Activated SKN-1 alters the longevity trajectory of long-lived C. elegans mutants

In the presence of stressful environments, the SKN-1 cytoprotective transcription factor is activated to induce the expression of gene targets that can restore homeostasis. However, constitutive activation of SKN-1 results in diminished health and a reduction of lifespan. Here we demonstrate the necessity to regulate the activity of SKN-1 for maintaining the longevity promoting responses associated with impaired daf-2/insulin receptor signaling, the eat-2 model of caloric restriction, and glp-1-dependent loss of germ cell proliferation. A hallmark of animals with constitutive SKN-1 activation is the age-dependent loss of somatic lipids and this phenotype is linked to the general reduction in survival in animals harboring the skn-1gf allele, but surprisingly, daf-2lf; skn-1gf double mutant animals do not redistribute somatic lipids which suggests the insulin signaling pathway functions downstream of SKN-1 in the maintenance of lipid distribution. As expected, eat-2lf; skn-1gf double mutant animals, which independently activate SKN-1, continue to display somatic lipid depletion in older ages with and without the skn-1gf activating mutation but animals lacking a proliferating germline do not redistribute somatic lipids, which supports a genetic model where SKN-1 activity is an important regulator of lipid mobilization in response to food availability to fuel the developing germline by engaging the daf-2/insulin receptor pathway. Overall design: Differential expression analysis to undestand the transcriptome differences between daf-2lf mutnats and daf-2lf;skn-1gf double mutants