Immunofluorescent analysis of rat cerebellum section costained with mouse monoclonal antibody to MeCP2 (MCA-5H12, dilution 1:2000, red), and rabbit polyclonal antibody to GFAP (RPCA-GFAP, dilution 1:5000, green). The blue is DAPI staining of nuclear DNA. Following transcardial perfusion of rat with 4% paraformaldehyde, brain was post fixed for 1 hour, cut to 45 μM, and free-floating sections were stained with above antibodies. MeCP2 is specifically expressed in nuclei of neuron cells. The GFAP antibody stains the network of glial cells.
Methyl-CpG Binding Protein 2 (MeCP2) is a nuclear protein heavily expressed in neurons. It functions as a transcriptional modulator that can alter gene expression epigenetically via binding to methylated CpG islands in DNA. It is involved not only in transcriptional silencing, but also in transcriptional activation, chromatin remodeling, and RNA splicing. The MeCP2 protein is unusually highly charged with 20% content of the basic amino acids Lysine and Arginine, resulting in a very basic isoelectric point of 9.88. This is likely the reason why the full length protein runs on SDS-PAGE at 74kDa rather than the expected 54kDa. The MeCP2 gene is located on the X-chromosome and mutations in the gene are linked to Rett syndrome (RTT) (2), a neurodevelopmental, autistic disorder that affects mainly females. Studies show that even the loss of a specific phosphorylation site of MeCP2 (e.g., S80, S421, and S424) disturbs normal maturation of the mammalian brain. Neuronal activity has been reported to trigger phosphorylation of MeCP2 at S421 in Vitro and in Vivo, which was further postulated to regulate activity-dependent gene transcription and neuronal spine maturation (3,4). Mutation of the S80 phosphorylation site reduces MeCP2 association with chromatin at several euchromatic gene promoters, alters transcription of several genes that are potentially important for neuronal function (5). The HGNC name for this protein is MECP2.
1: Klose RJ, Sarraf SA, Schmiedeberg L, McDermott SM, Stancheva I and Bird AP. DNA binding selectivity of MeCP2 due to a requirement for A/T sequences adjacent to methyl-CpG. Mol. Cell, 19, 667–678 (2005).
2: Amir RE, Van den Veyver IB, Wan M, Tran CQ, Francke U and Zoghbi HY. Rett syndrome is caused by mutations in X-linked MECP2, encoding methyl-CpG-binding protein 2. Nat. Genet., 23, 185–188 (1999).
3: Zhou Z, Hong EJ, Cohen S, Zhao WN, Ho HY, Schmidt L, Chen WG, Lin Y, Savner E, Griffith EC, Hu L, Steen JA, Weitz CJ, Greenberg ME. Brain-specific phosphorylation of MeCP2 regulates activity dependent Bdnf transcription, dendritic growth, and spine maturation.Neuron 52:255–269 (2006).
4: Deng JV, Rodriguz RM, Hutchinson AN, Kim IH, Wetsel WC, West AE. MeCP2 in the nucleus acumbens contributes to neural and behavioral responses to psychostimulants. Nat Neurosci. 13(9):1128-36 (2010).
5: Tao J, Hu K, Chang Q, Wu H, Sherman NE, Martinowich K, Klose RJ, Schanen C, Jaenisch R, Wang W, Sun YE. Phosphorylation of Mecp2 at Serine 80 regulates its chromatin association and neurological function. Proc Natl Acad Sci U S A 24;106(12) (2009).