EXOSC10/Rrp6 is essential for the eight-cell embryo/morula transition

The mouse 3′-5′ exoribonuclease EXOSC10/Rrp6 is required for rRNA processing, gametogenesis, brain development, erythropoiesis and blood cell enhancer function. The human ortholog is essential for mitosis in cancer cells and its enzymatic activity is inhibited by the anti-cancer drug 5-fluorouracil. Little is known, however, about the role of Exosc10 during embryo development and organogenesis. We generated an Exosc10 knockout model and find that Exosc10-/- mice show an embryonic lethal phenotype. We demonstrate that Exosc10 maternal mRNA is present in mutant oocytes and that the gene is expressed during early embryogenesis. Furthermore, we observe that EXOSC10 localizes to the periphery of nucleolar precursor bodies and nucleoli in blastomeres, which is consistent with the protein9s role in rRNA processing. Finally, we infer from genotyping data obtained with samples harvested at embryonic days e7.5, e6.5 and e4.5 and embryos cultured in vitro that Exosc10-/- mutants arrest at the eight-cell embryo/morula transition. Our results demonstrate a novel essential role for Exosc10 during early embryogenesis, and they are consistent with earlier work showing that impaired ribosome biogenesis causes a developmental arrest at the morula stage.