Four mutations (three novel, one founder) in TACSTD2 among Iranian GDLD patients.

PURPOSE: To perform a mutation screening of TACSTD2 in 13 Iranian Gelatinous Drop-like Corneal Dystrophy (GDLD) pedigrees. To assess genotype-phenotype correlations. To determine intragenic SNP haplotypes associated with the mutations, so as to gain information on their origin. METHODS: The coding region of TACSTD2 was sequenced in the probands of 13 unrelated Iranian GDLD pedigrees. Variations were assessed in other available affected and unaffected family members and in unrelated normal control subjects by restriction fragment length polymorphism (RFLP). The variations were classified as being associated with disease if they segregated with the disease phenotype in the families, were not observed in 100 control individuals, disrupted protein expression, or affected conserved positions in the coded protein. Three intragenic single-nucleotide polymorphisms (SNPs) were used to define haplotypes associated with putative disease-causing mutations. RESULTS: The probands were each homozygous for one of four putative disease-causing variations observed in TACSTD2: C66X, F114C, L186P, and E227K. Three of these are novel. E227K was found in 10 of the Iranian patients. There were some phenotypic differences among different patients carrying this mutation-for example, with respect to age at onset. Genotyping of intragenic SNPs identified four haplotypes. C66X, F114C, and L186P were each associated with a haplotype common among control chromosomes, whereas all E227K alleles were associated with a haplotype not found among the control chromosomes. CONCLUSIONS: Although mutations in TACSTD2 among Iranian patients with GDLD were heterogeneous, E227K was found to be a common mutation. It is suggested that E227K may be a founder mutation in this population. Based on positions of known mutations in TACSTD2, significance of the thyroglobulin domain of the TACSTD2 protein in the pathogenesis of GDLD is suggested.

Homozygous missense mutation in fibulin-5 in an Iranian autosomal recessive cutis laxa pedigree and associated haplotype.

Cutis laxa is a rare group of inherited and acquired disorders characterized by loose and redundant skin with reduced elasticity. Mutations in the elastin coding gene have been shown to cause autosomal dominant cutis laxa in three families. A homozygous mutation in the fibulin-5 coding gene was discovered in a Turkish pedigree showing recessive inheritance, and a different mutation in this gene was found in the heterozygous state in a sporadic case of the disease. Here, we report the third case of a mutation in the fibulin-5 coding gene in a recessive Iranian cutis laxa pedigree. The mutation is the same as previously reported in the Turkish pedigree, further confirming that it is causative of disease. A haplotype consisting of seven intragenic sequence variations common to both pedigrees is described for the mutation-carrying fibulin-5 allele.