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Reversal of Neurological Defects in a Mouse Model of Rett Syndrome

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Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.
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of Xa-methylated genes contains several genes
shown to escape X inactivation (18). However,
given that these genes still have an elevated Xa
expression level (18), the overall correlation
between gene-body methylation and expression
potentiality is maintained.
Male-to-female comparisons showed a more
complete methylation level on the male X (Fig.
3A and fig. S8). Furthermore, the sites that are
gene-body Xa-methylated in females are among
the most highly methylated sites in males,
highlighted even on the almost-complete meth-
ylation background of the male X chromosome
(fig. S9).
An Xa-specific methylation present in
somatic cells could reflect either methylation
occurring only on Xa or demethylation oc-
curring on Xi. The human embryonic stem
(ES) cell line hES-H7 represents a stage of
development just before X inactivation (19)
and has been shown to stably maintain the
appropriate characteristic methylation pattern
for this stage, including allele-specific meth-
ylation (20). At this stage of development, the
genome has presumably already undergone
global demethylation and the wave of de novo
methylation (2,21). Hence, we analyzed these
cells using the 500K array. Out of the 116
amplicons shown to be gene-body Xa meth-
ylated, 50 also have a heterozygous genotype
in H7 cells. We found that all 50 are bi-
allelically methylated. When examining all 154
amplicons informative both for H7 and for
13130 clones, we observed that only five are
monoallelically methylated in H7 cells, where-
as the expected one-third are monoallelically
methylated in the somatic clones (Fig. 3B).
Bisulfite sequencing further verified biallelic
methylation (fig. S10). Thus, given that bi-
allelic methylation is the beginning state, de-
methylation of the Xi must account for the
Xa-specific monoallelic pattern observed in
somatic cells.
A simple model may explain both the Xa
versus Xi and the gene versus intergenic dif-
ferential methylation we observed: Constantly
inactive regions, such as gene-poor regions
and the entire Xi, may be more prone to loss of
methylation maintenance (even if originally
highly methylated). The resulting methylation
decrease, for the entire Xi and for Xa intergenic
regions, would thus highlight Xa gene body
specific methylation. At the same time,
promoter CpG islands, which are protected from
methylation on Xa, would remain more meth-
ylated on Xi.
In contrast to the widely held view that X
chromosome allelespecific methylation is
restricted to CpG islands on the inactive X,
our global allele-specific methylation analy-
ses uncovered extensive methylation specifi-
cally affecting transcribable regions (gene
bodies) on the active X whether it is in the
male or the female. One aspect of sex chro-
mosome dosage compensation is the require-
ment for a chromosome-wide, likely epigenetic
mechanism with the ability to double X-linked
gene expression when necessary (i.e., in so-
matic cells but not in haploid germline cells).
Indeed, such a phenomenon was recently de-
scribedinmammals(22). Our finding of global
elevation of methylation levels at gene bodies
of both male and female active X chromo-
somes hints at such a chromosome-wide epi-
genetic control. Another example of a possible
role for methylation in (potentially) active chro-
matin regions recently came from plants, in
which extensive specific methylation of gene
bodies was discovered (23). These results, to-
gether with the findings introduced here, should
prompt reevaluation of the role of global DNA
methylation that occurs away from gene pro-
moters as well as the apparently complex rela-
tionship with chromatin activity.
Note added in proof. A second manuscript
reporting gene body methylation in plants was
recently published (29).
References and Notes
1. A. Bird, Genes Dev. 16, 6 (2002).
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Nat. Genet. 34, 187 (2003).
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13825 (1999).
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6. L. F. Lock, D. W. Melton, C. T. Caskey, G. R. Martin,
Mol. Cell. Biol. 6, 914 (1986).
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B. R. Migeon, Proc. Natl. Acad. Sci. U.S.A. 81, 2806
(1984).
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L. J. Shapiro, Proc. Natl. Acad. Sci. U.S.A. 81, 1759
(1984).
10. E. Viegas-Pequignot, B. Dutrillaux, G. Thomas, Proc. Natl.
Acad. Sci. U.S.A. 85, 7657 (1988).
11. Another recent study came to a conclusion that there is
hypomethylation at gene-poor regions of the X
chromosome, leading to an overall hypomethylation of Xi
(24). Their conclusions are based entirely on the
assumption that the single X chromosome of males is
identical to Xa in female cells. In any case, our direct
allele-specific analyses reveal only a modest
hypomethylation of Xi in gene-poor regions, but a strong
signature of Xi hypomethylation in gene bodies.
