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Amolecular link between dystonia 1 and dystonia 6.

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EDITORIAL
A Molecular Link Between Dystonia 1 and
Dystonia 6?
M
onogenic primary dystonias are a group of movement disorders that comprise ‘‘pure’’ dystonias, dystonia plus syndromes, and paroxysmal dystonias.1,2 The
various forms are assigned numbers, ie, dystonia 1, 2, etc.,
and the gene loci are referred to as DYT1, DYT2, etc.
Gene loci have been chromosomally assigned in at least 15
forms and the ‘‘disease gene’’ has been identified in 10 of
them.1 Identification of disease genes is a first step toward
the elucidation of pathological mechanisms underlying this
group of disorders. In particular, functional analysis of the
disease genes and their products facilitates the examination
of possible common pathways that might be affected in
different forms of primary dystonia.
In this issue of the Annals, 2 groups now present
data that might link 2 forms of ‘‘pure’’ primary dystonias—dystonia 1 and dystonia 6—at the molecular level.3,4
Almost all cases of dystonia 1 are caused by a trinucleotide
deletion (‘‘GAG-deletion’’) in exon 5 of the torsin A gene
(TOR1A).5 Mutations in the thanatos-associated protein
domain–containing, apoptosis–associated protein 1 gene
(THAP1) cause dystonia 6. The mutations can be located
in all 3 exons of the gene. Figure 1 shows the mutations
described so far at the polypeptide level. The THAP domain in THAP1 is a zinc-dependent DNA binding domain. By interacting with specific binding motifs in the
promoter region of various genes, THAP1 functions as a
transcription regulator of endothelial cell proliferation and
as a regulator of G1/S cell-cycle progression.6,7 THAP1
might also have pro-apoptotic activity.8
The authors argued that the transcription regulator
THAP1 might also influence genes involved in various
forms of primary dystonia. Owing to phenotypic similarities between dystonia 1 and dystonia 6, they chose to
study the TOR1A promoter for THAP-domain-binding
sequences (THABS). Human THAP-binding consensus
motifs are made up of an 11-bp fragment (XXTXXX
GGCAX).9,10 Both groups report an inverted THABS in
the promoter of TOR1A. Kaiser and colleagues4 highlight
this THABS as TGCCCTGA at position 33/26 from
the transcription start site (according to the TOR1A reference sequence). Gavarini and colleagues3 describe the same
THABS as CTGCCCTGAAG and give its position relative
C 2010 American Neurological Association
418 V
to the translation initiation site as 111/101 (Fig 2). In
addition, Kaiser and colleagues4 report a TACAGGCA core
motif in sense orientation at position 181/174 from
the transcription start site. Both groups then performed
chromatin immunoprecipitation (CHiP) experiments to
demonstrate in vivo TOR1A promoter binding. Kaiser and
colleagues4 used human epithelial cervical cancer (HeLa)
and neuroblastoma cells (SH-SY5Y) and Gavarini and colleagues3 used human umbilical vein endothelial cells
(HUVECs) and T98G glioblastoma cell lines. They demonstrated interaction between THAP1 and the TOR1A
promoter. Gavarini and colleagues3 confirmed these results
by electrophoretic mobility shift assays (EMSAs) with nuclear extracts from cells overexpressing THAP1 using a
TOR1A promoter fragment containing only the inverted
THABS (see Fig 2). This indicates that the inverted
THABS motif of the TOR1A promoter suffices for specific
binding of THAP1. EMSAs with nuclear extracts from
cells overexpressing mutant THAP1 (the same mutations
that were found in dystonia 6 patients) did not reveal an
interaction with the TOR1A promoter sequence.
