|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.
|Source:||Journal of neurophysiology 121(1): 285-297 (Journal)|
|Registered Authors:||Drapeau, Pierre|
|Keywords:||ALS, Neuromuscular junction, Synaptic defects, TDP-43, zebrafish|
|PubMed:||30461368 Full text @ J. Neurophysiol.|
Bose, P., Armstrong, G.A.B., Drapeau, P. (2018) Neuromuscular junction abnormalities in a zebrafish loss-of-function model of TDP-43. Journal of neurophysiology. 121(1):285-297.
ABSTRACTAlmost 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.