title: Allorecognition triggers autophagy and subsequent necrosis in the cnidarian Hydractinia symbiolongicarpus.
abstract: Transitory fusion is an allorecognition phenotype displayed by the colonial hydroid Hydractinia symbiolongicarpus when interacting colonies share some, but not all, loci within the allorecognition gene complex (ARC). The phenotype is characterized by an initial fusion followed by subsequent cell death resulting in separation of the two incompatible colonies. We here characterize this cell death process using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and continuous in vivo digital microscopy. These techniques reveal widespread autophagy and subsequent necrosis in both colony and grafted polyp assays. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays and ultrastructural observations revealed no evidence of apoptosis. Pharmacological inhibition of autophagy using 3-methyladenine (3-MA) completely suppressed transitory fusion in vivo in colony assays. Rapamycin did not have a significant effect in the same assays. These results establish the hydroid allorecognition system as a novel model for the study of cell death.
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA. leo.buss@yale.edu
authors.forename: Leo W
authors.initials: LW
authors.lastname: Buss
authors.forename: Christopher
authors.initials: C
authors.lastname: Anderson
authors.forename: Erica
authors.initials: E
authors.lastname: Westerman
authors.forename: Chad
authors.initials: C
authors.lastname: Kritzberger
authors.forename: Monita
authors.initials: M
authors.lastname: Poudyal
authors.forename: Maria A
authors.initials: MA
authors.lastname: Moreno
authors.forename: Fadi G
authors.initials: FG
authors.lastname: Lakkis
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects / Q000276:immunology*; D003063:Cnidaria / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D020287:In Situ Nick-End Labeling; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D009336:Necrosis / Q000276:immunology*; D020123:Sirolimus / Q000494:pharmacology
chemical_list: C025946:3-methyladenine; D000225:Adenine; D020123:Sirolimus