Both works investigate the outcome of the THAP1
interaction with the TOR1A promoter. Kaiser and colleagues4 transfected HeLa and SH-SY5Y cell lines overexpressing THAP1 with a plasmid containing a 977-bp
TOR1A promoter/exon 1 fragment ligated to a reporter
gene. They found a THAP1-mediated dose-dependent
decrease in the activity of the promoter construct; however, more direct experiments did not reveal an effect of
THAP1 on TOR1A expression. Both groups failed to
find altered TOR1A expression in lymphoblastoid cell
lines and fibroblasts from dystonia 6 patients. Furthermore, small interfering RNA (siRNA)-mediated repression of THAP1 in fibroblasts and HUVECs did not
have any effect on the cellular level of TOR1A messenger
RNA (mRNA). Overexpression of THAP1 in human
embryonic kidney (HEK293) cells and in HUVECs also
did not modulate TOR1A expression. These experiments
suggest that THAP1-mediated repression of TOR1A
expression occurs physiologically only in specific cell
types (striatal and possibly other neurons), if at all, and
might be developmentally regulated. This effect might be
Müller: A Molecular Link between Dystonia 1 and 6
FIGURE 1: Schematic of THAP protein. Mutations described in dystonia 6 so far are indicated. Mutations studied by Kaiser
and colleagues4 and by Gavarini and colleagues3 are highlighted. References are given for each mutation. If the same
mutation has been described by several authors, reference to the first describers is given only. Note that frameshift mutations
are described as in the published works. This does not correspond to the latest recommendations for description of frameshift
mutations. For example, S130fsX134 should now be described as S130fsX3. This indicates a frameshift change within amino
acid S130 as the first affected amino acid and the new reading frame being open for 3 amino acids up to the new stop
codon.26 The Ser130fsX134 mutation (388_389 del TC) was inadvertently given as V131fs133X in the original publication.20
[Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
mediated by a neuron-specific isoform of THAP1 in concert with genes expressed in a cell type–specific manner.
The 2 articles in this issue of the Annals set the stage
for further experiments. First, repression of TOR1A expression by THAP1 needs to be shown in a physiological
system. For example, postmortem brains from dystonia 6
patients could be studied. Alternatively, Thap1 transgenic
or knockdown mice might give conclusive results. How
derepression of TOR1A and the resulting higher levels of
torsin A might cause dystonia needs to be investigated
once THAP1-mediated modulation of TOR1A expression
has been shown. At least in mice, the opposite seems to be
the case. Motor deficits and hyperactivity are observed
when Tor1a is knocked down.11–13 However, dramatic and
thus nonphysiological overexpression of Tor1a in mice can
also result in motor symptoms.14 In this context, it is important to explain how the R13H mutation in THAP1
results in typical dystonia 6, but modifies TOR1A
FIGURE 2: Sequence of promoter and first exon of TOR1A. The 2 THABSs, 1 inverted, the other in sense orientation are
indicated by arrows. The transcription start site is indicated by an asterisk. The fragment used in EMSA by Gavarini and
colleagues3 is shaded. Note that the inverted THABS suffices for THAP1 binding.
October, 2010
419
ANNALS
of Neurology
expression in vitro only moderately.4 Another problem is
how to reconcile the apparent specificity of the TOR1A
GAG-deletion in the origin of dystonia 1 and modification of TOR1A expression as a possible pathological mechanism in dystonia. Furthermore, specificity of THAP1
action in dystonia needs to be addressed. Interestingly,
apart from promoters of many genes, THAP1 also binds
to the promoter region of a TAF1 transcript15 that is
implicated in another form of primary dystonia which is
clinically quite different, ie, adult-onset X-linked dystonia
parkinsonism.16,17 Given that THABSs are also in the 50
upstream region of other genes mutated in primary dystonia, it will be interesting to learn whether specific THAP1
function can be demonstrated for the promoters of these
genes.
In conclusion, the 2 articles in this issue of the Annals
are exciting in that they potentially link 2 primary dystonias
at the molecular level. This link is probably not just a simple THAP1-TOR1A promoter interaction but is likely to
involve other genes as well. As with most novel findings, the
reports raise more questions than they can presently solve. It
is hoped that these works precipitate new research into dystonia that might eventually result in the development of
novel therapies, as anticipated by Gavarini and colleagues.3
6.
Bessière D, Lacroix C, Campagne S, et al. Structure-function analysis of the THAP zinc finger of THAP1, a large C2CH DNA-binding
module linked to Rb/E2F pathways. J Biol Chem 2008;283:
4352–4363.
7.
Cayrol C, Lacroix C, Mathe C, et al. The THAP-zinc finger protein
THAP1 regulates endothelial cell proliferation through modulation
of pRB/E2F cellcycle target genes. Blood 2007;109:584–594.
8.
Roussigne M, Cayrol C, Clouaire T, et al. THAP1 is a nuclear proapoptotic factor that links prostate-apoptosis-response-4 (Par-4) to
PML nuclear bodies. Oncogene 2003;22:2432–2442.
9.
Clouaire T, Roussigne M, Ecochard V, et al. The THAP domain of
THAP1 is a large C2CH module with zinc-dependent sequencespecific DNA-binding activity. Proc Natl Acad Sci U S A 2005;102:
6907–6912.
10.
Sabogal A, Lyubimov AY, Corn JE, et al. THAP proteins target
specific DNA sites through bipartite recognition of adjacent major
and minor grooves. Nat Struct Mol Biol 2010;17:117–124.
11.
