Invention sharing is the mother of developmental biology (part 4)

Part 4 of this special issue releases four methods, two protocols, and two technical notes. Suzuki et al. (2022) developed a method for studying how cells communicate with each other using semaphorin and plexin proteins in a worm model. The method utilizes the infrared laser-evoked gene operator (IR-LEGO) system to activate genes in specific cells and observe the resulting influences on the worm vulva formation. Using this method, the authors demonstrated that the direction and level of semaphorin and plexin signaling are crucial for regulating cell behavior. Seki et al. (2023) developed a method for optogenetic behavior analysis in medaka (Oryzias latipes). Using the CRISPR/Cas9 knock-in method, the authors generated a transgenic medaka line expressing an optogenetic channel, Chloromonas oogama channelrhodopsin (CoChR), in the nervous system. The potential of this receptor to regulate the motor activity of the fish such as body bending, turning movements, and pectoral fin locomotion was evaluated by stimulating with different intensities, durations, or wavelengths of light. Ishii et al. (2023) developed an X-ray micro-computed tomography (microCT) method to observe the soft tissues of Xenopus tadpoles in three dimensions. Using this method, the authors revealed a transient ventricular contraction in the early stages of telencephalon regeneration. This method could potentially be applied to the analysis of other amphibian and fish larvae, facilitating comparative morphological studies of postembryonic development in vertebrates. Hasan et al. (2023) developed a method for preparing primary cell cultures from the limb tissue of an Iberian ribbed newt (Pleurodeles waltl). The Iberian ribbed newt is emerging as a model animal in the limelight, especially in regeneration studies. The limb tissues are cut into small pieces and seeded as “explants” in culture dishes coated with fibronectin and gelatin. The cells spread out from the explants can be cryopreserved with a proliferation capacity comparable to freshly prepared cells. Yoshimatsu et al. (2022) provided a step-by-step protocol for deriving transgene-free-induced pluripotent stem cells from the fibroblasts of multiple mammalian species, including human, mouse, marmoset, dog, pig, ferret, and Syrian hamster, a unique model of hibernation. The reprogramming factors are expressed by episomal transfection of DNA vectors. The episomal transfection may be followed by transfection of the mRNAs encoding these factors to increase the induction efficiency further. This protocol is expected to accelerate stem cell biology and regenerative medicine. Ikuta et al. (2023) provided a standard protocol for cardiac regeneration experiments in Iberian ribbed newts. This protocol describes tissue-amputation and cryo-injury techniques to inflict cardiac injuries for investigating subsequent regeneration processes. Both techniques are simple, require no special equipment, and can be applied to other newt and salamander species. As a Technical Note article, Fujimori et al. (2022) provided in vitro and in vivo gene transfer methods for Scyliorhinus torazame, a candidate model species of cartilaginous fish. These methods may contribute to gene manipulation such as genome editing and overexpression in cartilaginous fishes with evolutionarily unique morphological and physiological characteristics. Kondow et al. (2023) provide an improved workflow for automated contour extraction from light-sheet microscopy images of zebrafish blastula and gastrula. Their method involves rotating the image at multiple angles and superimposing the detected edges to achieve better accuracy and noise robustness than widely used edge detection methods. Our special issue “Methods and Protocols” consisting of Parts 1– 4, has provided new technical resources, including nine method articles, nine protocols, and two technical notes. The species used as the experimental materials include human, mouse, rat, marmoset, dog, pig, ferret, hamster (cultured cells), Xenopus, Iberian ribbed newt, zebrafish, medaka, anemonefish, sea urchin, sea lily, sand roller, nematodes (Caenorhabditis elegans and Pristionchus pacificus), planarians, and Arabidopsis thaliana. We believe that this special issue facilitates the development of the cross-species research platform and reveals the mechanisms generating the diversity of life on Earth, as we wrote in the preface at the start of this special issue (Ogino et al., 2021).