Brefeldin A-inhibited guanine exchange factor 2 regulates filamin A phosphorylation and neuronal migration

Periventricular heterotopia (PH) is a human malformation of cortical development associated with gene mutations in ADP-ribosylation factor guanine exchange factor 2 (ARFGEF2 encodes for Big2 protein) and Filamin A (FLNA). PH is thought to derive from neuroependymal disruption, but the extent to which neuronal migration contributes to this phenotype is unknown. Here, we show that Arfgef2 null mice develop PH and exhibit impaired neural migration with increased protein expression for both FlnA and phosphoFlnA at Ser2152. Big2 physically interacts with FlnA and overexpression of phosphomimetic Ser2512 FLNA impairs neuronal migration. FlnA phosphorylation directs FlnA localization toward the cell cytoplasm, diminishes its binding affinity to actin skeleton, and alters the number and size of paxillin focal adhesions. Collectively, our results demonstrate a molecular mechanism whereby Big2 inhibition promotes phosphoFlnA (Ser2152) expression, and increased phosphoFlnA impairs its actin binding affinity and the distribution of focal adhesions, thereby disrupting cell intrinsic neuronal migration.