Abstract

Background: Posterior polar cataract is a clinically distinctive opacity located at the back of the lens. It is commonly acquired in age related cataract, and may infrequently occur in pedigrees with congenital cataract. To date, five loci for autosomal dominant congenital posterior polar cataract have been identified. These include two genes, CRYAB and PITX3, on chromosomes 11q and 10q respectively, and three loci with as yet unknown genes on chromosomes 1p, 16q and 20p.

Purpose: To find the chromosomal location of a gene causing autosomal dominant congenital posterior polar cataract in three Moroccan Jewish families.

Methods: A whole genome scan was performed using microsatellite markers spaced at approximately 10 cM intervals. For fine mapping, five additional microsatellite markers were genotyped. Two-point lod scores were calculated using MLINK software, from the LINKAGE program package. After linkage was established, several positional candidate genes were assessed by PCR based DNA sequencing.

Results: The new cataract locus was mapped to an 11.3 cM interval between D14S980 and D14S1069 on chromosome 14q22-23. A maximum two point lod score of 5.19 at θ = 0 was obtained with the markersD14S274. The positional and functional candidate genes SIX1, SIX4, SIX6, OTX2, and ARHJ were excluded as the cause of cataract in these families.

Conclusion: An as yet unidentified gene associated with posterior polar cataract maps to the long arm of chromosome 14q22-23.