Image processing approaches for microtubule remodeling quantification at the immunological synapse

Immunological synapses result from a T cell polarization process, requiring cytoskeleton remodeling. Actin and microtubules drive synapse architecture and the localization of intracellular organelles, including Golgi and endolysosomal compartments, ensuring the directional localization of synapse components. Microtubule remodeling includes the centrosome polarization and the formation of a radial microtubules network, extending from the centrosome to the synapse periphery. Concomitantly, a ring of filamentous actin forms at the synapse periphery. Microtubule and actin remodeling facilitate vesicle fusion at the synapse, enabling T cell effector functions. Analyzing structural subtleties of cytoskeleton remodeling at the immunological synapse is crucial to understand its role in T cell functions. It may also pinpoint pathological states related with cytoskeletal dysfunctions. Quantifying filamentous protein network properties is challenging due to their complex and heterogeneous architectures and the inherent difficulty of segmenting individual filaments. Here, we describe the development of an image processing approach aimed at quantifying microtubule organization at the immunological synapse without the need for filament segmentation. The method is based on the analysis of the spatial and directional organization of microtubules growing from the centrosome to the synapse periphery. It is applied to investigate the importance of Adenomatous polyposis coli (Apc), a polarity regulator and tumor suppressor, in immunological synapse structure and functions and its potential implication in anti-tumor immune responses. We provide an open-source napari plugin of the outlined methods for analyzing filamentous networks.