PQM-1 controls hypoxic survival via regulation of lipid metabolism.

Worms were exposed to 5 mM CoCl2 at the early day 1 of adulthood stage for 6 hr and 20 hr. Untreated worms were used as controls. Worms were collected, RNA isolated and hybridized on 4x44K C. elegans arrays (Agilent) at 60C overnight, as previously described 1). Three biological replicates were used. Significant differentially-expressed gene sets were identified using one or two-class SAM 2). 1) Shaw, W. M., Luo, S., Landis, J., Ashraf, J. & Murphy, C. T. The C. elegans TGF-beta Dauer pathway regulates longevity via insulin signaling. Curr Biol 17, 1635-1645, doi:10.1016/j.cub.2007.08.058 (2007). 2) Tusher, V. G., Tibshirani, R. & Chu, G. Significance analysis of microarrays applied to the ionizing radiation response. Proc Natl Acad Sci U S A 98, 5116-5121, doi:10.1073/pnas.091062498 (2001).

Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult C. elegans

Reports that low-intensity microwave radiation can induce heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by very slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9-3 mW kg-1 for 6-well plates) that minimises the temperature differential between sham and exposed conditions to 0.1C. Comparable measurement and simulation studies of SAR distribution within this exposure system are presented. We compared 5 Affymetrix gene-arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against 5 gene-arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). Few genes showed consistent expression changes across all 5 comparisons, and all such expression changes appeared modest after applying standard normalisation procedures ( 30% up- or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131). As one example, an apparent up-regulation of the vit-3 vitellogenin gene by microwave exposure was not mirrored by similar changes affecting the other co-regulated members of the same vit gene family. We conclude that the pattern of gene expression in L4/adult C elegans is not substantially perturbed by low-intensity microwave radiation, and that the minor changes observed in this study may well be explicable as false positives. As a check on the sensitivity of the Affymetrix gene-arrays used, we also compared RNA samples from N2 worms subjected to a sub-heat-shock treatment (28C) against controls kept at 26 C (but using only 2 gene arrays per condition). After similar normalisation, many more genes (3712) showed substantial expression changes (i.e. > 2-fold at p < 0.05), including a group of six heat-shock genes which were strongly but unexpectedly down-regulated (by > 10-fold). However, further replication and confirmation by real-time RT-PCR would be needed to establish how many of these changes might also be false positives. Experimenter name: Adam Dawe Experimenter phone: +27 21 959 2364 adam@sanbi.ac.za Experimenter institute: South African National Bioinformatics Institute Experimenter address: University of Western Cape, Old Chemistry Building, University of Western Cape, Modderdam Road, Bellville 7530, Capetown Experimenter zip/postal_code: 7530 Experimenter country: South Africa Keywords: Microwave radiation, gene expression, gene arrays, Caenorhabditis elegans