Identifying the Genetic Basis of Avian Susceptibility to Mercury

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The Challenge: Mercury is a highly toxic element found throughout our environment. Although it occurs naturally in some environments, human industrial pollution has greatly increased the amount of mercury and the range of environments in which mercury is found. Recent studies have confirmed clear differences in the sensitivity of various bird species to methylmercury. Because the causes of these differences are unknown, prediction of mercury sensitivity is difficult in birds that have not or cannot be studied in the lab. Therefore, a method is needed that can predict sensitivity to mercury in poorly studied birds and can help identify susceptible populations.

The Science:Organisms have a variety of mechanisms that protect against mercury toxicity. Genetic variations and gene expression patterns related to these processes influence susceptibility and allow less sensitive species to survive, while their more sensitive counterparts succumb. To clarify the molecular basis for species-specific sensitivity to mercury, we are analyzing hepatic RNA expression patterns and sequence variations in three bird species exposed to multiple concentrations of methylmercury. These species show varying sensitivity to mercury: laughing gull (Larus atricilla - low sensitivity), American kestrel (Falco sparverius - high sensitivity) and osprey (Pandion haliaetus – high sensitivity).

The Future: These analyses will be used to identify affected molecular pathways and define genes that may play a role in species survival and susceptibility. Understanding the molecular mechanisms involved in a bird’s response to mercury provides a foundation upon which variations in susceptibility to mercury may be predicted and assessments of risks to exposed population can be based.