An RT-PCR Approach for Multiple Population Sequencing of Csk in Gasterosteus aculeatus
Cartwright, Haley N.
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The understanding of local adaptation and its genetics basis are crucial for the study of adaptive radiation and evolutionary biology as a whole. Local adaptation is significantly shaped by organisms' physical environment, available prey, and particular predators - including parasitic exploitation. The fish Gasterosteus aculeatus, commonly known as the stickleback, is an important organism in the study of adaptation due to its unique and well-studied evolutionary history, specifically in relation to parasites. Studies have found significant differences in parasite susceptibility between lake and stream populations. Further investigation into the genetic bases for variability in parasite resistance has identified one notable SNP peak (single nucleotide polymorphism) on chromosome II, indicating high divergence at this genomic location between lake and stream sticklebacks. Csk, an enzyme central to the proper regulation of immune responses, was recognized as the likely candidate for containing this sequence variation that associates with variation in parasite susceptibility among stickleback fish. In the current study, we performed RT-PCR to successfully amplify Csk cDNA from both lake and stream sticklebacks, previously collected from Farewell Lake, Farewell Stream, Roberts Lake, and Roberts Stream sites in British Columbia. Sequencing of the Csk transcripts was performed followed by multiple sequence alignment of lake and stream samples. Within the Csk sequence, one convincing SNP was identified between Farewell Lake and Stream samples as well as three potential SNPs between Roberts samples. The Farewell SNP was then found to be located in the 5'UTR in accordance with annotation of the stickleback genome in ensembl stickleback. These results represent important preliminary work in the investigation of Csk's role in stickleback local adaptation.