Collaborative Research: Biogenesis and evolution of hagfish slime and slime glands

鳗鱼是一群鳗鱼形状的动物，生活在世界各地的深海栖息地。八目鳗因其能够阻止鲨鱼等捕食者的攻击而臭名昭著，因为它们在被咬后不到一秒钟的时间里会产生大量堵塞鳃的黏液。这种粘液不仅在形成的速度上是独一无二的，而且因为它含有数千种被称为粘液线的丝状纤维。这个项目的一个目的是研究这些15厘米长的纤维是如何在被称为腺线细胞的特殊细胞的细胞质中产生的。为此，研究人员将使用活细胞显微镜成像技术观察腺线细胞的发育。这个项目的第二个目标是了解粘液腺是如何进化和多样化的。鳗鱼是一个古老的群体，大约有78个描述的物种，到目前为止，我们研究的两个物种的防御性粘液在显著方面有所不同。为了探索鳗鱼及其粘液腺的进化和多样化，研究人员将收集来自世界各地的许多鳗鱼物种的解剖和遗传数据。鳗鱼粘液线具有与高性能蜘蛛丝相媲美的材料特性；因此，了解它们是如何在细胞内制造的，可以为生产仿生纺织品提供有价值的信息。此外，该项目与一个名为“鼓舞生物学”的夏季推广计划相吻合，该计划旨在通过向少数群体介绍生物启发设计的概念，提高他们对科学的热情和参与。七目鳗是由78种海洋头骨组成的群体，在世界各地的海底生态系统中发挥着重要作用。它们最显著的适应能力之一是，它们能够在不到一秒钟的时间内产生大量堵塞鱼鳃的粘液，从而阻止鱼类捕食者的攻击。这种粘液由海水、粘液样的糖蛋白和数千种丝状蛋白质纤维的协同混合物组成，这种丝状蛋白纤维被称为“粘液线”。虽然人们对粘液的功能和机械特性了解很多，但对粘液腺中的主要粘液成分是如何产生的，或者粘液腺是如何进化的，人们知之甚少。该项目有两个目标。首先，研究人员将阐明在八头鳗腺线细胞内产生粘液线的细胞和分子机制。具体地说，关于粘液线如何在这些细胞内伸长、卷曲和成熟的几个机械假说将被测试。其次，研究人员将阐明鳗鱼粘液腺的进化起源和多样性。具体地说，他们将测试粘液腺起源于皮肤内陷的假说，或者它们是泄殖腔腺体的系列同系物并通过异构体复制和修饰而进化的假说。为了实现这些目标，他们将使用一种整合了细胞生物学、形态学、比较转录学和系统发育方法的方法。这些实验将确定对粘液产生最重要的基因，它们将阐明最接近和最终的机制，涉及一种独一无二的进化新颖性的起源，并对其有机体生物学至关重要。该奖项由整合组织系统部门的生理机制和生物力学项目以及分子和细胞生物学部门的细胞动力学和功能项目共同资助。该奖项反映了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。

Hagfishes are a group of eel-shaped animals that are found in deep ocean habitats around the world. Hagfishes are notorious for their ability to thwart attacks by predators such as sharks by producing large volumes of gill-clogging slime in a fraction of a second after they are bitten. The slime is unique both in the speed with which it forms, and because it contains thousands of silk-like fibers known as slime threads. One aim of this project is to investigate how these 15-cm long fibers are produced within the cytoplasm of specialized cells called gland thread cells. To do this, researchers will observe developing gland thread cells using live cell microscope imaging techniques. The second aim of this project is to understand how the slime glands evolved and diversified. Hagfishes are an ancient group of about 78 described species, and the two species we have examined thus far have defensive slime that differs in significant ways. To explore the evolution and diversification of hagfishes and their slime glands, researchers will collect anatomical and genetic data from many hagfish species from around the world. Hagfish slime threads have material properties that rival those of high performance spider silks; understanding how they are made within cells could thus provide valuable information for efforts to produce bio-inspired textiles. Furthermore, this project dovetails with a summer outreach program called "Inspiring Biology", which aims to increase enthusiasm and participation in the sciences by under-represented minorities by introducing them to the concept of bio-inspired design.Hagfishes are a group of 78 species of marine craniates that are important players in benthic ecosystems worldwide. One of their most remarkable adaptations is their ability to thwart attacks by fish predators by producing large volumes of gill-clogging slime in a fraction of a second. The slime consists of a synergistic mixture of seawater, mucus-like glycoproteins, and thousands of silk-like protein fibers known as "slime threads". While much is known about the function and mechanical properties of the slime, little is known about how the major slime components are produced within the slime glands or how the slime glands evolved. The project has two Aims. First, researchers will elucidate the cellular and molecular mechanisms involved in slime thread production within hagfish gland thread cells. Specifically, several mechanistic hypotheses about how the slime thread elongates, coils, and matures within these cells will be tested. Second, the researchers will elucidate the evolutionary origins and diversification of hagfish slime glands. Specifically, they will test the hypotheses that the slime glands arose from invagination of the skin, or that they are serial homologs of cloacal glands and evolved via metameric duplication and modification. To achieve these aims, they will use an approach that integrates cell biological, morphological, and comparative transcriptomic and phylogenetic methods. These experiments will identify the genes that are most important for slime production and they will illuminate the proximate and ultimate mechanisms involved in the origins of an evolutionary novelty unique to hagfishes and central to their organismal biology.This award was co-funded by the Physiological Mechanisms and Biomechanics Program in the Division of Integrative Organismal Systems and the Cellular Dynamics and Function Program in the Division of Molecular and Cell Biology.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.