Development of new Assisted Reproductive Technology (ART) and regenerative medicine based on regulating gene expression during preimplantation development

The high rate of early embryonic developmental arrest is common and presents a major obstacle to achieving better successful pregnancy outcome in assisted reproductive technology (ART) and also development of therapeutic cloning by somatic cell nuclear transfer (SCNT). After fertilization, the maternal genetic program governed by maternally derived RNAs and proteins is switched to the embryonic genetic program by de novo transcription; this switch is termed zygotic genome activation (ZGA). ZGA is essential for establishing pluripotency and genome stability. However, it is unclear how ZGA plays a role in development and preventing mitotic errors. Nuclear transfer embryonic stem cells (ntESCs) are assumed to be closer to embryonic stem cells (ESCs) than induced pluripotent stem cells (iPSCs). Initial attempts to produce human stem cells using SCNT failed, as only 16% (124 of 761) of ZGA transcripts were upregulated after genome exchange in SCNT human embryos. Histone deacetylase inhibitors (HDACi) supplementation during the first cell cycle induced zygotic transcription in SCNT embryos, which lead to isolate ntESCs giving rise to all three germ layers, including insulin-producing cells. Therefore, ZGA can be deemed indispensable for blastocyst development and stem cell derivation through SCNT. Mining gene-expression-profiling data identified a zygotic genome activation (ZGA) gene, we identified Zscan5b. Zscan5b-deficient ESCs showed random distribution of gaps in their chromosomes, elevated DNA-stress response and developed cancerous lesions. A co-immunoprecipitation analysis showed that ZSCAN5B bound to the linker protein histone H1. In addition, rescue analysis restored genome stability. Therefore, the Zscan5b gene can be classified as encoding a protein directly involved in DNA repair and protection of chromosomal architecture. Exploring reprogramming path based on ZGA can be useful for development not only of regenerative medicine but also of ART.