Figure 1. DAF-16 Acts Cell Nonautonomously to Regulate Muscle Aging and Autonomously to Regulate
mtl-1 and
dod-17 Expression (A) Intestinal DAF-16 protects
daf-16(-) muscles from age-dependent deterioration. Top: Extent of sarcomere degeneration on day 10 of adulthood (micrographs scored/animals analyzed) (see Supplemental Experimental Procedures) (Mann-Whitney-Wilcoxon test of all data points; n.s., not significant). Bottom: Percentages of animals with extensive degeneration (Class C, as defined by Herndon et al. [2002]) (Student's t test of independent experiments). A gap in the sarcomere of a day 10 Class C animal is shown; 250X magnification. Scale bar: 50 mm. Note that intestinal
daf-16(+) does not fully restore muscle quality to that seen in nontransgenic
daf-16(+);
daf-2(-) mutants, just as it does not extend life span to the extent seen in
daf-16(+);
daf-2(-) animals. (B) Left panels: A
mtl-1::rfp translational reporter is expressed mainly in the pharynx (ph) and intestine (i) of wild-type, and is upregulated in the intestines of
daf-2(-) mutants in a
daf-16-dependent manner. Right panels: intestinal GFP-tagged DAF-16 upregulates
mtl-1::rfp only in the intestine. Muscle or neuronal
daf-16 does not affect
mtl-1::rfp expression. The body is outlined.
daf-2(
e1370) and
daf-16(
mu86) mutations were used. Young adults, 100X magnification. Scale bar: 130 mm. (C) The
ges-1 promoter, which drives gfp::
daf-16 expression, is expressed in a mosaic fashion in the intestine (middle panel). DAF-16 turns on
mtl-1::rfp expression in the same cells (left panel). Young adults, 100X magnification. Scale bar: 130 mm. (D) Top panels: A nuclear-localized Pdod-17::rfp transcriptional reporter is expressed mainly in the intestine (i) of wild-type and is downregulated in the intestine of
daf-2(-) mutants and upregulated in
daf-16(-);
daf-2(-) mutants. Bottom panels: expression of
daf-16 in the intestine, but not muscles or neurons, suppresses Pdod-17::rfp expression. Inset:
daf-16 expression (green) is inversely correlated with
dod-17 expression (red). Note that Pdod-17::rfp expression is higher in an intestinal cell that does not express gfp::
daf-16 (arrowhead). The body and pharynx (ph) are outlined. Young adults, 250X magnification. Scale bar: 50 mm. Representative images from 2 or more experiments are shown for all figures.