 The expression of a few genes may be regulated through methylation of their CpG island, and MECP2 may play a role in a subset of these.Researchers have not yet determined which genes are targeted by the MeCP2 protein, but such genes are probably important for the normal function of the central nervous system.However, the first large-scale mapping of MECP2 binding sites in neurons found that only 6% of the binding sites are in CpG islands, and that 63% of MECP2-bound promoters are actively expressed and only 6% are highly methylated, indicating that MECP2's main function is something other than silencing methylated promoters.