and oncology, and colleagues demonstrate that deletion of part of one gene can cause the variety of anomalies found in children known to be missing a piece of chromosome 22 (22q11).
Children with chromosome 22 deletion syndrome, also known as DiGeorge syndrome, can suffer cardiac defects, abnormal facial features, immune deficiencies, cleft palate and low blood calcium. Although the defects seem unrelated to one another, all the affected tissues share a common embryologic origin, suggesting that a single gene may be important for both heart and facial formation.
The researchers discovered a candidate gene in mice. They then established that only one instead of the two usual copies of the gene are present in children known to have the chromosome 22 deletion. They confirmed their hypothesis that the presence of only one gene copy was sufficient to cause the associated physical anomalies by finding a child who exhibited the cardiac and facial defects characteristic of chromosome 22 deletion syndrome, and who had only a single copy of this gene while the rest of chromosome 22 was normal.
One in 4,000 children is born with chromosome 22 deletion syndrome, making
it one of the most common genetic abnormalities in children. Many children with
just facial or just cardiac defects also have the same deletion, which is the
second-most common genetic cause of congenital heart defects (CHD). CHD affects
Contact: Heather Stieglitz
UT Southwestern Medical Center