title: Functional Deficiencies in Fragile X Neurons Derived from Human Embryonic Stem Cells.
abstract: Fragile X syndrome (FXS), the most common form of inherited mental retardation, is a neurodevelopmental disorder caused by silencing of the FMR1 gene, which in FXS becomes inactivated during human embryonic development. We have shown recently that this process is recapitulated by in vitro neural differentiation of FX human embryonic stem cells (FX-hESCs), derived from FXS blastocysts. In the present study, we analyzed morphological and functional properties of neurons generated from FX-hESCs. Human FX neurons can fire single action potentials (APs) to depolarizing current commands, but are unable to discharge trains of APs. Their APs are of a reduced amplitudes and longer durations than controls. These are reflected in reduced inward Na(+) and outward K(+) currents. In addition, human FX neurons contain fewer synaptic vesicles and lack spontaneous synaptic activity. Notably, synaptic activity in these neurons can be restored by coculturing them with normal rat hippocampal neurons, demonstrating a critical role for synaptic mechanisms in FXS pathology. This is the first extensive functional analysis of human FX neurons derived in vitro from hESCs that provides a convenient tool for studying molecular mechanisms underlying the impaired neuronal functions in FXS.
  
  
  CONCLUSIONS
  Fragile X syndrome (FXS), the most common form of inherited mental retardation, is caused by silencing of the FMR1 gene. In this study, we describe for the first time the properties of neurons developed from human embryonic stem cells (hESCs) that carry the FMR1 mutation and are grown in culture for extended periods. These neurons are retarded compared with controls in several morphological and functional properties. In vitro neural differentiation of FX hESCs can thus serve as a most relevant system for the analysis of molecular mechanisms underlying the impaired neuronal functions in FXS.
authors.affiliation: Wolfe PGD-Stem Cell Laboratory, Racine IVF Unit, Lis Maternity Hospital, Tel-Aviv Sourasky Medical Center, Tel-Aviv 64239, Israel, Department of Cell and Developmental Biology, Sackler Medical School, Tel-Aviv University, Tel-Aviv 69978, Israel, and.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-7632-6942
authors.initials: M
authors.lastname: Telias
authors.affiliation: Wolfe PGD-Stem Cell Laboratory, Racine IVF Unit, Lis Maternity Hospital, Tel-Aviv Sourasky Medical Center, Tel-Aviv 64239, Israel, Department of Cell and Developmental Biology, Sackler Medical School, Tel-Aviv University, Tel-Aviv 69978, Israel, and.
authors.forename: Liron
authors.identifier: http://orcid.org/0000-0002-9705-6697
authors.initials: L
authors.lastname: Kuznitsov-Yanovsky
authors.affiliation: Department of Neurobiology, The Weizmann Institute, Rehovot 76100, Israel.
authors.forename: Menahem
authors.initials: M
authors.lastname: Segal
authors.affiliation: Wolfe PGD-Stem Cell Laboratory, Racine IVF Unit, Lis Maternity Hospital, Tel-Aviv Sourasky Medical Center, Tel-Aviv 64239, Israel, Department of Cell and Developmental Biology, Sackler Medical School, Tel-Aviv University, Tel-Aviv 69978, Israel, and dalitb@tlvmc.gov.il.
authors.forename: Dalit
authors.initials: D
authors.lastname: Ben-Yosef
mesh_terms: D000200:Action Potentials / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D018920:Coculture Techniques; D053595:Embryonic Stem Cells / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000235:genetics*; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000502:physiology*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D051381:Rats; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism / Q000473:pathology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; D010751:Phosphopyruvate Hydratase; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; C497683:FMR1 protein, human
keywords: action potential; disease modeling; fragile X syndrome; human embryonic stem cells; in vitro neural differentiation; synaptic deficiencies