NIBB Departments

Laboratory for Spatiotemporal Regulations

Staff

Website

Lab website

Research Summary

Our main interest is the mechanism of how the initial left-right asymmetry is determined in mammalian development. A small patch in a gastrulating mouse embryo called ‘the node’ generates leftward fluid flow by vortical motion of primary cilia on its ventral surface, and the flow direction is critically important to subsequent asymmetric gene expression and final organ arrangement. We are currently focused on the mechanism of how the flow is converted to the asymmetric gene expression, i.e. what kind of information is conveyed by the flow, chemical or mechanical, or something else, by combining techniques including whole embryo culture, light-sheet microscopy, etc.

Research Projects

• Left-right asymmetry in the positions of mother/daughter centrioles at the base of the node cilia
• Involvement of electrokinetic streaming current in sensing nodal flow

I. Initial step for left-right asymmetry

In mammalian development, the initial left-right asymmetry first appears as cilia-driven leftward fluid flow on the ventral surface of the node, and this flow provides the initial cue for asymmetric gene expressions that actually determine asymmetric morphogenesis. The mechanisms that convert the flow to asymmetric gene expression, i.e. the flow sensing mechanism, remain controversial, with several models being proposed, and the involvement of Ca²⁺ being suggested.

We pursued this question by measuring Ca²⁺ dynamics in the node and found that the node cells apparently cause stochastic elevation of Ca²⁺. The spatiotemporal distribution is equal on the left and right sides but becomes more prevalent on the left after the late headfold stage, when flow-induced commitment occurs. This asymmetry was disrupted in dynein mutant iv/iv and pkd2^-/-mutants, in accordance to their left-right phenotypes.

Figure 1. Left: Distribution of Ca²⁺ elevation in a 2-somite wild-type node. Right: Time course of Ca²⁺ elevation frequency at the left and the right sides.

Based on these findings, we are now examining the validity of the two major proposed models of flow sensing, mechanosensing and chemosensing, as well as a third novel mechanism.

II. Development of light-sheet microscopy

Light-sheet microscopy has become popular during this decade for benefits such as low photodamage and fast image acquisition. We are now running two light-sheet microscopes, one commercial and the other self-made, and are maintaining them for collaborations and our own research interest (this being left-right asymmetry).

Over several years, we have developed a fast light-sheet microscope named ezDSLM, in which the excitation light sheet and detection objective move instead of the specimen for z-scanning. We installed an electrically tunable lens (ETL) to achieve greater speed and the exclusion of mechanical vibrations that disturb continuous 4D imaging of floating or loosely held specimens.

Our light-sheet microscopes are available to other researchers via NIBB’s Collaborative Research and MEXT’s Advanced Bioimaging Support (ABiS) programs. Numerous collaborations are in progress including observation of moving Amoeba proteus, neuronal activity in Drosophila larvae, cell migration in zebrafish embryos, cleared mouse brains, and marine crustaceans, etc.

Figure 2. Images of floating volvox taken by ezDSLM with ETL. Left: Single optical section. Right: Maximum intensity projection.

PhD Program

This laboratory is currently recruiting graduate students.

Reports

Annual Report 2021（PDF）

Selected Publications

Taniguchi, A., Nishigami, Y., Kajiura-Kobayashi, H., Takao, D., Tamaoki, D., Nakagaki, T., Nonaka, S., and Sonobe, S. (2023). Light-sheet microscopy reveals dorsoventral asymmetric membrane dynamics of Amoeba proteus during pressure-driven locomotion. Biol. Open 12, bio059671.

Ichikawa, T., Nakazato, K., Keller, P. J., Kajiura-Kobayashi, H., Stelzer, E.H., Mochizuki, A., and Nonaka, S. (2013). Live imaging of whole mouse embryos during gastrulation: migration analyses of epiblast and mesodermal cells. PLoS One. 8, e64506.

Takao, D., Nemoto, T., Abe, T., Kiyonari, H., Kajiura-Kobayashi, H., Shiratori, H., and Nonaka, S. (2013). Asymmetric distribution of dynamic calcium signals in the node of mouse embryo during left-right axis formation. Dev. Biol. 376, 23-30.

Nonaka, S., Shiratori, H., Saijoh, Y., and Hamada, H. (2002). Determination of left-right patterning of the mouse embryo by artificial nodal flow. Nature 418, 96-99.