Unbalanced placental expression of imprinted genes in human intrauterine growth restriction.
ABSTRACT Imprinted genes control fetal and placental growth in mice and in rare human syndromes, but the role of these genes in sporadic intrauterine growth restriction (IUGR) is less well-studied. We measured the ratio of mRNA from a maternally expressed imprinted gene, PHLDA2, to that from a paternally expressed imprinted gene, MEST, by Northern blotting in 38 IUGR-associated placentae and 75 non-IUGR placentae and found an increase in the PHLDA2/MEST mRNA ratio in IUGR (p=0.0001). Altered expression of PHLDA2 and MEST was not accompanied by changes in DNA methylation within their imprinting centers, and immunohistochemistry showed PHLDA2 protein appropriately restricted to villous and intermediate cytotrophoblast in the IUGR placentae. We next did a genome-wide survey of mRNA expression in 14 IUGR placentae with maternal vascular under-perfusion compared to 15 non-IUGR placentae using Affymetrix U133A microarrays. In this series six imprinted genes were differentially expressed by ANOVA with a Benjamini-Hochberg false discovery rate of 0.05, with increased expression of PHLDA2 and decreased expression of MEST, MEG3, GATM, GNAS and PLAGL1 in IUGR placentae. At lower significance, we found IGF2 mRNA decreased and CDKN1C mRNA increased in the IUGR cases. We confirmed the significant reduction in MEG3 non-translated RNA in IUGR placentae by Northern blotting. In addition to imprinted genes, the microarray data highlighted non-imprinted genes acting in endocrine signaling (LEP, CRH, HPGD, INHBA), tissue growth (IGF1), immune modulation (INDO, PSG-family genes), oxidative metabolism (GLRX), vascular function (AGTR1, DSCR1) and metabolite transport (SLC-family solute carriers) as differentially expressed in IUGR vs. non-IUGR placentae.
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ABSTRACT: PLECKSTRIN HOMOLOGY-LIKE DOMAIN, FAMILY A, MEMBER 2 (PHLDA2) is a maternally expressed imprinted gene whose elevated expression has been linked to fetal growth restriction in a number of human studies. In mice, Phlda2 negatively regulates placental growth and limits the accumulation of placental glycogen. We previously reported that a three-copy transgene spanning the Phlda2 locus drove a fetal growth restriction phenotype late in gestation suggesting a causative role for Phlda2 in human growth restriction. However, in this model Phlda2 was overexpressed by 4-fold alongside over expression of a second imprinted gene, Slc22a18. Here we genetically isolate the role of Phlda2 in driving late fetal growth restriction. We furthermore show that this Phlda2-driven growth restriction is asymmetrical with a relative sparing of the brain followed by rapid catch-up growth after birth, classic features of placental insufficiency. Strikingly, fetal growth restriction showed strain-specific differences being apparent on the 129 genetic background and absent on the BL6 background. A key difference between these two strains is the placenta. Specifically, BL6 placenta possess a more extensive endocrine compartment and substantially greater stores of placental glycogen. Taken together, these data support a direct role for elevated Phlda2 in limiting fetal growth but also suggest that growth restriction may only manifest when there is limited placental reserve. These findings should be taken into account in interpreting the results from human studies.Disease Models and Mechanisms 08/2014; 7(10). DOI:10.1242/dmm.017079 · 5.54 Impact Factor
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ABSTRACT: In utero growth restriction is the failure of a fetus to achieve its genetic growth potential during gestation. Elevated expression of the maternally expressed imprinted gene PHLDA2, has been reported in the human placenta of growth restricted pregnancies. A mouse modelling this alteration has been generated and also displays fetal growth restriction suggesting that increased expression of PHLDA2 is not an effect but rather a cause of growth restriction in human pregnancies. Here we review the current data linking PHLDA2 to growth restriction and the data from human and animal model studies suggesting that placental PHLDA2 expression may be responsive to environmental stimuli such as maternal lifestyle. Further investigation is warranted in larger studies of human placentas with the aim of determining whether placental PHLDA2 expression could be used as a diagnostic tool to identify or sub-classify growth restricted infants and to inform more effective interventions and treatment for IUGR in the future.Placenta 05/2014; 35(8). DOI:10.1016/j.placenta.2014.04.018 · 3.29 Impact Factor
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ABSTRACT: In pre-eclampsia, placental leptin is up-regulated and leptin is elevated in maternal plasma. To investigate potential epigenetic regulation of the leptin (LEP) gene in normal and complicated pregnancy, DNA methylation was assessed at multiple reported regulatory regions in placentae from control pregnancies (n=111), and those complicated by early onset pre-eclampsia (EOPET; arising <34 weeks; n=19), late onset pre-eclampsia (LOPET; arising ⩾34 weeks; n=18) and normotensive intrauterine growth restriction (nIUGR; n=13). The LEP promoter was hypomethylated in EOPET, but not LOPET or nIUGR placentae, particularly at CpG sites downstream of the transcription start site (-10.1%; P<0.0001). Maternal plasma leptin was elevated in EOPET and LOPET (P<0.05), but not nIUGR, compared with controls. EOPET cases showed a trend towards biallelic LEP expression rather than skewed allelic expression observed in control placentae, suggesting that loss of normal monoallelic expression at the LEP locus is associated with hypomethylation, leading to increased overall LEP expression.Molecular and Cellular Endocrinology 12/2012; 367(1-2). DOI:10.1016/j.mce.2012.12.018 · 4.24 Impact Factor