The Journal of Neuroscience, August 12, 2009 • 29(32):9941–9942 • 9941

Journal Club

Editor’s Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see http://www.jneurosci.org/misc/ifa_features.shtml.

MeCP2 Function in the Basolateral in

Synphen H. Wu* and Vladimir Camarena* Sackler Institute of Graduate Biomedical Studies, Skirball Institute of Biomolecular Medicine, Program in Molecular Neurobiology, New York University School of Medicine, New York, New York 10016 Review of Adachi et al.

Two parents watch with wonder as their first acterized by stereotypic hand motions, a knock out and demonstrated impaired child, a daughter, develops. As an infant, search for a sex-linked genetic basis was motor coordination, increased anxiety- she charms them with her smiles and bab- initiated. In 1999, mutations in a single like behaviors, impaired cue-dependent bling. By 9 months, she is excellent com- on the X —MECP2— fear conditioning, and abnormal social pany, able to sit in her highchair for meals was discovered to be the basis of the dis- interactions, indicating that loss of fore- and stuff her mouth with animal crackers. ease (Amir et al., 1999). The methyl CpG- MeCP2 contributes to a wide spec- Peek-a-boo is her favorite game, and binding 2 (MeCP2) binds to trum of Rett syndrome symptoms (Chen when her parents laugh, she joins in. methylated CpGs in DNA and was known et al., 2001, Gemelli et al., 2006). Then, over a few months, everything at the time to associate with the Sin3 ho- To link behavioral symptoms with spe- changes. Normally happy and alert, she molog A protein (Sin3A) and histone cific brain regions, Adachi et al. (2009) becomes withdrawn, sometimes crying deacetylase, regulators that re- sought to lower MeCP2 levels in the baso- for prolonged periods of time. Before, she press transcription. Based on these obser- lateral amygdala (BLA), a region that is loved grabbing at her parents’ thumbs. vations, the neurological dysfunction seen central to emotional responses. Since Now she fixates on her own hands, often in Rett syndrome was hypothesized to there are no known markers for BLA neu- rubbing them together intently. She no result from the loss of MeCP2-mediated rons that allow genetic knockdown in that longer speaks the simple words she had repression of critical target in particular subset of cells, the authors learned. Soon she will not be able to hold a . targeted the region using an adeno- cracker or reach for her toys. Her parents To examine the functions of MeCP2 associated virus that expresses Cre. In know something is very wrong, and after in vivo, knock-out mice were generated floxed Mecp2 mice, the virus induces ex- many doctors’ visits and tests, they receive by two groups of investigators (Chen et pression of the recombinase and knock a diagnosis: Rett syndrome. al., 2001; Guy et al., 2001). These mice re- out of MeCP2 in infected cells. The au- This devastating progression of devel- capitulated neurological degeneration thors injected the Cre-expressing virus opmental milestones gained then dramat- similar to that observed in patients with into the BLA of the previously generated ically lost is the picture of Rett syndrome, Rett syndrome. Additionally, conditional floxed Mecp2 mice (Chen et al., 2001) and one of the Spectrum Disorders. knock-out mice were generated to induce confirmed transgene expression using flu- First described by the Austrian neurolo- tissue-specific deletion of MeCP2. Mice in orescent in situ hybridization and BLA gist Andreas Rett in 1966, the collection of which Mecp2 was flanked by loxP sites in microdissection followed by mRNA and symptoms received attention as a clinical all cells were crossed to mice expressing protein analysis. Cre expression led to the presentation in 1983 (Hagberg et al., Cre recombinase under the control of knockdown of MeCP2 to ϳ50% of nor- 1983). Because predominantly females tissue-specific promoters, allowing Cre- mal levels for the region as a whole. present with the disorder, which is char- mediated recombination of the loxP sites, Mice were subjected to a battery of excision of Mecp2 in Cre-expressing cells, motor and behavior tests. In two tests of Received June 1, 2009; revised July 1, 2009; accepted July 9, 2009. and deletion of MeCP2 from those tissues. anxiety, the open field test and the ele- *S.H.W. and V.C. contributed equally to this work. Mice that lacked MeCP2 in forebrain vated plus maze, mice with BLA-specific Correspondence should be addressed to Synphen H. Wu, 540 First Ave- nue, SK 5-15, New York, NY 10016. E-mail: [email protected]. structures (hippocampus, cortex, stria- MeCP2 knockdown exhibited heightened DOI:10.1523/JNEUROSCI.2540-09.2009 tum, and amygdala) recapitulated much anxiety-like behavior. In fear-conditioning Copyright©2009SocietyforNeuroscience 0270-6474/09/299941-02$15.00/0 of the neurological dysfunction of the full assays, the mice demonstrated impaired 9942 • J. Neurosci., August 12, 2009 • 29(32):9941–9942 Wu and Camarena • Journal Club cue-dependent fear learning but intact null and overexpressing mice found that The findings of Adachi et al. (2009) are context-dependent fear learning. These 85% of the genes were downregulated in important because they not only link cer- findings were similar to those seen in a null animals and upregulated in overex- tain behaviors to the BLA, but they also previous study using forebrain-specific pressing animals (Chahrour et al., 2008). exclude motor behavior and social inter- knock-out mice (Gemelli et al., 