Dang MT, Yokoi F, Pence MA, Li Y. Motor deficits and hyperactivity in Dyt1 knockdown mice. Neurosci Res 2006;56:470–474.
12.
Dang MT, Yokoi F, McNaught KS, et al. Generation and characterization of Dyt1 DeltaGAG knock-in mouse as a model for earlyonset dystonia. Exp Neurol 2005;196:452–463.
13.
Goodchild RE, Kim CE, Dauer ET. Loss of the dystonia-associated
protein torsinA selectively disrupts the neuronal nuclear envelope.
Neuron 2005;48:923–932.
14.
Grundmann K, Reischmann B, Vanhoutte G, et al. Overexpression
of human wildtype torsinA and human DeltaGAG torsinA in a
transgenic mouse model causes phenotypic abnormalities. Neurobiol Dis 2007;27:190–206.
15.
Mazars R, Gonzales-de-Peredo A, Cayrol C, et al. The THAP-Zinc
finger protein THAP1 associates with coactivator HCF-1 and 0GLcNAc transferase. J Biol Chem 2010;285:13364–13371.
Acknowledgments
16.
I thank Dr Dagmar Nolte for stimulating discussions
and comments on the manuscript. Thanks also to Silke
Reichmann for preparation of the figures.
Herzfeld T, Nolte D, Müller U. Structural and functional analysis
of the human TAF1/DYT3 multiple transcript system. Mamm
Genome 2007;18:787–795.
17.
Nolte D, Niemann S, Müller U. Specific sequence changes in multiple transcript system DYT3 are associated with X-linked dystonia
parkinsonism. Proc Natl Acad Sci U S A 2003;100:10347–10352.
18.
Fuchs T, Gavarini S, Saunders-Pullman R, et al. Mutations in the
THAP1 gene are responsible for DYT6 primary torsion dystonia.
Nat Genet 2009;3:286–288.
19.
Bressman SB, Fuchs T, Heimann GA, et al. Mutations in THAP1
(DYT6) in early-onset dystonia: a genetic screening study. Lancet
Neurol 2009;8;441–446.
Ulrich Müller, MD, PhD
20.
Institut für Humangenetik
Justus-Liebig-Universität
Gießen, Germany
Djarmati A, Schneider SA, Lohmann K, et al. Mutations in THAP1
(DYT6) and generalised dystonia with prominent spasmodic dysphonia: a genetic screening study. Lancet Neurol 2009;8:447–452.
21.
Paisán-Ruiz C, Ruiz-Martinez J, Ruibal M, et al. Identification of a
novel THAP1 mutation at R29 amino-acid residue in sporadic
patients with early-onset dystonia. Mov Disord 2009;24:2428–2443.
22.
Bonetti M, Barzaghi C, Brancati F, et al. Mutation screening of the
DYT6/THAP1 gene in Italy. Mov Disord 2009;24:2424–2427.
23.
Houlden H, Schneider SA, Paudel R, et al. THAP1 mutations
(DYT6) are an additional cause of early-onset dystonia. Neurology
2010;74:846–850.
24.
Xiao J, Zhao Y, Bastian RW, et al. Novel THAP1 sequence variants
in primary dystonia. Neurology 2010;74:229–238.
25.
Söhn AS, Glöckle N, Doetzer AD, et al. Prevalence of THAP1
mutations in a large cohort of German patients with primary dystonia. Mov Disord (in press). DOI: 10.1002/mds.23207.
26.
Human Genome Variation Society. Discussions regarding the
description of sequence variants. Available at: http://www.hgvs.
org/mutnomen/disc.html#indel. Accessed August 14, 2010.
Potential Conflicts of Interest
Nothing to report.
References
1.
Müller U. The monogenic primary dystonias. Brain 2009;132:
2005–2025.
2.
Albanese A, Asmus F, Bhatia KP, et al. EFNS guidelines on diagnosis and treatment of primary dystonias. Eur J Neurol 2010 (in
press). DOI: 10.1111/j.1468-.2010.03042.x.
3.
Gavarini S, Cayrol C, Fuchs T, et al. A direct interaction between
causative genes of DYT1 and DYT6 primary dystonia. Ann Neurol
2010;68:456–461.
4.
5.
420
Kaiser FJ, Osmanovic A, Rakovic A, et al. The dystonia gene
DYT1 is repressed by the transcription factor THAP1 (DYT6). Ann
Neurol 2010;68:462–468.
Ozelius LJ, Hewett JW, Page CE, et al. The early-onset torsion
dystonia gene (DYT1) encodes an ATP-binding protein. Nat Genet
1997;17:40–48.
DOI: 10.1002/ana.22183
Volume 68, No. 4
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