Collaborative Research: Differential Expression of Oxygen-binding Proteins in Antarctic Fishes Affects Nitric Oxide-mediated Pathways of Angiogenesis and Mitochondrial Biogenesis.

目前环绕南极洲的极地海洋是地球上最冷、最热稳定的海洋环境。由于氧气在海水中的溶解度与温度成反比，寒冷的南极海洋是一个异常富氧的水生栖息地。一个单一的鲈形亚目，Notothenioidei的八个家庭，占主导地位，目前南极洲周围的鱼类区系。南极鱼约占南极极地锋以南鱼类物种的35%和鱼类生物量的90%。因此，在一系列非常不寻常的条件下，密切相关的Notothenioid物种的辐射迅速发生：由于绕极洋流和环绕大陆的深海沟，海洋学上与其他动物群相对隔离，长期以来，水温极低，氧气供应非常高，在南大洋的物种灭绝中，生态位竞争水平非常低，这是由于鱼类物种多样性的急剧下降，从第三纪中期到现在这些特征使南极鱼成为研究低温生理生化适应的一个独特的有吸引力的群体。南极鱼类的一些独特的功能是独特的表达模式的氧结合蛋白在一个notothenioid家庭，南极冰鱼科（南极冰鱼）。所有的沟鱼科鱼类都缺乏循环氧结合蛋白，血红蛋白（Hb）;细胞内氧结合蛋白，肌红蛋白（Mb）在这个家族的物种中并不均匀表达。这两种蛋白质通常被认为是向动物的有氧平衡组织充分输送氧气所必需的。为了弥补血红蛋白的缺乏，冰鱼有发达的大心脏，快速循环大量的血液，并拥有更大的内腔直径比在红血鱼中看到的复杂的脉管系统。氧化肌肉中Mb表达的丧失与细胞内线粒体密度的急剧升高相关，尽管每个细胞器中的呼吸蛋白密度较低。在氧气运动的框架内，更大的血管密度和线粒体群体的适应意义是可以理解的，但这些特征的发展机制仍然未知。答案可能在于Hb和Mb的另一个主要功能，即降解普遍存在的生物活性化合物一氧化氮（NO）。这项研究将测试这样一个假设，即冰鱼血红素蛋白表达的丧失导致NO水平的增加，NO水平的增加介导了血管系统的修饰和氧化组织中线粒体种群的扩张。本研究的目的是定量测定+Hb和-Hb类南极鱼视网膜血管密度，表征南极鱼视网膜和心肌中NOS同工酶和催化活性，评价血管生成下游因子的表达水平（在视网膜组织中）和线粒体生物发生（在心肌），并确定是否在体内抑制NOS的结果在冰鱼血管生成和线粒体生物反应的回归。 更广泛的影响包括基础生物学，通过培训青年科学家，提高对临床相关生物医学过程的理解。

The polar ocean presently surrounding Antarctica is the coldest, most thermally stable marine environment on earth. Because oxygen solubility in seawater is inversely proportional to temperature, the cold Antarctic seas are an exceptionally oxygen-rich aquatic habitat. Eight families of a single perciform suborder, the Notothenioidei, dominate the present fish fauna surrounding Antarctica. Notothenioids account for approximately 35% of fish species and 90% of fish biomass south of the Antarctic Polar Front. Radiation of closely related notothenioid species thus has occurred rapidly and under a very unusual set of conditions: relative oceanographic isolation from other faunas due to circumpolar currents and deep ocean trenches surrounding the continent, chronically, severely cold water temperatures, very high oxygen availability, very low levels of niche competition in a Southern Ocean depauperate of species subsequent to a dramatic crash in species diversity of fishes that occurred sometime between the mid-Tertiary and present. These features make Antarctic notothenioid fishes an uniquely attractive group for the study of physiological and biochemical adaptations to cold body temperature. Few distinctive features of Antarctic fishes are as unique as the pattern of expression of oxygen-binding proteins in one notothenioid family, the Channichthyidae (Antarctic icefishes). All channichthyid icefishes lack the circulating oxygen-binding protein, hemoglobin (Hb); the intracellular oxygen-binding protein, myoglobin (Mb) is not uniformly expressed in species of this family. Both proteins are normally considered essential for adequate delivery of oxygen to aerobically poised tissues of animals. To compensate for the absence of Hb, icefishes have developed large hearts, rapidly circulate a large blood volume and possess elaborate vasculature of larger lumenal diameter than is seen in red-blooded fishes. Loss of Mb expression in oxidative muscles correlates with dramatic elevation in density of mitochondria within the cell, although each individual organelle is less densely packed with respiratory proteins. Within the framework of oxygen movement, the adaptive significance of greater vascular density and mitochondrial populations is understandable but mechanisms underlying development of these characteristics remain unknown. The answer may lie in another major function of both Hb and Mb, degradation of the ubiquitous bioactive compound, nitric oxide (NO). The research will test the hypothesis that loss of hemoprotein expression in icefishes has resulted in an increase in levels of NO that mediate modification of vascular systems and expansion of mitochondrial populations in oxidative tissues. The objectives of the proposal are to quantify the vascular density of retinas in +Hb and -Hb notothenioid species, to characterize NOS isoforms and catalytic activity in retina and cardiac muscle of Antarctic notothenioid fishes, to evaluate level of expression of downstream factors implicated in angiogenesis (in retinal tissue) and mitochondrial biogenesis (in cardiac muscle), and to determine whether inhibition of NOS in vivo results in regression of angiogenic and mitochondrial biogenic responses in icefishes. Broader impacts range from basic biology, through training of young scientists, to enhanced understanding of clinically relevant biomedical processes.