Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and the most common known cause of autism. FXS belongs to the category of human diseases classified as Repeat Expansion Disorders (REDs). This group of disorders is caused by the expansion of a tandem array of a simple repeat tract in a single specific gene. FXS is caused by the expansion of a CGG-repeat tract in the 5’-UTR of the FMR1 gene. Expansion of the CGG-repeats causes gene silencing by heterochromatin formation and results in the absence of its protein product, FMRP. Repeat-mediated chromatin changes are also seen in other REDs, suggesting a common underlying mechanism.
The main goal of my current research is to delineate the mechanisms involved in the repeat-mediated FMR1 gene silencing. This will allow us to design treatment strategies based on gene reactivation. For this, I am developing an induced pluripotent stem cell (iPSC) model for FXS that will aid in understanding the process involved in the developmentally regulated FMR1 gene silencing. I am also using neural stem cells derived from these iPSCs to conduct a drug screen to identify compounds that can restore FMR1 gene expression. Furthermore, I am studying the disease phenotypes in neurons generated from FXS iPSCs to identify markers that can be used to evaluate the efficacy of any drugs that show therapeutic potential. In addition to being useful for FXS, the knowledge gained from these studies will also help us understand the mechanisms involved in other REDs.
The areas that need further study include mechanisms involved in the expansion of CGG-repeats, the role of expanded CGG-repeats in FMR1 gene silencing, and the functions of the FMR1 gene product, FMRP.