Non-synonymous Variants in Pre-B Cell Leukemia Homeobox (PBX) Genes Are Associated with Congenital Heart Defects

Congenital cardiac malformations are one of the most common birth defects and most are believed to be multigenic/multifactorial in nature. Recently mice lacking Pre-B cell leukemia transcription homeobox (PBX) genes were created and found to have a range of ventricular outflow tract (OFT) malformations. Therefore, we screened 95 patients with congenital heart defects, including OFT malformations, for variants in genes encoding PBX proteins, as well as interacting proteins. The coding exons of PBX1-4, PKNOX1, PKNOX2, MEIS1-3, and PBXIP1 were amplified by polymerase chain reaction and the products analyzed on a lightscanner. Samples with abnormal melting profiles were analyzed by DNA sequencing. Seven non-synonymous variants (6 novel and 1 SNP) were identified in 5 proteins (Pbx3, Pbx4, Meis1, Meis3 and Pknox1). One Pbx3 variant, p.A136V, is located in a highly conserved polyalanine tract and predicted to be deleterious. This variant was present in 5.2% of heart defect patients compared with 1.3% of 380 race- and ethnicity-matched controls (P<0.05). None of the other variants were predicted to be damaging. In conclusion, our results support the Pbx3 Ala136Val variant as a modifier or risk allele for congenital heart defects and implicate PBX-related genes as candidates for CHD, especially those affecting the cardiac outflow tract.