EFFECTS OF 5-AZACYTIDINE ON THE DEVELOPMENT OF PARTHENOGENETIC MOUSE EMBRYOS

This study describes the effects of 5-azacytidine (5-azaC) on the deve lopment of diploid parthenogenetic embryos (PE) of CBA, C57BL/6 and (C BA x C57BL/6)F-1 mice in vitro at the 1-cell or the blastocyst stage o r in vivo after implantation. Our findings indicate that genomic impri nting is modulated by genetic background. Non-fertilized C57BL/6 eggs form diploid parthenogenetic blastocysts at a much higher frequency th an CBA eggs. Eggs from F-1 hybrid females form parthenogenetic blastoc ysts at an approximately intermediate level between these inbred strai ns of mice. C57BL/6 PE do not develop to the somite stages. In contras t, CBA PE and F-1 PE develop to various somite stages. Following admin istration of 5-azaC at 1.0 mu mol/L in vitro at the 1-cell stage, the number of implantations of C57BL/6 PE transferred to pseudopregnant fe males increased. In contrast, the number of implantations and somite F -1 PE did not significantly change following exposure to 5-azaC. Howev er, administration of 5-azaC at the 1-cell stage stimulates developmen t of somite F-1 PE. Administration of 5-azaC at 0.2 and 1.0 mu mol/L i n vitro at the blastocyst stage did not change the number of implantat ions of C57BL/6 PE. However, the number of implantations and somite CB A PE decreased. After injection of 5azaC at 0.24 mg/kg in vivo at day 8 of gestation, some F-1 PE developed to 26-35 somites compared with a maximum of 25 somites in controls. The different effects of 5-azaC on the development of PE depend upon the mouse strain used and the stage of development.