Dynamics of parental genomic imprinting during human male germ cell development

It is generally assumed that parental DNA imprinting is complete before the onset of meiosis in human spermatogenesis. Conversely, we here demonstrate dynamic DNA methylation in multiple imprinted regions during meiosis and subsequent maturation of spermatids. This suggests a role for these genes in spermatogenesis and has implications for the effectiveness and safety of assisted conception using testicular sperm. A total of 25 pooled testicular cell samples were analyzed (n=5 patients per sample pool). Testicular tissue fragments were obtained from 50 healthy adult men with obstructive azoospermia, including vasectomy reversal, in the age range of 28 – 60 that visited the Center for Reproductive Medicine in Amsterdam, The Netherlands for TESE/IVF. Testicular morphology was visualized by hematoxylin/eosin staining and intact spermatogenesis was confirmed across most seminiferous tubules in the full cohort of patients, concurrent with a high yield of sperm cells obtained after TESE. Seminal fluid samples were obtained from an additional 25 adult fertile men that came to the clinic for semen collection for IVF based on a female subfertility indication.