Global Gene Expression Analysis of the Living Human Fetus Using Cell-Free Messenger RNA in Amniotic Fluid
- Paige B. Larrabee, MD;
- Kirby L. Johnson, PhD;
- Chaoqiang Lai, PhD;
- Jose Ordovas, PhD;
- Janet M. Cowan, PhD;
- Umadevi Tantravahi, PhD;
- Diana W. Bianchi, MD
- Author Affiliations: Department of Pediatrics, Divisions of Newborn Medicine (Dr Larrabee) and Genetics (Drs Johnson, Cowan, and Bianchi), Tufts–New England Medical Center, Boston, Mass; Nutrition and Genomics Laboratory, Jean Mayer–United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston (Drs Lai and Ordovas); and Department of Pathology and Laboratory Medicine, Women and Infants Hospital, Brown University, Providence, RI (Dr Tantravahi).
- Corresponding Author: Diana W. Bianchi, MD, 750 Washington St, NEMC #394, Tufts–@New England Medical Center, Boston, MA 02111 (dbianchi{at}tufts-nemc.org).
Abstract
Context 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.
Design, Setting, and Patients 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.
Main Outcome Measure 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.
