Germline minisatellite mutations in herring gulls: Induced mutations at colonies situated near steel mills

Abstract

<p>The study of induced heritable mutations occurring in nature is difficult as mutations are extremely rare and large sample sizes are needed to measure statistical differences between populations. Minisatellites are tandemly repeated units of DNA, 10 to 100 bp in length, predominantly found in non-coding regions of the genome. With multi-locus DNA fingerprinting, several loci are examined simultaneously increasing the sampling efficiency. Minisatellites have the highest mutation rate detected in the genome to date, making them ideal targets for mutational screening. I examined minisatellite mutation rates in herring gulls (Larus argentalus ) colonizing areas near steel mills, urban centers, and rural areas of the Great Lakes, to assess the application of minisatellite DNA mutation rates as biomarkers for induced germline mutations. I showed that gulls inhabiting contaminated environments near steel mills inherit significantly more mutations than gulls from rural locations. I found a negative correlation between proximity to industrial coking ovens and minisatellite mutations; the mutation rate increased almost 3 fold from rural to the most heavily impacted site. My data were not consistent with either of the alternative hypotheses put forth to explain differences in minisatellite mutation rates: (1) genetic differences in the populations and (2) differences in the age of parents sampled (i.e., older parents may be more susceptible to mutations). I suggest that minisatellite mutations are induced by chemical contaminants in the industrial environment, and that minisatellite DNA provides a sensitive biomarker for induced germline mutations in urban industrial environments. I investigated the levels of DNA adducts in herring gulls from our primary steel industry site, Hamilton, Ontario, and from one rural location, in order to clarify exposure. The levels and patterns of DNA adducts in erythrocytes of gulls from these two locations were identical, suggesting that DNA adducts in gull erythrocytes are not appropriate biomarkers of exposure.</p>