Fig. 1

Analyses of human sperm DNA-methylation patterns in different groups. Principal component analysis (PCA) of Illumina 450K methylation-array beta values showed that OA separated from N and SN in the PC1 and PC2 planes (a), and that N separated from SN in the PC3 and PC4 planes (b). Venn diagram of significantly differentiated loci among groups in the number of CpG loci (c) and genes (d). e Hierarchical clustering of spermatozoal DNA-methylation patterns with differentiated loci among groups. f The methylation level on the cg11193865 site of the DLK1 gene. N normozoospermic men without smoking; SN normozoospermic men with heavy smoking; OA oligoasthenozoospermic patients without smoking. **p  < 0.01 compared to the N group