Evaluating Autophagy in Preimplantation Embryos

Autophagy is an essential cellular degradation pathway in the mammalian preimplantation embryo. In this review, the process of autophagy is outlined and its function pertaining to preimplantation embryos is discussed. The current methods of measuring autophagy in preimplantation embryos are also summarized, with highlights of advances and challenges that one may encounter when examining preimplantation embryo autophagy. This article identifies the techniques, assays, and available models that are viable but infrequently used in the context of examining autophagy in preimplantation embryos. We aim to bring attention to alternative assays that could contribute to future analysis of autophagic pathways in preimplantation embryos. Abbreviations: AMBRA1: Activating molecule in Beclin-1-regulated autophagy 1; ATG: Autophagy-related protein; AL: Autolysosome; BCL-2: B-cell lymphoma 2; BECN1: Beclin-1; CQ: Chloroquine; ER: endoplasmic reticulum; ES cells: Embryonic stem cells; GFP: Green fluorescent protein; ICM: Inner cell mass; IF: Immunofluorescence; LC3: Light chain 3; LC3-II: Light chain 3 (lipid-conjugated); MAPK: mitogen-activating protein kinase; mTOR: Mammalian target of rapamycin; p62/SQSTM1: Sequestome 1; PA: Palmitic acid; PG: Phagophore; PtdIns3K: Phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3 phosphate; qPCR: Quantitative polymerase chain reaction; RFP: Red fluorescent protein; ROS: Reactive oxygen species; SNARE: Soluble N-ethylmaleimide-sensitive factor attachment protein receptor; TS cells: Trophoblast stem cells; ULK1: UNC-51-like kinase 1; WB: Western blot.