Developmental exposure of male germ cells to 5-azacytidine results in abnormal preimplantation development in rats.
Methylation of cytosine residues in mammalian DNA is established during gametogenesis and embryogenesis; it plays an important role in gene regulation and normal embryonic development and has also been implicated in genomic imprinting. In the present study, we evaluated whether paternal administration of 5-azacytidine, a drug that is incorporated into DNA and blocks DNA methylation, could alter male germ cell development and function. A drug that does not block methylation, 6-azacytidine, served as a control. Adult male Sprague-Dawley rats (n = 4-8 per group) were treated i.p., three times per week for 4 and 11 wk, with saline or 2.5 (low dosage) or 5.0 (high dosage) mg/kg of 5-azacytidine and 6-azacytidine. After each of the treatment periods, males were mated to determine effects on fertility and embryo development. Although neither 6-azacytidine nor 4 wk of 5-azacytidine treatment affected male reproductive organ weights or sperm counts, 11 wk of 5-azacytidine resulted in dose-dependent reductions in testis and epididymal weights and sperm counts. Both dosages of 5-azacytidine resulted in significant increases in preimplantation loss, and the high dosage of 5-azacytidine caused a decrease in fertility. Examination of embryos on Day 2 of gestation revealed a striking dose-dependent increase in the average number of abnormal embryos per litter sired by the males treated with 5-azacytidine (saline, 0.33 +/- 0.24; low dosage, 2.64 +/- 0.92; high dosage, 10.09 +/- 0.95). In summary, paternal administration of 5-azacytidine interfered with normal male germ cell development and resulted in alterations in fertilization and early embryo development. We suggest that 5-azacytidine-induced alterations in germ cell DNA methylation patterns may be one of the underlying mechanisms, since similar dosages of the analogue 6-azacytidine had no effect on male reproduction and progeny outcome.
Department of Pediatrics, Pharmacology & Therapeutics, McGill University, Montreal, Quebec, Canada.
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Doerksen
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Trasler
D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology*; D001835:Body Weight / Q000187:drug effects; D047108:Embryonic Development; D004906:Erythrocyte Count; D005260:Female; D005313:Fetal Death; D007958:Leukocyte Count; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013076:Sperm Count; D013094:Spermatozoa / Q000187:drug effects* / Q000502:physiology*; D013154:Spleen / Q000033:anatomy & histology; D013737:Testis / Q000033:anatomy & histology
D001374:Azacitidine; C040881:6-azacytidine