The mature mammalian central nervous system (CNS) possesses only a restricted ability to repair itself, mainly due to its limited capacity in generating and properly targeting new neural cell types. The long-term goal of the proposed studies is to better understand the regulatory circuits that may be necessary for stimulating CNS-resident neural stem/progenitor cells for repair of the CNS and in particular the myelin sheath that is a prerequisite for fast and efficient nerve conduction. More specifically, the current proposal investigates the central hypothesis that the choroid plexus released protein phosphodiesterase-Ialfa/autotaxin (PD-Ialfa/ATX), via its enzymtically active lyso-PLD site, represents one of the factors regulating cell fate and migration of myelinating cells, i.e. oligodendrocytes (OLGs), in the postnatal mammalian forebrain. The studies described in the two Specific Aims of the proposal and addressing the above central hypothesis will be done primarily at the Federal University of Rio de Janeiro (Brazil) in collaboration with Cecilia Hedin-Pereira as an extension to NIH grant 5R01NS045883.
In Specific Aim 1, we will determine the role of PD-Ialfa/ATX and in particular its lysoPLD-active site for OLG cell fate determination in the rodent forebrain. OLG specification has been shown to occur in the postnatal forebrain within a specialized region, namely the subventricular zone (SVZ). We will investigate the effects of lysophosphatidic acid (LPA), the endproduct of PD-Ialfa/ATX's enzymatic activity, fully functional PD-Ialfa/ATX and enzymatically inactive PD-Ialfa/ATX on OLG cell fate specification using SVZ explant cultures. To further characterize the LPA/PD-Ialfa/ATX-mediated effects on the OLG lineage, we will assess the contribution of the known LPA receptors by using pharmacological and siRNA approaches. In addition, we will perform in vivo experiments, in which cycling cells of the SVZ will be labeled using retroviral injections. PD-Ialfa/ATX and enzymatically inactive PD-Ialfa/ATX will additionally be injected and the effects on cell fate specification will be determined using immunohistochemistry and confocal imaging.
In Specific Aim 2, we will determine the role of PD-Ialfa/ATX and in particular its lysoPLD-active site for migration of newly generated OLG progenitor cells (OPCs) within the rodent forebrain. We will use the same experimental paradigms as used in the studies to Specific Aim 1. Here we will, however, focus our analysis on the migratory pathways of OPCs. Taken together, the proposed sets of experiments are expected to yield novel insight into the regulatory mechanisms that control 1) OLG specification and 2) OPC migration in the developing forebrain. Most importantly, these studies are anticipated to lead to subsequent investigations aimed at stimulating endogenous neural stem/progenitor cells to contribute to repair of the myelin sheath under pathological conditions. Public Health Relevance: The mature mammalian central nervous system (CNS) possesses only a restricted ability to repair itself after injury and under pathological conditions. Stimulation of CNS-resident neural stem/progenitor cells represents a promising, yet currently poorly characterized, possibility for restoring CNS function including fast and efficient nerve conduction that is ultimately dependent on the presence of an undamaged myelin sheath. As an attempt to better understand the regulatory circuits that may be necessary for stimulating endogenous repair of the myelin sheath, the present grant application investigates the potential role of the extracellular factor phosphodiesterase-Ialfa/autotaxin (PD-Ialfa/ATX) in stimulating the generation and migration of myelinating cells, i.e. oligodendrocytes.