Functional decline at the aging neuromuscular junction is associated with altered laminin-α4 expression
Kah Meng Lee1, Kirat K Chand1,2, Luke A Hammond3
1School of Biomedical Sciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.
Abstract:
Laminin-α4 is involved in the alignment of active zones to postjunctional folds at the neuromuscular junction (NMJ). Prior study has implicated laminin-α4 in NMJ maintenance, with altered NMJ morphology observed in adult laminin-α4 deficient mice (lama4-/-). The present study further investigated the role of laminin-α4 in NMJ maintenance by functional characterization of transmission properties, morphological investigation of synaptic proteins including synaptic laminin-α4, and neuromotor behavioral testing. Results showed maintained perturbed transmission properties at lama4-/- NMJs from adult (3 months) through to aged (18-22 months). Hind-limb grip force demonstrated similar trends as transmission properties, with maintained weaker grip force across age groups in lama4-/-. Interestingly, both transmission properties and hind-limb grip force in aged wild-types resembled those observed in adult lama4-/-. Most significantly, altered expression of laminin-α4 was noted at the wild-type NMJs prior to the observed decline in transmission properties, suggesting that altered laminin-α4 expression precedes the decline of neurotransmission in aging wild-types. These findings significantly support the role of laminin-α4 in maintenance of the NMJ during aging.
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