Capturing epigenetic dynamics during pre-implantation development using live cell imaging.

During mammalian fertilization and pre-implantation development, the highly differentiated gametes revert to undifferentiated cell types following syngamy and then gradually differentiate into individual cell lineages. These processes involve changes in male and female gamete chromatin structure, in global epigenetic modifications and in nuclear architecture. We have developed a live cell imaging technique for oocytes and early embryos to understand these series of phenomena. Using this technique, we were able to observe dynamic changes in DNA methylation status in living embryos. Furthermore, epigenetic abnormalities were detected in reconstructed embryos generated by round spermatid injection or by somatic cell nuclear transfer. In this review, I will discuss the usefulness and possibilities of this imaging technique in studies on nuclear dynamics during fertilization and pre-implantation development.