Fine mapping of the Schnyder's crystalline corneal dystrophy locus.
ABSTRACT Schnyder's crystalline corneal dystrophy (SCCD) is a rare autosomal dominant eye disease with a spectrum of clinical manifestations that may include bilateral corneal clouding, arcus lipoides, and anterior corneal crystalline cholesterol deposition. We have previously performed a genome-wide linkage analysis on two large Swede-Finn families and mapped the SCCD locus to a 16-cM interval between markers D1S2633 and D1S228 on chromosome 1p36. We have collected 11 additional families from Finland, Germany, Turkey, and USA to narrow the critical region for SCCD. Here, we have used haplotype analysis with densely spaced microsatellite markers in a total of 13 families to refine the candidate interval. A common disease haplotype was observed among the four Swede-Finn families indicating the presence of a founder effect. Recombination results from all 13 families refined the SCCD locus to 2.32 Mbp between markers D1S1160 and D1S1635. Within this interval, identity-by-state was present in all 13 families for two markers D1S244 and D1S3153, further refining the candidate region to 1.58 Mbp.
- SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: To identify the molecular defect causing Schnyder crystalline corneal dystrophy (SCCD) in a Chinese family with bilateral corneal abnormalities. The Chinese SCCD family was subjected to a complete ophthalmic examination that included slit-lamp examination and slit-lamp photography to assess and document the crystalline deposits and arcus lipoides. In vivo laser scanning confocal microscopy and Fourier-domain OCT were also performed on both eyes of SCCD patients. Blood samples were taken for subsequent genetic analysis. The two coding exons of the UbiA prenyltransferase domain-containing protein 1 (UBIAD1) gene were screened for mutations by direct sequencing. We report on a novel heterozygous mutation of UBIAD1, G98S, in two patients with SCCD. The identified molecular defect cosegregates with the disease and is not found in 50 unaffected individuals. Morphological evaluation on SCCD by in vivo laser scanning confocal microscopy and Fourier-domain OCT highlighted pathological observations at the level of Bowman's membrane and anterior stroma. The newly identified mutation expands the spectrum of mutations in UBIAD1 that may cause pathological corneal cholesterol deposition. Observations by in vivo laser scanning confocal microscopy and Fourier-domain OCT were consistent with the previous histopathologic descriptions of SCCD.Molecular vision 02/2009; 15:1463-9. · 1.99 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Schnyder corneal dystrophy (SCD) is an autosomal dominant disease characterized by germline variants in UBIAD1 introducing missense alterations leading to deposition of cholesterol in the cornea, progressive opacification, and loss of visual acuity. UBIAD1 was recently shown to synthesize menaquinone-4 (MK-4, vitamin K(2) , but causal mechanisms of SCD are unknown. We report a novel c.864G>A UBIAD1 mutation altering glycine 177 to glutamic acid (p.G177E) in six SCD families, including four families from Finland who share a likely founder mutation. We observed reduced MK-4 synthesis by UBIAD1 altered by SCD mutations p.N102S, p.G177R/E, and p.D112N, and molecular models showed p.G177-mutant UBIAD1 disrupted transmembrane helices and active site residues. We show UBIAD1 interacts with HMGCR and SOAT1, enzymes catalyzing cholesterol synthesis and storage, respectively, using yeast two-hybrid screening and immunoprecipitation. Docking simulations indicate cholesterol binds to UBIAD1 in the substrate binding cleft and binding overlaps with GGPP binding, a MK-4 substrate, suggesting potential competition between these metabolites. Impaired MK-4 synthesis is a biochemical defect identified in SCD suggesting UBIAD1 links vitamin K and cholesterol metabolism through physical contact between enzymes and metabolites. Our data suggests a role for endogenous MK-4 in maintaining cornea health and visual acuity.Human Mutation 11/2012; · 5.21 Impact Factor
- Journal of the Korean Ophthalmological Society 01/2010; 51(3).