Differential Methylation of Syncytin-1 and 2 Distinguishes Fetal Growth Restriction from Physiologic Small for Gestational Age

Abstract

Objective The retroviral genes encoding Syncytin-1 (SYN1) and Syncytin-2 (SYN2) are epigenetically regulated, uniquely expressed in the placenta and critical to placental function. We sought to determine if placental expression and methylation patterns of SYN1 and SYN2 from pregnancies complicated by fetal growth restriction (FGR) differed from physiologic small for gestational age (SGA) and appropriate for gestational age (AGA) controls.

Study Design Placental biopsies were obtained from AGA, SGA and FGR neonates delivered at >36 weeks gestation. SGA and FGR were defined as birth weight <10% with FGR additionally requiring abnormal fetal testing. We quantified DNA methylation of SYN1 and SYN2 by EpiTyper and gene expression by RT-qPCR.

Results We identified 10 AGA, 9 SGA and 7 FGR placentas. There was decreased methylation in SYN1 and SYN2 in FGR relative to AGA and SGA. When the sum of SYN1 and SYN2 methylation was used for prediction of FGR from SGA, the area under the receiver operator characteristic curve was 0.9048 (0.7602, 1).

Conclusion SYN1 and SYN2 methylation marks differ in FGR and SGA. We plan future studies to examine these markers in cell free DNA to determine if these methylation changes could be used as a biomarker for FGR.

Keywords

retroelements - syncytin - methylation - placenta - fetal growth restriction - intrauterine growth restriction

Presentation Information

Findings presented at the 36th Annual Pregnancy Meeting, Society for Maternal Fetal Medicine, Atlanta, Georgia, February 1–6, 2016

• References

• 1 American College of Obstetricians and Gynecologists. ACOG Practice bulletin no. 134: fetal growth restriction. Obstet Gynecol 2013; 121 (05) 1122-1133
• 2 Dudley NJ. A systematic review of the ultrasound estimation of fetalweight. Ultrasound Obstet Gynecol 2005; 25 (01) 80-89
• 3 Gifford WD, Pfaff SL, Macfarlan TS. Transposable elements as genetic regulatory substrates in early development. Trends Cell Biol 2013; 23 (05) 218-226
• 4 Friedli M, Turelli P, Kapopoulou A. , et al. Loss of transcriptional control over endogenous retroelements during reprogramming to pluripotency. Genome Res 2014; 24 (08) 1251-1259
• 5 Rawn SM, Cross JC. The evolution, regulation, and function of placenta-specific genes. Annu Rev Cell Dev Biol 2008; 24: 159-181
• 6 Reiss D, Zhang Y, Mager DL. Widely variable endogenous retroviral methylation levels in human placenta. Nucleic Acids Res 2007; 35 (14) 4743-4754
• 7 Muir A, Lever A, Moffett A. Expression and functions of human endogenous retroviruses in the placenta: an update. Placenta 2004; 25 (Suppl A): S16-S25
• 8 Weiss RA, Stoye JP. Virology. Our viral inheritance. Science 2013; 340 (6134): 820-821
• 9 Dupressoir A, Lavialle C, Heidmann T. From ancestral infectious retroviruses to bona fide cellular genes: role of the captured syncytins in placentation. Placenta 2012; 33 (09) 663-671
• 10 Gao Y, He Z, Wang Z. , et al. Increased expression and altered methylation of HERVWE1 in the human placentas of smaller fetuses from monozygotic, dichorionic, discordant twins. PLoS One 2012; 7 (03) e33503
• 11 Ruebner M, Strissel PL, Langbein M. , et al. Impaired cell fusion and differentiation in placentae from patients with intrauterine growth restriction correlate with reduced levels of HERV envelope genes. J Mol Med (Berl) 2010; 88 (11) 1143-1156
• 12 Langbein M, Strick R, Strissel PL. , et al. Impaired cytotrophoblast cell-cell fusion is associated with reduced syncytin and increased apoptosis in patients with placental dysfunction. Mol Reprod Dev 2008; 75 (01) 175-183
• 13 Kudaka W, Oda T, Jinno Y, Yoshimi N, Aoki Y. Cellular localization of placenta-specific human endogenous retrovirus (HERV) transcripts and their possible implication in pregnancy-induced hypertension. Placenta 2008; 29 (03) 282-289
• 14 Ruebner M, Strissel PL, Ekici AB. , et al. Reduced syncytin-1 expression levels in placental syndromes correlates with epigenetic hypermethylation of the ERVW-1 promoter region. PLoS One 2013; 8 (02) e56145
• 15 Alexander GR, Himes JH, Kaufman RB, Mor J, Kogan M. A United States national reference for fetal growth. Obstet Gynecol 1996; 87 (02) 163-168
• 16 Gimenez J, Montgiraud C, Oriol G. , et al. Comparative methylation of ERVWE1/syncytin-1 and other human endogenous retrovirus LTRs in placenta tissues. DNA Res 2009; 16 (04) 195-211
• 17 Skaar DA, Li Y, Bernal AJ, Hoyo C, Murphy SK, Jirtle RL. The human imprintome: regulatory mechanisms, methods of ascertainment, and roles in disease susceptibility. ILAR J 2012; 53 (3-4): 341-358
• 18 Kainz B, Shehata M, Bilban M. , et al. Overexpression of the paternally expressed gene 10 (PEG10) from the imprinted locus on chromosome 7q21 in high-risk B-cell chronic lymphocytic leukemia. Int J Cancer 2007; 121 (09) 1984-1993
• 19 Schulte AM, Lai S, Kurtz A, Czubayko F, Riegel AT, Wellstein A. Human trophoblast and choriocarcinoma expression of the growth factor pleiotrophin attributable to germ-line insertion of an endogenous retrovirus. Proc Natl Acad Sci U S A 1996; 93 (25) 14759-14764
• 20 Liang CY, Wang LJ, Chen CP, Chen LF, Chen YH, Chen H. GCM1 regulation of the expression of syncytin 2 and its cognate receptor MFSD2A in human placenta. Biol Reprod 2010; 83 (03) 387-395
• 21 Ehrich M, Nelson MR, Stanssens P. , et al. Quantitative high-throughput analysis of DNA methylation patterns by base-specific cleavage and mass spectrometry. Proc Natl Acad Sci U S A 2005; 102 (44) 15785-15790
• 22 Himes KP, Koppes E, Chaillet JR. Generalized disruption of inherited genomic imprints leads to wide-ranging placental defects and dysregulated fetal growth. Dev Biol 2013; 373 (01) 72-82
• 23 Bianchi DW. Circulating fetal DNA: its origin and diagnostic potential-a review. Placenta 2004; 25 (Suppl A): S93-S101
• 24 Hatt L, Aagaard MM, Graakjaer J. , et al. Microarray-based analysis of methylation status of CpGs in placental DNA and maternal blood DNA: potential new epigenetic biomarkers for cell free fetal DNA-based diagnosis. PLoS One 2015; 10 (07) e0128918
• 25 Benton SJ, McCowan LM, Heazell AE. , et al. Placental growth factor as a marker of fetal growth restriction caused by placental dysfunction. Placenta 2016; 42: 1-8