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Macular corneal dystrophy in a Chinese family related with novel mutations of CHST6.

Dang X, Zhu Q, Wang L, Su H, Lin H, Zhou N, Liang T, Wang Z, Huang S, Ren Q, Qi Y - Mol. Vis. (2009)

Bottom Line: The two transversions resulted in the substitution of a stop codon for glutamine at codon 298 (p.Q298X) and a missense mutation at codon 358, tyrosine to histidine (p.Y358H).Those novel compound heterozygous mutations were thought to contribute to the loss of CHST6 function, which induced the abnormal metabolism of keratan sulfate (KS) that deposited in the corneal stroma.It could be proved by the observation of a positive stain reaction and the enlarged collagen fibers as well as hyperplastic fibroblasts under microscopes.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.

ABSTRACT

Purpose: To identify mutations in the carbohydrate sulfotransferase gene (CHST6) for a Chinese family with macular corneal dystrophy (MCD) and to investigate the histopathological changes in the affected cornea.

Methods: A corneal button of the proband was obtained by penetrating keratoplasty. The half button and ultrathin sections from the other half button were examined with special stains under a light microscope (LM) and an electron microscope (EM) separately. Genomic DNA was extracted from peripheral blood of 11 family members, and the coding region of CHST6 was amplified by the polymerase chain reaction (PCR) method. The PCR products were analyzed by direct sequencing and restriction enzyme digestion.

Results: The positive reaction to colloidal iron stain (extracellular blue accumulations in the stroma) was detected under light microscopy. Transmission electron microscopy revealed the enlargement of smooth endoplasmic reticulum and the presence of intracytoplasmic vacuoles. The compound heterozygous mutations, c.892C>T and c.1072T>C, were identified in exon 3 of CHST6 in three patients. The two transversions resulted in the substitution of a stop codon for glutamine at codon 298 (p.Q298X) and a missense mutation at codon 358, tyrosine to histidine (p.Y358H). The six unaffected family individuals carried alternative heterozygous mutations. These two mutations were not detected in any of the 100 control subjects.

Conclusions: Those novel compound heterozygous mutations were thought to contribute to the loss of CHST6 function, which induced the abnormal metabolism of keratan sulfate (KS) that deposited in the corneal stroma. It could be proved by the observation of a positive stain reaction and the enlarged collagen fibers as well as hyperplastic fibroblasts under microscopes.

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Related in: MedlinePlus

Direct sequencing analysis of the coding region of CHST6. A: Normal sequence at codon 298. B: Sequence of the coding region of CHST6 in the proband revealed a change of the nucleotide at codon 298 (CAG→TAG). C: Normal sequence at codon 358. D: Sequence of the coding region of CHST6 in the proband showed a substitution at codon 358 (TAC→CAC).
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f5: Direct sequencing analysis of the coding region of CHST6. A: Normal sequence at codon 298. B: Sequence of the coding region of CHST6 in the proband revealed a change of the nucleotide at codon 298 (CAG→TAG). C: Normal sequence at codon 358. D: Sequence of the coding region of CHST6 in the proband showed a substitution at codon 358 (TAC→CAC).

Mentions: CHST6 is 16.9 kb in length and consists of four exons of which only exon 3 contains the coding region. Two mutations, c. 892C>T and c. 1072T>C, were identified on each allele of exon 3. The first heterozygous change from the maternal allele, a c. 892C>T transition, occurred at the first nucleotide position of codon 298, predicting a change of amino acid glutamine to a stop codon (p.Q298X). The other change on the paternal allele, a c. 1072T>C transition, was identified at the second nucleotide position of codon 358, changing the amino acid from tyrosine to histidine (p.Y358H; Figure 5). Each patient (III:2, III:4, and III:6) in this family was found to have these two mutations within CHST6. The unaffected individuals II-2, III:1, and IV-1 were heterozygous with the nonsense change, c. 892C>T, while the other unaffected individuals II-3, III-5, and IV-2 were heterozygous with the missense change, c. 1072T>C.


