title: The identification of zebrafish mutants showing alterations in senescence-associated biomarkers.
abstract: There is an interesting overlap of function in a wide range of organisms between genes that modulate the stress responses and those that regulate aging phenotypes and, in some cases, lifespan. We have therefore screened mutagenized zebrafish embryos for the altered expression of a stress biomarker, senescence-associated beta-galactosidase (SA-beta-gal) in our current study. We validated the use of embryonic SA-beta-gal production as a screening tool by analyzing a collection of retrovirus-insertional mutants. From a pool of 306 such mutants, we identified 11 candidates that showed higher embryonic SA-beta-gal activity, two of which were selected for further study. One of these mutants is null for a homologue of Drosophila spinster, a gene known to regulate lifespan in flies, whereas the other harbors a mutation in a homologue of the human telomeric repeat binding factor 2 (terf2) gene, which plays roles in telomere protection and telomere-length regulation. Although the homozygous spinster and terf2 mutants are embryonic lethal, heterozygous adult fish are viable and show an accelerated appearance of aging symptoms including lipofuscin accumulation, which is another biomarker, and shorter lifespan. We next used the same SA-beta-gal assay to screen chemically mutagenized zebrafish, each of which was heterozygous for lesions in multiple genes, under the sensitizing conditions of oxidative stress. We obtained eight additional mutants from this screen that, when bred to homozygosity, showed enhanced SA-beta-gal activity even in the absence of stress, and further displayed embryonic neural and muscular degenerative phenotypes. Adult fish that are heterozygous for these mutations also showed the premature expression of aging biomarkers and the accelerated onset of aging phenotypes. Our current strategy of mutant screening for a senescence-associated biomarker in zebrafish embryos may thus prove to be a useful new tool for the genetic dissection of vertebrate stress response and senescence mechanisms.
authors.affiliation: Schepens Eye Research Institute, Harvard Medical School, Boston, Massachusetts, United States of America. shuji.kishi@schepens.harvard.edu
authors.forename: Shuji
authors.initials: S
authors.lastname: Kishi
authors.forename: Peter E
authors.initials: PE
authors.lastname: Bayliss
authors.forename: Junzo
authors.initials: J
authors.lastname: Uchiyama
authors.forename: Eriko
authors.initials: E
authors.lastname: Koshimizu
authors.forename: Jie
authors.initials: J
authors.lastname: Qi
authors.forename: Purushothama
authors.initials: P
authors.lastname: Nanjappa
authors.forename: Shintaro
authors.initials: S
authors.lastname: Imamura
authors.forename: Asiful
authors.initials: A
authors.lastname: Islam
authors.forename: Donna
authors.initials: D
authors.lastname: Neuberg
authors.forename: Adam
authors.initials: A
authors.lastname: Amsterdam
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Roberts
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D015870:Gene Expression; D006801:Humans; D008136:Longevity; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology / Q000235:genetics* / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D035341:Telomeric Repeat Binding Protein 2; D029961:Zebrafish Proteins; D001616:beta-Galactosidase