The mutants are characterized by muscle weakness and abnormal gait, which become apparent at four weeks of age (average onset 4 +/-0.5. weeks, n=74); an intense body tremor can be observed at 3 weeks or younger. The animals die relatively young (at approximately 6-9 weeks of age), i.e. prior to most phenotype screening, and a colony needs to be maintained through ovarian transplants.
Whole muscle mounts of the hind limb of a mutant (23 days of age) labeled with fluorescent-labeled bungarotoxin, SV2, and SMI 31 revealed abnormal formation of the neuromuscular junctions. The receptors appeared broken up and have not resolved into a smooth continuous shape. Standard pathology work-up on six additional mutants (23-30 days of age) showed vacuolation in the white matter of the medulla, cerebellum, and spinal cord. In addition, the eyes of affected mutants showed multi-focal abnormalities in the
retina.
Nuclei of the outer nuclear layer were displaced into the photoreceptor layer. Histology performed on one dead pup (~24 hours old) revealed a high septal defect in the heart. Hearts from the other mutants appeared normal.
