Lew Valerie, Khetani Sukaynah, Kaur Simran, Woodward William, Sandhu Sukmin, Rawat Radhika, Elul Tamira
Department of Foundational Biomedical Sciences, College of Osteopathic Medicine, Touro University California, Vallejo, CA, United States.
College of Osteopathic Medicine, Touro University Nevada, Henderson, NV, United States.
Front Cell Neurosci. 2025 Jul 22;19:1572298. doi: 10.3389/fncel.2025.1572298. eCollection 2025.
Cadherin adhesive and actomyosin signaling are key cytomechanical cues required for neuronal circuit formation, but whether they function together to sculpt developing neurons is not known. Previously, we demonstrated that a β-catenin mutant (β-catNTERM) that disrupts binding of endogenous, full length β-catenin to α-catenin in the Cadherin adhesion complex, and a pharmacological inhibitor for actin regulator, non-muscle Myosin II (Blebbistatin), resulted in growth cones with fewer and more filopodia or filopodia-like protrusions than control growth cones of retinal ganglion cells (RGCs) in brains from embryos.
Here, we assessed whether perturbation of β-catenin adhesive and Myosin II signaling specifically impacted additional, diverse yet interrelated, parameters of growth cone morphology and axon pathfinding, including two novel measures of growth cone contours.
Among other findings, we show that growth cones of individual RGCs expressing β-catenin NTERM have less complex contours (lower fractal dimension) and axons that are more undulatory than control growth cones and axons. In contrast, contours of Blebbistatin exposed growth cones are less concave (lower fractional concavity) and their axons extend more branches compared to control RGCs. In additional experiments, an α-catNTERM mutant and ROCK inhibitor phenocopied the specific effects of β-catNTERM and Blebbistatin on complexity and concavity of growth cone contours.
This data suggests that β-catenin-α-catenin and actomyosin interactions differentially regulate growth cone contours as well as axonal undulation and branching of RGCs in whole brains. Broadly, our results provide insight into cytomechanical mechanisms of neuronal circuit formation normally, and neuronal connectivity defects in human neurodevelopment disorders associated with mutations in Cadherin and β-catenin.
钙黏蛋白黏附作用和肌动球蛋白信号传导是神经元回路形成所需的关键细胞力学信号，但它们是否共同作用塑造发育中的神经元尚不清楚。此前，我们证明了一种β-连环蛋白突变体（β-catNTERM），它破坏了钙黏蛋白黏附复合物中内源性全长β-连环蛋白与α-连环蛋白的结合，以及一种肌动蛋白调节剂非肌肉肌球蛋白II的药理学抑制剂（blebbistatin），导致胚胎脑内视网膜神经节细胞（RGC）的生长锥与对照生长锥相比，丝状伪足或丝状伪足样突起更少且更多。
在此，我们评估了β-连环蛋白黏附作用和肌球蛋白II信号传导的扰动是否特别影响生长锥形态和轴突导向的其他各种但相互关联的参数，包括生长锥轮廓的两个新测量指标。
在其他发现中，我们表明，表达β-连环蛋白NTERM的单个RGC的生长锥轮廓复杂性较低（分形维数较低），其轴突比对照生长锥和轴突更起伏不平。相比之下，与对照RGC相比，暴露于blebbistatin的生长锥轮廓的凹陷程度较小（分数凹陷较低），其轴突延伸出更多分支。在额外的实验中，α-catNTERM突变体和ROCK抑制剂模拟了β-catNTERM和blebbistatin对生长锥轮廓复杂性和凹陷性的特定影响。
这些数据表明，β-连环蛋白-α-连环蛋白和肌动球蛋白相互作用以不同方式调节全脑RGC的生长锥轮廓以及轴突起伏和分支。广泛而言，我们的结果为正常情况下神经元回路形成的细胞力学机制以及与钙黏蛋白和β-连环蛋白突变相关的人类神经发育障碍中的神经元连接缺陷提供了见解。
