title: Mutations in the CHST6 gene in patients with macular corneal dystrophy: immunohistochemical evidence of heterogeneity.
abstract: OBJECTIVE
  Macular corneal dystrophy (MCD) is an autosomal recessive disorder leading to severe visual impairment. The carbohydrate sulfotransferase 6 (CHST6) gene, which encodes the corneal N-acetylglucosamine 6-O-sulfotransferase on 16q22 has been identified as a causative gene for MCD. The purpose of this study was to identify mutations in CHST6 in Japanese patients with MCD and evaluate them by means of immunohistochemistry.
  
  
  METHODS
  CHST6 was screened in 7 patients and 45 healthy control subjects. Genomic DNA was isolated, and the open reading frame (ORF) of CHST6 was amplified by polymerase chain reaction (PCR). PCR products were analyzed by direct sequencing and restriction enzyme digestion. Immunohistochemistry with a monoclonal anti-keratan sulfate (KS) antibody was performed on corneas of four patients from three families.
  
  
  RESULTS
  Three novel mutations (P204Q, R205L, and R177H) and two previously reported mutations (R211W and A217T) were identified in the ORF of CHST6. P204Q, R205L, and R211W were found to be homozygous and R177H and A217T compound heterozygous with R211W on another allele. Immunohistochemistry revealed that R205L homozygous cornea had negative reactivity against the anti-KS antibody, representing type I MCD, and that R211W homozygous and R211W/A217T compound heterozygous corneas had negative or very weak reactivity in the stroma with antibody positive deposits, which were distinct from any previously reported types.
  
  
  CONCLUSIONS
  Two mutations (homozygoous R211W and compound heterozygous R211W/A217T) should be subclassified immunohistochemically into new phenotypes of MCD. This heterogeneity could provide further insights into the pathogenesis of MCD.
authors.affiliation: Department of Ophthalmology, School of Medicine, Juntendo University, Tokyo, Japan. hasenobu@tkg.att.ne.jp
authors.forename: Nobuko
authors.initials: N
authors.lastname: Iida-Hasegawa
authors.forename: Atushi
authors.initials: A
authors.lastname: Furuhata
authors.forename: Hiroo
authors.initials: H
authors.lastname: Hayatsu
authors.forename: Akira
authors.initials: A
authors.lastname: Murakami
authors.forename: Keiko
authors.initials: K
authors.lastname: Fujiki
authors.forename: Kiyoo
authors.initials: K
authors.lastname: Nakayasu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kanai
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D003315:Cornea / Q000201:enzymology; D003317:Corneal Dystrophies, Hereditary / Q000201:enzymology* / Q000235:genetics*; D004252:DNA Mutational Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D018740:Genetic Heterogeneity; D006801:Humans; D007632:Keratan Sulfate / Q000097:blood; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D016366:Open Reading Frames; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015238:Sulfotransferases / Q000235:genetics* / Q000378:metabolism*; D000097811:Carbohydrate Sulfotransferases
chemical_list: D000911:Antibodies, Monoclonal; D007632:Keratan Sulfate; D015238:Sulfotransferases; D000097811:Carbohydrate Sulfotransferases