Wild-type and A315T mutant TDP-43 exert differential neurotoxicity in a Drosophila model of ALS

• Published in: Human molecular genetics Vol. 20; no. 12; pp. 2308 - 2321
• Main Authors: ESTES, Patricia S, BOEHRINGER, Ashley, ZWICK, Rebecca, TANG, Jonathan E, GRIGSBY, Brianna, ZARNESCU, Daniela C
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 15.06.2011
• Subjects: Alleles; Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Animal models; Animals; Apoptosis; Apoptosis - physiology; Biological and medical sciences; Chaperones; Danio rerio; DNA-Binding Proteins - genetics; DNA-Binding Proteins - toxicity; Drosophila; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; HSP70 Heat-Shock Proteins - metabolism; Hsp70 protein; Larva - physiology; Locomotion; Locomotion - genetics; Missense mutation; Molecular and cellular biology; Molecular modelling; Motor neurons; Mutation, Missense - genetics; Neurodegenerative diseases; Neuromuscular Junction - cytology; Neuromuscular Junction - metabolism; Neuromuscular junctions; Neurons - metabolism; Neurotoxicity; Phenotype; Proteasome Endopeptidase Complex - metabolism; proteasomes; RNA Interference; RNA-binding protein; RNA-mediated interference; Neurotoxicity; Arthropoda; Insecta; Genetics; Models; Mutation; Invertebrata; Wild type; Drosophila melanogaster; Diptera; Drosophilidae
• ISSN: 0964-6906; 1460-2083
• DOI: 10.1093/hmg/ddr124

The RNA-binding protein TDP-43 has been linked to amyotrophic lateral sclerosis (ALS) both as a causative locus and as a marker of pathology. With several missense mutations being identified within TDP-43, efforts have been directed towards generating animal models of ALS in mouse, zebrafish, Drosophila and worms. Previous loss of function and overexpression studies have shown that alterations in TDP-43 dosage recapitulate hallmark features of ALS pathology, including neuronal loss and locomotor dysfunction. Here we report a direct in vivo comparison between wild-type and A315T mutant TDP-43 overexpression in Drosophila neurons. We found that when expressed at comparable levels, wild-type TDP-43 exerts more severe effects on neuromuscular junction architecture, viability and motor neuron loss compared with the A315T allele. A subset of these differences can be compensated by higher levels of A315T expression, indicating a direct correlation between dosage and neurotoxic phenotypes. Interestingly, larval locomotion is the sole parameter that is more affected by the A315T allele than wild-type TDP-43. RNA interference and genetic interaction experiments indicate that TDP-43 overexpression mimics a loss-of-function phenotype and suggest a dominant-negative effect. Furthermore, we show that neuronal apoptosis does not require the cytoplasmic localization of TDP-43 and that its neurotoxicity is modulated by the proteasome, the HSP70 chaperone and the apoptosis pathway. Taken together, our findings provide novel insights into the phenotypic consequences of the A315T TDP-43 missense mutation and suggest that studies of individual mutations are critical for elucidating the molecular mechanisms of ALS and related neurodegenerative disorders.