Despite dramatic increases in human lifespan, aging is still associated with increased risk of disease and a declining healthspan. Genetic factors contribute significantly to the variability in human lifespan and healthspan. Identifying genes regulating these complex processes is a critical first step in designing effective risk assessments and therapeutic interventions. Mice get the same diseases of aging as humans and share genetic loci influencing lifespan and healthspan. Hence, mice are a powerful model system to dissect mechanisms relevant to human aging. By integrating GWAS longevity hits with a transcriptome-wide expression study (TWAS) to detect genes showing differential age-related expression in the CHARGE consortium and including mouse QTL data, we identified 145 candidate genes that potentially play a role in aging. We are testing orthologs of these genes for effects on lifespan in C. elegans by RNAi knockdown and have identified 70 that extend lifespan in the worm. We hypothesize that a subset of these genes will also extend lifespan in mammals. To test the hypothesis, we will establish an Aging Knockout Mouse Project (Aging KOMP) to measure lifespan and disease phenotypes relevant to human aging in inbred mouse strains carrying single gene knockout (KO) mutations. Critical to this work is the prioritization of candidate genes. The initial tier selects a primary set of genes from human and mouse GWAS/TWAS, ensuring from the outset that the candidate list has a putative link to mammalian aging. Lifespan extension in C. elegans upon gene knockdown will serve as a second level of prioritization. The third tier will consist of additional phenotyping in the knockdown worms to identify traits known to be associated with increased lifespan. A parallel tier will consist of gens identified in mouse QTL studies for which there are no worm orthologs that can be tested in tiers 2 and 3 but that are nonetheless strong, compelling candidates.
The specific aims are to:
Aim 1. Test candidate genes using RNAi and knockout mutants in C. Elegans for effects on (a) lifespan, (b) healthspan and reproduction, and (c) interaction with known aging pathways. (a) Effects of each gene knockdown on lifespan in C. elegans will be established. A subset of genes for which knockdown produces a significant increase in lifespan will be selected for further characterization in C. elegans, including (b) healthspan (thrashing, pharyngeal pumping, and motility), reproduction (brood size), and (c) epistatic interaction with known aging pathways (e.g. insulin/IGF-1-like signaling).
Aim 2. (a) Determine lifespan and (b) perform healthspan studies in mice. Cohorts of control (C57BL/6NJ) and KO mice from each strain will be used in lifespan studies and phenotyping of traits relevant to human aging and age-related diseases. Upon completion and following expert review and statistical analysis, data will be migrated to the community databases, including the Mouse Genome Database and Mouse Phenome Database, which will enable broader discovery and integration with a wealth of information resources.
Our lifespan and susceptibility to disease as we age are influenced by genetic factors. Notably, mice and humans share genes influencing lifespan and age-related disease risk. Studies in mice, therefore, provide an avenue to identify genes regulating the complex process of aging as a critical first step in designing effective risk assessments and therapeutic interventions. Based on data obtained in human population studies, we have identified genes that we hypothesize influence human lifespan. We will first test these genes in a simple model organism, the worm (C. elegans), that is a powerful, fast, and cost-effective screening tool often used to screen genes for their effects on longevity. The genes that increase lifespan in the worm will then be tested in mice that have been genetically engineered to specifically lack each of those genes individually. Lifespan will be determined, and we will measure health-related parameters as the mice age. In this way, we will identify novel genes and pathways that influence aging.
