Linkage analysis in keratoconus: replication of locus 5q21.2 and identification of other suggestive Loci.
OBJECTIVE
Keratoconus (KC) is the most common indication for corneal transplantation in the Western world, with etiologic mechanisms still poorly understood. The disease prevalence in the general population is approximately 1:2000, and familial aggregation, together with increased familial risk, suggests important genetic influences on its pathogenesis. To date, several loci for familial keratoconus have been described, without the identification of any responsible gene in the respective mapped intervals. The aim of this study was to identify causative/susceptibility genes for keratoconus.


METHODS
A total of 133 individuals (77 affected and 59 unaffected) of 25 families from southern Italy were genotyped using microsatellite markers and included in a genome-wide scan. Nonparametric and parametric analysis using an affected-only strategy were calculated by using genetic algorithm software.


RESULTS
The chromosomal regions 5q32-q33, 5q21.2, 14q11.2, 15q2.32 exhibited the strongest evidence of linkage by nonparametric analysis (NPL = 3.22, 2.73, 2.62, and 2.32, respectively). The regions 5q32-q33 and 14q11.2 were also supported by multipoint parametric analysis, for which heterogeneity LOD (HLOD) scores of 2.45 (alpha = 0.54) and 2.09 (alpha = 0.46), respectively, were obtained under an affected-only dominant model.


CONCLUSIONS
This study represents the first KC linkage replication study on the chromosomal region 5q21.2 and reports evidence of suggestive linkage in several regions for which suggestive or significant linkage has been previously detected in different populations.
Bisceglia
Luigi
L
Medical Genetics Service,San Giovanni Rotondo, Italy. l.bisceglia@operapadrepio.it
De Bonis
Patrizia
P
Pizzicoli
Costantina
C
Fischetti
Lucia
L
Laborante
Antonio
A
Di Perna
Michele
M
Giuliani
Francesco
F
Delle Noci
Nicola
N
Buzzonetti
Luca
L
Zelante
Leopoldo
L
D000465:Algorithms; D002874:Chromosome Mapping; D002883:Chromosomes, Human, Pair 14 / Q000235:genetics; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics*; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007640:Keratoconus / Q000235:genetics*; D008126:Lod Score; D018895:Microsatellite Repeats; D010375:Pedigree