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.

PFOS (pluorooctane sulfonic acid) and PCB 180 (2,2′,3,4,4′,5,5′-heptachlorobiphenyl) are endocrine-disrupting chemicals (EDCs) ubiquitously found throughout the environment, given their persistence and extreme long biological half-life. PFOS and PCB 180 are predicted to disrupt retinoic acid receptor (Rar) signaling, interfering with important events of brain development, including neural differentiation and proliferation. Despite accumulating reports on the adversities of these EDCs, studies on the underlying mechanism continue to be largely unknown. The aim of this study was to validate transcriptional markers predictive of Rar disruption and to assess whether the same effects are induced by PFOS and PCB 180 exposure. Murine neural progenitor C17.2 cells were employed to mimic the developing brain. The cells were exposed to increasing nanomolar concentrations (nM) of Rar (ant)agonist, PFOS, and PCB 180. Interestingly, of all the transcriptional markers investigated, Ccn2 (cellular communication network factor 2), Il18 (Interleukin -18), and Ntn1(Netrin 1) were significantly altered by the Rar agonist (P< 0.05). Likewise, the expression of Il18 and Ntn1 was also altered by developmental exposure to PFOS and PCB 180. Altogether, these findings indicate that Il18 and Ntn1 may be promising markers for studying developmental neurotoxicity induced by disruption of the retinoic acid pathway.