Retinal Pathology in a Canine Model of Late Infantile Neuronal Ceroid Lipofuscinosis
Martin L. Katz 1*,
Joan R. Coates 2,
Jocelyn J. Cooper 3,
Dennis P. O'Brien 2,
Manbok Jeong 2,
and
Kristina Narfstrom 2
1 Ophthalmology, University of Missouri School of Medicine, Columbia, Missouri, United States
2 Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, United States
3 Department of Small Animal Clinical Sciences, Texas A&M University, College Station, Texas, United States
* To whom correspondence should be addressed. E-mail: katzm{at}health.missouri.edu.
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Abstract |
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PURPOSE. Late infantile neuronal ceroid lipofuscinosis (NCL) is an inherited disorder characterized by progressive vision loss. The disease results from mutations in the TPP1 (CLN2) gene. Studies were undertaken to characterize the effects of a TPP1 frameshift mutation on the retina in Dachshunds.
METHODS. A litter of 4 puppies consisting of one homozygous affected dog, two heterozygotes, and one homomzygous normal dog were monitored for neurological and retinal changes to 10 months of age. The affected and homozygous normal dogs, as well as one of the heterozygotes, were then euthanized and the retinas were examined morphologically.
RESULTS. The affected dog exhibited normal visual behavior and retinal function at 3 months of age, but vision was clearly impaired by 7 months, with markedly reduced ERG b-wave amplitudes. Beyond 7 months of age, the affected dog was functionally blind and pupillary light reflexes and ERG response amplitudes continued to decline through 10 months of age. Both rod and cone system functions were severely impaired. The retina exhibited accumulation of autofluorescent storage bodies with distinctive curvilinear contents. Substantial cell loss occurred in the inner nuclear layer, with a smaller reduction in photoreceptor cell density.
CONCLUSIONS. The canine TPP1 mutation results in progressive vision loss and retinal degeneration similar to that which occurs in human late infantile NCL. With the canine model, the natural history of disease progression in the retina provides a better understanding of the disease pathology and provides objective markers that can be used to assess the efficacy of therapeutic interventions.
Key Words:
electroretinography, genetic diseases, outer segments, retinal degeneration, scotopic sensitivity
