CONICET | Buscador de Institutos y Recursos Humanos

Study of FGD6 function in neuronal physiology and its potential role in epilepsyFunctional relevance of FGD6 in organisation of actin cytoskeleton and the impact in neuronal physiology.Regulation of neuronal morphology and activity-dependent synaptic modifications involves reorganization of the actin cytoskeleton, controlled by small GTPases of the Rho family, such as RhoA, Rac1 and Cdc42. Precise spatial and temporal regulation of Rho family GTPases is required for proper neuronal morphology. FGD6 (FYVE, RhoGEF and PH domain-containing protein 6) function in CNS is not established. It belongs to a FGD family (FGD1-6), in which some of the members have a known function such as Cdc42 GEF (guanine exchange factors) activators. We studied FGD6 expression by qRT-PCR in SK-N-SH neuroblastoma cells, and we observed a decrease in gene expression when the cells differentiate to a more mature phenotype (p≤0,05), followed by a raise in FGD6 mRNA as the cells continue to differentiate. Similar results were obtained in rat primary cortical neurons. In the neuroblastoma cells, FGD6 knockdown expression using siRNA transfection (~50% reduction) caused actin disorganization and changes in cell shape, with no changes in total actin pool by Western blot analysis. Moreover, when the gene is transiently knocked down, there was a significant ~40% reduction in Arp2 protein expression as determined by Western blots, with no changes in mRNA levels. Additionally, fibroblasts from epileptic patients homozygous for a mutation in FGD6 presented a striking disorganization in the actin cytoskeleton. Our results suggest that in neurons FGD6 expression is tightly regulated during cell maturation, and that FGD6 lack of function affects cytoskeleton dynamics which in turn hampers neuronal function such as differentiation and neuronal activity.