A human stem cell line derived from embryos that were identified by preimplantation genetic diagnosis (PGD) to carry the mutation for fragile X syndrome has provided an unprecedented view of early events associated with this disease.
In addition to giving scientists fresh insight into fragile X, results from this unique model system have emphasized the value of this new source of embryonic stem cells and may have a significant impact on the way that genetic diseases are studied in the future. The research is published in the November issue of the journal Cell Stem Cell, published by Cell Press.
Fragile X syndrome, the most common cause of inherited mental impairment and of autism, is caused by the absence of the fragile X mental retardation protein (FMRP). Most individuals with fragile X exhibit a specific mutation in the fragile X mental retardation 1 (FMR1) gene that usually coincides with epigenetic DNA modifications. However, the developmental timing and mechanisms associated with acquisition of these characteristics are not clear due to the absence of appropriate cellular and animal models.
To examine developmentally regulated events involved in fragile X pathogenesis, Dr. Nissim Benvenisty and Dr. Rachel Eiges from the Hebrew University Department of Genetics in Jerusalem, Israel, together with Dr. Dalit Ben-Yosef from the IVF unit at the Tel-Aviv Sourasky Medical Center, established a human embryonic stem cell (HESC) line from a preimplantation fragile X-affected embryo identified by PGD. The fragile X cell line, called HEFX, displayed all characteristics typical of an HESC line and possessed the full genetic mutation observed in fragile X patients.