|Reactivating the FMR1 (Fragile X) Gene
by Michael Tranfaglia MD FRAXA Medical Director, 8/1/2004
Several years ago, this group made an
interesting finding when they were
studying cells from an individual who
had an unusual case of Fragile X. This
person had a large expansion of the FMR1
gene but it was unmethylated (not shut down), so that the gene
continued to function, resulting in normal intelligence. When
cells from this unusual individual were fused with typical, fully
methylated Fragile X cells in a test tube, the methylated full
mutation chromosomes quickly became demethylated and
started to function normally. Apparently, there is some active
ingredient in the unusual cells which is able to restore function
to typical Fragile X cells. The team is working to identify this
active ingredient and exploit this knowledge for future treatment.
by Violeta Stoyanova, 6/2003
In Fragile X syndrome, the FMR1 gene does not function because it is switched off by a chemical modification, called methylation, of a commanding part of the DNA (the promoter). Our studies were performed by growing cells from Fragile X patients in test tubes. In these cells, we can specifically reverse the methylation of the FMR1 gene – an important step toward restoring its normal function.
Rare individuals exist who have long repeats in their FMR1 gene, but for some unknown reason the gene is not methylated and functions normally, so these people do not have Fragile X. We plan to investigate the pattern of gene expression in these healthy people and compare it to that of Fragile X patients. We hope to identify genes important for switching on (demethylating) the silenced FMR1 gene. We are studying cells from members of a family in which some individuals have a methylated FMR1 gene, and are affected by the syndrome, and others whose FMR1 gene is not silenced, in spite of long repeats. Using this strategy, we hope to identify important players in the process which prevents methylation or is even able to reverse the methylated state of the FMR1 gene in Fragile X patients.
Restoring FMRP Expression in Cells from Fragile X Patients
by Katie Clapp, 3/2001
In people with fragile X Syndrome, a mutation in the FMR1 gene shuts down the gene, so that no gene product, FMRP, is produced. Methylation is the chemical switch which shuts down the gene: several different sites on the promoter region of the gene are methylated. One possible strategy for the treatment of fragile X is to reverse the methylation of the gene, in order to restore FMRP production.
These studies are aimed at removing or preventing methylation in cells from fragile X patients by using antisense strategies. One promising antisense strategy is to use PNAs, artificial molecules that can be constructed to bind to a specific stretch of DNA. The result of this binding can be to alter the function of a gene. PNAs are particularly useful because they are relatively stable and not easily neutralized by a cell's natural housekeeping mechanisms which defend against viruses and other foreign bodies. PNAs have been shown to have the ability to pry apart the strands of inactivated, methylated DNA and actually cause demethylation, which in turn, in the case of the fragile X gene, could restore its normal function.
Dr. Hoogeveen and his team have produced a panel of PNAs, each directed at a specific site in the FMR1 gene. They have demonstrated that these PNAs can cross the blood brain barrier to reach brain cells. They are testing the various PNAs to see which ones can effectively reverse methylation of the gene. The timing of expression and the targeting to the brain will be major challenges. This is a time-consuming process because multiple sites of the FMR1 gene are methylated and no one knows which one(s) must be reversed in order to reactivate the gene so that it can produce protein.