Mice with endogenous TDP_43 mutations exhibit gain of splicing function and characteristics of amyotrophic lateral sclerosis

Authors
P Fratta, P Sivakumar, J Humphrey, K Lo, T Ricketts, et al.

Lab
Unidad de Investigación, Hospital Universitario de Canarias, Fundación Canaria de Investigación Sanitaria and Instituto de Tecnologías Biomédicas (CIBICAN), La Laguna, Spain

Journal
The EMBO Journal

Abstract
TDP_43 (encoded by the gene TARDBP) is an RNA binding protein central to the pathogenesis of amyotrophic lateral sclerosis (ALS). However, how TARDBP mutations trigger pathogenesis remains unknown. Here, we use novel mouse mutants carrying point mutations in endogenous Tardbp to dissect TDP_43 function at physiological levels both in vitro and in vivo. Interestingly, we find that mutations within the C_terminal domain of TDP_43 lead to a gain of splicing function. Using two different strains, we are able to separate TDP_43 loss_ and gain_of_function effects. TDP_43 gain_of_function effects in these mice reveal a novel category of splicing events controlled by TDP_43, referred to as “skiptic” exons, in which skipping of constitutive exons causes changes in gene expression. In vivo, this gain_of_function mutation in endogenous Tardbp causes an adult_onset neuromuscular phenotype accompanied by motor neuron loss and neurodegenerative changes. Furthermore, we have validated the splicing gain_of_function and skiptic exons in ALS patient_derived cells. Our findings provide a novel pathogenic mechanism and highlight how TDP_43 gain of function and loss of function affect RNA processing differently, suggesting they may act at different disease stages.

BIOSEB Instruments Used:
Grip strength test (BIO-GS3)