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. Author manuscript; available in PMC: 2018 Nov 1.
Published in final edited form as: Curr Opin Toxicol. 2017 Oct 12;7:95–101. doi: 10.1016/j.cotox.2017.10.004

Figure 4.

Figure 4

Epigenetic modifications during spermatogenesis (39). During the different steps of spermatogenesis, several epigenetic modifications involving DNA methylations and histone modifications occur. (1) Primordial germ cells (PGCs) undergo a process of demethylation involving DNA (with erasure of genomic imprinting) and histones (namely, K4 and K9 residues of histone H3, the testis-specific H3 variant in mammals). Also, a process of H4 deacetylation is present. DNA methyltransferases (DNMT3A, DNMT3B, and DNMT3L) are expressed at this time. (2) In spermatogonia, a progressive DNA methylation occurs, with establishment of paternal methylation. (3) In spermatocytes, histone H3 lysine 9;(H3K9) and histone H3 lysine 4 (H3K4) methylation are observed. (4) In round spermatids, H4 becomes hyperacetylated, DNMT1 is expressed, and the transition from histones to transition proteins (TPs) occurs. (5) Elongated spermatids show a maintenance of DNA methylation, together with H3K9 demethylation. The transition from TPs to protamines occurs at this step. (6) In spermatozoa, the genomic imprinting is maintained. Image taken from [39]. Use of this image is under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the authors give appropriate credit to the original author(s) and the source (BioMed Central-the Open Access Publisher).