12. Details about the Affymetrix 500K SNP mapping array
are available online (www.affymetrix.com).
13. A number of medium- to high-throughput assays have
been described to analyze DNA methylation (15,2328).
Our methodology is most similar to the assay that used
the 10K array (28).
14. The cocktail includes Aci I, BsaH I, Hha I, Hpa II, and
HpyCH4 IV.
15. A. Schumacher et al.,Nucleic Acids Res. 34, 528
(2006).
16. R. C. Allen, H. Y. Zoghbi, A. B. Moseley, H. M. Rosenblatt,
J. W. Belmont, Am. J. Hum. Genet. 51, 1229 (1992).
17. Materials and methods are available as supporting
material on Science Online.
18. L. Carrel, H. F. Willard, Nature 434, 400 (2005).
19. L. M. Hoffman et al.,Stem Cells 23, 1468
(2005).
20. P. J. Rugg-Gunn, A. C. Ferguson-Smith, R. A. Pedersen,
Nat. Genet. 37, 585 (2005).
21. D. Frank et al.,Nature 351, 239 (1991).
22. D. K. Nguyen, C. M. Disteche, Nat. Genet. 38,47
(2006).
23. X. Zhang et al.,Cell 126, 1189 (2006).
24. M. Weber et al.,Nat. Genet. 37, 853 (2005).
25. M. Bibikova et al.,Genome Res. 16, 383 (2006).
26. I. Keshet et al.,Nat. Genet. 38, 149 (2006).
27. C. M. Valley, H. F. Willard, Curr. Opin. Genet. Dev. 16,
240 (2006).
28. E. Yuan et al.,Cancer Res. 66, 3443 (2006).
29. D. Zilberman, M. Gehring, R. K. Tran, T. Ballinger,
J. Henikoff, Nat. Genet. 39, 61 (2007).
30. We thank H. Cedar, D. Housman, and J. Lee for
discussions and comments and the staff of Harvard
Medical SchoolPartners Healthcare Center for Genetics
and Genomics Microarray Facility for Affymetrix array
experiments. Support came from the NIH (to A.C.).
Supporting Online Material
www.sciencemag.org/cgi/content/full/315/5815/1141/DC1
Materials and Methods
SOM Text
Figs. S1 to S10
Tables S1 to S9
16 October 2006; accepted 22 January 2007
10.1126/science.1136352
Reversal of Neurological Defects in a
Mouse Model of Rett Syndrome
Jacky Guy,
1
Jian Gan,
2
Jim Selfridge,
1
Stuart Cobb,
2
Adrian Bird
1
*
Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of
the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is
not a neurodegenerative disorder. An important question for future therapeutic approaches to this
and related disorders concerns phenotypic reversibility. Can viable but defective neurons be
repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a
mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads
to striking loss of advanced neurological symptoms in both immature and mature adult animals.
Mutations in the X-linked MECP2 gene
are the primary cause of Rett syn-
drome (RTT), a severe autism spec-
trum disorder with delayed onset that affects
1 in 10,000 girls (1). MECP2 mutations are also
found in patients with other neurological condi-
tions, including learning disability, neonatal en-
cephalopathy, autism, and X-linked mental
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retardation (2). RTT patients show abnormal
neuronal morphology, but not neuronal death
(3), which implies that it is a neurodevelopmen-
tal rather than a neurodegenerative disorder.
MeCP2 is expressed widely, but is most abun-
dant in neurons of the mature nervous system
(4). Conditional deletion and neuron-specific ex-
pression of Mecp2 in mice showed that the
mutant phenotype is specifically due to absence
ofMeCP2inneurons(57). The persistent via-
bility of mutant neurons in RTT patients raises
the possibility that reexpression of MeCP2 might
restore full function and, thereby, reverse RTT.
Alternatively, MeCP2 may be essential for neu-
ronal development during a specific time win-
dow,afterwhichdamagecausedbyitsabsence
is irreversible. To distinguish these possibilities,
we created a mouse in which the endogenous
Mecp2 gene is silenced by insertion of a lox-
Stop cassette (8), but can be conditionally
activated under the control of its own pro-
moter and regulatory elements by cassette dele-
tion (9) (fig. S1). Western blots (Fig. 1A) and
in situ immunofluorescence (Fig. 1B) con-
firmed absence of detectable MeCP2 protein in
Mecp2
lox-Stop/y
(Stop/y) animals. Like Mecp2-
null mice (6), Stop/y males developed symp-
toms at ~6 weeks and survived for 11 weeks,
on average, from birth (Fig. 1C). We concluded
that the Mecp2
lox-Stop
allele behaves as a null
mutation.
