title: Functional complementation in Drosophila to predict the pathogenicity of TARDBP variants: evidence for a loss-of-function mechanism.
abstract: The human TAR DNA binding protein 43 (TDP-43), encoded by the gene TARDBP, plays a central role in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. TDP-43 inclusions are also found in up to approximately 60% of Alzheimer's disease (AD) brains. Although ALS-causing TARDBP mutations cluster in the C-terminal glycine-rich region of the protein, the pathogenic nature of the atypical missense variants p.A90V (located between the bipartite nuclear localization signal) and p.D169G (located in the first RNA-binding domain) is unclear. In addition, whether causal ALS mutations represent gain or loss-of-function alleles remains unknown. We recently reported that loss-of-function of the highly conserved TARDBP ortholog in Drosophila (called TBPH) leads to death of bursicon neurons resulting in adult maturation and wing expansion defects. Here, we compared wild-type TARDBP, 2 typical ALS-causing mutations (p.G287S and p.A315T) and 2 atypical variants (p.A90V and p.D169G), for their ability to complement neuronal TBPH loss-of-function. Although p.D169G rescued organismal pupal lethality and neuronal loss to a similar extent as wild-type TARDBP, p.A90V, p.G287S, and p.A315T were less efficient. Accordingly, p.A90V, p.G287S, and p.A315T but not p.D169G or wild-type protein promoted a shift of TDP-43 from the nucleus to the cytoplasm in approximately 12%-14% of bursicon neurons. Finally, we found that the carrier frequency of rare variant p.A90V was higher in French-Belgian AD cases (5/1714, 0.29%) than in controls of European descent (5/9436, 0.05%) (odds ratio = 5.5; 95% confidence interval, 1.6-19.0; p = 0.009). We propose that pathogenic TARDBP mutations have partial loss-of-function properties and that TARDBP p.A90V may increase AD risk by the same mechanism.
authors.affiliation: Laboratory of Behavioral and Developmental Genetics, Center of Human Genetics, University of Leuven, Leuven, Belgium; VIB Center for the Biology of Disease, University of Leuven, Leuven, Belgium.
authors.forename: Lies
authors.initials: L
authors.lastname: Vanden Broeck
authors.affiliation: VIB Department of Molecular Genetics, Antwerpen, Belgium; Institute Born-Bunge, University of Antwerp, Antwerpen, Belgium.
authors.forename: Gernot
authors.initials: G
authors.lastname: Kleinberger
authors.affiliation: Inserm U744, Institut Pasteur de Lille, Université de Lille Nord de France, Lille, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Chapuis
authors.affiliation: Laboratory of Behavioral and Developmental Genetics, Center of Human Genetics, University of Leuven, Leuven, Belgium; VIB Center for the Biology of Disease, University of Leuven, Leuven, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Gistelinck
authors.affiliation: Inserm U744, Institut Pasteur de Lille, Université de Lille Nord de France, Lille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Amouyel
authors.affiliation: VIB Department of Molecular Genetics, Antwerpen, Belgium; Institute Born-Bunge, University of Antwerp, Antwerpen, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Van Broeckhoven
authors.affiliation: Inserm U744, Institut Pasteur de Lille, Université de Lille Nord de France, Lille, France.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Lambert
authors.affiliation: Laboratory of Behavioral and Developmental Genetics, Center of Human Genetics, University of Leuven, Leuven, Belgium; VIB Center for the Biology of Disease, University of Leuven, Leuven, Belgium. Electronic address: patrick.callaerts@cme.vib-kuleuven.be.
authors.forename: Patrick
authors.initials: P
authors.lastname: Callaerts
authors.affiliation: Inserm U744, Institut Pasteur de Lille, Université de Lille Nord de France, Lille, France; Center for Medical Genetics, Ghent University Hospital, Gent, Belgium. Electronic address: bart.dermaut@pasteur-lille.fr.
authors.forename: Bart
authors.initials: B
authors.lastname: Dermaut
mesh_terms: D000483:Alleles; D000544:Alzheimer Disease / Q000235:genetics*; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D004330:Drosophila / Q000235:genetics*; D005260:Female; D005544:Forecasting; D057180:Frontotemporal Dementia / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D008297:Male; D009154:Mutation; D009474:Neurons / Q000473:pathology
chemical_list: D004268:DNA-Binding Proteins; C000598624:TARDBP protein, human
keywords: AD; ALS; Drosophila; FTD; Loss-of-function; TDP-43