Biophysical Society Thematic Meeting| Aussois 2019

Biology and Physics Confront Cell-Cell Adhesion

Wednesday Speaker Abstracts

PLANAR CELL POLARITY-DISRUPTING MUTATION ALTERS CELSR1- MEDIATED CELL ADHESION AND DYNAMICS Sara N Stahley ; Danelle Devenport 1 ; 1 Princeton University, Molecular Biology, Princeton, New Jersey, USA Planar cell polarity (PCP), the collective polarization of cells along a tissue plane, is fundamental to early embryonic development and tissue organization in complex, multicellular organisms. Compromised PCP results in severe developmental disorders including neural tube defects, ciliopathies and cardiomyopathies. A hallmark of PCP is the asymmetric localization of core PCP components at cell junctions bridged by principle PCP protein, Celsr, an atypical cadherin. We lack a detailed understanding of Celsr1 extracellular interactions at the molecular level. Overall, this work seeks to elucidate how Celsr1 mediates cell adhesion to coordinate functional PCP and how this is altered by the PCP-disrupting mutation Crash (Crsh). Crsh maps to the cadherin repeats within Celsr1s extracellular domain, suggesting it may perturb Celsr1 adhesion. Using the mammalian epidermis as a model system and a combination of junctional recruitment and cell aggregation assays, we show that Celsr1 mediates calcium-dependent, homophilic cell adhesion through its extracellular domain. Surprisingly, Crsh mediates cell aggregation comparable to wildtype (WT), demonstrating this variant mediates trans-adhesive interactions. Yet when mixed, Crsh and WT expressing cells sort out into distinct aggregates, indicating this point mutation alters Celsr1 adhesive properties. Crsh displays more diffuse cell surface distribution and reduced junctional stability as measured by FRAP, suggesting Crsh is defective in lateral clustering. Importantly, chemically induced cis-dimerization of Crsh rescues junctional enrichment and trans-interactions with WT, indicating a role for cis-interactions to stabilize Celsr1 adhesion. Finally, we use super-resolution imaging to investigate the subcellular organization of PCP junctions and reveal how alterations in Celsr1 adhesion affect this organization. Collectively, our results support a model in which the Crsh-pertaining region of Celsr1 is responsible for mediating cis-interactions that function to stabilize and reinforce the adhesive complex, a critical prerequisite for PCP organization and functional asymmetry.

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