To control the activation of Mecp2,wecom-
bined a transgene expressing a fusion between
Cre recombinase and a modified estrogen re-
ceptor (cre-ER) with the Mecp2
lox-Stop
allele
(10). The Cre-ER protein remains in the cyto-
plasm unless exposed to the estrogen analog
tamoxifen (TM), which causes it to translocate
to the nucleus. To verify that the Cre-ER mole-
cule did not spuriously enter the nucleus in the
absence of TM and cause unscheduled deletion
of the lox-Stop cassette, we looked for signs of
lox-Stop deletion in Mecp2
lox-Stop/+
,cre-ER
(Stop/+,cre) females by Southern blotting. Even
after 10 months in the presence of cytoplasmic
Cre-ER, there was no sign of the deleted allele
(Fig. 1D). The absence of spontaneous deletion
of the lox-Stop cassette was independently
confirmed by the finding that Stop/y males
showed identical survival profiles in the pres-
ence or absence of Cre-ER (Fig. 1C). There-
fore, in the absence of TM, the Cre-ER molecule
does not cause detectable deletion of the lox-Stop
cassette.
We next tested the ability of TM to delete
the lox-Stop cassette in Mecp2
lox-Stop/y
,cre-ER
(Stop/y,cre) male mice. Five daily injections 3 to
4 weeks after birth caused 75 to 81% deletion of
the cassette in brain (Fig. 1E, lanes 3, 4, and 6)
and led to reexpression of the Mecp2 gene as
measured by Western blotting (Fig. 1A, lanes 4
and 5) and MeCP2 immunostaining of neurons
(Fig. 1B). Activation of Mecp2 in Stop/y,cre
males at this stage [(Fig. 2A), bracket TM-1],
before symptom onset, revealed toxicity asso-
ciated with abrupt Mecp2 reactivation, as 9 out
of 17 mice developed neurological symptoms
and died soon after the daily TM injection se-
ries (fig. S2). The remaining eight mice, how-
ever, did not develop any detectable symptoms,
showed wild-type survival (fig. S2), and were
able to breed. Four retained mice have survived
for >15 months. Death of about half of animals
was not due to intrinsic TM toxicity, because
injected controls, including mice that had either
the Stop allele or the cre-ER transgene (but not
both), were unaffected. The toxic effects re-
sembled those caused by overexpression of an
Mecp2 transgene in mice (7, 11), although the
reactivated Mecp2 gene retains its native pro-
moter. The data indicate that sudden widespread
activation of the Mecp2 gene leads to either
rapid death or complete phenotypic rescue.
We found that a more gradual Mecp2 acti-
vation induced by weekly TM injections followed
by three daily booster treatments eliminated
toxicity. Using this scheme, we asked whether
Stop/y,cre male mice with advanced symptoms
[(Fig. 2A), bracket TM-2] could be rescued by
restoration of MeCP2. To monitor the specific
features of the RTT-like mouse phenotype, we
devised simple observational tests for inertia,
gait, hind-limb clasping, tremor, irregular breath-
ing, and poor general condition. Each symptom
was scored weekly as absent, present, or severe
(scores of 0, 1, and 2, respectively). Wild-type
mice always scored zero (Fig. 2B), whereas
Stop/y animals typically showed progression of
aggregate symptom scores (e.g., from 3 to 10)
during the last 4 weeks of life (Fig. 2, C and
E). By contrast, five out of six symptomatic
Stop/y,cre animals were rescued by TM treat-
1
Wellcome Trust Centre for Cell Biology, Edinburgh
University, The Kings Buildings, Edinburgh EH9 3JR, UK.
2
Neuroscience and Biomedical Systems, Institute of
Biomedical and Life Sciences, West Medical Building,
University of Glasgow, Glasgow G12 8QQ, UK.
*To whom correspondence should be addressed. E-mail:
a.bird@ed.ac.uk
Fig. 1. Insertion of a lox-Stop cassette into intron 2 of the mouse Mecp2 gene creates an allele
that is effectively null, but can be activated by TM treatment. (A) Western blot analysis of MeCP2
protein (solid arrow) in brains of wild-type (wt), Stop/y, and Stop/y,cre mice before and after TM.
