Functional assessment of CELSR1 variants associated with human developmental defects

During development, collective and oriented cell behaviors that drive organ formation and tissue patterning require coordination among neighboring cells governed by the highly conserved planar cell polarity (PCP) pathway. Deficiencies in PCP gene function result in severe developmental defects in model systems from flies to mice, while PCP gene mutations are associated with human birth defects impacting the neural tube and heart. Atypical cadherin Celsr1 engages in cell-cell adhesion to coordinate the asymmetric localization of Fz6 and Vangl2 to opposing sides of the PCP junction between neighboring cells. However, whether CELSR1 genetic variations disrupt function or contribute to disease pathogenesis remains poorly understood. Using cell-based assays for Celsr1 function, along with in silico modeling, we test a cohort of 17 Celsr1 mutations previously identified in patients with neural tube and congenital heart defects. In junctional enrichment assays, we find 13 variants displayed altered enrichment at cell borders relative to WT, including both loss- and gain-of-function behaviors. Further analysis of select Celsr1 mutations revealed defects in membrane mobility and perturbed co-recruitment of PCP protein Fz6. Our findings link Celsr1 mutations associated with human birth defects to functional defects in adhesion and PCP. In addition, our approach supports a framework for evaluating PCP function alongside genomics and in silico predictions toward understanding the pathophysiology impacts of genetic variations associated with human developmental disorders and gaining insight into Celsr1 function during development.