A novel mutation of M1S1 gene found in a Vietnamese patient with gelatinous droplike corneal dystrophy.

To identify the genetic defect in the M1S1 gene responsible for gelatinous droplike corneal dystrophy (GDLD) in a Vietnamese family.Experimental study. Blood samples were collected from a patient and the unaffected members of a GDLD-affected family. Fifty normal unrelated subjects of Vietnamese origin were used as controls. Genomic DNA was extracted from blood leukocytes. DNA analysis of the M1S1 gene was performed using polymerase chain reaction and direct sequencing. Sequencing of the M1S1 gene revealed a deletion of a 12-base-pair (bp) fragment from nucleotide positions 772 to 783 [772 to 783del(ATCTATTACCTG)], resulting in a loss of four amino acids at codons 258 to 261 (L258-liter261del). Yet, an insertion of nucleotide T in place of the missing sequence (772insT) was found. This combined mutation was homozygous in the GDLD-affected patient and heterozygous in his unaffected son and younger sister. Such genetic alteration was excluded in the control population. This is the first report of a mutational analysis performed in a Vietnamese patient with GDLD. In this family, the novel 772 to 783del(ATCTATTACCTG) + 772insT mutation on the M1S1 gene was well cosegregated with the phenotype and thus expected to cause GDLD. Although the M1S1 gene was responsible for GDLD in Vietnamese patients, the mutation found here is completely different from that previously reported in Japanese patients, where GDLD is most frequently seen.