title: Global gene expression analysis of the living human fetus using cell-free messenger RNA in amniotic fluid.
abstract: BACKGROUND
  No molecular biological tests are available to monitor the ongoing development of human fetuses in vivo.
  
  
  OBJECTIVE
  To determine whether cell-free fetal messenger RNA (mRNA) in amniotic fluid can be detected using oligonucleotide microarrays to study large-scale gene expression in living human fetuses, with analysis of sex, gestational age, and fetal pathology as variables.
  
  
  METHODS
  Four samples of cell-free amniotic fluid were analyzed from pregnant women between 20 and 32 weeks' gestation and undergoing amnioreduction for polyhydramnios associated with twin-twin transfusion syndrome or hydrops fetalis (cases). The control consisted of 6 pooled amniotic fluid samples from women at 17 weeks' gestation and undergoing genetic amniocentesis. After extraction from the normally discarded fraction of amniotic fluid, RNA was amplified twice, labeled, and analyzed using gene expression microarrays.
  
  
  METHODS
  Relative mRNA expression in cell-free samples of amniotic fluid from fetuses with polyhydramnios at different gestational ages vs cell-free amniotic fluid from a pooled control.
  
  
  RESULTS
  Thirty-six percent of 22,283 probe sets represented on the arrays were present in the cell-free amniotic fluid, and a median of 20% of all probe sets differed between cases and the pooled control. Only male samples expressed 1 Y chromosome transcript. The expression of some developmental transcripts, such as surfactant proteins, mucins, and keratins, changed with gestational age by up to 64-fold. A water transporter gene transcript was increased up to 18-fold in both twin-twin transfusion samples. Placental gene transcripts were not present in any samples.
  
  
  CONCLUSIONS
  This pilot study demonstrates that cell-free fetal mRNA can be extracted from amniotic fluid and successfully hybridized to gene expression microarrays. Preliminary analysis suggests that gene expression changes can be detected in fetuses of different sexes, gestational age, and disease status. Cell-free mRNA in amniotic fluid appears to originate from the fetus and not the placenta.
authors.affiliation: Department of Pediatrics, Division of Newborn Medicine, Tufts-New England Medical Center, Boston, Mass 02111, USA.
authors.forename: Paige B
authors.initials: PB
authors.lastname: Larrabee
authors.forename: Kirby L
authors.initials: KL
authors.lastname: Johnson
authors.forename: Chaoqiang
authors.initials: C
authors.lastname: Lai
authors.forename: Jose
authors.initials: J
authors.lastname: Ordovas
authors.forename: Janet M
authors.initials: JM
authors.lastname: Cowan
authors.forename: Umadevi
authors.initials: U
authors.lastname: Tantravahi
authors.forename: Diana W
authors.initials: DW
authors.lastname: Bianchi
mesh_terms: D000649:Amniocentesis; D005260:Female; D047109:Fetal Development / Q000235:genetics*; D005865:Gestational Age; D006801:Humans; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D010865:Pilot Projects; D012333:RNA, Messenger / Q000032:analysis*
chemical_list: D012333:RNA, Messenger