The Zoological Society of Japan, Hokkaido Branch, 615th Branch Lecture Meeting

Date and Time: Monday, September 7, 2026, 13:00 - 14:00

Location: Hokkaido University, School of Science, Building No. 5, 3rd Floor, Room 305

Speaker: Dr. Yusuke Mitsui (Institute for Life and Medical Sciences, Kyoto University)

Title: Mechanism by which the secreted signal Wnt determines cell polarity independently of a concentration gradient and its in vitro reconstitution system

Abstract: In embryonic development, the precise regulation of cell position and directional information is critically important, and secreted signaling proteins have been thought to be involved in this regulation by forming concentration gradients. As an example, Wnt is known to be involved in the regulation of positional information and planar cell polarity (PCP), a type of cell polarity. However, little is known about the actual distribution of Wnt proteins in vertebrates, and the concentration gradient theory has not been directly tested.

PCP is established by a group of proteins called PCP factors that exhibit polarized localization within individual cells. Based on the visualization of Wnt11, which is involved in PCP regulation, in Xenopus embryos, we worked to elucidate its regulatory mechanism. As a result, we discovered that Wnt11 does not form a concentration gradient, but rather exhibits a polarized distribution on the cell membrane similar to PCP factors. We found that this unique distribution arises from Wnt11 forming a complex with PCP factors, and furthermore, that Wnt11 regulates PCP by stabilizing this complex (Mii et al., Science Advances 2026). While the conventional concentration gradient theory implicitly assumed that Wnt regulates PCP in a top-down manner, we revealed a bottom-up mechanism of action based on local interactions.

Inspired by observations in Xenopus embryos, we also succeeded in reproducing PCP in a culture system (Matsuo et al., bioRxiv 2026). Furthermore, while PCP factors have traditionally been thought to exert their physiological functions through polarization, we have used this experimental system as a starting point to discover that "non-polarized" PCP factors also play physiological roles related to tissue homeostasis and fundamental tissue architecture, such as the regulation of cell proliferation and epithelial barrier function. We would like to discuss these latest findings as well.

Caretaker:

Chika Fujimori (Faculty of Science, Hokkaido University)

c-fujimori[a]sci.hokudai.ac.jp

Please change [a] to @.

Ezo squirrel (Provided by Minorukaz Nagahara, Asahikawa Medical University RI Research Facility)