Linkage of a gene for macular corneal dystrophy to chromosome 16.
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ABSTRACT:
SUBMITTER: Vance JM
PROVIDER: S-EPMC1914688 | biostudies-other | 1996 Apr
REPOSITORIES: biostudies-other
Publications
Linkage of a gene for macular corneal dystrophy to chromosome 16.
Vance J M JM Jonasson F F Lennon F F Sarrica J J Damji K F KF Stauffer J J Pericak-Vance M A MA Klintworth G K GK
American journal of human genetics 19960401 4
Autosomal recessive macular corneal dystrophy (MCD) is a heterogeneous disorder leading to visual impairment. Sixteen American and Icelandic families (11 type I and 5 type II) were analyzed for linkage, by use of 208 polymorphic microsatellite markers. A significant maximum LOD score Zmax of 7.82 at a maximum recombination fraction (thetamax) of .06 was found with the 16q22 locus D16S518 for MCD type I. In addition, a peak LOD score of 2.50 at a recombination fraction of .00 was obtained for the ...[more]
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Project description:PurposeTo identify the molecular genetic cause of macular corneal dystrophy (MCD) in four probands, and characterize phenotypic similarities between MCD and keratoconus.MethodsWe performed ophthalmological examination, Scheimpflug imaging (Pentacam, Oculus Inc.), histopathological examination of excised corneal buttons, and direct sequencing of the CHST6 coding region.ResultsPentacam measurements were taken in six eyes of three probands. All showed diffuse corneal thinning with paracentral steepening of the anterior corneal surface that was graded as keratoconus by the integrated software, but without associated ectasia of the posterior corneal surface or regional thinning. Homozygous or compound heterozygous CHST6 mutations were identified in all cases, including two novel mutations, c.13C>T; p.(Arg5Cys) and c.289C>T; p.(Arg97Cys).DiscussionLocalized elevation of the anterior corneal curvature can occur in MCD in the absence of other features of keratoconus. The identification of a further two Czech probands with the compound allele c.[484C>G; 599T>G] supports the enrichment of this allele in the study population.
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Project description:PurposeTo perform a genome-wide linkage screen with a single-nucleotide polymorphism (SNP) linkage panel to identify regions of genetic linkage in Fuchs endothelial corneal dystrophy (FECD) and to analyze affected individuals for mutations in the COL8A2 gene.MethodsNinety-two individuals from 22 families with FECD were identified from our multiplex FECD family cohort. A genome-wide linkage scan was performed using an SNP linkage panel. Parametric two-point linkage analyses were calculated and nonparametric multipoint linkage analyses were performed on chromosomes with two-point LOD scores (HLOD) > 1.0. All affected individuals were analyzed for the two previously reported FECD mutations in the COL8A2 gene (L450W and Q455K).ResultsThe genome-wide analysis identified five regions with linkage signals from all analyses on chromosomes 1, 7, 15, 17, and X. The highest two-point HLODs were found on the long arm of chromosome 15 with an HLOD of 3.26 for the recessive model and 2.48 for the dominant model. Multipoint linkage analysis also identified a linkage peak on the long arm of chromosome 15 with a LOD > 1. The region of linkage on chromosome 1p, driven by two multigenerational FECD families with a two-point LOD > 2, was adjacent to the previously identified COL8A2 gene; however, the two reported mutations in COL8A2 were not identified in any of the 56 affected individuals in the 92 samples tested.ConclusionsGenome-wide linkage analysis was used to identify potential linkage regions on chromosomes 1, 7, 15, 17, and X for FECD. The previously reported mutations in the COL8A2 gene were not found in the 92 samples tested.
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Project description:Macular corneal dystrophy (MCD) is an autosomal recessive disorder mainly caused by gene mutations of carbohydrate sulfotransferase (CHST6) leading to bilateral visual impairment. Because the mechanism underlying this degeneration remains poorly understood, we investigated molecular alterations and pathways that may be involved in MCD in this issue. Different mutation sites were screened by direct sequencing of the coding region of CHST6. In addition, we described morphological changes in MCD keratocytes by light microscopy and electron microscopy and determined the relationship between the development of this disease and the occurrence of apoptosis through flow cytometry, cell counting kit-8, colony formation assay and other experiments. Western blotting and quantitative real-time polymerase chain reaction were used to determine if endoplasmic reticulum (ER) stress was activated. We found 10 kinds of mutations among these families with 3 novel mutations included. The percentage of apoptotic keratocytes increased in MCD patients; furthermore, the expression of apoptosis related protein B-cell lymphoma-2 (Bcl-2) was down-regulated while Bcl-2 associated X protein was upregulated. Finally, ER stress was activated with the upregulation of glucose-regulated protein 78 and CCAAT-enhancer-binding protein homologous protein. Our clinical and in vitro results suggest that the CHST6 mutation associated with MCD is associated with apoptosis, and ER stress is probably involved in this apoptosis pathway.
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Project description:PURPOSE: To characterize mutations within the carbohydrate sulfotransferase 6 (CHST6) gene in Iranian subjects from 12 families with macular corneal dystrophy (MCD). METHODS: Genomic DNA was extracted from peripheral blood of 20 affected patients and 60 healthy volunteers followed by polymerase chain reaction (PCR) and direct sequencing of the CHST6 coding region. The observed nucleotide sequences were then compared with those found by investigators in other populations with MCD and in the controls. RESULTS: Analysis of CHST6 revealed 11 different mutations. These mutations were comprised of six novel missense mutations (p.F55L, p.P132L, p.S136G, p.C149Y, p.D203Y, and p.H249R), one novel nonsense mutation (p.S48X), one novel frame shift (after P297), and three previously reported missense mutations (p.P31L, p.C165Y, and p.R127C). The majority of the detected MCD mutations are located in the binding sites or the binding pocket, except the p.P31L and p.H249R mutations. CONCLUSIONS: Nucleotide changes within the coding region of CHST6 are predicted to significantly alter the encoded sulfotransferase within the evolutionary conserved sequences. Our findings show that CHST6 mutations are responsible for the pathogenesis of MCD in Iranian patients. Moreover, the observation that some cases of MCD cannot be explained by mutations in the coding region of CHST6 suggests that MCD may result from possible upstream rearrangements in the CHST6 genomic region.
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Project description:Bietti crystalline corneoretinal dystrophy (BCD) is an autosomal recessive retinal degeneration characterized by multiple glistening intraretinal dots scattered over the fundus, degeneration of the retina, and sclerosis of the choroidal vessels, ultimately resulting in progressive night blindness and constriction of the visual field. Although BCD has been associated with abnormalities in fatty-acid metabolism and absence of fatty-acid binding by two cytosolic proteins, the genetic basis of BCD is unknown. We report linkage of the BCD locus to D4S426 (maximum LOD score [Z(max)] 4.81; recombination fraction [straight theta] 0), D4S2688 (Zmax=3.97; straight theta=0), and D4S2299 (Zmax=5.31; straight theta=0), on chromosome 4q35-4qtel. Multipoint analysis confirmed linkage to the region telomeric of D4S1652 with a Z(max) of 5.3 located 4 cM telomeric of marker D4S2930.
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