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

对哺乳动物来说，氧气是维持生命所必需的。然而，一些海洋哺乳动物具有特殊的适应性，使它们能够一次呼吸就在水下呆很长时间。在长时间的潜水中，红细胞是如何移动的，氧气是如何输送到工作肌肉的，这一点还没有得到很好的理解。此外，并非所有的海洋哺乳动物都具有相同的适应能力和基因。一个遗传差异是鳍足类动物（如海狮）没有编码CMP-Neu5AC羟化酶的基因，而鲸目动物（如海豚）没有。CMP-Neu5AC羟化酶修饰包裹在细胞表面的糖残基，可以显著影响氧的运输。该项目汇集了一组具有海洋哺乳动物生物学、血红蛋白结构、光谱学、细胞和分子生物学专业知识的研究人员，以验证鳍足类动物和鲸类动物在携带氧气的红细胞如何到达活跃的骨骼肌、氧气如何从红细胞中释放以及氧气如何通过细胞膜转移等方面存在差异的假设。下一代科学家将在不同的研究环境中进行实验，并从几个专业领域中汲取答案，以回答复杂的生物学问题，这将为他们提供独特的培训机会。通过与教育发展专家和培训教师合作，为代表性不足的学生提供服务，我们将把我们关于哺乳动物潜水的氧气运输工作中的研究性内容整合到符合“下一代科学标准”的科学课程中，并与当地和全国的教师分享。对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极低的氧气环境，而且在这种条件下也能茁壮成长。他们的成功部分源于系统水平上明确的潜水反应（心动过缓和血管收缩）。然而，外周微血管-肌细胞水平的氧交换尚不清楚。此外，由于鳍足类动物的基因缺失，而鲸类动物的外周氧转运可能存在差异。该基因编码CMP-Neu5AC羟化酶（CMAH）， CMAH可以改变包括红细胞在内的细胞表面，潜在地影响外周氧运输。我们的中心假设是鳍足动物和鲸类动物具有不同的外围形态适应和氧气调节机制。这一假设将由具有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O2模型互补专业知识的研究人员使用三种方法进行验证：1。评估和模拟加利福尼亚海狮（CaSL, Pinniped, Cmah-）和宽吻海豚（BD, Cetacean, Cmah+）在模拟潜水期间和之后的体内氧气输送。2. 阐明和模拟鳍足类和鲸类动物调节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过表达或唾液酸调节中的O2储存和扩散参数。该项目跨越多个组织层面，将揭示海洋哺乳动物在潜水时突破生理极限的适应机制。它推进了使哺乳动物在低氧环境中生存的细胞机制的知识。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。

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.