Three novel mutations of the RPGR gene exon ORF15 in three Japanese families with X‐linked retinitis pigmentosa

We describe three new mutations in a recently identified exon, ORF15, of the retinitis pigmentosa GTPase regulator gene (RPGR) in three unrelated Japanese families (Families 1–3) with X‐linked retinitis pigmentosa (XLRP). The affected males had typical retinitis pigmentosa (RP), whereas the obligate carrier females showed a wide clinical spectrum, ranging from minor symptoms to severe visual disability. Some carrier females in Families 1 and 2 showed typical RP, most carriers manifested high myopia and astigmatism, and their corrected visual acuity was insufficient. They showed an impairment of cone function following the rod dysfunction and accompanied by refractive errors. Microsatellite analysis of Family 1 revealed that the RP in the family was linked to the RP3 locus. Although one patient in the family had no mutation in the previously published exons 1–19 including exon 15a, he had a single‐nucleotide insertion in exon ORF15 (g.ORF15 + 753–754 insG). Likewise, patients in Families 2 and 3 had two‐base insertion/deletion in the exon, i.e., g.ORF15 + 833–834delGG and g.ORF15 + 861–862insGG, respectively. These insertional/deletional mutations observed in the three families are all different and new, and are predicted to lead to a frameshift, resulting in a truncated protein. These findings may support the previous hypothesis that RPGR‐ORF15 is a mutational hot spot. © 2001 Wiley‐Liss, Inc.