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Mapping a new genetic locus for X linked retinitis pigmentosa to Xq28
  1. A Melamud1,
  2. G-Q Shen2,
  3. D Chung3,
  4. Q Xi2,
  5. E Simpson3,
  6. L Li2,
  7. N S Peachey4,
  8. H Zegarra5,
  9. S A Hagstrom4,
  10. Q K Wang2,
  11. E I Traboulsi3
  1. 1Cole Eye Institute, The Cleveland Clinic Foundation, Cleveland, OH, USA
  2. 2Center for Molecular Genetics, Department of Molecular Cardiology, Center for Cardiovascular Genetics, Department of Cardiovascular Medicine, The Cleveland Clinic Foundation, Cleveland, OH, USA
  3. 3Center for Genetic Eye Diseases, Cole Eye Institute, The Cleveland Clinic Foundation, Cleveland, OH, USA
  4. 4Department of Ophthalmic Research, Cole Eye Institute, The Cleveland Clinic Foundation, and Cleveland VA Medical Center, Cleveland, OH, USA
  5. 5Retina Associates, Cleveland, OH, USA
  1. Correspondence to:
 Dr E I Traboulsi
 Center for Genetic Eye Diseases, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA; traboue{at}


We have defined a new genetic locus for an X linked form of retinitis pigmentosa (RP) on chromosome Xq28. We examined 15 members of a family in which RP appeared to be transmitted in an X linked manner. Ocular examinations were performed, and fundus photographs and electroretinograms were obtained for selected patients. Blood samples were obtained from all patients and an additional seven family members who were not given examinations. Visual acuity in four affected individuals ranged from 20/40 to 20/80+. Patients described the onset of night blindness and colour vision defects in the second decade of life, with the earliest at 13 years of age. Examined affected individuals had constricted visual fields and retinal findings compatible with RP. Based on full field electroretinography, cone function was more severely reduced than rod function. Female carriers had no ocular signs or symptoms and slightly reduced cone electroretinographic responses. Affected and non-affected family members were genotyped for 20 polymorphic markers on the X-chromosome spaced at 10 cM intervals. Genotyping data were analysed using GeneMapper software. Genotyping and linkage analyses identified significant linkage to markers DXS8061, DXS1073, and DXS1108 with two point LOD scores of 2.06, 2.17, and 2.20, respectively. Haplotype analysis revealed segregation of the disease phenotype with markers at Xq28.

  • ERG, electroretinography
  • MAGUK, membrane associated guanylate kinase homologue
  • RP, retinitis pigmentosa
  • RPGR, retinitis pigmentosa GTPase regulator
  • XLRP, X linked retinitis pigmentosa
  • X-linked
  • mapping
  • new locus
  • retinitis pigmentosa

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  • The first two authors contributed equally to this work.

  • Competing interests: there are no competing interests