Mutational screening of VSX1, SPARC, SOD1, LOX, and TIMP3 in keratoconus.

PURPOSE: To evaluate the involvement of Visual System Homeobox 1 (VSX1), Secreted Protein Acidic and Rich in Cysteine (SPARC), Superoxide Dismutase 1 (SOD1), Lysyl Oxidase (LOX), and Tissue Inhibitor of Metalloproteinase 3 (TIMP3) in sporadic and familial keratoconus. METHODS: Mutational analysis of the five genes was performed by sequencing and fragment analysis in a large cohort of 302 Italian patients, with a diagnosis of keratoconus based on clinical examination and corneal topography. The variants identified in VSX1 and SPARC were also assessed in the available relatives of the probands. RESULTS: A novel mutation p.G239R and previously reported mutations were found in VSX1. Novel and already reported variants were identified in SPARC and SOD1, whose pathogenic significance has not been established. No pathogenic variants have been identified in LOX and TIMP3. CONCLUSIONS: Molecular analysis of the five genes in a cohort of 225 sporadic and 77 familial keratoconus cases confirms the possible pathogenic role of VSX1 though in a small number of patients; a possible involvement of LOX and TIMP3 could be excluded; and the role played by SOD1 and SPARC in determining the disease as not been definitively clarified. Further studies are required to identify other important genetic factors involved in the pathogenesis and progression of the disease that in the authors' opinion, and according with several authors, should be considered as a complex disease.

VSX1 mutational analysis in a series of Italian patients affected by keratoconus: detection of a novel mutation.

PURPOSE: Keratoconus is a noninflammatory corneal disorder that is clinically and genetically heterogeneous. Mutations in the VSX1 (visual system homeobox 1) gene have been identified for two distinct, inherited corneal dystrophies: posterior polymorphous corneal dystrophy and keratoconus. To evaluate the possible role of the VSX1 gene in a series of Italian patients, 80 keratoconus-affected subjects were screened for mutations. METHODS: The diagnosis of keratoconus was made on the basis of clinical examination and corneal topography. The whole coding region and the exon-intron junctions of the VSX1 gene were analyzed by direct sequencing. RESULTS: Three already-described changes, D144E, G160D, and P247R, and a novel L17P mutation were found in 7 of 80 unrelated patients (8.7%). Two undescribed intronic polymorphisms are also reported. CONCLUSIONS: Mutational analysis of the VSX1 gene in a series of Italian patients revealed one novel mutation and confirmed an important role played by this gene in a significant proportion of patients affected by keratoconus, when it is inherited as an autosomal dominant trait with variable expressivity and incomplete penetrance.

Linkage analysis in keratoconus: replication of locus 5q21.2 and identification of other suggestive Loci.

PURPOSE: 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.