title: Autophagy gene-dependent clearance of apoptotic cells during embryonic development.
abstract: Autophagy is commonly observed in metazoan organisms during programmed cell death (PCD), but its function in dying cells has been unclear. We studied the role of autophagy in embryonic cavitation, the earliest PCD process in mammalian development. Embryoid bodies (EBs) derived from cells lacking the autophagy genes, atg5 or beclin 1, fail to cavitate. This defect is due to persistence of cell corpses, rather than impairment of PCD. Dying cells in autophagy gene null EBs fail to express the "eat-me" signal, phosphatidylserine exposure, and secrete lower levels of the "come-get-me" signal, lysophosphatidylcholine. These defects are associated with low levels of cellular ATP and are reversed by treatment with the metabolic substrate, methylpyruvate. Moreover, mice lacking atg5 display a defect in apoptotic corpse engulfment during embryonic development. We conclude that autophagy contributes to dead-cell clearance during PCD by a mechanism that likely involves the generation of energy-dependent engulfment signals.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Xueping
authors.initials: X
authors.lastname: Qu
authors.forename: Zhongju
authors.initials: Z
authors.lastname: Zou
authors.forename: Qihua
authors.initials: Q
authors.lastname: Sun
authors.forename: Kate
authors.initials: K
authors.lastname: Luby-Phelps
authors.forename: Pengfei
authors.initials: P
authors.lastname: Cheng
authors.forename: Robert N
authors.initials: RN
authors.lastname: Hogan
authors.forename: Christopher
authors.initials: C
authors.lastname: Gilpin
authors.forename: Beth
authors.initials: B
authors.lastname: Levine
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D051017:Apoptosis Regulatory Proteins; D001343:Autophagy / Q000235:genetics*; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D002952:Citric Acid Cycle; D047108:Embryonic Development; D053595:Embryonic Stem Cells; D004707:Endoderm / Q000166:cytology; D006801:Humans; D008168:Lung / Q000166:cytology; D008244:Lysophosphatidylcholines / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D010587:Phagocytosis / Q000235:genetics*; D010718:Phosphatidylserines / Q000378:metabolism; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D019289:Pyruvic Acid / Q000031:analogs & derivatives; D012160:Retina / Q000166:cytology; D015398:Signal Transduction
chemical_list: D051017:Apoptosis Regulatory Proteins; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D008244:Lysophosphatidylcholines; D008869:Microtubule-Associated Proteins; D010718:Phosphatidylserines; D011506:Proteins; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate