Postnatal knockdown of dok-7 gene expression in mice causes structural defects in neuromuscular synapses and myasthenic pathology.
The neuromuscular junction (NMJ) is a synapse between a motor neuron and skeletal muscle and is required for muscle contraction. The formation and maintenance of NMJs are governed by the muscle-specific receptor tyrosine kinase MuSK. We previously showed that the muscle cytoplasmic protein Dok-7 is an essential activator of MuSK. Indeed, mice lacking either Dok-7 or MuSK form no NMJs, and defects in the human DOK7 gene underlie a congenital myasthenic syndrome (an NMJ disorder). However, it remains unproven whether Dok-7 is required for the postnatal maintenance of NMJs. In this study, we generated recombinant adeno-associated virus (AAV) vectors encoding short hairpin RNAs targeting the mouse dok-7 gene (AAV-shD7). Systemic administration of AAV-shD7 into 2-week-old mice down-regulated dok-7 expression in muscle and induced myasthenic symptoms including reduction in body weight and motor function. Moreover, AAV-shD7 treatment suppressed MuSK-dependent gene expression of NMJ components and reduced the size of NMJs. These results demonstrate that correct, physiological levels of dok-7 expression are required for the postnatal maintenance of NMJs.
Division of Genetics, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan.
Takahiro
T
Eguchi
Division of Genetics, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan.
Tohru
T
Tezuka
Division of Genetics, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan.
Sadanori
S
Miyoshi
Division of Genetics, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan.
Yuji
Y
Yamanashi
D000818:Animals; D055785:Gene Knockdown Techniques; D005822:Genetic Vectors; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism*; D009157:Myasthenia Gravis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009469:Neuromuscular Junction / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism
C511694:Dok-7 protein, mouse; D009124:Muscle Proteins; D034741:RNA, Small Interfering