Netrin-1 Favors Neuroblast Lineage Plasticity in SVZ of Injured Neonatal Brain

Infants born extremely preterm and with very low birthweight are susceptible to hypoxia-induced diffuse white matter injury (DWMI), leading to loss of oligodendrocytes, myelin abnormalities, and long-term behavioral disorders. Endogenous progenitor cells in the developing brain hold great potential for preventing or reversing DWMI caused by hypoxic events. Using a model of chronic hypoxia in the perinatal rodent, which produces DWMI analogous to the injury observed in preterm infants, we employed genetic lineage tracing to demonstrate that distinct progenitor/stem cell populations are capable of regenerating oligodendrocytes in white matter (WM) after injury. These populations include cells expressing Glial Fibrillary Acidic Protein (GFAP), Platelet Derived Growth Factor Receptor-α (PDGFRα), Ascl1 (Mash1), and Glutamate Decarboxylase-65 (GAD65). We go on to demonstrate a hypoxia-induced increase in the expression of chemotropic factor netrin-1 (NTN1) in both the subventricular zone (SVZ) and choroid plexus (CP). GAD65⁺ progenitors express NTN1 receptors including deleted in colorectal cancer (DCC), uncoordinated homolog 2 (Unc5H2) and Unc5H4. Using both in vivo and in vitro methods, we demonstrate a NTN1-mediated migratory effect on GAD65-expressing progenitors in the SVZ, resulting in an increase in GAD65-derived oligodendrocytes in the overlying WM. NTN1 also plays a role in lineage determination, as treating SVZ progenitors with NTN1 leads to generation of oligodendrocytes and astrocytes derived from GAD65-expressing cells. Our study demonstrates novel sources of glia in the developing brain following DWMI and reveals NTN1 to be a molecular signal associated with GAD65-progenitor migration and lineage plasticity in the postnatal brain.