Body pigmentation is a limitation for in vivo imaging and thus for the performance of longitudinal studies in biomedicine. A possibility to circumvent this obstacle is the employment of pigmentation mutants, which are used in fish species like zebrafish and medaka. To address the basis of aging, the short-lived African killifish Nothobranchius furzeri has recently been established as a model organism. Despite its short lifespan, N. furzeri shows typical signs of mammalian aging including telomere shortening, accumulation of senescent cells and loss of regenerative capacity. Here, we report the generation of a transparent N. furzeri line by simultaneous inactivation of three key loci responsible for pigmentation. We demonstrate that this stable line, named klara, can serve as a tool for different applications including behavioral experiments and the establishment of a senescence reporter by integration of a fluorophore into the cdkn1a (p21) locus and in vivo microscopy of the resulting line.

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Differences between the sexes are of increasing interest in basic and applied research with regard to development, behavior, aging, and diseases. Although the African turquoise killifishNothobranchius furzeri, a model for aging research well known for its remarkably short life span, develops strong sexual dimorphism in adulthood, there is no visible indicator of its sex in embryonic and juvenile stages. To address this issue, we developed a molecular sexing assay exploiting two large sequence polymorphisms in the minimal sex-determining region (SDR) ofN. furzeri. These polymorphisms are sequence deletions on the Y chromosome that involve the lack or truncation of one or multiple microsatellites. The simple polymerase chain reaction (PCR) readout of the assays described here allows the sexing ofN. furzeriembryos and larvae in a medium- to high-throughput and cost-efficient manner.

Body pigmentation is a major limitation for in vivo imaging and thus for the performance of longitudinal studies in biomedicine. A possibility to circumvent this obstacle is the employment of pigmentation mutants, which are used in fish species like zebrafish and medaka. To address the molecular basis of aging, the short-lived African killifish Nothobranchius furzeri has recently been established as a model organism. Despite its short lifespan, N. furzeri shows typical signs of mammalian aging including telomere shortening, accumulation of senescent cells and loss of regenerative capacity. Here, we report the generation of a transparent N. furzeri line by simultaneous inactivation of three key loci responsible for pigmentation. We demonstrate that this stable line, named klara, can serve as a tool for different in vivo applications including behavioral experiments addressing mate choice and the establishment of a senescence reporter by homology-directed repair-mediated integration of a fluorophore into the cdkn1a (p21) locus.

Sarcopenia, the age‐related decline in muscle function, places a considerable burden on health‐care systems. While the stereotypic hallmarks of sarcopenia are well characterized, their contribution to muscle wasting remains elusive, which is partly due to the limited availability of animal models. Here, we have performed cellular and molecular characterization of skeletal muscle from the African killifish—an extremely short‐lived vertebrate—revealing that while many characteristics deteriorate with increasing age, supporting the use of killifish as a model for sarcopenia research, some features surprisingly reverse to an “early‐life” state in the extremely old stages. This suggests that in extremely old animals, there may be mechanisms that prevent further deterioration of skeletal muscle, contributing to an extension of life span. In line with this, we report a reduction in mortality rates in extremely old killifish. To identify mechanisms for this phenomenon, we used a systems metabolomics approach, which revealed that during aging there is a striking depletion of triglycerides, mimicking a state of calorie restriction. This results in the activation of mitohormesis, increasing Sirt1 levels, which improves lipid metabolism and maintains nutrient homeostasis in extremely old animals. Pharmacological induction of Sirt1 in aged animals was sufficient to induce a late life‐like metabolic profile, supporting its role in life span extension in vertebrate populations that are naturally long‐lived. Collectively, our results demonstrate that killifish are not only a novel model to study the biological processes that govern sarcopenia, but they also provide a unique vertebrate system to dissect the regulation of longevity.