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STRONG SELECTIVE SIGNAL AND HIGH GENETIC VARIABILITY AT AN IMMUNE SYSTEM LOCUS IN CONTAMINATED AND UNCONTAMINATED POPULATIONS OF AN ESTUARINE FISH
Citation:
Cohen, S. STRONG SELECTIVE SIGNAL AND HIGH GENETIC VARIABILITY AT AN IMMUNE SYSTEM LOCUS IN CONTAMINATED AND UNCONTAMINATED POPULATIONS OF AN ESTUARINE FISH. Presented at Annual Meeting of the Society of Environmental Toxiccology and Chemistry, Nashville, TN, November 12-16, 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 produce genetic changes at MHC loci that can affect immune system function. I 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. Two hallmark features of MHC in higher vertebrates were demonstrated using these fish populations: the antigen binding locus DRB 1 was extraordinarily polymorphic within populations; and, antigen-binding sites inferred from mammalian models were highly variable and showed 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. In addition, MHC loci were examined in fish indigenous to an EP A Superfund site that demonstrate inherited resistance to some of the toxic effects of PCBs and also show abnormal patterns of parasitism. In comparison to fish from reference sites, fish from the Superfund site had a 13% incidence of unusually divergent MHC DRB 1 alleles. These alleles may reflect genetic adaptation associated with multi-generational exposures to PCBs 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 populations.