Antibodies against MeCP2 were from J. Pevsner (left panel) and Upstate (right panel). Internal
controls are nonspecific cross-reacting bands (asterisk) and bands generated by a histone H4
specific antibody (open arrow). (B) Detection of MeCP2 by in situ immunofluorescence in dentate
gyrus of wild-type (wt), Stop/y, and TM-treated Stop/y,cre mice. White scale bar, 50 mm. Green cells
that did not stain with DAPI (4´,6´-diamidino-2-phenylindole) in the upper Stop panel are
nonnucleate erythrocytes showing background fluorescence. The DAPI channel was changed from
blue to red using Adobe Photoshop to contrast with the green MeCP2 signal. (C) Comparison of the
survival of Stop/y mice with and without the cre-ER transgene. (D) A Southern blot assay for
deletion of the lox-Stop cassette in brains of heterozygous Stop/+,cre females (f) aged 10 months
(lanes 2 and 3) that had not been exposed to TM. Restriction fragments from the Mecp2 lox-Stop
(Stop; see male Mecp2
lox-Stop/y
, lane 1), Mecp2
D
with Stop deleted (D, see lane 4), and the wild-type
(wt) alleles are indicated. (E) Southern blot assay for conversion of the Stop allele to the Mecp2
D
allele (D) in male mouse brains after five daily TM injections. Lanes 2 and 5 show the wt allele.
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ment. These animals initially had symptom
scores of 2 or 3 and would be expected to
survive for up to 4 weeks from the date of the
first injection. Instead, they showed mild symp-
toms (see fig. S3 for examples of detailed scores)
and survived well beyond the maximum-
recorded life span of Mecp2
lox-Stop/y
animals
(17 weeks) (Fig. 2, D to F, and fig. S4; see
movies S1 and S2). The weekly TM injection
regime, plus booster injections, gave the same
level of lox-Stop cassette deletion as five daily
TM injections (~80%) (Fig. 2G). The one
animal that died had reduced lox-Stop cassette
deletion (~50% compared with ~80%), which
may explain failure to rescue.
RTT results from mosaic expression of
mutant and wild-type MECP2 alleles in the
brain caused by the random inactivation of one
X-linked MECP2 allele during early female de-
velopment. Heterozygous female mice may be
the most appropriate model for human RTT
(12), because both Mecp2
+/
(6)andStop/+ fe-
males (Fig. 3, A, B, and E) develop RTT-like
symptoms, including inertia, irregular breathing,
abnormal gait, and hind-limb clasping, at 4 to
12 months of age. As in humans, the phenotype
stabilizes, and the animals have an apparently
normal life span. The mice often become obese,
which is not a feature of the human condition.
In an attempt to reverse the neurological pheno-
type in mature female heterozygotes, we TM-
treated Stop/+,cre females with clear neu-
rological symptoms. These mice progressively
reverted to a phenotype that scored at or close to
wild type (Fig. 3, C to E, and fig. S5 and movie
S3; see fig. S3 for examples of detailed scores),
including normalized weight (Fig. 3D and fig.
S6). Mouse 5, for example, had a phenotypic
score close to the usual plateau level and was
obese at commencement of the weekly TM in-
jection regime, but these features were both re-
versed (Fig. 3D). On the other hand, Stop/+
females lacking Cre-ER did not respond to TM.
Southern blots showed levels of cassette deletion
in Stop/+,cre females that were consistently close
to 50% (Fig. 3F). As the great majority of neu-
rons became MeCP2-positive after TM treatment
(fig. S7), we suspect that recombination predom-
inantly occurs on the active X-chromosome (see
legend to fig. S7). The results demonstrate that
late-onset neurological symptoms in mature adult
Stop/+,cre heterozygotes are reversible by de
novo expression of MeCP2.
We also assessed the effect of Mecp2 acti-
vation on neuronal signaling. Long-term poten-
tiation (LTP) is reduced in the hippocampus of
Mecp2-mutant male mice (13,14), but hetero-
zygous females have not been tested. We per-
formed electrophysiological analysis of Mecp2
+/
heterozygous females (6) before and after onset
of overt symptoms using both high-frequency
stimulation and theta-burst (TBS) LTP induction
protocols. Stimulation-response curves showed
that the strength of basal synaptic transmission
did not differ between symptomatic or presymp-
tomatic Mecp2
+/
female mice and wild-type
littermate controls (Fig. 4A). In addition, no
significant difference in hippocampal LTP be-
tween wild-type and presymptomatic females
was detected. After symptom onset, however,
LTP was significantly reduced in Mecp2
+/
females with both protocols (Fig. 4, B and C).
