Table 1.
Studies comparing DNA methylation and imprinting/epigenetic diseases in ART infants and natural conceived infants. AGA, appropriate for gestational age; ART, assisted reproductive technology; DMRs, differentially methylated region; DNA, deoxyribonucleic acid; ICSI, intracytoplasmic sperm injection; IVF, conventional in vitro fertilization; MI, methylation indices; NC, naturally conceived; NR, not reported; OI, ovulation induction; RNA, ribonucleic acid; SD, standard deviation; SGA, small for gestational age. Adapted with permission from Ref [43].
| Study | Design | Study Group (n) | Control Group (n) | Outcome Measures | Association | |
|---|---|---|---|---|---|---|
| ART vs. NC Infants | ICSI vs. IVF Infants | |||||
| Gomes et al., 2009 [44] | Prospective cohort | ART infants (18) | Negative controls: healthy NC infants (30). Positive controls: Beckwith-Wiedemann syndrome NC infants (3) | Gene studied: KvDMR1 Genomic DNA was obtained from peripheral blood (12 of 18) and placenta (6 of 18) in ART infants; umbilical cord and placenta samples (8 of 30) and peripheral blood (22 of 30) in negative controls; peripheral blood samples (3 of 3) in positive controls |
Hypomethylation at KvDMR1 was observed in 3 of 18 clinically normal infants conceived by ART (2 conceived through IVF and 1 through ICSI). Nevertheless, discordant methylation was observed in three dizygotic ART twins. Normal methylation was observed in negative controls and hypomethylation was observed in positive controls. |
Hypomethylation was found in both IVF and ICSI infants, suggesting that hypomethylation may not be restricted to a specific method of fertilization. Furthermore, infertility cause was not associated with hypomethylation, thus suggesting that hypomethylation may not be restricted to the presence of male factor infertility |
| Kanber et al., 2009 [45] | Prospective cohort | Small for gestational age ICSI infants (19) | Normal weight NC infants (29) | Genes studied: KCNQ1OT1, PEG1, PEG3, GTL2, IGF2, H19, PLAG1 Genomic DNA was obtained from buccal smears |
Hypermethylation of KCNQ1OT1 and borderline hypermethylation of PEG1 in one ICSI child only. ICSI was used due to male factor infertility (oligozoospermia), but the parents of the affected child had normal methylation patterns. The other studied ICSI children had normal methylation patterns | NR |
| Tierling, et al., 2010 [46] | Prospective cohort | ART infants (112; 35 IVF and 77 ICSI infants) | NC infants (73) | Genes studied: KvDMR1, H19, SNRPN, MEST, GRB10, DLK1/ MEG3 IG-DMR, GNAS, NEsP55, GNAS NESPas, GNAS XL-alpha-s, GNAS Exon1A Genomic DNA was obtained from maternal peripheral blood, umbilical cord and placenta |
ART infants did not show a higher degree of imprinting variability. However, the mean methylation indices (MI) for one DMR (MEST) were higher in maternal peripheral blood (mean MI ± SD: 0.40 ± 0.03) and umbilical cord (0.41 ± 0.03) of IVF infants compared to NC infants (0.38 ± 0.04; p = 0.02, maternal peripheral blood and 0.38 ± 0.03; p = 0.003, umbilical cord). | The mean methylation indices for one DMR (MEST) were higher in maternal peripheral blood (mean MI ± SD: 0.40 ± 0.03) and umbilical cord (0.41 ± 0.03) of IVF infants than ICSI infants (0.37 ± 0.04; p = 0.0007, maternal peripheral blood and 0.38 ± 0.03; p = 0.003, umbilical cord) |
| King et al., 2010 [47] | Prospective cohort | ART infants (22) | NC infants (31) | Gene studied: XCI Genomic DNA was obtained from cord blood |
