Identification of mutations in the myocilin (MYOC) gene in Taiwanese patients with juvenile-onset open-angle glaucoma

Purpose: To investigate mutations in the promoter and coding regions of the myocilin (MYOC) gene in Taiwanese patients suffering from juvenile-onset open-angle glaucoma (JOAG). Methods: MYOC was analyzed for mutations in 48 unrelated Taiwanese probands with JOAG and in 100 healthy control subjects. Genomic DNA was extracted from peripheral blood leukocytes and then subjected to PCR to amplify exons, flanking introns and promoter regions of the MYOC gene. The amplified products were screened for base mutations by autosequence. Data from the two groups were then compared using the χ2 test. Finally, the levels of MYOC transcripts were predicted by a neural network prediction system to study whether the intron mutations have any effect on the level of mRNA expression. Results: The analysis revealed four MYOC mutations and six polymorphisms. The prevalence of MYOC gene mutations in this study was 12.5% (6/48). The mutations included one nonsense mutation (Arg46Stop; 3/ 6), one missense mutation (Val56A1a; 1/6), one intron mutation (c.604+228A>T; 1/6) as well as one mutation in the T-untranslated region (c.1515+73G>C; 1/6). In addition, although c.604+228A>T is an intron mutation and does not alter the content of the amino acid residue, the neural network prediction system revealed that it can potentially create a novel accept splice site during transcription. This mutation might affect the protein structure and consequently the normal function of myocilin. Conclusions: Our results indicate that the c.136C>T (Arg46Stop), c.158T>C (Val56A1a), c.604+228A>T, and c. 1515+73G>C mutations of MYOC may be associated with JOAG. In addition, we suggest that the c. 136C>T (Arg46Stop) mutation of MYOC is a hot spot in Taiwanese patients with JOAG.