Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult Caenorhabditis elegans.
Reports that low-intensity microwave radiation induces heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by 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 temperature differentials between sham and exposed conditions (< or =0.1 degrees C). Parallel measurement and simulation studies of SAR distribution within this exposure system are presented. We compared five Affymetrix gene arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against five gene arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). No genes showed consistent expression changes across all five comparisons, and all expression changes appeared modest after normalisation (< or =40% 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). We conclude that the pattern of gene expression in L4/adult C. elegans is substantially unaffected by low-intensity microwave radiation; the minor changes observed in this study could well be false positives. As a positive control, we compared RNA samples from N2 worms subjected to a mild heat-shock treatment (30 degrees C) against controls at 26 degrees C (two gene arrays per condition). As expected, heat-shock genes are strongly up-regulated at 30 degrees C, particularly an hsp-70 family member (C12C8.1) and hsp-16.2. Under these heat-shock conditions, we confirmed that an hsp-16.2::GFP transgene was strongly up-regulated, whereas two non-heat-inducible transgenes (daf-16::GFP; cyp-34A9::GFP) showed little change in expression.
Dawe
Adam S
AS
South African National Bioinformatics Institute, University of Western Cape, Cape Town, South Africa.
Bodhicharla
Rakesh K
RK
Graham
Neil S
NS
May
Sean T
ST
Reader
Tom
T
Loader
Benjamin
B
Gregory
Andrew
A
Swicord
Mays
M
Bit-Babik
Giorgi
G
de Pomerai
David I
DI
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects*; D005786:Gene Expression Regulation / Q000528:radiation effects*; D007814:Larva / Q000235:genetics*; D008872:Microwaves; D020411:Oligonucleotide Array Sequence Analysis; D013329:Structure-Activity Relationship