title: Hydra, a powerful model for aging studies.
abstract: CnidarianHydrapolyps escape senescence, most likely due to the robust activity of their three stem cell populations. These stem cells continuously self-renew in the body column and differentiate at the extremities following a tightly coordinated spatial pattern. Paul Brien showed in 1953 that in one particular species,Hydra oligactis, cold-dependent sexual differentiation leads to rapid aging and death. Here, we review the features of this inducible aging phenotype. These cellular alterations, detected several weeks after aging was induced, are characterized by a decreasing density of somatic interstitial cell derivatives, a disorganization of the apical nervous system, and a disorganization of myofibers of the epithelial cells. Consequently, tissue replacement required to maintain homeostasis, feeding behavior, and contractility of the animal are dramatically affected. Interestingly, this aging phenotype is not observed in allH. oligactisstrains, thus providing a powerful experimental model for investigations of the genetic control of aging. Given the presence in the cnidarian genome of a large number of human orthologs that have been lost in ecdysozoans, such approaches might help uncover novel regulators of aging in vertebrates.
authors.affiliation: Faculty of Sciences, Department of Genetics and Evolution, University of Geneva , Geneva , Switzerland.
authors.forename: Szymon
authors.initials: S
authors.lastname: Tomczyk
authors.affiliation: Department of Biology, University of Alabama at Birmingham UAB , Birmingham , AL , USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Fischer
authors.affiliation: Department of Biology, University of Alabama at Birmingham UAB , Birmingham , AL , USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Austad
authors.affiliation: Faculty of Sciences, Department of Genetics and Evolution, University of Geneva , Geneva , Switzerland.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Galliot
keywords: Cold-sensitive strain; Hydra oligactis; inducible aging; loss of somatic stem cells; neurodegeneration; sexual differentiation