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GENETIC VARIATION AT AN IMMUNE SYSTEM LOCUS PROVIDES BOTH A GENERALIZED AND SPECIFIC STRESS INDICATOR: EFFECTS OF PERSISTENT, BIOACCUMULATIVE AND TOXIC CONTAIMINANT EXPOSURES ON AN ESTUARINE FISH POPULATION
Citation:
Cohen, S. AND D E. Nacci. GENETIC VARIATION AT AN IMMUNE SYSTEM LOCUS PROVIDES BOTH A GENERALIZED AND SPECIFIC STRESS INDICATOR: EFFECTS OF PERSISTENT, BIOACCUMULATIVE AND TOXIC CONTAIMINANT EXPOSURES ON AN ESTUARINE FISH POPULATION. Presented at 5th Annual NHEERL Symposium: Indicators in Health and Environmental Risk Assessment, Research Triangle Park, NC, June 6-8, 2000.
Description:
The major histocompatibility complex (MHC) is a group of linked genes that mediates the adaptive immune response in vertebrates. Studies using mammals and birds have shown that environmental stressors can directly and indirectly produce genetic changes at MHC loci that can affect immune system function. We isolated MHC loci in the common non-migratory estuarine fish, Fundulus heteroclitus, and compared sequence variation within and between populations to determine if MHC loci operate similarly in fish. We showed that two hallmark features of MHC in higher vertebrates are also demonstrated in wild fish populations and that a highly stressed population shows unusual allelic patterns at MHC loci. First, the antigen binding locus DRB1 is extraordinarily polymorphic within populations. Therefore, variation at this locus serves as an indicator of immune system versatility and a sensitive marker of genomic genetic diversity in study populations. Second, antigen-binding sites inferred from mammalian models are highly variable and show a strong signal of positive selection. Thus, alleles at this MHC locus should reflect the influence of specific antigenic challenges or stressors that have acted as selective forces on wild fish populations. MHC loci were examined in fish indigenous to an EPA Superfund site that demonstrate inherited resistance to some of the toxic effects of a specific class of persistent, bioaccumulative and toxic contaminants (PBTs) and also show abnormal patterns of parasitism. In comparison to fish from reference sites, fish from the Superfund site have a 13% incidence of unusually divergent MHC DRB1 alleles. These alleles may reflect genetic adaptation associated with multi-generational exposures to PBTs and other stressors. Further sampling and challenge experiments are underway to test this linkage. These features show that MHC variation is an informative indicator of chronic effects of anthropogenic stressors on wild fish population and a potentially important predictor of long-term risks to ecosystem health. This abstract does not necessarily reflect US EPA policy.