Mildly skewed X chromosome inactivation (XCI) was present in 2 of 22 (9.1%) ART infants and 2 of 31 (6.5%) control infants. Extremely skewed X chromosome inactivation was present in 2 of 22 (9.1%) ART infants and 0 of 31 control infants. Neither difference was statistically significant; however, there was a trend toward a higher mean percentage of skewed X chromosome inactivation among ART infants | No risk difference for XCI skewing between ICSI (13) and IVF (9) groups (75.7% vs. 65.4%) |
| Turan, et al., 2010 [48] | Prospective cohort | ART infants (45) | NC infants (56) | Genes studied: IGF2/H19, IGF2R
Genomic DNA was obtained from cord blood, cord and placenta |
Aberrant methylation patterns at the IGF2/H19 locus were more common in ART infants. | NR |
| Wong, et al., 2011 [49] | Prospective cohort | ART infants (77; 25 IVF-AGA, 7 IVF-SGA, 32 ICSI-AGA and 13 ICSI-SGA) | NC infants (12; 7 NC-AGA and 5 NC-SGA) | Genes studied: H19, IGF2
Genomic DNA was obtained from placenta in all cases and umbilical cord in 7 of 77 ART infants |
No significant differences in mean methylation between ART infants and NC infants. Mean ± SD methylation values were 44.68% ± 4.18% in NC-AGA and 44.63% ± 3.60% in NC-SGA. | No significant differences in mean methylation between IVF vs. ICSI infants. Mean ± SD methylation values were 45.52% ± 4.86% in IVF-AGA, 47.25% ± 5.77% in IVF-SGA, 45.64% ± 6.06% in ICSI-AGA, and 42.73% ± 4.39% in ICSI-SGA. |
| Li et al., 2011 [50] | Prospective cohort | ART twins (29) | NC twins (30) | Genes studied: H19, IGF2, PEG1, KvDMR1 Genomic DNA was obtained from umbilical cord in all cases |
Methylation indices were not significantly different between ART twins (45.68%) and NC twins (42.88%) in paternally methylated H19/IGF2 DMRs, nor were these indices different between ART twins (51.14%) and NC twins (50.67%) in maternally methylated KvDMR1/PEG1 DMRs. | NR |
| Feng et al., 2011 [51] | Prospective cohort | ART infants (60; 30 IVF and 30 ICSI) | NC infants (60) | Genes studied: L3MBTL, PEG10, PHLDA2, PWCR1, SNRPN, UBE3A, TP73, GNAS, MEG3 Genomic DNA was obtained from umbilical cord blood and peripheral blood |
The expression levels of PEG10 (p = 0.018) and L3MBTL (p = 0.000) were significantly higher in ART infants than NC infants. The levels of PHLDA2 (p = 0.000) in ART infants were significantly lower than NC infants | NR |
| Oliver et al., 2012 [52] | Prospective cohort | ART infants (66; 34 IVF and 32 ICSI) | NC infants (69) | Genes studied: H19, SNRPN, KCNQ1OT1, IGF2 Genomic DNA was obtained from peripheral blood samples |
No significant differences in percentage of methylation between ART and control groups | NR |
| Rancourt et al., 2012 [53] | Prospective cohort | ART infants (59) and infants conceived by OI (27) | NC infants (61) | Genes studied: GRB10, MEST, SNRPN, KCNQ1, H19, IGF2 Genomic DNA was obtained from umbilical cord blood and placenta tissue in all cases |
Significant differences in median methylation levels were observed comparing infants conceived by OI to NC infants: in the placenta for H19 (40.2% OI vs. 44.6% NC; p < 0.0001), in the cord blood for KCNQ1 (43.6% OI vs. 42.3% NC; p = 0.003), and in both cord blood (42.5% OI vs. 40.4% NC; p = 0.047) and placenta (43.2% OI vs. 41.1% NC; p = 0.005) for SNRPN. Likewise, significant differences in median methylation levels were observed comparing infants conceived by ART to NC: in the placenta for H19 (43.4% ART vs. 44.7% NC; p = 0.01) and SNRPN (42.1% ART vs. 40.4% NC; p = 0.008), in the cord blood for KCNQ1 (42.9% ART vs. 42.3% NC; p = 0.02). Additionally, MEST had lower methylation levels in the placenta of ART group than NC (48% vs. 51.4% p < 0.0001). Despite of that, differences in methylation levels did not translate into differences in overall gene expression | NR |
