These gulls are mutants... read on below and here:

Detecting Induced Heritable Mutations in situ

Germline mutations in Great Lakes herring gulls:

My lab has been studying germline mutation rates in herring gulls nesting at various sites on the Great Lakes for over 10 years. We capture breeding adults on their nests late in the egg-incubation period, and take a small blood sample from each.

We then wait for the eggs to hatch, and return to take a small blood sample from each chick.

In the laboratory we extract DNA from the blood of parents and offspring from each family, and genetically profile them using multilocus DNA fingerprinting. This produces the familiar barcode-like pattern seen commonly in textbooks and on TV. According to general rules of inheritance, offspring must inherit half of their genetic material from each parent. This means that all bands in the DNA fingerprint must have come from one parent or the other. Portions of the genetic profile that cannot be attributed to either parent are considered mutations.

Life Near Integrated Steel Mills Induces Mutations:

The general lesson we have learned after sampling and genetically profiling many gull families is that colonies close to integrated steel mills transmit DNA mutations to their offspring more frequently than those at rural sites. In addition, the closer the colony to steel mills, the higher the mutation rate. These results were published in the following two papers:

1)     Yauk,C.L. and Quinn,J.S. (1996) Multilocus DNA fingerprinting reveals high rate of heritable genetic mutation in herring gulls nesting in an industrialized urban site. Proceedings of the National Academy of Science USA 93: 12137-12141.

2)     Yauk,C.L., Fox,G.A., McCarry,B.E., and Quinn,J.S. (2000) Induced minisatellite germline mutations in herring gulls (Larus argentatus) living near steel mills. Mutation Research 452: 211-218.

Why Do Steel Gulls Mutate?

Our gull studies provided clear evidence that steel mills were associated with elevated DNA mutation rates. We hypothesized that chemical contaminants released into the environment during steel production caused the genetic damage we were observing. We were concerned that these contaminants might also affect other wildlife and humans living nearby. The next step was to attempt to determine where the DNA-damaging pollution was coming from.

Was the route of exposure through the air, or through a diet of contaminated fish from polluted water? If air pollution was a major route of exposure, it would have the potential to reach many humans living near steel mills all over the world. Because of their potentially complex exposure to environmental contaminants through both air and diet, herring gulls could not be used to answer this question.

An Experimental System to Test Airborne Contaminants: Exposing Lab Mice in situ:

To address the route of exposure question, we needed a controlled experimental system. Lab mice offered us the chance to expose animals to ambient air conditions while controlling for factors such as genetic background, nutritional status, disease status, and food and water sources.

We exposed groups of male and female lab mice to ambient air at two sites in southern Ontario: (1) Hamilton Harbour, 1 km downwind from 2 steel mills, and (2) Freelton, on a private farm in a rural area away from major point sources of pollution. Mice were housed in cages inside of modified utility sheds as shown below.

Exposures lasted 10 weeks during the fall of 1999. During that time we gave mice at both sites commercial food and bottled water from the same source. The only difference between groups was the quality of the air they were breathing during the environmental exposure.

Six weeks after exposing mice outdoors we bred them, monitored pup development for 5 days, and sampled DNA from complete families.

We genetically profiled mouse families from the two exposure sites using DNA fingerprinting in a manner similar to the herring gull studies. The results are published in:

1)     Somers, C. M., Yauk, C. L., White, P. A., Parfett, C. L. J., and Quinn, J. S. (in press) Air Pollution Induces Heritable DNA Mutations. Proceedings of the National Academy of Sciences, USA

The General Message: Air Pollution Alone is Enough

Our genetic analyses of environmentally exposed mice revealed that offspring from the steel site inherited nearly double the frequency of DNA mutations compared to their rural counterparts. Clearly, air pollution near integrated steel mills can induce genetic damage. At this time we cannot identify the class of chemical pollutant responsible, but suggest that polycyclic aromatic hydrocarbons, by-products of coal combustion, are a likely candidate.

What Next?

The results of our first outdoor mouse exposure have provided us with some very important information: air pollution may be posing a risk to future generations.

We are currently investigating HEPA filtration as a way to prevent this problem. In the picture below, we show a subsequent mouse experiment where mice in the Hamilton Harbour utility shed were housed both inside and outside of a chamber receiving HEPA filtered air. It is our hope that removing the bulk of small particles from the air prior to inhalation will reduce mutation induction. We are currently performing genetic analyses to determine whether this is true.

We have tested the ability of air pollution to induce heritable mutations, but what about the possibility that a contaminated fish diet is also a factor? We are in the midst of testing that possibility also. To do this, we designed a special diet for mice that included 58% homogenized whole smelt and alewife from Hamilton Harbour.

These two fish species represent close to 60% of the diet of herring gulls. Below, an experimental mouse feeds on a gel diet medium containing 58% alewife from Hamilton Harbour.

Mice in the fish diet study bred recently, and genetic analyses will begin very soon. Despite their small body size, preliminary contaminant analyses of the smelt and alewife have shown moderate levels of organochlorine pesticides and polychlorinated biphenyls (PCBs). Whether these are sufficient to produce heritable mutations through diet in mice is yet to be determined.

Acknowledgements:
NCIC
TSRI
Health Canada
CWS
NSERC
EcoWise
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