CHST6 Mutations and Histopathologic Study in Macular Corneal Dystrophy
|School||Dalian Medical University|
|Keywords||Macular corneal dystrophy CHST6 gene Gene mutation Histopathology|
Objective: macular corneal dystrophy (Macular Corneal Dystrophy, MCD) is a rare corneal stroma dystrophy, autosomal recessive genetic disease. Groenouw first described in 1980, it is also known Groenouw II type corneal dystrophy. Clinical manifestations of progressive loss of vision, photophobia, and ocular discomfort, etc., both eyes slit lamp examination showed diffuse stromal haze, between (or) with focal patchy white turbid, from the central to peripheral and deep development, and eventually require a corneal transplant. 2000 Akama, etc.  first identified genes that cause macular corneal dystrophy as a new carbohydrate sulfotransferase gene that CHST6 gene, located on chromosome 16q22 and on. CHST6 gene encoding N-acetylglucosamine cornea -6 - sulfotransferase (corneal N-acetylglucosamine-6-sulphotransferase, GlcNAc6ST), an enzyme of the sulfate ions is passed to N-acetyl glucosamine sulfate, the substance in the cornea keratin protein polysaccharide biosynthesis. CHST6 mutations cause this enzyme activity decreased or disappeared, making the cornea keratan sulfate (keratan sulphate, KS) and other glycosaminoglycan synthesis abnormalities, abnormal material deposited in the cornea, corneal cells and destroy the fiber structure, eventually leading to corneal opacity [2 ]. After numerous scholars have since Akama in their countries MCD patients CHST6 gene mutations were found, China's macular corneal dystrophy have more research, but most are limited to case reports and histopathological studies on gene mutations have less reported. The experiment in Northeast China a macular corneal dystrophy pedigrees three positive signs were studied: DNA was extracted from peripheral venous blood drawn and make CHST6 gene sequencing of positive and negative way; pair of penetrating keratoplasty for corneal tissue disease patients physical examination, to further explore and CHST6 macular corneal dystrophy gene mutation study the relationship and histopathological changes. Methods: Northeast China a macular corneal dystrophy pedigrees have been found in the same generation three patients were male and 2 female one person. Was extracted from peripheral blood 2ml, extraction of genomic DNA. CHST6 gene has four exons coding region in the third exon, polymerase chain reaction (PCR) for CHST6 gene coding region of the gene was amplified, and then sequenced. Two patients were taken keratoplasty 1/2 rows of 4% formaldehyde corneal lesions were fixed, paraffin-embedded sections were alcian blue (AB) and alcian blue - periodic acid Gaucher (AB-PAS ) staining were observed under light microscope; against other 1/2 corneal lines were fixed in 2.5% glutaraldehyde, embedded in epoxy resin, after staining and transmission electron microscopy imaging. Results: Three patients in the pedigree of the gene coding region CHST6 pros bidirectional sequencing and found a common mutation point: The third exon 62 bp insertion at nucleotide G, former Article 62 bp T → A, resulting in an open reading frame of the change; AB staining: visible corneal stroma cytoplasm and spandex blue staining; AB-PAS staining is visible in the corneal epithelial thinning, a large red and blue skin on the patchy staining substances ; transmission electron microscopy shows a large circular subepithelial corneal substance. Conclusion: This study confirms the CHST6 coding region mutations c.61 6 2insG this is due to macular corneal dystrophy pedigrees direct cause corneal opacity, this mutation has not been found so far.