A deletion mutation in the 3' end of the alpha 5(IV) collagen gene in juvenile-onset Alport syndrome.

Alport syndrome is a hereditary progressive glomerular basement membrane disorder in which juvenile-or adult-onset renal failure is often accompanied by sensorineural deafness and ocular abnormalities. Recently, mutations have been found in the type IV collagen alpha 5 chain gene in patients with X-linked Alport syndrome. This study searched for gene mutations in seven unrelated Japanese patients by the use of conventional Southern blot analysis with cDNA probes for the carboxyl-terminal noncollagenous domain that is encoded by exons 46 to 51. A deletion mutation was found in a patient who developed juvenile-onset (age 15) ESRD with typical ultrastructural glomerular basement membrane destruction and sensorineural hearing loss but no characteristic ocular abnormalities. His mother showed hematuria and proteinuria with normal renal function, suggesting that she may be the heterozygous carrier. Exon-specific polymerase chain reaction amplified the coding sequence of exon 48 but not exons 49 to 51. Analysis with pulsed-field gel electrophoresis revealed that the deletion is approximately 10 kb in length and does not involve the CpG island, which is located in the 3' distal site of the gene. Identification of this novel deletion causing juvenile-type Alport syndrome would contribute to elucidating the mechanisms of renal failure progression in the syndrome.