The magnitude of the defect was similar to that
reported in Mecp2-null mice (13). To test for
reversal of this effect, we measured LTP in six
Stop/+,cre females that were TM-treated follow-
ing the appearance of symptoms. LTP was mea-
sured 18 to 26 weeks after commencement of
TM treatment. Control Stop/+ and wild-type
animals were also TM-treated and analyzed. The
hippocampal LTP deficit was evident in symp-
tomatic Stop/+ mice lacking the cre-ER trans-
gene, but in TM-treated Stop/+,cre mice, LTP
was indistinguishable from wild type (Fig. 4D),
which demonstrates that this pronounced
electrophysiological defect is abolished in ma-
ture adults by restoration of MeCP2.
Our data show that developmental absence
of MeCP2 does not irreversibly damage neu-
rons, which suggests that RTT is not strictly a
neurodevelopmental disorder. The delayed onset
of behavioral and LTP phenotypes in Mecp2
+/
females emphasizes the initial functional integ-
rity of MeCP2-deficient neurons and fits with
the proposal that MeCP2 is required to stabilize
and maintain the mature neuronal state (4, 6).
Consistent with the maintenance hypothesis, the
time taken for major symptoms to appear post-
natally in females heterozygous for an MECP2
mutation is similar in humans (6 to 18 months)
andmice(4to12months),despitefundamental
interspecies differences in developmental matu-
rity at this time. The restoration of neuronal
function by late expression of MeCP2 suggests
that the molecular preconditions for normal
MeCP2 activity are preserved in its absence. To
explain this, we propose that essential MeCP2
target sites in neuronal genomes are encoded
solely by patterns of DNA methylation that are
established and maintained normally in cells
lacking the protein. According to this hypothesis,
newly synthesized MeCP2 molecules home to
their correct chromosomal positions as dictated
by methyl-CpG patterns and, once in place, re-
Fig. 2. Reversal of the neurological phenotype by activation of the Mecp2
gene in Stop/y,cre males. (A)TimecourseoftheStop/y phenotype. (B,C,and
D) Plots of the phenotypic scores () and weights (x) of individual wild-type
(wt)(B),Stop/y (Stop)(C),andMecp2
lox-Stop/y
,cre-ER (Stop-cre)(D)animals
after TM injections (vertical arrows). (See also fig. S2.) Stars in (D) indicate
when the clips shown in movies S1 and S2 were recorded. (E) Aggregate
symptom score profiles following TM injection of Stop/y,cre (,n=3to6,
except *, which was a single animal) and Stop/y (,n= 4 to 5; except ## and
#,whichare2and1datapoints,respectively)mice.(F) Survival profiles of
TM-treated Stop/y,cre mice and control Stop/y mice. (G)Southernblot
showing deletion of the lox-Stop cassette (lanes 3 and 5) after a weekly TM
injection regime + booster injections.
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Fig. 3. Reversal of late-onset neurological symptoms by Mecp2 gene induc-
tion in mature adult Stop/+,cre females. (A) Time course of symptom onset.
TM administration began during the bracketed period (TM3). (B,C,andD)
Phenotype () and weight (x) profiles for a Stop/+ female (B) and two
Stop/+,cre females (C and D). All animals shown were subjected to either five
daily TM injections or five weekly plus three booster TM injections (vertical
arrows). Animals subject to weekly injection regimes were scored blind as
part of a mixed genotype cohort. (E) Plot of average symptom scores for
females with wt (,n= 5 to 6), Stop/+ (,n= 6 to 7), and Stop,+,cre
(,n= 5 to 11) genotypes. Repeated measures analysis of variance
(ANOVA) compared Stop/+ and Stop/+,cre female scores in weeks 11 to 16.
(F)SouthernblotanalysisoftheeffectsofTMtreatmentonacohort
including six Stop/+,cre (lanes 5 to 10), six wt (lanes 11 to 16) and six Stop/+
(lanes 17 to 22) females. All three genotypes received TM. Restriction
fragments derived from Mecp2 lox-Stop (Stop), deleted Mecp2
D
(D) and wild
type (wt) are marked with arrows. Brain DNA from animals 32 and 5 shown
above are in lanes 9 and 6, respectively. Lanes 1 to 4 show blots of wt male,
Stop/y male, Stop/+ female, and Mecp2
D/+
female, respectively.
Fig. 4. A deficit in long-
term potentiation (LTP)
accompanies onset of
symptoms in mature
adult Mecp2
lox-Stop/+
het-
erozygous females and is
reversed by Mecp2 reac-
tivation. (A) Stimulation-
response curves in
symptomatic (blue) or
presymptomatic (red)
Mecp2
+/
female mice
and wt littermate con-
trols (black; all P>0.05).
