Global analysis of the methyl-CpG binding protein MeCP2
View/ Open
Skene2010.doc (21.48Mb)
Date
2010Author
Skene, Peter J.
Metadata
Abstract
MeCP2 was initially identified as an abundant protein in the brain, with an affinity for
methylated DNA in vitro. Interestingly, both deficiency and excess of the protein leads to
severe neurological problems, such as Rett syndrome, which is the result of mutations in the
MECP2 gene. Subsequent transfection experiments showed that MeCP2 can recruit corepressor
complexes and inhibit gene expression in vivo. MeCP2 was therefore thought to
repress specific gene targets and the aetiology of Rett syndrome was proposed to result from
aberrant gene expression in the MeCP2-deficient brain. Although gene expression is
perturbed in the Mecp2-null mouse brain, few specific targets have been verified and
alternative hypotheses for MeCP2 function have been put forward. Previous binding studies
have also failed to clearly identify MeCP2 targets. To shed light on these matters, a novel
technique was generated to isolate neuronal and glial nuclei and established that the amount
of MeCP2 is unexpectedly high in neurons, with an abundance approaching that of the
histone octamer. Chromatin immunoprecipitation experiments on mature mouse brain
showed widespread binding of MeCP2, consistent with its high abundance, tracking the
methyl-CpG density of the genome. MeCP2 deficiency results in global changes in neuronal
chromatin structure, including elevated histone acetylation and a doubling of histone H1.
The mutant brain also shows elevated transcription of repetitive elements, which are
distributed throughout the mouse genome. Based on this data, we propose that MeCP2 binds
genome wide and suppresses spurious transcription through binding in a DNA methylation
dependent manner.