title: Human embryos developing in vitro are susceptible to impaired epithelial junction biogenesis correlating with abnormal metabolic activity.
abstract: BACKGROUND
  Blastocyst biogenesis occurs over several cell cycles during the preimplantation period comprising the gradual expression and membrane assembly of junctional protein complexes which distinguish the outer epithelial trophectoderm (TE) cells from the inner cell mass (ICM). In the human, TE integrity and the formation of a junctional seal can often be impaired. Embryos likely to result in a successful pregnancy after transfer are mostly selected according to morphological criteria. Recent data suggest that non-invasive measurement of amino acid turnover may be useful to complement such morphological scores. Whether morphological and metabolic criteria can be linked to poor TE differentiation thereby underpinning developmental predictions mechanistically remains unknown.
  
  
  METHODS
  We examined TE intercellular junction formation in human embryos by immunofluorescence and confocal microscopy and correlated this process with morphological criteria and amino acid turnover during late cleavage.
  
  
  RESULTS
  Our results show that TE differentiation may be compromised by failure of membrane assembly of specific junction constituents. This abnormality relates more closely to metabolic profiles than morphological criteria.
  
  
  CONCLUSIONS
  Our data identify that amino acid turnover can predict TE differentiation. These findings are the first to link two mechanisms, metabolism and junction membrane assembly, which contribute to early embryo development.
authors.affiliation: School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, UK. jje@soton.ac.uk
authors.forename: Judith J
authors.initials: JJ
authors.lastname: Eckert
authors.forename: Franchesca D
authors.initials: FD
authors.lastname: Houghton
authors.forename: Judith A
authors.initials: JA
authors.lastname: Hawkhead
authors.forename: Adam H
authors.initials: AH
authors.lastname: Balen
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Leese
authors.forename: Helen M
authors.initials: HM
authors.lastname: Picton
authors.forename: Iain T
authors.initials: IT
authors.lastname: Cameron
authors.forename: Tom P
authors.initials: TP
authors.lastname: Fleming
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D001755:Blastocyst / Q000473:pathology / Q000502:physiology* / Q000648:ultrastructure; D004848:Epithelium; D006801:Humans; D066298:In Vitro Techniques; D009028:Morula / Q000473:pathology / Q000502:physiology* / Q000648:ultrastructure; D019108:Tight Junctions / Q000502:physiology*
chemical_list: D000596:Amino Acids