A mutation within exon 14 of the TGFBI (BIGH3) gene on chromosome 5q31 causes an asymmetric, late-onset form of lattice corneal dystrophy.
OBJECTIVE
Two forms of autosomal-dominant lattice corneal dystrophy (LCD), types I and IIIA, have previously been shown to be caused by different mutations within the transforming growth factor, beta-induced (TGFBI) gene. A clinical and molecular analysis of three unrelated kindreds with a clinically distinct late-onset LCD was undertaken to determine whether this phenotype is also caused by mutations within the TGFBI gene.


METHODS
Experimental study.


METHODS
Thirty-two members of three kindreds with corneal dystrophy. DNA from 100 normal control subjects was used as a control population.


METHODS
Members of three kindreds with LCD were examined clinically, and blood samples were taken for DNA analysis. Mutation analysis was undertaken on all individuals for the coding region of the TGFBI gene by means of polymerase chain reaction (PCR) followed by single-stranded conformation polymorphism/heteroduplex analysis, subcloning, and sequencing.


METHODS
Detection of mutations within the TGFBI gene.


RESULTS
Clinical examination revealed a form of LCD that was bilateral in all but one case, with onset around the fourth to fifth decade. The majority of cases showed significant asymmetry, and in one case there was evidence of onset directly after minor superficial corneal trauma. Molecular analysis in all families demonstrated sequence changes within exon 14 of the TGFBI gene on chromosome 5q31, at codon 622 in family 3, and at codon 626 in families 1 and 2, which are presumed to be responsible for the disease.


CONCLUSIONS
Previously, a late-onset form of LCD, termed IIIA, was shown to be caused by a P501T mutation in exon 11 of TGFBI. The authors present the first description of mutations in exon 14 of TGFBI causing an LCD, also of late onset. Although the condition presented is morphologically and histopathologically typical of an isolated lattice dystrophy, the age of onset and clinical course is not typical of type I, III, or IIIA lattice dystrophy. This, in conjunction with recent developments in our understanding of the molecular genetics of these disorders, calls into question the usefulness and validity of the current classification of the isolated lattice dystrophies.
D000328:Adult; D017668:Age of Onset; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics*; D003315:Cornea / Q000473:pathology; D003317:Corneal Dystrophies, Hereditary / Q000235:genetics* / Q000473:pathology; D004247:DNA / Q000032:analysis; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D005091:Exons / Q000235:genetics*; D016326:Extracellular Matrix Proteins; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D016212:Transforming Growth Factor beta / Q000235:genetics*; D000099222:betaIG-H3 Protein