Incomplete activation of and leads to preimplantation arrest in cloned mouse embryos.

Differentiated cell nuclei can be reprogrammed after nuclear transfer (NT) to oocytes and the produced NT embryos can give rise to cloned animals. However, development of NT embryos is often hampered by recurrent reprogramming failures, including the incomplete activation of developmental genes, yet specific genes responsible for the arrest of NT embryos are not well understood. Here, we searched for developmentally important genes among the reprogramming-resistant H3K9me3-repressed genes and identified and by siRNA screening. Gene knockout of and by the CRISPR/Cas9 system resulted in early developmental arrest in mice. was needed for the proper formation of inner cell mass by regulating , whereas deficiency led to apoptosis. The supplement of and mRNA supported efficient preimplantation development of cloned embryos. and were silenced in NT embryos partially because of the repressed expression of by H3K9me3. Thus, our study shows that the H3K9me3-repressed genes contain developmentally required genes, and the incomplete activation of such genes results in preimplantation arrest of cloned embryos.