Transcriptomic comparison of long- vs. short-lived C. elegans

Variability in lifespan among individuals of the same species is a poorly understood phenomenon. Even among isogenic C. elegans reared in identical environments, we observe considerable variance in lifepsan. To better understand the differences in gene expression that underly this variability, we characterized the transcriptomes associated with long vs. short lifespan. We isolated the longest- and shortest-lived members from their respective populations using biomarkers of aging--predictive markers whose expression levels correlate with an individual's future lifespan. Specifically, we sorted animals by the expression of lin-4p::GFP, mir-243p::GFP, mir-240/786p::GFP, and autofluorescence. All populations were chronologically five days old at time of sorting. We subsequently compared the transcriptomes of future lifespan within and between different biomarkers to identify a gene expression signature of future lifespan. Transgenic C. elegans strains were grown containing lifespan-predictive biomarkers lin-4p::GFP, mir-243p::GFP, and mir-240/786p::GFP. To sterilize animals, all strains also contained a temperature sensitive mutation in the spermatogenesis gene spe-9. Populations were synchronized by hypochlorite treatment and cultured at the restrictive temperature of 25 degrees C on NGM plates seeded with E. coli OP50. After five days, worms were sorted by the fluorescence intensity of each transgenic biomarker, as well as by autofluorescence in the “red” channel. Between 3-6 sorts were carried out for each biomarker, with “high” and “low” fluorescence defined as the top or bottom tenth percentile relative to the rest of the populations. Animals in these high and low categories were recovered, lysed, and total RNA was collected.