Exclusion of the candidate genes ACE and Bcl-2 for six families with nephronophthisis not linked to the NPH1 locus.

Background: Nephronophthisis (NPH) is an autosomal recessively transmitted kidney disease, characterized by cyst formation at the cortico-medullary junction, and a sclerosing tubulointerstitial nephropathy. Juvenile nephronophthisis (NPH1) is the most common genetic cause of renal failure in children and maps to chromosome 2q12-q13. The responsible gene NPHP1 has been identified and encodes for nephrocystin. Not all families with NPH demonstrate linkage to that locus.

Methods: We studied six families with NPH without linkage to the NPH1 locus. In order to attempt identification of a new causative gene, the candidate genes ACE (angiotensin converting enzyme) and Bcl-2 (B cell leukaemia/lymphoma 2 gene) originating from mouse models, were examined. For the six families highly polymorphic microsatellites covering the whole candidate gene regions were haplotyped and linkage analysis was performed.

Results: Haplotype analyses of all families examined were incompatible with linkage of the disease status to ACE or Bcl-2. Linkage analysis excluded both candidate gene regions with a LOD-score of < -2.

Conclusions: This study excluded the candidate genes ACE and Bcl-2 for NPH. Additional linkage studies need to be performed in order to identify further genes responsible for nephronophthisis.