"The findings are extraordinary, and are of relevance not only to Rett Syndrome but to a much broader class of disorders, including autism and schizophrenia. The successful restoration of normal function demonstrated in the mouse models suggests that if we can develop therapies to address the loss of MECP2 we may be able to reverse neurological damage in children and adults with Rett, autism and related neuropsychiatric disorders," commented Zoghbi.
The reversal experiments were carried out in the Bird lab by research assistant Jacky Guy. Employing technology known as Cre-lox recombination, she created mouse models in which MECP2 was silenced by insertion of a Stop cassette into the gene, resulting in the neurological deficits seen in RTT. Silencing could be reversed at will by removing the Stop cassette, thereby reactivating the MECP2 gene. This was achieved by treating the mice with a drug that caused the enzyme Cre to enter the cell nucleus where it could splice out the cassette.
As well as losing overt behavioral defects, the mice also recovered a key electrophysiological function of the brain. This was determined by measuring LTP (long-term potentiation) which provides a quantifiable measurement of the ability of neurons to respond to stimulation. LTP has long been thought to reflect the cellular basis of learning and memory. Though LTP in RTT mice models was defective, it was restored to normal function by the reversal experiments.
"The reversal of neurological defects, reported in the remarkable article by Guy et al, is surprising because the cause of the symptoms occurred early in development
Contact: Monica Coenraads
Rett Syndrome Research Foundation