Purpose: To identify the disease locus for autosomal recessive congenital cataracts in two consanguineous Pakistani families.
Methods: Two Pakistani families were ascertained, ophthalmologic examination including slit lamp biomicroscopy was performed on all members, blood samples were collected and DNA was extracted. A genome-wide scan was performed using 382 polymorphic microsatellite markers on genomic DNA from affected and unaffected family members. Two-point logarithm of odds (LOD) scores were calculated using the LINKAGE program package.
Results: All the affected individuals of family PKCC009 show bilateral membranous cataract, whereas the affected individuals of family PKCC039 show bilateral posterior sub-capsular cataract. Other ocular abnormalities include corneal opacities, microcornea and nystagmus in the affected individuals of PKCC009. Maximum two point LOD scores were obtained with D1S186 (4.14 at theta = 0), D1S432 (4.01 at theta = 0), D1S2892 (4.11 at theta = 0), and D1S2797 (4.07 at theta = 0) for family PKCC009 and with D1S496 (4.73 at theta = 0), D1S2892 (4.34 at theta = 0), D1S3721 (4.83 at theta = 0), and D1S2797 (4.32 at theta = 0) for family PKCC039. The common linked region, 20.76 cM (20.80 Mb), is flanked by markers D1S2729 and D1S2890 and co-segregates with the disease in both families, placing the disease locus on chromosome 1p34.3-p32.2.
Conclusions: Linkage analysis of autosomal recessive cataracts in two consanguineous Pakistani families localizes a novel locus for autosomal recessive congenital cataract on chromosome 1p.