Collagenous connective tissue is responsible for body integrity in all multicellular organisms and has many biomedical applications within a multibillion-dollar industry. An inspiration for a new generation of collagen-based biomaterials with a wide range of applications may come from echinoderms, a group of marine invertebrates that includes sea stars, sea cucumbers, brittle stars, sea urchins, and sea lilies. Echinoderms are capable of reversibly controlling the pliability of certain connective tissue components (i.e., tendons and ligaments) that are composed of mutable collagenous tissue (MCT). The MCTs variable tensility allows echinoderms to perform unique functions, including energy-saving posture maintenance, autotomy, and asexual reproduction. It is known that neurosecretory juxtaligamental cells in the nervous system control the MCT. These cells release substances that either soften or stiffen the MCT. So far, only a few of these substances have been purified and characterized, and the genomics behind MCT biology are still mostly unknown. Therefore, we propose to identify the putative MCT-related genes in echinoderms and better understand the biology of the juxtaligamental cells. Our research improves our knowledge about the MCT molecular control mechanism, with the ultimate goal of unlocking new biomaterial applications. In this project, we utilize RNA-Seq to identify and annotate differentially expressed genes in the MCT structures of the brittle star Ophiomastix wendtii.