title: MeCP2 expression in human cerebral cortex and lymphoid cells: immunochemical characterization of a novel higher-molecular-weight form.
abstract: Most cases of Rett syndrome are associated with mutations in the coding region of MECP2. Here we characterized a novel MeCP2 immunoreactivity, initially detected in normal cerebral cortex, by using a panel of MeCP2 antibodies and a combination of immunochemical techniques. We found that a novel higher-molecular-weight form (approximately 100 kDa) of MeCP2 is detected in human frontal cortex nuclear and synaptic fractions and in lymphoid cells. Although in the cortex the higher-molecular-weight form is relatively more abundant than the standard approximately 75 kDa immunoreactivity, in extranuclear locations, lymphocyte lysates show a predominance of the standard 75 kDa band. Lymphoblasts revealed a more complex pattern of MeCP2 expression, with prominent higher-molecular-weight form and both higher-molecular-weight form and 75 kDa MeCP2 immunoreactivities encompassing several closely migrating bands. We also successfully immunoprecipitated both the 75 kDa immunoreactivity and the higher-molecular-weight form MeCP2 from cerebral cortex with a C-terminal antibody and confirmed their identities by immunoblotting with C- and N-terminal antibodies. Our data provide compelling evidence for the existence of a novel MeCP2 molecular form, most likely the result of post-translational modification. Detection in both brain and lymphoid cells suggests an important role for higher-molecular-weight form in MeCP2-dependent processes. The presence of higher-molecular-weight form MeCP2 in postsynaptic fractions indicates a possible involvement in linking synaptic activity and transcriptional repression that, in turn, could play a role in the pathogenesis of Rett syndrome and other neurologic disorders.
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Mohammed H
authors.initials: MH
authors.lastname: Jarrar
authors.forename: Charles G
authors.initials: CG
authors.lastname: Danko
authors.forename: Sriram
authors.initials: S
authors.lastname: Reddy
authors.forename: Ye-Jin M
authors.initials: YJ
authors.lastname: Lee
authors.forename: Genila
authors.initials: G
authors.lastname: Bibat
authors.forename: Walter E
authors.initials: WE
authors.lastname: Kaufmann
mesh_terms: D000293:Adolescent; D000328:Adult; D018929:Cell Culture Techniques; D002540:Cerebral Cortex / Q000737:chemistry*; D002648:Child; D002675:Child, Preschool; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000235:genetics*; D005260:Female; D005625:Frontal Lobe / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000737:chemistry*; D008297:Male; D051783:Methyl-CpG-Binding Protein 2; D008875:Middle Aged; D008970:Molecular Weight; D009154:Mutation; D011233:Precipitin Tests; D012097:Repressor Proteins; D015518:Rett Syndrome / Q000235:genetics*; D013347:Subcellular Fractions; D013569:Synapses / Q000737:chemistry
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2; D012097:Repressor Proteins