Rett Syndrome (RTT) is a severe neurological disorder diagnosed almost exclusively in girls. Children with RTT appear to develop normally until 6 to 18 months of age, when they enter a period of regression, losing speech and motor skills. Most develop repetitive hand movements, irregular breathing patterns, seizures and extreme motor control problems. RTT leaves its victims profoundly disabled, requiring maximum assistance with every aspect of daily living. There is no cure.
The instructions needed to make the cells of all living organisms are contained in their DNA, which is organized as two complementary strands with bonds between them that can be "unzipped" like a zipper. DNA is encoded with building blocks called bases which can be abbreviated A, T, C, G. Each base "pairs up" with only one other base: A-T, T-A, C-G, G-C create the bonds that connect the complementary strands. Long stretches of base pairs make up genes.
All genes found in the human body are present in every one of our cells. What allows the same cells to develop into a heart in one instance and a kidney in another? The answer is gene expression. In a typical human cell only one tenth of the genes are expressed; the rest are shut down.
One way that genes are shut down is by attaching a small "tag" called a methyl group to the C base. The number and placement of the methyl tags dictates when a gene should be silenced. The protein, MeCP2, binds to these methyl groups to silence particular genes.