National Institute for Basic Biology and Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Japan.
The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan.
Elife. 2021 Apr 27;10:e55108. doi: 10.7554/eLife.55108.
The mechanism of intercellular transport of Wnt ligands is still a matter of debate. To better understand this issue, we examined the distribution and dynamics of Wnt8 in embryos. While Venus-tagged Wnt8 was found on the surfaces of cells close to Wnt-producing cells, we also detected its dispersal over distances of 15 cell diameters. A combination of fluorescence correlation spectroscopy and quantitative imaging suggested that only a small proportion of Wnt8 ligands diffuses freely, whereas most Wnt8 molecules are bound to cell surfaces. Fluorescence decay after photoconversion showed that Wnt8 ligands bound on cell surfaces decrease exponentially, suggesting a dynamic exchange of bound forms of Wnt ligands. Mathematical modeling based on this exchange recapitulates a graded distribution of bound, but not free, Wnt ligands. Based on these results, we propose that Wnt distribution in tissues is controlled by a dynamic exchange of its abundant bound and rare free populations.
Wnt 配体的细胞间运输机制仍存在争议。为了更好地理解这个问题，我们检测了 Wnt8 在 胚胎中的分布和动态。虽然 Venus 标记的 Wnt8 被发现存在于靠近 Wnt 产生细胞的细胞表面，但我们也检测到了它在 15 个细胞直径的距离上的扩散。荧光相关光谱和定量成像的组合表明，只有一小部分 Wnt8 配体自由扩散，而大多数 Wnt8 分子与细胞表面结合。光转化后的荧光衰减表明，细胞表面结合的 Wnt8 配体呈指数衰减，表明 Wnt 配体结合形式的动态交换。基于这种交换的数学建模再现了结合的，但不是自由的，Wnt 配体的梯度分布。基于这些结果，我们提出组织中 Wnt 的分布是由其丰富的结合形式和稀少的游离形式的动态交换所控制的。
