Mutations in the myocilin gene (MYOC) are causative for 10% of cases with 
juvenile open-angle glaucoma and 3-4% of those with primary open-angle glaucoma. 
Myocilin is a secreted protein with relatively ill-defined matricellular 
properties. Despite its high expression in the eye, myocilin-deficient mice have 
originally been reported to have no obvious ocular phenotype. Here we revisited 
the ocular phenotype of myocilin-deficient mice and detected a higher number of 
neurons in their inner (INL) and outer (ONL) nuclear layers, as well as a higher 
number of retinal ganglion cells (RGC) and their axons. The increase in retinal 
neurons appears to be caused by a decrease in programmed developmental cell 
death, as apoptosis of retinal neurons between postnatal days 4 and 10 was found 
to be attenuated when compared to that of wildtype littermates. In contrast, 
when Myoc(-/-) mice were crossed with βB1-crystallin-MYOC mice with ectopic 
overexpression of myocilin in the eye, no differences in developmental 
apoptosis, RGC number and INL thickness were observed when compared to wildtype 
littermates. The amounts of the anti-apoptotic Bcl-2-like protein 1 (BCL2L1, 
Bcl-xL) and its mRNA were increased in retinae of Myoc(-/-) mice, while lower 
amounts of BCL2L1 and its mRNA were detected in mixed 
Myoc(-/-)/βB1-crystallin-MYOC mice. The structural differences between Myoc(-/-) 
mice and wildtype littermates did not result in functional differences as 
measured by electroretinography. Noteworthy though mixed 
Myoc(-/-)/βB1-crystallin-MYOC mice with ocular overexpression of myocilin had 
significant cone function deficits. Myocilin appears to modulate apoptotic death 
of retinal neurons likely by interacting with the intrinsic apoptotic pathway.