A Missense Mutation in the M1S1 Gene Found in a Turkish Patient With Gelatinous Droplike Corneal Dystrophy

Abstract

To report a missense mutation in the M1S1 gene found in a Turkish patient with gelatinous droplike corneal dystrophy (GDLD). A Turkish patient with GDLD was examined. Keratoplasty was performed and a diagnosis of GDLD was made by histopathologic and electron microscopic studies. Genomic DNA was extracted from peripheral blood and the paraffin-embedded tissue of the corneal button. A 248-bp DNA fragment of the M1S1 gene was amplified, and sequencing reactions were analyzed. The results were compared with those of 30 healthy, nonrelated individuals. On light microscopic examination, sheets of amorphous amyloid deposits were observed in subepithelial regions and in the anterior and midcorneal stroma. Electron microscopy revealed dense collagen fibrils and entrapped filamentous amyloid fibrils in the corneal stroma. A substitution of T-->C at nucleotide 557 was found in the peripheral blood DNA sequence analysis, which resulted in an amino acid substitution of L-->P (L186P). Results were confirmed by direct DNA sequencing analysis of the paraffin-embedded corneal button. The patient with GDLD was homozygous for the mutation, resulting in amino acid substitution L186P. This is the first report, to our knowledge, of a homozygous mutation (L186P) in the M1S1 gene found in a Turkish patient. The clinical examination may be insufficient in sporadic cases, and histopathologic examination and molecular genetic analysis can accelerate and improve the accuracy of diagnosis in patients with GDLD.