Optic nerve alterations in PTEN +/- mice.

PURPOSE To study the morphologic characteristics of the optic nerve (ON) by using an experimental model of knockout mice for the expression of the PTEN gene, mainly involved in cell cycle arrest, apoptosis control, and cell size regulation. METHODS The eyeballs with the retrobulbar ON attached were obtained from 26-week-old mice. By using morphologic and morphometric techniques, light and electron transmission microscopy, the ON characteristics were determined in two groups of mice: 1) 'wild type' mice as the control group (C-G; n=15), 2) heterozygous knockout mice (+/-) for the PTEN gene (PTEN-G; n=15). Glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) were studied using Western blot and immunoblotting approaches. RESULTS The ON cross-sectional area was significantly higher in the PTEN-G than in the C-G (p<0.001). The axon sizes in mutant animals were much larger than in wild-type mice (p<0.001). No significant differences were noticed between those groups regarding the number of axons forming the ON and the presence of intra-axonal degeneration, myelin sheath alterations, or axoplasm density. No differences were detected in developmental marker protein expression. CONCLUSIONS The morphologic and morphometric results suggest that heterozygous PTEN knockout mice had hypertrophic ON without ultrastructural alterations.