Myocilin and glaucoma: facts and ideas

Area of Science:

• Ophthalmology
• Genetics
• Molecular Biology

Background:

• Mutations in the MYOC gene, encoding myocilin, are linked to primary open-angle glaucoma (POAG).
• Myocilin is a secreted glycoprotein found in ocular tissues, particularly the trabecular meshwork (TM).
• Its precise role in aqueous humor dynamics and glaucoma pathogenesis is debated.

Purpose of the Study:

• To investigate the function of myocilin in the context of primary open-angle glaucoma.
• To explore the impact of MYOC mutations on myocilin secretion and cellular accumulation.
• To understand the relationship between myocilin expression and intraocular pressure regulation.

Main Methods:

• Analysis of MYOC gene mutations and their localization within the myocilin protein structure.
• Investigation of myocilin's presence and localization in ocular tissues and aqueous humor.
• Studies using recombinant myocilin and viral gene transfer to assess effects on aqueous humor outflow.
• Examination of myocilin expression regulation by dexamethasone, TGF-beta, and mechanical stretch.
• Phenotypic analysis of MYOC knockout mice.

Main Results:

• Most POAG-associated MYOC mutations are in the conserved olfactomedin domain.
• Conflicting results exist regarding myocilin's effect on aqueous humor outflow resistance.
• Myocilin expression in TM cells is induced by dexamethasone, TGF-beta, and mechanical stretch.
• MYOC knockout mice show no phenotype, suggesting glaucoma is not due to loss-of-function.
• Mutated myocilin appears to accumulate intracellularly rather than being secreted.

Conclusions:

• Mutated myocilin's intracellular accumulation may disrupt TM function, potentially leading to glaucoma.
• The exact physiological function of myocilin in the eye remains to be elucidated.
• Further research is needed to clarify myocilin's role in aqueous humor outflow and glaucoma development.