Objective: To determine the causative mutation of myocilin gene and to investigate its pathogenic function in a large Chinese pedigree (GZ.1) with familial open-angle glaucoma.
Methods: Genome-wide scanning was performed and the Lod scores were calculated. Candidate gene was amplified and screened for mutations using direct sequencing. To elucidate its expression, distribution and cytotoxicity of mutant myocilin, human trabecular cells (HTM) cells were transfected with pcDNA-wild-type and mutant myocilin vectors using liposomes.
Results: Mutation analysis of the myocilin gene showed a C-to-T transition at the 1, 109 th nucleotide in exon 3 resulting in a change of amino acid from proline to leucine (Pro370Leu). This mutation cosegregated with all affected individuals (16/16) and never presented in unaffected individuals (0/8). In transfected HTM cells, the mutant myocilin protein was not correctly processed in ER and accumulated as aggresome-like structures in the cytoplasma instead of being secreted. In addition, the expression of mutant protein also led to apoptosis of trabecular cells and the occurrence of.
Conclusion: The mutation of Pro370Leu in myocilin gene could cause the accumulation of misfolding myocilin protein in HTM cells, which might lead to glaucoma in GZ.1 pedigree.