Biology subjects

Kishi, K.

Publications and source records attributed to Kishi, K..

5 recordsLinked to original sources

bioRxiv2024

Dynamics of morphogen source formation in a growing tissue

A tight regulation of morphogen production is key for morphogen gradient formation and thereby for reproducible and organised organ development. Although many genetic interactions involved in the establishment of morphogen production domains are known, the biophysical mechanisms of morphogen source formation are poorly understood. Here we addressed this by focusing on the morphogen Shh in the vertebrate neural tube. Shh is produced by the adjacently located notochord and by the floor plate of the neural tube. Using a data-constrained computational screen, we identified different possible mechanisms by which floor plate formation can occur, only one of which is consistent with experimental data. In this mechanism, the floor plate is established rapidly in response to Shh from the notochord and the dynamics of regulatory interactions within the neural tube. In this process, uniform activators and Shh-dependent repressors are key for establishing the floor plate size. Subsequently, the floor plate becomes insensitive to Shh and increases in size due to tissue growth, leading to scaling of the floor plate with neural tube size. In turn, this results in scaling of the Shh amplitude with tissue growth. Thus, this mechanism ensures a separation of time scales in floor plate formation, so that the floor plate domain becomes growth dependent after an initial rapid establishment phase. Our study raises the possibility that the time scale separation between specification and growth might be common strategy for scaling the morphogen gradient amplitude in growing organs. The model that we developed provides a new opportunity for quantitative studies of morphogen source formation in growing tissues.

systems biology↗

bioRxiv2023

Functional and long-lived melanocytes from human pluripotent stem cells with transient ectopic expression of JMJD3

BackgroundMelanocytes are an essential part of the epidermis, and their regeneration has received much attention because propagation of human adult melanocytes in vitro is too slow for clinical use. Differentiation from human pluripotent stem cells to melanocytes has been reported, but the protocols to produce them require multiple and complex differentiation steps. MethodWe differentiated human embryonic stem cells (hESCs) that transiently express JMJD3 to pigmented cells. We investigated whether the pigmented cells have melanocytic characteristics and functions by qRT-PCR, immunocytochemical analysis and flow cytometry. We also investigated their biocompatibility by injecting the cells into immunodeficient mice for clinical use. ResultWe successfully differentiated and established a pure culture of melanocytes. The melanocytes maintained their growth rate for a long time, approximately 200 days, and were functional. They exhibited melanogenesis and transfer of melanin to peripheral keratinocytes. Moreover, melanocytes simulated the developmental processes from melanoblasts to melanocytes. The melanocytes had high engraftability and biocompatibility in the immunodeficient mice. ConclusionThe robust generation of functional and long-lived melanocytes are key to developing clinical applications for the treatment of pigmentary skin disorders.

cell biology↗

bioRxiv2022

An ImageJ-based tool for three-dimensional registration between different types of microscopic images

Three-dimensional (3D) registration (i.e. alignment) between two microscopic images is substantially helpful to study tissues not adhere to substrates such as mouse embryos and organoids which are often three-dimensionally rotated during imaging. However, there is no 3D registration tool easily accessible for experimental biologists. Here we developed an ImageJ-based tool which achieves 3D registration accompanying both quantitative evaluation of the accuracy and reconstruction of 3D rotated images. In this tool, several landmarks are manually provided in two images to be aligned, and 3D rotation is computed so that the distances between the paired landmarks from the two images are minimized. By simultaneously providing multiple points (e.g. all nuclei in the regions of interest) other than the landmarks in the two images, the correspondence of each point between the two images is quantitatively explored: a certain nucleus in one image corresponds to which nucleus in another image. Furthermore, the 3D rotation is applied to one of the two images, resulting in reconstruction of 3D rotated images. We demonstrated that this tool successfully achieved 3D registration and reconstruction of images in mouse pre-implantation embryos, where one image was obtained during live imaging and another image from fixed embryos after live imaging. This approach provides a versatile tool applicable for various tissues and species.

developmental biology↗

bioRxiv2021

In vivo label-free observation of tumor-related blood vessels in small animals using a newly designed photoacoustic 3D imaging system

IntroductionPhotoacoustic technology can be used for non-invasive imaging of blood vessels. In this paper, we report on our prototype photoacoustic imaging system with a newly designed ultrasound sensor and its visualization performance of microvascular in animal. MethodsWe fabricated an experimental system for animals using a high-frequency sensor. The system has two modes: still image mode by wide scanning and moving image mode by small rotation of sensor array. Optical test target, euthanized mice and rats, and live mice were used as objects. ResultsThe results of optical test target showed that the spatial resolution was about 2 times higher than that of our conventional prototype. The image performance in vivo was evaluated in euthanized healthy mice and rats, allowing visualization of detailed blood vessels in the liver and kidneys. In tumor-bearing mice, different results of vascular induction were shown depending on the type of tumor and the method of transplantation. By utilizing the video imaging function, we were able to observe the movement of blood vessels around the tumor. ConclusionWe have demonstrated the feasibility of the system as a less invasive animal experimental device, as it can acquire vascular images in animals in a non-contrast and non-invasive manner.

cancer biology↗

bioRxiv2020

Stem cell lineage survival as a noisy competition for niche access

Understanding to what extent stem cell potential is a cell-intrinsic property, or an emergent behavior coming from global tissue dynamics and geometry, is a key outstanding question of stem cell biology. Here, we propose a theory of stem cell dynamics as a stochastic competition for access to a spatially-localized niche, giving rise to a "stochastic conveyor-belt" model. Cell divisions produce a steady cellular stream which advects cells away from the niche, while random rearrangements enable cells away from the niche to be favourably repositioned. Importantly, even when assuming that all cells in a tissue molecularly equivalent, the model predicts a common ("universal") functional dependence of the long-term clonal survival probability on the position within the niche, as well as the emergence of a well-defined number of "functional" stem cells, dependent only on the rate of random movements vs. mitosis-driven advection. We test the predictions of this theory on datasets on pubertal mammary gland tips, embryonic kidney tips as well homeostatic intestinal crypt, and find good quantitative agreement for the number of functional stem cells in each organ, as well as the predicted functional dependence of the competition.

biophysics↗