Novel mutations in the helix termination motif of keratin 3 and keratin 12 in 2 Taiwanese families with Meesmann corneal dystrophy.
OBJECTIVE
To analyze mutations of the keratin 3 gene (KRT3) and keratin 12 gene (KRT12) in 2 Taiwanese families with Meesmann corneal dystrophy (MCD).


METHODS
Diagnosis of MCD was confirmed by slit-lamp examination of the cornea in 4 members of family 1 and 6 members of family 2. All exons and flanking intron boundaries of KRT3 and KRT12 were amplified by polymerase chain reaction (PCR), and products were subjected to direct sequencing. Restriction fragment length polymorphism analysis (RFLP) with created mismatch primers, Bst XI and Nsp I, was used to confirm the presence of the mutations in affected individuals in family 1 and family 2, respectively.


RESULTS
A novel heterozygous missense mutation (1508G-->C), predicting the substitution of a proline for an arginine (R503P) was detected in the helix termination motif of the keratin 3 polypeptide in family 1. Another novel heterozygous missense mutation (1286A-->G), predicting the substitution of a cysteine for a tyrosine at codon 429 (Y429C) was detected in the helix termination motif of the keratin 12 polypeptide in family 2. These 2 mutations were excluded from 50 normal controls by RFLP analysis, indicating that they were not common polymorphisms.


CONCLUSIONS
A novel missense mutation (R503P) in KRT3 and another novel missense mutation (Y429C) in KRT12 lead to MCD in 2 unrelated Taiwanese families. The mutant codons in our study are all located in the highly conserved alpha-helix-termination motif, which is essential for keratin filament assembly. Mutation at this area may account for the disruption of keratin filament assembly, leading to MCD.
Chen
Ying-Ting
YT
Department of Ophthalmology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Tseng
Sung-Huei
SH
Chao
Sheau-Chiou
SC
D002648:Child; D003315:Cornea / Q000473:pathology; D003317:Corneal Dystrophies, Hereditary / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D004247:DNA / Q000235:genetics*; D005091:Exons; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D053551:Keratin-12; D053558:Keratin-3; D007633:Keratins / Q000235:genetics*; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D013624:Taiwan
C507494:KRT12 protein, human; C479360:KRT3 protein, human; D053551:Keratin-12; D053558:Keratin-3; D007633:Keratins; D004247:DNA