2006). These results suggest that MeCP2 may action from BLA regulation. The virus- However, in tests of motor skills and so- predominantly activate genes. In support mediated technique they use to deliver cial interactions, BLA-specific deletion of of this, MeCP2 associated with CREB1 in Cre recombinase could be applied gener- MeCP2 did not produce any changes. the promoters of activated genes. ally to knock down genes in regions for From these findings, the authors conclude The findings of Adachi et al. (2009) which there are no good genetic markers. that the BLA is involved in the anxiety and might be reconciled with these other stud- Additionally, the anxiety effects produced fear-learning phenotypes but not the mo- ies if the role of MeCP2 in gene transcrip- by SAHA infusion may have implications tor or social interaction deficits of the tion is context dependent, as determined for inhibitor use as a forebrain conditional knock out. by the methylated status of a genomic re- potential therapeutic for other condi- The authors determined that these be- gion and also by the interactions with tions. The controversial issue of whether havioral phenotypes were attributable to transcriptional modulators like CREB1 or MeCP2 is acting as a repressor or an acti- loss of MeCP2-mediated repression be- Sin3A. MeCP2 might act mainly as a re- vator in the BLA can be clarified by more cause histone H3 acetylation, a mark of pressor in the amygdala while acting specific analysis to determine which target activated genes, was increased. They hy- mainly as activator in the . genes are controlled by MeCP2, and what pothesized that infusion of the BLA with a Adachi et al. (2009) argue in favor of their roles are in anxiety. histone deacetylase inhibitor would reca- MeCP2 as a repressor based on two find- pitulate the loss of MeCP2 by relieving ings: (1) After virus-mediated knock- References Adachi M, Autry AE, Covington HE 3rd, Monteggia genes of repression. They chronically in- down of MeCP2 in BLA, there is an LM (2009) MeCP2-mediated transcription re- fused SAHA, an inhibitor of class I and II increased amount of acetylated histone H3, pression in the basolateral amygdala may under- histone deacetylases, into the BLA bilater- and (2) infusion of histone deacetylase in- lie heightened anxiety in a mouse model of Rett ally. To confirm that gene transcription hibitor caused anxiety-like behavior that syndrome. J Neurosci 29:4218–4227. was active, they probed for acetylated his- mimicked the phenotype seen in BLA- Amir RE, Van den Veyver IB, Wan M, Tran CQ, tone H3 and histone H4, both of which specific MeCP2 knockdown mice. One ca- Francke U, Zoghbi HY (1999) Rett syn- were increased. veat to the first argument is that although an drome is caused by mutations in X-linked MECP2, encoding methyl-CpGbinding pro- The motor skills and behavior of these increase of acetylated histone H3 suggests an tein 2. Nat Genet 23:185–188. mice were similar to those of the mice in increase in transcription, the finding is not Chahrour M, Jung SY, Shaw C, Zhou X, Wong ST, which MeCP2 was knocked down specif- specific. When the authors examined the Qin J, Zoghbi HY (2008) MeCP2, a key ically in the BLA. SAHA-infused mice levels of several genes—Crh, Sgk, FK506, contributor to neurological disease, acti- demonstrated increased anxiety-like be- gephyrin, ␣-actinin and BDNF—they were vates and represses transcription. Science havior and impaired cue-dependent unable to detect increased amounts of tran- 320:1224–1229. Chen RZ, Akbarian S, Tudor M, Jaenisch R (2001) fear learning with no significant differ- scription. Moreover, they did not detect an Deficiency of methyl-CpG binding protein-2 in ence in context-dependent fear learn- increase in histone H4 acetylation, which is CNS neurons results in a Rett-like phenotype in ing. Additionally, there were no deficits also found in active genes. Although SAHA mice. Nat Genet 27:327–331. in social interaction, motor locomotion, infusion recapitulated the anxiety pheno- Gemelli T, Berton O, Nelson ED, Perrotti LI, or motor coordination. Therefore, the type of BLA-specific MeCP2 knockdown Jaenisch R, Monteggia LM (2006) Postnatal authors conclude that MeCP2 mediates mice, anxiety is a complex behavior that is loss of methyl-CpG binding protein 2 in the forebrain is sufficient to mediate behavioral these behaviors in the BLA by acting as a mediated by a combination of genes, and aspects of Rett syndrome in mice. Biol Psychi- repressor. SAHA infusion is likely to target genes that atry 59:468–476. Although MeCP2 was initially described are not regulated by MeCP2. Indicative of Guy J, Hendrich B, Holmes M, Martin JE, Bird A as a global repressor of transcription in this broader effect of SAHA, histone (2001) A mouse Mecp2-null mutation causes vitro, this function has been questioned. deacetylase inhibition led to acetylation of neurological symptoms that mimic Rett syn- Gene array studies do not show a global histone H4, which was not seen in the drome. Nat Genet 27:322–326. increase of transcription in Rett syndrome BLA-specific MeCP2 knockdown mouse. Hagberg B, Aicardi J, Dias K, Ramos O (1983) A progressive syndrome of autism, dementia, patients nor in Mecp2 knock-out mice. Also, the authors do not demonstrate that ataxia, and loss of purposeful hand use in girls: On the contrary, a microarray analysis the structures around the BLA were not Rett’s syndrome: report of 35 cases. Ann Neurol comparing the hypothalamus from Mecp2 affected by the SAHA infusion. 14:471–479.