MeCP2 is thought to be a repressor of transcription. In RS mutations in the MECP2 gene cause the absence of functioning MeCP2 protein. It is possible that RS is due to the expression of genes that should be turned off in certain tissues, although no such gene has yet been identified. Identifying these genes will help shed light on possible treatments. The function of the abnormal MeCP2 protein must also be determined.
Females have two X chromosomes while males have one X chromosome.
In order for males and females to have the same amount of genetic material, females must silence one of their X chromosomes in every cell. DNA methylation acts on a more global scale to silence one X chromosome in every female cell. Genomic imprinting, which is characterized by the differential expression of a gene depending on whether it was maternally or paternally inherited, also relies on methylation to silence genes. The process by which gene expression is altered without changing the genetic structure of the gene is called epigenetics.