Conditionally deleting Tbx5 from the SHF with two SHF Cre-mouse models (Mef2c-AHF-Cre and Gli1-Cre-ERT2) revealed that Tbx5 expression in the pSHF is critical to the development of the DMP as in both conditional Tbx5 knockout models a fully penetrant incomplete AVSD phenotype (ostium primum defect) was found [77]. This evidence concerns the gene TBX5 and familial atrioventricular septal defect.