Table 1.
Number of informative heterozygous samples for H19, IGF2 and IGF2R for each gestational age class.
Figure 1.
Relative expression from H19 and IGF2 alleles in the human placenta.
Shaded bars for (A) H19 and (B) IGF2 represent the proportion of expression (%) from each allele. Samples 1–38 are from first trimester (6–12 weeks of gestation) placentae and samples 39–69 are from term (37–42 weeks of gestation) placentae.
Figure 2.
Relative expression from IGF2R alleles in the human placenta.
Shaded bars for (A) IGF2R rs1570070 and (B) IGF2R rs998075 represent the proportion of expression (%) in first trimester placentae. (C) Allelic expression ratios for IGF2R measured two SNP loci in the same sample. These paired samples indicate both SNP loci are equivalent (paired t-test, P = 0.42) for evaluating IGF2R allele-specific expression.
Figure 3.
Allelic expression ratios for H19, IGF2 and IGF2R in the human placenta.
The 50∶50 ratio represents equal expression from both alleles and 0∶100 ratio represents expression exclusively from one allele. Each point on the graph represents the allelic expression ratio measured in an individual placental sample. H19 and IGF2 samples are from first trimester and term placentae, IGF2R samples are all from first trimester placentae.
Figure 4.
Ratio of expression from each allele in human first trimester and term placentae measured by pyrosequencing.
Each point on the graph represents the allelic expression ratio observed in an individual placental sample. (A) H19 allelic expression ratio for each gestational age class. (B) Expression from the H19 repressed allele is significantly higher (*P<0.001) in first trimester placental samples. (C-D) IGF2 allelic expression ratios are similar for each gestational age class (C) with no significant difference (D) between first trimester and term. First trimester samples are 6–12 weeks of gestation term samples are 37–42 weeks of gestation.
Table 2.
Relative levels of repressed allele expression in human first trimester and term placentae.
Figure 5.
Relative level of expression from repressed alleles in samples heterozygous for both H19 rs217727 and IGF2 rs680.
Graph shows increased expression from the H19 repressed allele is not correlated (P = 0.09, r = 0.54) with expression from the IGF2 repressed allele.
Figure 6.
Placental methylation levels in regions upstream and covering the H19 transcription start site (TSS).
Each genomic region where DNA methylation was measured is highlighted in yellow and numbered 1–3. DNA methylation levels for individual CpG loci are shown for first trimester (red circles, n = 13) and term (blue circles, n = 18) placentae. Distance (bp) of cytosine nucleotide from H19 TSS is represented on x-axis. Each data point represents the mean methylation level for the gestational age class. * Indicates a significant difference in methylation levels between first trimester and term placentae at individual CpG sites. Error bars represent SEM and when not present SEM was too low to depict on the graph. The schematic representation below the graph highlights the regions between H19 and IGF2 where bisulfite DNA pyrosequencing was performed. Region 1 covers 5 CpG sites (Chr11∶2021011–2021070), region 2 covers 12 CpG sites (Chr11∶2021011–2021070) and region 3 covers 5 CpG sites (Chr11∶2019079–2019145). Genomic coordinates refer to reference assembly GRCh37/hg19.
Figure 7.
Levels of H19 repressed allele expression and DNA methylation in human first trimester placentae.
(A) Increased expression from the repressed H19 allele is positively correlated (P = 0.0016, r = 0.61) with increased DNA methylation in region 1. (B & C) H19 repressed allele expression is not correlated with DNA methylation in region 2 (P = 0.3626, r = 0.08) or region 3 (P = 0.4791, r = 0.04). Each point on the graph represents individual first trimester placenta samples. Methylation levels in each region represent the average methylation from 5 CpG sites in region 1 (Chr11∶2021011–2021070), 12 CpG sites in region 2 (Chr11∶2021011–2021070) and 5 CpG sites in region 3 (Chr11∶2019079–2019145). Genomic coordinates refer to reference assembly GRCh37/hg19.