Actin dynamics regulation by TTC7A/PI4KIIIα axis limits DNA damage and cell death during leukocyte migration

The actin cytoskeleton has a crucial role in the maintenance of the immune homeostasis by controlling various cell processes, including cell migration. Mutations in the TTC7A gene have been described as the cause of a primary immunodeficiency associated to different degrees of gut involvement and alterations in the actin cytoskeleton dynamics. Although several cellular functions have been associated with TTC7A, the role of the protein in the maintenance of the immune homeostasis is still poorly understood. Here we leverage microfabricated devices to investigate the impact of TTC7A deficiency in leukocytes migration at the single cell level. We show that TTC7A-deficient leukocytes exhibit an altered cell migration and reduced capacity to deform through narrow gaps. Mechanistically, TTC7A-deficient phenotype resulted from impaired phosphoinositides signaling, leading to the downregulation of the PI3K/AKT/RHOA regulatory axis and imbalanced actin cytoskeleton dynamic. This resulted in impaired cell motility, accumulation of DNA damage and increased cell death during chemotaxis in dense 3D gels. Our results highlight a novel role of TTC7A as a critical regulator of leukocyte migration. Impairment of this cellular function is likely to contribute to pathophysiology underlying progressive immunodeficiency in patients.