Macular corneal dystrophy in a Chinese family related with novel mutations of CHST6.

Dang X, Zhu Q, Wang L, Su H, Lin H, Zhou N, Liang T, Wang Z, Huang S, Ren Q, Qi Y - Mol. Vis. (2009)

Direct sequencing analysis of the coding region of CHST6. A: Normal sequence at codon 298. B: Sequence of the coding region of CHST6 in the proband revealed a change of the nucleotide at codon 298 (CAG→TAG). C: Normal sequence at codon 358. D: Sequence of the coding region of CHST6 in the proband showed a substitution at codon 358 (TAC→CAC).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2666773&req=5

f5: Direct sequencing analysis of the coding region of CHST6. A: Normal sequence at codon 298. B: Sequence of the coding region of CHST6 in the proband revealed a change of the nucleotide at codon 298 (CAG→TAG). C: Normal sequence at codon 358. D: Sequence of the coding region of CHST6 in the proband showed a substitution at codon 358 (TAC→CAC).
Mentions: CHST6 is 16.9 kb in length and consists of four exons of which only exon 3 contains the coding region. Two mutations, c. 892C>T and c. 1072T>C, were identified on each allele of exon 3. The first heterozygous change from the maternal allele, a c. 892C>T transition, occurred at the first nucleotide position of codon 298, predicting a change of amino acid glutamine to a stop codon (p.Q298X). The other change on the paternal allele, a c. 1072T>C transition, was identified at the second nucleotide position of codon 358, changing the amino acid from tyrosine to histidine (p.Y358H; Figure 5). Each patient (III:2, III:4, and III:6) in this family was found to have these two mutations within CHST6. The unaffected individuals II-2, III:1, and IV-1 were heterozygous with the nonsense change, c. 892C>T, while the other unaffected individuals II-3, III-5, and IV-2 were heterozygous with the missense change, c. 1072T>C.

Bottom Line: The two transversions resulted in the substitution of a stop codon for glutamine at codon 298 (p.Q298X) and a missense mutation at codon 358, tyrosine to histidine (p.Y358H).Those novel compound heterozygous mutations were thought to contribute to the loss of CHST6 function, which induced the abnormal metabolism of keratan sulfate (KS) that deposited in the corneal stroma.It could be proved by the observation of a positive stain reaction and the enlarged collagen fibers as well as hyperplastic fibroblasts under microscopes.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.

ABSTRACT

Purpose: To identify mutations in the carbohydrate sulfotransferase gene (CHST6) for a Chinese family with macular corneal dystrophy (MCD) and to investigate the histopathological changes in the affected cornea.

Methods: A corneal button of the proband was obtained by penetrating keratoplasty. The half button and ultrathin sections from the other half button were examined with special stains under a light microscope (LM) and an electron microscope (EM) separately. Genomic DNA was extracted from peripheral blood of 11 family members, and the coding region of CHST6 was amplified by the polymerase chain reaction (PCR) method. The PCR products were analyzed by direct sequencing and restriction enzyme digestion.

Results: The positive reaction to colloidal iron stain (extracellular blue accumulations in the stroma) was detected under light microscopy. Transmission electron microscopy revealed the enlargement of smooth endoplasmic reticulum and the presence of intracytoplasmic vacuoles. The compound heterozygous mutations, c.892C>T and c.1072T>C, were identified in exon 3 of CHST6 in three patients. The two transversions resulted in the substitution of a stop codon for glutamine at codon 298 (p.Q298X) and a missense mutation at codon 358, tyrosine to histidine (p.Y358H). The six unaffected family individuals carried alternative heterozygous mutations. These two mutations were not detected in any of the 100 control subjects.

Conclusions: Those novel compound heterozygous mutations were thought to contribute to the loss of CHST6 function, which induced the abnormal metabolism of keratan sulfate (KS) that deposited in the corneal stroma. It could be proved by the observation of a positive stain reaction and the enlarged collagen fibers as well as hyperplastic fibroblasts under microscopes.

Show MeSH
Related in: MedlinePlus