Identification of a novel deletion of the entire OCRL1 gene detected by FISH analysis in a family with Lowe syndrome.

The oculocerebrorenal syndrome of Lowe (OCRL) is a rare X-linked multisystem disorder affecting the lens, kidney and brain. The gene involved (OCRL1) has been identified and is known to encode a phosphatidylinositol 4,5-bisphosphate 5-phosphatase. Mutations in OCRL1 have been shown to be causative of OCRL. To date, most of the mutations identified have consisted of simple or point mutations and there is one report of a 1.4-kb deletion. We investigated the OCRL1 gene in a male patient with OCRL by the polymerase chain reaction and found that the entire OCRL1 gene was deleted. Fluorescence in situ hybridisation analysis (FISH), with cosmid probes that span the entire OCRL1 gene, was used to confirm this deletion and subsequently identify it in the proband's mother. This is the first report of a whole gene deletion of OCRL1 and thus expands the range of mutations that give rise to OCRL. The use of the FISH technique facilitated carrier and prenatal testing for the deletion in the family.