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Optic nerve degeneration in a murine model of juvenile ceroid lipofuscinosis.

PURPOSE
To investigate optic nerve degeneration associated with CLN3 deficiency in a murine model of juvenile neuronal ceroid lipofuscinosis (Batten disease).


METHODS
Using light and electron microscopy, the density and diameter of axons and the thickness of myelin in optic nerve were compared between age-matched cln3 knock-out (cln3-/-) and wild-type (129ev/TAC) mice. Western blot analysis was used to assay expression of Cln3 in mouse and primate retina and optic nerve.


RESULTS
Morphologically identified mast cells were present in the meningeal sheaths surrounding the cln3-/- nerve and in the nerve itself. The cln3-/- optic nerve exhibited an overall loss of uniformity and integrity. Axon density in cln3-/- optic nerve was only 64% of that in wild-type optic nerve (P < 0.01). Accounting for differences in axon density, the diameter of axons in cln3-/- optic nerve was 1.2 times greater than in wild-type optic nerve (P < 0.01). Electron micrographs revealed large spaces between axons and 32% thinner myelin surrounding axons in cln3-/- mice than in wild type (P < 0.01). Western blot analysis demonstrated that Cln3 was expressed in retinas and optic nerves of mouse and primate.


CONCLUSIONS
The presence of apparent mast cells in cln3-/- optic nerve suggests compromise of the blood-brain barrier. The absence of Cln3 causes loss of axons, axonal hypertrophy, and a reduction in myelination of retinal ganglion cells. Furthermore, expression of CLN3 in mouse and primate optic nerve links degeneration to loss of Cln3.