Two-stage genome-wide linkage scan in keratoconus sib pair families

PURPOSE. To identify susceptibility gene loci for keratoconus. METHODS. A genome-wide linkage analysis was performed with data from 67 keratoconus sib pair families with 110 affected sib pairs of white or Hispanic origin. A total of 351 subjects were genotyped for 380 microsatellite markers along the genome at similar to 10-cM density. An additional 58 microsatellite markers at similar to 2-cM density in the identified linkage regions on chromosomes 4, 5, 9, 12, and 14 were also genotyped. Multipoint linkage analysis was performed in all pedigrees by nonparametric methods and maximum likelihood estimates of identity by descent sharing as implemented in GeneHunter ( http://linkage.rockefeller.edu/soft/gh/provided in the public domain by Rockefeller University, New York, NY). RESULTS. The strongest evidence of linkage was observed at the telomere ( 159 cM) of chromosome 9 ( lod = 4.5) in all pedigrees. Other regions suggestive of linkage were identified at 176 cM of chromosome 4 ( lod = 2.7), 143 cM of chromosome 5 ( lod = 2.0), 7 cM of chromosome 9 ( lod = 2.8), 12 cM of chromosome 11 ( lod = 2.3), 27 cM of chromosome 12 ( lod = 2.3), and 14 cM of chromosome 14 ( lod = 2.9). Two significant linkage regions were also observed on chromosomes 17 at 86 cM ( lod = 3.9) and 9 at 34 cM ( lod = 3.8) in the Hispanic subjects only. After fine mapping these regions ( with the exception of chromosomes 11 and 17), most linkage peaks remained similar ( lod = 2.2 at 176 cM on chromosome 4; lod = 1.7 at 146 cM on chromosome 5; lod = 3.5 at 160 cM on chromosome 9; lod = 2.5 at 7 cM on chromosome 12; and lod = 2.6 at 19 cM on chromosome 14). CONCLUSIONS. These results indicate that one or more loci may contribute to keratoconus susceptibility.