Developmental Study of Fragile X Syndrome Using Human Embryonic Stem Cells Derived from Preimplantation Genetically Diagnosed Embryos

Abstract

We report on the establishment of a human embryonic stem cell (HESC) line from a preimplantation fragile X-affected embryo and demonstrate its value as an appropriate model to study developmentally regulated events that are involved in the pathogenesis of this disorder. Fragile X syndrome results from FMR1 gene inactivation due to a CGG expansion at the 5'UTR region of the gene. Early events in FMR1 silencing have not been fully characterized due to the lack of appropriate animal or cellular models. Here we show that, despite the presence of a full mutation, affected undifferentiated HESCs express FMR1 and are DNA unmethylated. However, epigenetic silencing by DNA methylation and histone modification occurs upon differentiation. Our unique cell system allows the dissection of the sequence by which these epigenetic changes are acquired and illustrates the importance of HESCs in unraveling developmentally regulated mechanisms associated with human genetic disorders.

Les cellules souches pluripotentes humaines

“…L'obtention de ces cellules repose actuellement sur deux méthodes : (1) la déri-vation de CSEh à partir d'embryons obtenus par fécondation in vitro et écartés du programme de procréation à la suite d'un diagnostic pré-implantatoire (DPI) car porteurs de la mutation causale d'une maladie monogénique ; (2) la conversion de cellules somatiques en cellules souches pluripotentes (hiPS, pour induced pluripotent stem cells) par manipulation génétique. En 2007, Nissim Benvenisty et ses collaborateurs ont été les premiers à démontrer que certains mécanismes moléculaires du syndrome de l'X fragile (X-Fra) pouvaient être reproduits dans les CSEh portant la mutation responsable [2]. À la suite de l'identification des techniques de reprogrammation génique [3], plusieurs équipes ont tenté de reproduire de la même façon les mécanismes de pathologies monogéniques à l'aide de lignées hiPS (Tableau I).…”

Human stem cells for modeling neurological disorders: Accelerating the drug discovery pipeline

“…When derived from blastocysts identified by preimplantation genetic diagnosis (PGD) as carrying congenital mutations for specific disease states [Verlinsky et al, 2005;Mateizel et al, 2006;Eiges et al, 2007;Ben-Yosef et al, 2008;Peura et al, 2008] or following genetic manipulation [Urbach et al, 2004], human ES cells afford new and relevant perspectives on human disorders. Combined with effective methods of differentiation, they should prove better than conventional mouse stem cell models for recapitulating the human phenotype, and at the very least are complementary to in vivo mouse models.…”

“…Combined with effective methods of differentiation, they should prove better than conventional mouse stem cell models for recapitulating the human phenotype, and at the very least are complementary to in vivo mouse models. Despite their potential, only a few human ES cell models of CNS diseases have been reported [Urbach et al, 2004;Verlinsky et al, 2005;Mateizel et al, 2006;Eiges et al, 2007]. Moreover, the pharmaceutical industry has been slow to adopt human ES cell-based screening despite a long standing use of in vitro cellular assays and the provision of guidelines for human ES cell research by organizations such as the National Academy of Sciences (http://www.nasonline.org/), the National Institutes of Health (http://www.nih.gov/), and the International Society of Stem Cell Research (http://www.isscr.org/).…”

“…While normal PGD-embryos can be used for assisted reproduction, mutant embryos can provide human ES cells exhibiting the same genotype and related defects [Verlinsky et al, 2005;Mateizel et al, 2006;Eiges et al, 2007;Ben-Yosef et al, 2008;Peura et al, 2008]. Once generated, cell lines can be used to decode the pathways through which mutations cause an inherited phenotype.…”

“…Once generated, cell lines can be used to decode the pathways through which mutations cause an inherited phenotype. Examples of PGD-derived ES cells representing CNS related disorders include lines for Huntington's disease [Verlinsky et al, 2005] and fragile X syndrome [Eiges et al, 2007]. Once established, these and other PGD-cell lines have the potential to provide a valuable and unlimited source of undifferentiated and differentiating ES cells and derivative neurons, glia, and other somatic cells for investigating the cause, effect, and treatment of aberrant human biology on a cellular level.…”