Among the altered genes, we have more extensively analysed the expression pattern of Hif1α. The down-regulation of Hif1α (both at the mRNA and protein levels) following blocking of retinoic acid intake in the developing mouse, its recovery after oral supplementation with folic acid and its localisation in the cardiac primordia suggest that the observed congenital heart malformation might be due to a de-regulation of Hif1α and its downstream targets (e.g. Cited2). The gene discussed is CITED2; the disease is congenital heart malformation.