Collaborative Research: IntBIO: Micro level oxygen transport mechanisms in elite diving mammals: Capillary RBC to myofiber

对于哺乳动物来说，氧气是生命所必需的。然而，一些海洋哺乳动物具有特殊的适应能力，使它们能够在水下一口气呆上很长一段时间。一个还不太清楚的适应是，在长时间潜水过程中，红细胞如何运动，氧气是如何输送到工作肌肉的。此外，并不是所有的海洋哺乳动物都具有相同的适应能力和基因。其中一个遗传差异是，鳍脚类动物(如海狮)中编码cMP-Neu5Ac羟基酶的基因丢失，而鲸目动物(如海豚)则不是。CMP-Neu5Ac羟基酶修饰覆盖在细胞表面的糖残基，这可能会显著影响氧气的运输。该项目汇集了一组在海洋哺乳动物生物学、血红蛋白蛋白质结构、光谱学以及细胞和分子生物学方面具有专业知识的研究人员，以验证以下假设：在携氧红细胞如何到达活跃的骨骼肌、如何从红细胞中卸载氧气以及氧气如何跨细胞膜转移方面，鳍足动物和鲸目动物之间存在差异。将为下一代科学家提供独特的培训机会，因为他们在不同的研究环境中进行实验，并从几个专门领域回答复杂的生物学问题。通过与教育发展专家合作并培训为人数不足的学生提供服务的教师，我们将把潜水哺乳动物氧气运输工作中基于研究的内容整合到符合下一代科学标准的科学课中，并将与当地和全国的教师分享。呼吸空气的海洋哺乳动物的氧气储存管理研究表明，潜水哺乳动物不仅能忍受非常低的氧气环境，而且实际上在这些条件下能够茁壮成长。他们的成功部分来自于全身水平上明确的潜水反应(心动过缓和血管收缩)。然而，在外周微血管-心肌细胞水平上的O2交换还不是很清楚。此外，可能存在外周O2转运的差异，这是由于鳍足类中的一个基因丢失，而不是鲸目动物。该基因编码CMP-Neu5Ac羟基酶(CMAH)，它改变包括红细胞在内的细胞表面，潜在地影响外周O2的运输。我们的中心假设是，鳍脚类和鲸目动物具有不同的外周形态适应和氧气调节机制，以适应延长潜水。这一假设将由在海洋哺乳动物生物学、Hb/Mb蛋白质结构、高级光谱/EPR和细胞/分子氧气模型方面具有互补专业知识的研究人员使用三种方法进行验证：1.在模拟潜水过程中和之后立即评估和模拟加州海狮(CASL、鳍足动物、CMAH-)和宽吻海豚(BD、鲸目动物、CMAH+)的氧气输送。2.阐明和模拟控制鳍足类和鲸目动物RBC HB-O2卸载动力学的生化机制。3.阐明CASL和BD骨骼肌内皮细胞+/-CMAH过表达或唾液酸调控的氧储存和扩散参数。这个项目跨越了多个组织层面，将揭示海洋哺乳动物在潜水过程中突破生理极限的适应机制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

For mammals, oxygen is essential for life. However, some marine mammals have specialized adaptations that allow them to spend long time periods underwater on a single breath. One adaptation that is not well understood is how red blood cells travel and oxygen is delivered to working muscles during a long duration dive. Further, not all marine mammals have evolved with the same adaptations and genes. One genetic difference is the loss of a gene that encodes for the enzyme CMP-Neu5AC hydroxylase in pinnipeds (e.g., sea lions) but not cetaceans (e.g., dolphins). CMP-Neu5AC hydroxylase modifies sugar residues coating the surface of cells, which could significantly affect oxygen transport. This project brings together a team of researchers with expertise in marine mammal biology, hemoglobin protein structure, spectroscopy, and cell and molecular biology to test the hypothesis that there are differences between pinnipeds and cetaceans in how oxygen-carrying red blood cells reach active skeletal muscles, how oxygen is unloaded from red blood cells and how oxygen is transferred across cell membranes. Unique training opportunities will be provided for next generation scientists as they perform experiments in diverse research settings and draw from several specialized fields to answer a complex biological question. By partnering with education development experts and training teachers who serve underrepresented students, we will integrate research-based content from our oxygen transport work on diving mammals into science lessons that meet Next Generation Science Standards and will be shared with teachers locally and nationally.O2 storage management studies in air-breathing marine mammals demonstrate that diving mammals not only tolerate very low O2 environments, but actually thrive under these conditions. Part of their success derives from a well-defined dive response at the systemic level (bradycardia and vasoconstriction). However, O2 exchange at the peripheral microvessel-myocyte level is not well understood. Further, there may be differences in peripheral O2 transport due to the loss of a gene in pinnipeds but not cetaceans. This gene encodes for CMP-Neu5AC hydroxylase (CMAH) which alters cell surfaces including red blood cells, potentially affecting peripheral O2 transport. Our central hypothesis is that pinnipeds and cetaceans have distinct peripheral morphological adaptations and O2 regulatory mechanisms for extended diving. This hypothesis will be tested by investigators with complementary expertise in marine mammal biology, Hb/Mb protein structure, advanced spectroscopy/EPR, and cell/molecular O2 models using three approaches: 1. Evaluate and model in vivo O2 delivery in California sea lions (CaSL, Pinniped, Cmah-) and bottlenose dolphins (BD, Cetacean, Cmah+) during and immediately after a simulated dive. 2. Elucidate and model the biochemical mechanisms regulating RBC Hb-O2 off-loading kinetics in pinnipeds and cetaceans. 3. Elucidate O2 storage and diffusion parameters in CaSL and BD skeletal muscle endothelial cells +/- CMAH overexpression or sialic acid modulation. This project spans multiple organizational levels and will uncover adaptive mechanisms by which marine mammals push physiological limits during dives. It advances knowledge of the cellular mechanisms that enable mammalian survival in low oxygen environments.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.