Downstream targets of methyl CpG binding protein 2 and their abnormal expression in the frontal cortex of the human Rett syndrome brain.
BACKGROUND
The Rett Syndrome (RTT) brain displays regional histopathology and volumetric reduction, with frontal cortex showing such abnormalities, whereas the occipital cortex is relatively less affected.


RESULTS
Using microarrays and quantitative PCR, the mRNA expression profiles of these two neuroanatomical regions were compared in postmortem brain tissue from RTT patients and normal controls. A subset of genes was differentially expressed in the frontal cortex of RTT brains, some of which are known to be associated with neurological disorders (clusterin and cytochrome c oxidase subunit 1) or are involved in synaptic vesicle cycling (dynamin 1). RNAi-mediated knockdown of MeCP2 in vitro, followed by further expression analysis demonstrated that the same direction of abnormal expression was recapitulated with MeCP2 knockdown, which for cytochrome c oxidase subunit 1 was associated with a functional respiratory chain defect. Chromatin immunoprecipitation (ChIP) analysis showed that MeCP2 associated with the promoter regions of some of these genes suggesting that loss of MeCP2 function may be responsible for their overexpression.


CONCLUSIONS
This study has shed more light on the subset of aberrantly expressed genes that result from MECP2 mutations. The mitochondrion has long been implicated in the pathogenesis of RTT, however it has not been at the forefront of RTT research interest since the discovery of MECP2 mutations. The functional consequence of the underexpression of cytochrome c oxidase subunit 1 indicates that this is an area that should be revisited.
Gibson
Joanne H
JH
Western Sydney Genetics Program, The Children's Hospital at Westmead, Sydney, Australia. jgibson@mit.edu
Slobedman
Barry
B
K N
Harikrishnan
H
Williamson
Sarah L
SL
Minchenko
Dimitri
D
El-Osta
Assam
A
Stern
Joshua L
JL
Christodoulou
John
J
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D051152:Clusterin / Q000235:genetics; D034284:Dynamin I / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D028361:Mitochondrial Diseases / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D015518:Rett Syndrome / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D055815:Young Adult
C495242:CLU protein, human; D051152:Clusterin; C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D003576:Electron Transport Complex IV; D034284:Dynamin I