Data from: Association mapping reveals candidate loci for resistance and anemic response to an emerging temperature-driven parasitic disease in a wild salmonid fish

Even though parasitic infections are often costly or deadly for the host, we know very little which genes influence parasite susceptibility and disease severity. Proliferative kidney disease (PKD) is an emerging and, at elevated water temperatures, potentially deadly disease of salmonid fishes that is caused by the myxozoan parasite Tetracapsuloides bryosalmonae. By screening > 7.6 K SNPs in 255 wild brown trout (Salmo trutta) and combining association mapping and random forest approaches, we identified several candidate genes for both the parasite resistance (inverse of relative parasite load; RPL) and the severe anemic response to the parasite. The strongest RPL-associated SNP mapped to a noncoding region of the congeneric Atlantic salmon (S. salar) chromosome 10, whereas the second strongest RPL-associated SNP mapped to an intronic region of PRICKLE2 gene, which is a part of the planar cell polarity signaling pathway involved in kidney development. The top SNP associated with anemia mapped to the intron of the putative PRKAG2 gene. The human ortholog of this gene has been associated with hematocrit and other blood-related traits, making it a prime candidate influencing parasite-triggered anemia in brown trout. Our findings demonstrate the power of association mapping to pinpoint genomic regions and potential causative genes underlying climate change-driven parasitic disease resistance and severity. Furthermore, this work illustrates the first steps towards dissecting genotype-phenotype links in a wild fish population using closely related genome information.

尽管寄生虫感染通常会给宿主带来高昂代价甚至致死，但我们对哪些基因会影响宿主的寄生虫易感性与疾病严重程度仍知之甚少。增殖性肾病（Proliferative Kidney Disease, PKD）是鲑科鱼类的一种新发传染病，在水温升高时可引发致命性后果，其病原体为黏孢子虫*Tetracapsuloides bryosalmonae*。本研究通过对255尾野生褐鳟（*Salmo trutta*）的7600余个单核苷酸多态性（Single Nucleotide Polymorphism, SNP）位点进行分型，并结合关联作图与随机森林分析方法，鉴定出多个与寄生虫抗性（即相对寄生虫载量的倒数，RPL）以及宿主针对寄生虫的重度贫血反应相关的候选基因。与RPL关联最强的SNP定位于同属大西洋鲑（*S. salar*）10号染色体的非编码区域，而关联强度次之的SNP则定位于PRICKLE2基因的内含子区域；该基因是参与肾脏发育的平面细胞极性信号通路的组成部分。与贫血反应关联度最高的SNP则定位于推定的PRKAG2基因的内含子区域。该基因的人类直系同源基因已被证实与血细胞比容及其他血液相关性状存在关联，因此它是影响褐鳟寄生虫诱导性贫血的关键候选基因。本研究结果证实，关联作图方法可有效定位气候变化驱动的寄生虫病抗性与疾病严重程度相关的基因组区域及潜在致病基因。此外，本研究还展示了利用近缘物种基因组信息解析野生鱼类种群基因型-表型关联的初步探索。