(B)MeasurementsofLTP
using a high-frequency
stimulation (HFS) para-
digm in presymptomatic
(n=9;P> 0.05),
symptomatic (n=9;P<
0.05) Mecp2
+/
mice, and
wt female littermate con-
trol groups (n=7and8;
pooled data plotted).
(C)MeasurementsofLTP
using theta-burst stimu-
lation in presymptomatic
(n=9;P>0.05),
symptomatic (n=9;
P<0.05)Mecp2
+/
mice, and wt female lit-
termate control groups
(n= 7 and 8). (D) HFS-induced LTP measurements in TM-treated symptomatic Stop/+ mice (n= 11; P< 0.05), Stop/+,cre mice (n=10;P>0.05),andwt
mice (n=9;P> 0.05). Recombination data are shown in Fig. 3F. Insets in (B) to (D) show representative voltage traces before (1) and after (2) LTP induction.
Two-way repeated measures ANOVA was used to assess significance throughout.
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sume their canonical role as interpreters of the
DNA methylation signal (15, 16).
Our study shows that RTT-like neurological
defects due to absence of the mouse Mecp2 gene
can be rectified by delayed restoration of that
gene. The experiments do not suggest an
immediate therapeutic approach to RTT, but they
establish the principle of reversibility in a mouse
model and, therefore, raise the possibility that
neurological defects seen in this and related
human disorders are not irrevocable.
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for reagents; and to D. Kleinjan, I. Vida, and R. Morris for
comments on the manuscript. The work was funded by
the Wellcome Trust, the Rett Syndrome Research
Foundation (USA), and Rett Syndrome UK/Jeans for Genes.
Supporting Online Material
www.sciencemag.org/cgi/content/full/315/5815/1143/DC1
Materials and Methods
Figs. S1 to S7
References
Movies S1 to S3
4 December 2006; accepted 18 January 2007
10.1126/science.1138389
www.sciencemag.org SCIENCE VOL 315 23 FEBRUARY 2007 1147
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originally published online February 8, 2007
(5815), 1143-1147. [doi: 10.1126/science.1138389]315Science
(February 8, 2007)
Jacky Guy, Jian Gan, Jim Selfridge, Stuart Cobb and Adrian Bird
Syndrome
Reversal of Neurological Defects in a Mouse Model of Rett
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... To analyze the effect of tandospirone treatment on the pathological phenotype of Rett syndrome, the "Score test" was evaluated in Mecp2-KO mice according to a previous report adopted in the study of the Mecp2 null mouse model [24,38]. In detail, the pharmacological treatment started at 4 weeks of age. ...
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Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the gene that encodes methyl CpG-binding protein 2 (MECP2) and is characterized by the loss of acquired motor and language skills, stereotypic movements, respiratory abnormalities and autistic features. There has been no effective treatment for this disorder until now. In this study, we used a Mecp2-null (KO) mouse model of RTT to investigate whether repeated intraperitoneal treatment with the 5-HT1A receptor agonist tandospirone could improve the RTT phenotype. The results showed that administration of tandospirone significantly extended the lifespan of Mecp2-KO mice and obviously ameliorated RTT phenotypes, including general condition, hindlimb clasping, gait, tremor and breathing in Mecp2-KO mice. Tandospirone treatment significantly improved the impairment in GABAergic, glutaminergic, dopaminergic and serotoninergic neurotransmission in the brainstem of Mecp2-KO mice. Decreased dopaminergic neurotransmission in the cerebellum of Mecp2-KO mice was also significantly increased by tandospirone treatment. Moreover, RNA-sequencing analysis found that tandospirone modulates the RTT phenotype, partially through the CREB1/BDNF signaling pathway in Mecp2-KO mice. These findings provide a new option for clinical treatment.
... MeCP2-deficient mice exhibit multiple changes in synaptic communication, affecting both excitatory and inhibitory neurotransmission and circuit-level connectivity. Excitatory transmission is bidirectionally modulated by MeCP2 knockout (Nelson et al., 2006;Chao et al., 2007) and overexpression (Na et al., 2012), and long-term synaptic plasticity is also impaired in MeCP2-deficient mice (Asaka et al., 2006;Guy et al., 2007). Inhibitory signaling is also altered in several different brain areas (Dani et al., 2005;Medrihan et al., 2008). ...
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The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
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