GSK3 and Lamellipodin balance lamellipodial protrusions and focal adhesion maturation in mouse neural crest migration

Neural crest cells are multipotent cells that delaminate from the neuroepithelium, migrating to distant destinations throughout the embryo. Aberrant migration has severe consequences, such as congenital disorders. While animal models have improved our understanding of neural crest anomalies, the in vivo contributions of actin-based protrusions are still poorly understood. Here, we demonstrate that murine neural crest cells use lamellipodia and filopodia in vivo. Using neural crest-specific knockouts or inhibitors, we show that the serine-threonine kinase, Glycogen Synthase Kinase-3 (GSK3), and the cytoskeletal regulator, Lamellipodin (Lpd), are required for lamellipodia formation whilst preventing focal adhesion maturation. We consequently identified Lpd as a novel substrate of GSK3 and found that phosphorylation of Lpd favours Lpd interactions with the Scar/WAVE complex (lamellipodia formation) at the expense of Ena/VASP protein interactions (adhesion maturation and filopodia formation). All together, we provide an improved understanding of cytoskeletal regulation in mammalian neural crest migration, which has general implications for neural crest anomalies and cancer.