Actin filaments as an indicator of impaired neuronal differentiation mediated by disruption of the retinoic acid signalling pathway

Abstract: Retinoic acid (RA) is a well-known neurodevelopmental signaling molecule. It is reported to induce effects on neurite formation in differentiating neurons and to interfere with the actin cytoskeleton. Therefore, this project aimed to investigate the mechanisms behind effects of RA on the actin cytoskeleton of developing neurons using the C17.2 neural progenitor cells (NPCs) in vitro model. The goal was to evaluate the morphological effects the growth cone had upon exposure to RA agonist and antagonist, and to analyze the expression of three genes: Coronin actin-binding protein 1C(Coro1c), Cdc42 effector protein 4 gene (Cdc42), and Fibronectin (Fn1). These genes were selected because of their relation to actin dynamics and/or their regulation by the Wnt pathway, which regulates/affects actin reorganization. Since the Wnt pathway was also shown to be affected by RA, this study aimed to investigate the relationship between RA and actin through the Wnt pathway. Cdc42 and Fn1 are related to both the Wnt pathway and actin dynamics, whereas Coro1cis a known actin-related protein. The expressions showed significant increase with Coro1c, while Cdc42 and Fn1 had a similar overall trend increase with the RA agonist. The RA antagonist showed no significant effect, except a trend decrease in all the genetic expressions. All genetic expression effects subside with the increase of RA agonist and antagonist concentrations. The results suggest the changes in actin filaments are related to a low dose effect of RA. The findings indicate a possibility of a regulation mechanism that controls actin-related gene expression in response to RA. This mechanism is possibly not restricted to the Wnt pathway seeing that a non-Wnt related gene was affected as well.