ZFIN ID: ZDB-PUB-181127-39
Neuromuscular junction abnormalities in a zebrafish loss-of-function model of TDP-43
Bose, P., Armstrong, G.A.B., Drapeau, P.
Date: 2018
Source: Journal of neurophysiology   121(1): 285-297 (Journal)
Registered Authors: Drapeau, Pierre
Keywords: ALS, Neuromuscular junction, Synaptic defects, TDP-43, zebrafish
MeSH Terms:
  • 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
  • Alleles
  • Animals
  • Animals, Genetically Modified
  • CRISPR-Cas Systems
  • Calcium Channel Agonists/pharmacology
  • Calcium Channels, L-Type/metabolism
  • DNA-Binding Proteins/genetics*
  • DNA-Binding Proteins/metabolism*
  • Disease Models, Animal
  • Genotype
  • Loss of Function Mutation*
  • Motor Activity/drug effects
  • Motor Activity/physiology
  • Neuromuscular Junction/drug effects
  • Neuromuscular Junction/growth & development
  • Neuromuscular Junction/metabolism*
  • Neuromuscular Junction/pathology*
  • Synaptic Transmission/drug effects
  • Synaptic Transmission/physiology
  • TDP-43 Proteinopathies/drug therapy
  • TDP-43 Proteinopathies/metabolism
  • TDP-43 Proteinopathies/pathology
  • Zebrafish
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/metabolism*
PubMed: 30461368 Full text @ J. Neurophysiol.
Almost 90% of ALS cases are characterized by the presence of aggregates of insoluble, misfolded cytoplasmic TAR DNA binding protein of 43 kDa (TDP-43). Distal axonopathy with impaired neuromuscular junctions (NMJs) prior to motor neuron degeneration or clinical onset of symptoms has been hypothesized as an early pathology in ALS. However, synaptic defects at the NMJ caused by TDP-43 mutations have not been characterized. In this study, we examined a previously reported zebrafish line expressing the tardbpY220X/Y220X variant, which results in an unstable and degraded protein. These tardbp-/- larvae, however, mature normally due to the upregulated expression of an alternative splice variant of the tardbp paralog tardbp-like, or tardbpl. We generated a mutant line with a CRISPR/Cas9-mediated 5 base pair deletion encompassing the ATG start codon of tardbpl and in-crossed these with tardbp-/- mutants to obtain tardbp-/- and tardbpl-/- double mutants herein, referred to as hom/hom. We subsequently characterized morphological, coiling, locomotor, synaptic and NMJ structural abnormalities in the hom/hom mutants and in their genotypic controls. We observed that hom/hom mutants displayed gross morphological defects, early lethality, reduced locomotor function, aberrant quantal transmission and perturbed synapse architecture at the NMJ. We further employed pharmacological manipulations in an effort to rescue phenotypic defects and observed that tardbp+/-; tardbpl-/- (herein referred to as het/hom) mutants, but not hom/hom mutants, were sensitive to chronic treatments of Bay K 8644, an L-type calcium channel agonist. This result highlights the importance of partial vs complete loss of allelic functions of TDP-43.