Although the majority of the progeny (93.9%; n = 132 mice) died immediately after birth, likely due to congenital heart disease caused by MMP21 abrogation39,40, we analyzed the APCMin-Villin-RasV12-MMP21 KO mice that were born healthy, grew normally, and did not exhibit apparent diseases. This evidence concerns the gene MMP21 and congenital heart disease.