Delphinapterus leucas skin transcriptome sequencing and assembly, and comparison between two Canadian populations

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population in Canada is endangered, and endocrine disrupting contaminants such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and other halogenated flame retardants (HFRs) have been identified as a threat to the recovery of this population. While targeted approaches such as quantitative reverse transcription PCR (RT-qPCR) have been widely used to assess the impacts of contaminants on marine mammals, including SLE beluga, few studies have employed transcriptomics. Here, we (1) evaluate the skin transcriptome profiles of adult male SLE beluga and adult males from a Arctic population less exposed to contaminants (Eastern Beaufort Sea; EBS) used as a reference to identify gene transcripts and biological pathways associated with blubber concentrations of organic contaminants (i.e., PCBs, PBDEs and other HFRs), and (2) assess correlations between several gene transcripts previously identified as biomarkers of organic contaminants in marine mammals and organohalogen concentrations in both populations and estimate threshold values in beluga skin for potential biological effects. Results will provide new and valuable knowledge that identify biological pathways associated with organic contaminant exposure in beluga, which may serve as predictors for higher-level health effects in at-risk populations such as SLE beluga.

加拿大圣劳伦斯河口湾（St. Lawrence Estuary, SLE）的白鲸（Delphinapterus leucas）种群处于濒危状态，而多氯联苯（polychlorinated biphenyls, PCBs）、多溴二苯醚（polybrominated diphenyl ethers, PBDEs）及其他卤系阻燃剂（halogenated flame retardants, HFRs）等内分泌干扰污染物已被证实为该种群恢复的潜在威胁。尽管定量反转录PCR（quantitative reverse transcription PCR, RT-qPCR）等靶向检测方法已被广泛应用于评估污染物对包括SLE白鲸在内的海洋哺乳动物的影响，但采用转录组学技术开展的相关研究仍较为稀缺。本研究旨在完成两项任务：（1）以受污染物暴露程度更低的北极种群——东博福特海（Eastern Beaufort Sea, EBS）种群作为参照，对比分析成年雄性SLE白鲸与成年雄性EBS白鲸的皮肤转录组特征，以识别与鲸脂中有机污染物（即PCBs、PBDEs及其他HFRs）浓度相关的基因转录本与生物学通路；（2）评估此前被认定为海洋哺乳动物有机污染物生物标志物的多个基因转录本，与两个种群中有机卤化物浓度之间的相关性，并估算白鲸皮肤中引发潜在生物效应的污染物阈值。本研究结果将为识别白鲸有机污染物暴露相关的生物学通路提供全新且具有价值的科学认知，这些通路可作为SLE白鲸等濒危种群更高层级健康效应的预测指标。