PARENT SESSION

(W309) DYNAMICS OF HISTONE VARIANT H2A.Z DURING PREIMPLANTATION DEVELOPMENT IN MICE.

Liu, Honglin¹, Kageyama , Shun-Ichiro¹, Aoki, Fugaku ¹, ¹ University of Tokyo, Kashiwa, Japan

ABSTRACT- The nuclear localization of H2A.Z protein was investigated in mouse preimplantation embryos. Immunocytochemistry showed that H2A.Z was localized in the nucleus throughout preimplantation development. However, the relative nuclear amount of H2A.Z, which was determined by measuring the intensity of antibody fluorescence on the basis of DNA content, decreased as embryos developed. When the amount in the male pronuclei of one-cell embryos was set as 1, the relative fluorescence values were 0.69, 0.47, 0.30, 0.13, and 0.06 in the female pronuclei and the nuclei of two-cell embryos, four-cell embryos, morulae, and blastocysts, respectively. The amount of H2A.Z protein in the male pronuclei was four-fold the amount in fully grown oocytes. The accumulation of H2A.Z protein in the nuclei of embryos after fertilization was tested by microinjecting H2A.Z-EGFP fusion expression vector into male pronuclei of one-cell embryos. The fusion protein was detected in the nuclei of two-cell embryos. The accumulation of H2A.Z was also observed in the nucleus of a somatic cell when the nucleus was transferred into an enucleated oocyte. The nucleus of an NIH 3T3 cell was transferred into an enucleated unfertilized oocyte (transferred before activation, TA protocol) or an activated oocyte (activated before transfer, AT protocol). It is known that somatic nuclei are efficiently reprogrammed in enucleated oocytes when they are transferred by the TA protocol but not by the AT protocol. Although the increase of H2A.Z was observed in the nuclei transferred by either protocol, the extent of the increase differed: the amount of H2A.Z was much higher in the nucleus transferred by the TA protocol than in that transferred by the AT protocol. Our results suggest that the accumulation of H2A.Z protein in the nuclei of embryos is necessary for the reprogramming of parental genomes at the beginning of development

KEY WORDS: preimplantation embryos, H2A.Z, nuclear transfer, genome reprogramming