mortality/aging
• ~90% of mice die at birth, with phenotype similar to Nrg1tm1Cbm homozygous embryos
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nervous system
• Schwann cells are absent from intramuscular motor axons between E13.5-E16.5
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• motor neurons are defasciculated and disorganized
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• in developing muscle, motor axons largely retract by birth; by E18.5, motor axons and terminals are absent
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• at diaphragm synapses, band of acetylcholine receptors (AChRs) is wider (17.5% of muscle length) than in wild-type muscle (7% of muscle length)
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