Evaluation of potential modifiers of the cardiac phenotype in the 22q11.2 deletion syndrome.

BACKGROUND

The phenotype associated with deletion of the 22q11.2 chromosomal region is highly variable, yet little is known about the source of this variability. Cardiovascular anomalies, including tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, perimembranous ventricular septal defects, and aortic arch anomalies, occur in approximately 75% of individuals with a 22q11.2 deletion.

METHODS

Data from 343 subjects enrolled in a study of the 22q11.2 deletion syndrome were used to evaluate potential modifiers of the cardiac phenotype in this disorder. Subjects with and without cardiac malformations, and subjects with and without aortic arch anomalies were compared with respect to sex and race. In addition, in the subset of subjects from whom a DNA sample was available, genotypes for variants of four genes that are involved in the folate-homocysteine metabolic pathway and that have been implicated as risk factors for other birth defects were compared. Five variants in four genes were genotyped by heteroduplex or restriction digest assays. The chi-square or Fisher's exact test was used to evaluate the association between the cardiac phenotype and each potential modifier.

RESULTS

The cardiac phenotype observed in individuals with a 22q11.2 deletion was not significantly associated with either sex or race. The genetic variants that were evaluated also did not appear to be associated with the cardiovascular phenotype.

CONCLUSIONS

Variation in the cardiac phenotype observed between individuals with a 22q11.2 deletion does not appear to be related to sex, race, or five sequence variants in four folate-related genes that are located outside of the 22q11.2 region.