Novel mutations in TARDBP (TDP-43) in patients with familial amyotrophic lateral sclerosis.
The TAR DNA-binding protein 43 (TDP-43) has been identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U), defining a novel class of neurodegenerative conditions: the TDP-43 proteinopathies. The first pathogenic mutations in the gene encoding TDP-43 (TARDBP) were recently reported in familial and sporadic ALS patients, supporting a direct role for TDP-43 in neurodegeneration. In this study, we report the identification and functional analyses of two novel and one known mutation in TARDBP that we identified as a result of extensive mutation analyses in a cohort of 296 patients with variable neurodegenerative diseases associated with TDP-43 histopathology. Three different heterozygous missense mutations in exon 6 of TARDBP (p.M337V, p.N345K, and p.I383V) were identified in the analysis of 92 familial ALS patients (3.3%), while no mutations were detected in 24 patients with sporadic ALS or 180 patients with other TDP-43-positive neurodegenerative diseases. The presence of p.M337V, p.N345K, and p.I383V was excluded in 825 controls and 652 additional sporadic ALS patients. All three mutations affect highly conserved amino acid residues in the C-terminal part of TDP-43 known to be involved in protein-protein interactions. Biochemical analysis of TDP-43 in ALS patient cell lines revealed a substantial increase in caspase cleaved fragments, including the approximately 25 kDa fragment, compared to control cell lines. Our findings support TARDBP mutations as a cause of ALS. Based on the specific C-terminal location of the mutations and the accumulation of a smaller C-terminal fragment, we speculate that TARDBP mutations may cause a toxic gain of function through novel protein interactions or intracellular accumulation of TDP-43 fragments leading to apoptosis.
Rutherford
Nicola J
NJ
Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America.
Zhang
Yong-Jie
YJ
Baker
Matt
M
Gass
Jennifer M
JM
Finch
Nicole A
NA
Xu
Ya-Fei
YF
Stewart
Heather
H
Kelley
Brendan J
BJ
Kuntz
Karen
K
Crook
Richard J P
RJ
Sreedharan
Jemeen
J
Vance
Caroline
C
Sorenson
Eric
E
Lippa
Carol
C
Bigio
Eileen H
EH
Geschwind
Daniel H
DH
Knopman
David S
DS
Mitsumoto
Hiroshi
H
Petersen
Ronald C
RC
Cashman
Neil R
NR
Hutton
Mike
M
Shaw
Christopher E
CE
Boylan
Kevin B
KB
Boeve
Bradley
B
Graff-Radford
Neill R
NR
Wszolek
Zbigniew K
ZK
Caselli
Richard J
RJ
Dickson
Dennis W
DW
Mackenzie
Ian R
IR
Petrucelli
Leonard
L
Rademakers
Rosa
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D015331:Cohort Studies; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D019636:Neurodegenerative Diseases / Q000235:genetics / Q000378:metabolism; D010375:Pedigree
D004268:DNA-Binding Proteins