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

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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.