Research Paper Volume 11, Issue 8 pp 2295—2311

Cell-autonomous and non-autonomous roles of daf-16 in muscle function and mitochondrial capacity in aging C. elegans

Figure 1. Increased mitochondrial capabilities are associated with enhanced mobility during aging. (A) Animals treated with riboflavin and methylene blue which can increase the activity of dysfunctional mitochondria show increased mobility compared to control treated animals. The mobility of wild-type adult day 5 animals, treated with or without mitochondrial activators riboflavin (2.6 mM) and methylene blue (75 mM), was assessed by the measurement of thrashing behavior in liquid. The scatter plot graphs show the average numbers of body bends during a 30 second period. N = 12 for all genotypes and ages. * represents p < 0.05 by t‐test. (B) Reductions in daf-2 insulin-like signaling in the daf-2/IGFR mutant result in preserved mobility during aging. The mobility of aging wild-type and daf-2(e1371) mutant animals was assessed through the measurement of thrashing behavior in liquid. The bar graphs show the average numbers of body bends during a 30 second period on days 1, 3, 5, and 8 of adulthood. N = 12 for all genotypes and ages. * represents p < 0.05 by t‐test. (C) daf-2 mutants exhibit increased muscle mitochondrial mass as shown by digital imaging and quantitation of a muscle-expressed mitochondrial targeted GFP protein. Bars represents average muscle GFP fluorescence on adult days 1, 3, 5, and 8 in daf-2 mutant and wild-type animals. N >12 animals for all genotypes and ages. * represents p < 0.05 by t‐test. (D) daf-2 mutant and wild-type animals show similar expression of muscle filaments as revealed by digital imaging and quantitation of a muscle-expressed MYO-3::GFP fusion protein. N >12 animals for all ages and genotypes. (E) Confocal images showing muscle mitochondria in animals expressing a mitochondrial-localized GFP reveal that on adult day 5, the mitochondrial in daf-2 mutant animals show a well-organized interconnected reticulum of mitochondria. In wild-type animals, the mitochondria network shows some gaps and consists of fewer mitochondria as a longer exposure time is needed to capture an image with similar brightness to the daf-2 mutant. By adult day 8, the wild-type animals show a significant breakdown of the network with the formation of large abnormally-shaped mitochondria. In contrast, the filamentous network is still largely intact in the daf-2 mutants.