| Puumala, et al., 2012 [54] | Prospective cohort | ART infants (67) | NC infants (31) | Genes studied: H19, KvDMR, IGF2, IGF2R Genomic DNA was obtained from peripheral blood and buccal smears |
No significant differences in the percentage of methylation between ART infants and NC infants. | NR |
| Hiura et al., 2012 [55] | Nationwide epidemiological study and prospective cohort study | ART infants diagnosed with imprinting diseases (6). One infant diagnosed with Beckwith-Wiedemann syndrome (ICSI) and five diagnosed with Silver-Russell syndrome (IVF) | NC infants diagnosed with imprinting diseases (16). Six infants diagnosed with Beckwith-Wiedemann syndrome and ten infants diagnosed with Silver-Russell syndrome. | Genes studied: H19, KCNQ1OT1, PEG1, GRB10, INPP5F, ZNF597, FAM50B, ZDBF2, PEG10, ZNF331, NESPAS Genomic DNA was obtained from blood or buccal smears |
A 10-fold increase in the frequency of Beckwith-Wiedemann syndrome (0.03% vs. 8.6%) and Silver-Russell syndrome (0.02% vs. 9.5%) in ART infants compared to NC infants (based on the 2009 population of Japan: 127,510,000). No significant differences were found in the methylation ratios of infants diagnosed with imprinting diseases conceived by ART or naturally | NR |
| Nelissen et al., 2013 [56] | Prospective cohort | ART infants (35; 5 IVF and 30 ICSI) | NC infants (35) | Genes studied: MEST, PEG3, KCNQ1OT1, SNRPN, H19, DLK1, MEG3 Genomic DNA was obtained from placenta |
Hypomethylation at H19 and MEST and increased RNA expression of H19 were observed in placentas from ART infants but not in placentas of NC infants. | NR |
| Sakian et al., 2015 [57] | Prospective cohort | ART infants (107; 56 through IVF and 41 through ICSI) | NC infants (22) | Genes studied: H19, IGF2 Genomic DNA was obtained from placenta |
Both IVF and ICSI placental tissue displayed higher H19 expression than controls (1.8 and 1.9 fold higher, respectively). IGF2 was significantly decreased in both IVF and ICSI groups (0.8 and 0.7 fold lower, respectively) when compared with the NC group | No differences were observed between IVF and ICSI placentas |
| Melamed et al., 2015 [58] | Prospective cohort | IVF infants (10) | NC infants (8) | Genome-wide approach in cord blood (total 27,578 CpG sites) | A total of 733 (2.7%) of the CpG sites were differentially methylated between the 2 groups (p < 0.05), with an overall significant higher relative hypomethylation in IVF infants than NC infants (p < 0.001) | NR |
| Vincent et al., 2016 [59] | Case-control study | ART infants (182; 101 IVF and 81 ICSI) | NC infants (82) | Genes studied: PLAGL1, KCNQ1OT1, PEG10, CDKN1C, IGF2, YWHAZ, KvDMR1, LINE-1 Genomic DNA was obtained from umbilical cord blood and/or placenta |
DNA methylation at PLAGL1 was significantly higher in IVF (47.9%) than ICSI (45.9%) and NC (45.9%) cord blood (p < 0.01). PLAGL1 expression was lower in both IVF (p < 0.01) and ICSI (p = 0.02) cord blood groups than in NC infants. | DNA methylation at PLAGL1 was significantly higher in IVF (47.9%) than ICSI (45.9%) (p < 0.01). No differences were found in DNA methylation between IVF and ICSI for KvDMR1 and LINE-1 in cord blood and placenta as well as PLAGL1 and PEG10 in placenta villi |