A critical region for congenital heart disease has been designated to a 0.65 Mb region in 3p25 and four candidate genes have been proposed: SLC6A1 (MIM 137165), HRH1 (MIM 600167), ATG7 (MIM 608760) and CRELD1 (MIM 607170) [24,25,30]. The gene discussed is HRH1; the disease is congenital heart disease.