Autophagy Is Essential for Preimplantation Development of Mouse Embryos

TLDR

After fertilization, maternal proteins in oocytes are degraded and new proteins encoded by the zygotic genome are synthesized. Autophagy, activated by fertilization and up‑regulated in early mouse embryos, is essential for preimplantation development, as Atg5‑deficient oocytes fail to progress beyond the four‑ and eight‑cell stages unless fertilized by wild‑type sperm, and protein synthesis is reduced in autophagy‑null embryos.

Abstract

After fertilization, maternal proteins in oocytes are degraded and new proteins encoded by the zygotic genome are synthesized. We found that autophagy, a process for the degradation of cytoplasmic constituents in the lysosome, plays a critical role during this period. Autophagy was triggered by fertilization and up-regulated in early mouse embryos. Autophagy-defective oocytes derived from oocyte-specific Atg5 (autophagy-related 5) knockout mice failed to develop beyond the four- and eight-cell stages if they were fertilized by Atg5-null sperm, but could develop if they were fertilized by wild-type sperm. Protein synthesis rates were reduced in the autophagy-null embryos. Thus, autophagic degradation within early embryos is essential for preimplantation development in mammals.