Abstract :
[en] The phylum Echinodermata is characterised by the development of a unique connective tissue, capable of dynamically modifying its mechanical properties. This mutable collagenous tissue (MCT) can shift from a stiff state to a viscous soft state independently of muscle contraction. Thanks to this ability, echinoderms can minimise energy expenditures during various behaviours linked to locomotion, reproduction, or defence. Previous investigations on sea cucumbers have revealed that the tissue is controlled by the nervous systems, enabling effector proteins to be released rapidly. These proteins, called stiffeners and softeners, are involved in the formation or removal of transient cross-bridges between collagen fibrils. For the last 20 years, MCT has been recognized as an important concept generator and resource for the design of soft actuators in robotics, medicine, and tissue engineering due to its advantageous properties. Despite the genuine interest that the tissue has aroused over the years, the current model remains ambiguous as to the role played by these effectors, which hinders the improvement of MCT-inspired biomaterials.
In order to fill this information gap on the MCT, proteomic and interactomic data were collected on the dermis of Holothuria forskali and compared to available knowledge. The molecular fingerprint of the tissue was measured by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, and complemented by tandem mass spectrometry of collagen fibrils. Analysis revealed that while type I collagen was abundant, evidence of a rarer type of collagen could be detected. The MCT interactome was predicted in silico and further explored based on the affinity of soluble proteins for collagen fibrils. Integrative databases were unable to identify MCT related clusters, nonetheless potential partners corresponding to, as of yet, uncharacterized proteins were identified and could be of important function for the MCT.
