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R. Uppala, R. Lyle, R. Raval, J.–L. Blouin, R. Singh, J.V. U.C. Patel5, J.V. Solanki, M.A. Morris, V. Himabindu,P6, Vittalrao, V6, Satti, R. Uppala, S.E. Antonarakis; The ‘X–Linked’ Severe Form of Myopia Locus at Xq28 (MYP1): Narrowing of the Critical Region and Exclusion of Twelve Known Genes Localized in the Interval . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3814.
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Purpose: Myopia is a common vision problem experienced by approximately one–third of the general population with a prevalence of 0.5–2.5% in Western Europe and US populations. Families with X–linked, autosomal dominant and recessive modes of inheritance have been reported. The genes responsible for MYP1, MYP2, MYP3, MYP4, MYP5 and MYP6 have been mapped to chromosomes Xq28(Clin Genet.38: 281–6, 1990); 18p11.31(Am J Hum Genet 63: 109–119, 1998); 12q21–q23(Am. J. Hum. Genet. 63: 1419–24, 1998); 7q36(J. Med. Genet. 39: 118–24, 2002); 17q21–q22(Invest. Ophthal. Vis. Sci. 44: 1830–36, 2003); and 22q12(Am. J. Hum. Genet. 75: 448–59, 2004) respectively, but no specific gene mutations have yet been identified. We studied two large four–generation Indian pedigrees(UR006 & UR077) with isolated, non–syndromic myopia, with apparent X–linked inheritance (MYP1; MIM310460). The anomaly was only present in male members of the pedigree. The degree of myopia was variable ranged from –6 to –16.5 D with a mean of –13.33 D. Methods: In order to map the myopia locus in these families, we performed linkage analysis on 41 samples, 12 affected and 29 normals in both families, using polymorphic microsatellite markers covering the entire X chromosome. Results: Marker DXYS154, located in the pseudoautosomal region (PAR) in distal Xq28, showed no recombination with the phenotype with a maximum LOD score of 3.99 at theta = 0 under an autosomal recessive model. Other markers in the region (near but not within the PAR) that showed no recombination with the phenotype included DXS1108, DXS8087 and F8i13. Conclusions: Observation of recombination in family UR006 refined the disease locus to 1.2 cM region flanked by markers DXS1073 and DXYS154. Mutations in the CTAG2, GAB3, MPP1, F8Bver, VBP1, RAB39B, CLIC2 and TMLHE and pseudoautosomal (PAR) HSRY3, SYBL1, IL9R, SPRY3, CXYorf1 were excluded by direct sequence analysis.
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