Presentation/Session Information

Session Information

Session Title: Physiology: Aging and Stress II Session Type: Parallel
Session Location: Carnesale Palisades Ballroom Session Time: Fri, Jun 26 8:30AM - 11:30AM

Presentation Information

Program Number: 84 Presentation Time: 11:06AM - 11:18AM

Presentation Content

Somatic expression of a germline program does not extend lifespan in C. elegans.Andrew Knutson, Susan Strome. Department of Molecular, Cell, and Developmental Biology, UC Santa Cruz, Santa Cruz, CA 950

Maintenance of the germ-soma distinction ensures proper cellular identity and function.  A 2009 study reported that long-lived daf-2 mutants of C. elegans ectopically express a germline program in their somatic cells, including mRNAs for the P-granule factors PGL-1 and PGL-3 (Curran et al. Nature 459: 1079-1084, 2009).  Importantly, knock-down of several germline factors via RNAi in adult daf-2 worms resulted in a slight decrease in those worms’ lifespan, suggesting that those proteins confer some lifespan extension to daf-2 mutants.  Our lab’s interest in germline development, regulators of the germ-soma distinction, and the possibility that some of the immortality of germ cells can be harnessed to extend somatic lifespan led us to explore and extend the daf-2 findings.  Our results have shown that somatic expression of a germline program does not extend lifespan in C. elegans:  1) We do not detect ectopic expression of P-granule proteins in daf-2 worms, as assayed by immunostaining for PGL proteins and by expression of a PGL-1::GFP transgene under the control of the pgl-1 promoter.  2) Simultaneous depletion of 4 constitutive components of P granules (PGL-1, PGL-3, GLH-1, and GLH-4) from daf-2 mutants did not decrease lifespan but instead slightly extended lifespan.  3) Expressing a PGL-1::GFP fusion protein in the intestine of wild-type worms did not alter lifespan.  4) Six synMuv mutants that ectopically express germline proteins in their somatic cells at 24oC are not long-lived compared to wild type.  We also tested the effect of loss of the master germline chromatin regulator MES-4 on the lifespan of daf-2 worms.  Compared to daf-2 single mutants, fertile daf-2; mes-4 double mutants had the same lifespan, while sterile daf-2; mes-4 double mutants were dramatically longer-lived.  We attribute this hyper-increased longevity to the synergistic effects of reduced insulin-like signaling and absence of a germline.  Taken together, our results show that extreme extension of lifespan can be accomplished by combining loss of DAF-2 with absence of germ cells, and that somatic expression of germline proteins does not extend lifespan, arguing against the appealing possibility that expression of a germline progam in somatic cells can provide the somatic body with partial “germline immortality.”.

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