Cognitive dysfunction in mice with passively induced MuSK antibody seropositive myasthenia gravis

Recent reports on cognitive dysfunction, in addition to skeletal muscle fatigue, in muscle-specific tyrosine kinase antibody seropositive (MuSK+) myasthenia gravis (MG) patients led us to study cognition in mice with MuSK+ passive transfer MG (PTMG). Twelve 7-week-old female wild-type C57BL/6J mice were passively immunized with IgG from MuSK+ MG patients and 12 control mice received intraperitoneal saline injections. Mice were evaluated with clinical, neurophysiological and behavioral tests (Barnes maze (BM) and novel object recognition (NOR)), and the muscles were immunostained to evaluate the neuromuscular junction in the end of the study. Two-thirds of the immunized mice developed clinically distinct MuSK+ PTMG. MuSK+ PTMG mice spent less time exploring the novel object in the NOR test (MuSK+ mice 36.4% ± 14.0 vs controls 52.4% ± 13.0, p = .02), unrelated to the muscle weakness and regardless of rodents' innate preference of novelty. In the BM test, control mice were more eager to use the direct strategy than the MuSK+ mice (MuSK+ 17.3% vs controls 29.5%, p = .02). Our findings shed new light on cognition dysfunction in human MuSK+ MG patients and indicate that recognition memory in the perirhinal cortex could be affected in MuSK+ MG.