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Molecular Characterization of Expressed DQA and DQB Genes in the California Sea Lion (Zalophus Californianus)

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To date, there are no published MHC sequences from the California sea lion Zaophus cahfornianus, a thriving species that, by feeding high on the marine food web, could be a sentinel for disturbances in marine and coastal ecosystems. In this study, degenerate primers and RACE technology were used to amplily near-full- length A4hcZaca-DQB and full-length MhcZaca-DQA expressed class II MHC gene products from the periph- eral blood mononuclear cells of two California sea lions in rehabilitation. Five unique Zaca-DQA sequences and eight unique Zaca-DQB sequences, all encoding functional proteins, were identified in the two animals, indicating the presence of multiple DQ- loci in this species. An additional three Zaca-DQB sequences containing features compatible with pseudogenes or null alleles were also identified. Despite the identification of multiple DQA and DQB sequences, the degree of heterogeneity between them was extremely low. To confirm the limited degree of Zaca-DQ nucleotide variation between individuals, we used denaturing gradient gel electrophoresis to examine putative peptide binding region sequences from the peripheral blood leukocyte-derived RNAs of 19 wild-caught California sea lions from physically distinct populations. The paflem of Zaca-DQ sequence rnigration was identical between individuals and independent of geographical region. This apparent Zaca-DQ sequence identity between sea lions was confirmed by direct sequencing of individual bands. In combination, these fmdings raise important questions regarding immunoge- netic diversity within this thriving species, and should prompt flirther research into the existence of a highly polymorphic sea lion class II MHC molecule with sequence features that support traditional peptide binding functions.

Subject Categories:

  • Genetic Engineering and Molecular Biology
  • Biology
  • Medicine and Medical Research
  • Physical and Dynamic Oceanography

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