Fig. 5

Analysis of the influence of the SNP rs2071094 on the H19 methylation levels. (a) Schematic representation of the H19 CTCF6 locus showing the CpGs analysed by DBS (red and numbers 1–14) and the SNP-masked CpG (red). SNPs in high linkage disequilibrium are shown in green. Numbers on top refer to hg38 coordinates of chromosome 11. (b) Principal component analysis (PCA) of the 14 CpG sites in the H19 locus obtained by DBS for the 40 normal controls (NC), 77 normally methylated oligozoospermic (NMO) and one abnormally methylated oligozoospermic (AMO) colour-coded according to the SNP rs2071094 genotype: T/T black, T/G orange, G/G light blue. (c) Box plot showing the distribution of the CpG3 methylation in the 118 patients subdivided according to the SNP rs2071094 genotype. Statistically significant differences are denoted by letters: a—TG different from TT, b—GG different from TG and TT. P values are denoted by the number of letters, e.g. aaa p < 0.001 (Wilcoxon rank-sum test; Additional file 1: Tables S13 and S15). (d) Box plot showing the CpG3 methylation in the T versus the G allele of the 49 TG patients (Additional file 1: Table S14 and S15). aaa p < 0.001 (Mann-Whitney U test). (e) Box plot showing the CpG3 methylation in the 40 normal controls (NC, teal) and 77 normally methylated oligozoospermic (NMO, purple) divided according to the SNP rs2071094 genotype. No significant differences between normal and oligozoospermic patients sharing the same genotype (Wilcoxon rank-sum test; Additional file 1: Tables S13 and S15)