Mutant TDP-43 Causes Early-Stage Dose-Dependent Motor Neuron Degeneration in a TARDBP Knockin Mouse Model of ALS

Summary: Rare mutations in TARDBP, the gene encoding TDP-43, cause amyotrophic lateral sclerosis (ALS), and TDP-43 pathology is seen in a large majority of ALS patients, suggesting a central pathogenic role of this regulatory protein. The consequences of TARDBP mutations on TDP-43 function and the mechanism by which mutant TDP-43 causes neurodegeneration remain uncertain. Here, we characterize a series of knockin mice carrying disease-associated TARDBP mutations. We demonstrate that TDP-43M337V and TDP-43G298S are functional, each rescuing the lethality of TDP-43 loss of function. In a subset of aged heterozygous knockin mice, we observe the earliest signs of selective motor neuron degeneration, demonstrating that physiological levels of mutant TDP-43 are sufficient to initiate disease. Furthermore, aged homozygous mutants develop selective, asymmetric motor neuron pathology, providing in vivo evidence of TDP-43 dose-dependent neurotoxicity. These knockin mice represent a faithful in vivo model of early-stage ALS and enable future exploration of TDP-43-associated neurodegeneration. : In a series of knockin mice carrying ALS-associated TARDBP mutations, Ebstein et al. demonstrate that the mutant alleles TDP-43M337V and TDP-43G298S are functional but in a dose-dependent manner cause early, selective motor neuron degeneration in a subpopulation of aged mice. This represents a faithful in vivo model of early-stage ALS. Keywords: TARDBP, TDP-43, amyotrophic lateral sclerosis, knockin mouse, motor neuron disease, neurodegeneration, muscle denervatio