Abnormal development of the neuromuscular junction in Nedd4-deficient mice.
Nedd4 (neural precursor cell expressed developmentally down-regulated gene 4) is an E3 ubiquitin ligase highly conserved from yeast to humans. The expression of Nedd4 is developmentally down-regulated in the mammalian nervous system, but the role of Nedd4 in mammalian neural development remains poorly understood. Here we show that a null mutation of Nedd4 in mice leads to perinatal lethality: mutant mice were stillborn and many of them died in utero before birth (between E15.5-E18.5). In Nedd4 mutant embryos, skeletal muscle fiber sizes and motoneuron numbers are significantly reduced. Surviving motoneurons project axons to their target muscles on schedule, but motor nerves defasciculate upon reaching the muscle surface, suggesting that Nedd4 plays a critical role in fine-tuning the interaction between the nerve and the muscle. Electrophysiological analyses of the neuromuscular junction (NMJ) demonstrate an increased spontaneous miniature endplate potential (mEPP) frequency in Nedd4 mutants. However, the mutant neuromuscular synapses are less responsive to membrane depolarization, compared to the wildtypes. Ultrastructural analyses further reveal that the pre-synaptic nerve terminal branches at the NMJs of Nedd4 mutants are increased in number, but decreased in diameter compared to the wildtypes. These ultrastructural changes are consistent with functional alternation of the NMJs in Nedd4 mutants. Unexpectedly, Nedd4 is not expressed in motoneurons, but is highly expressed in skeletal muscles and Schwann cells. Together, these results demonstrate that Nedd4 is involved in regulating the formation and function of the NMJs through non-cell autonomous mechanisms.
Liu
Yun
Y
Department of Neuroscience, UT Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9111, USA.
Oppenheim
Ronald W
RW
Sugiura
Yoshie
Y
Lin
Weichun
W
D000818:Animals; D001369:Axons / Q000378:metabolism; D004594:Electrophysiology; D004622:Embryo, Mammalian / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism; D009154:Mutation; D000075702:Nedd4 Ubiquitin Protein Ligases; D009469:Neuromuscular Junction / Q000196:embryology* / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
D056827:Endosomal Sorting Complexes Required for Transport; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases