Season of conception (SoC) and maternal periconceptional nutritional status predict methylation at VTRNA2-1. (a) Bisulfite pyrosequencing data on 215 Gambian children according to SoC. The rank plot (left) highlights the markedly different distribution according to SoC. The histogram (right) shows that individuals conceived in the dry season are under-represented for intermediate methylation expected at an imprinted locus (40 to 60%, highlighted) and over-represented for hypomethylation (P = 0.004). (b) In 80 Gambian infants with pyrosequencing data on both HF and PBL (left), VTRNA2-1 methylation in HF is highly correlated with that in PBL. Rank plot of average VTRNA2-1 methylation in HF of Gambian infants (right) shows that the SoC effect in HF is similar to that in PBL. (c) 450k array data on 120 Gambian children, according to SoC. Shown are 15 CpGs mapping to the VTRNA2-1 locus. The box highlights 10 CpGs corresponding to the imprinted DMR. The SoC effect on hypomethylation spans the entire imprinted DMR (P = 0.02, chi-squared test). (d) Rank plot of 450k array data at VTRNA2-1. Each box represents the methylation values across the 10 CpG sites spanning the imprinted DMR for one individual. (e) Seasonal variation in 13 methyl donor-related biomarkers and associated derivatives, back-extrapolated to time of conception and adjusted for gestation age (n = 164 pregnant mothers) . Biomarkers are expressed as percentage of bi-season geometric mean. ANOVA P-values of seasonal differences: *<0.05; **<0.01, ***<0.001. (f) Maternal nutritional status biomarkers around the time of conception predict VTRNA2-1 hypomethylation (<40%) in her infant. Low maternal vitamin B2 or methionine (MET) status increases risk of VTRNA2-1 hypomethylation (P = 0.05 and P = 0.01, respectively). Low maternal dimethylglycine (DMG) is protective (P = 0.05). (g) Repeat measurements by bisulfite pyrosequencing in 55 Gambians indicate that VTRNA2-1 methylation in PBL is highly stable over a period of 10 years.