Doctoral Dissertation Research: Investigating Genomic and Expression-level Adaptations for Detoxification in Primates

氰化物是一种在植物中很常见的毒药，对大多数动物都有毒。尽管如此，三种竹狐猴的大部分进食时间都集中在马达加斯加巨竹的不同部位，这使狐猴每天暴露在其估计致死剂量的12-50倍的氰化物中。该项目将研究竹狐猴氰化物解毒的潜在生理学和基因组学。除了解决这些狐猴如何能够摄入大量氰化物这一几十年来的难题外，这项研究还可能为人类接触氰化物的治疗、解毒剂或预防措施的发展提供信息。在这项工作的过程中，PI和联合PI将邀请和招募肯特州立大学麦克奈尔学者计划的本科生，该计划的任务是帮助第一代低收入本科生进入博士学位课程。联合项目负责人还将利用与俄亥俄州东北部公共图书馆和学校的密切联系，向学生和公众展示这个项目。这项研究的核心问题集中在已知的路线氰化物解毒的哺乳动物。低剂量的毒素可以通过多种保守的机制代谢，其中最重要的是使用硫转移酶的途径。这种机制的限制因素似乎是这些酶的相对表达水平和硫供体分子（例如硫代硫酸盐）的可用性。因此，本研究的第一个有效假设是，金黄色葡萄球菌通过积极选择参与硫或含硫氨基酸代谢的基因，适应了对其高度产氰的饮食进行解毒。这一假设将通过组装和挖掘金黄色葡萄球菌的参考质量基因组，并将其与从狐猴基因组组装中获得的数据进行比较来验证，狐猴是饮食通用型物种中关系最密切的物种。进一步的假设是，金黄色葡萄球菌通过对血液成分的适应性改变来解毒其高水平的循环氰化物。第二种假设将通过转录组学和代谢组学方法进行验证，以便分别比较自由放养的金黄色葡萄球菌和圈养的L. catta的表达谱和硫代硫酸盐水平。总之，这些方法将检查金黄色葡萄球菌基因组的适应性变化，以及全血转录组和代谢组，这与该物种的特殊氰化物耐受性有关。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Cyanide is a poison that is common among plants and toxic to most animals. Nonetheless, three species of bamboo lemur focus most of their feeding time on various parts of Malagasy giant bamboo, which exposes the lemurs to 12-50 times their estimated lethal dose of cyanide on a daily basis. This project will examine the underlying physiology and genomics of cyanide detoxification in bamboo lemurs. In addition to addressing the decades-old puzzle of how these lemurs are able to consume high levels of cyanide, this study may inform the development of therapies, antidotes, or prophylactics to cyanide exposure in humans. During the course of this work, the PI and co-PI will invite and recruit undergraduates from Kent State University's McNair Scholars Program, whose mission is to help first-generation, low-income undergraduates matriculate to a doctoral degree program. The co-PI will also utilize close ties with Northeast Ohio's public libraries and schools to present this project to students and the general public.The central questions of this study focus on known routes of cyanide detoxification among mammals. Low doses of the poison can be metabolized by a variety of conserved mechanisms, foremost among which is a pathway that uses sulfurtransferase enzymes. The limiting factors for this mechanism appear to be relative expression levels for these enzymes and the availability of sulfur-donor molecules (e.g., thiosulfate). Therefore, the first working hypothesis of this study is that H. aureus has adapted to detoxify its highly cyanogenic diet through positive selection on genes involved in the metabolism of sulfur or sulfur-containing amino acids. This hypothesis will be tested by assembling and mining a reference-quality genome for H. aureus and comparing it to data taken from a proposed genome assembly for Lemur catta, the most closely related species of dietary generalist. It is further hypothesized that H. aureus detoxifies its high levels of circulating cyanide through adaptive changes to the composition of the bloodstream. This second hypothesis will be tested by transcriptomic and metabolomic methods in order to compare the expression profiles and thiosulfate levels, respectively, of free-ranging H. aureus and captive L. catta. Together, these methods will examine adaptive changes in the H. aureus genome, as well as the whole-blood transcriptome and metabolome, which are related to the exceptional cyanide tolerance of this species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.