A novel de novo frameshift mutation of RPGR ORF15 is associated with X-linked retinitis pigmentosa in a Chinese family.

PURPOSE To identify the genetic basis of disease in a Chinese family with retinitis pigmentosa (RP). METHODS Linkage analysis was performed for 15 family members in the RP family using microsatellite markers flanking candidate genetic loci for known autosomal dominant RP (adRP) and markers covering the entire X chromosome by every 10 cM. To screen for a mutation causing RP, PCR and DNA sequence analyses of the complete coding region (including ORF15) and exon-intron boundaries of the retinitis pigmentosa GTPase regulator (RPGR) gene associated with X-linked RP (xlRP) were carried out for the proband in the RP family. After the mutation was identified, direct DNA sequence analysis was preformed for all 15 family members and 101 controls to determine whether the mutation co-segregated with RP in the family and whether it was present or absent in the controls. RESULTS Linkage analysis excluded all known adRP loci. However, positive linkage was identified with two markers on the X chromosome, DXS993 and DXS1068, where the RPGR gene is located. Direct DNA sequence analysis revealed a hemizygous mutation, g.ORF15+1166delA (c.2919delA), in affected males. The deletion results in a frameshift leading to early termination of RPGR. The g.ORF15+1166delA mutation arose de novo and co-segregated with all male patients, but was not present in normal family members and 101 controls. The clinical features of the mutation carriers showed intrafamilial variability. CONCLUSIONS The novel g.ORF15+1166delA mutation of RPGR causes X-linked RP in a four generation Chinese family. The deletion arose de novo. An interesting feature of mutation g.ORF15+1166delA is that it was associated with RP in all hemizygous males and four of five heterozygous female carriers in the Chinese family. These results revealed the broader xlRP genotypic and phenotypic spectrum of RPGR mutations.