Haploinsufficiency of HNF1B, which encodes a transcription factor critical for renal tubulogenesis (Ma et al., 2007), is likely to be causative of RCAD in 17q12 deletion patients, as loss-of-function mutations in HNF1B alone are autosomal dominant for renal abnormalities (Bellanné-Chantelot et al., 2004; Bingham et al., 2001; Edghill et al., 2006). This evidence concerns the gene HNF1B and renal cysts and diabetes syndrome.