Gene Profiles and Electrophysiology of Doublecortin-Expressing Cells in the Subventricular Zone after Ischemic Stroke

Abstract

Stroke increases neuroblasts in the subventricular zone (SVZ) of the lateral ventricle and these neuroblasts migrate toward the ischemic boundary to replace damaged neurons. Using brain slices from the nonischemic adult rat and transgenic mice that expressed enhanced green fluorescent protein (EGFP) concomitantly with doublecortin (DCX), a marker for migrating neuroblasts, we recorded electrophysiological characteristics while simultaneously analyzing the gene expression in single SVZ cells. We found that SVZ cells expressing the DCX gene from the nonischemic rat had a mean resting membrane potential (RMP) of À30 mV. DCX-EGFP-positive cells in the nonischemic SVZ of the transgenic mouse had a mean RMP of À25±7 mV and did not exhibit Na + currents, characteristic of immature neurons. However, DCX-EGFP-positive cells in the ischemic SVZ exhibited a hyperpolarized mean RMP of À54±18 mV and displayed Na + currents, indicative of more mature neurons. Single-cell multiplex RT-PCR analysis revealed that DCX-EGFP-positive cells in the nonischemic SVZ of the transgenic mouse expressed high neural progenitor marker genes, Sox2 and nestin, but not mature neuronal marker genes. In contrast, DCX-EGFP-positive cells in the ischemic SVZ expressed tyrosine hydroxylase, a mature neuronal marker gene. Together, these data indicate that stroke changes gene profiles and the electrophysiology of migrating neuroblasts. IntroductionIn the adult rodent brain, neurogenesis occurs primarily in the subventricular zone (SVZ) of the lateral ventricle and in the subgranular zone of the dentate gyrus (Gage et al, 1995;Luskin et al, 1997;Kirschenbaum et al, 1999;Alvarez-Buylla et al, 2000). The SVZ of adult rodent brain contains the migratory neuroblasts, actively proliferating progenitor cells and quiescent neural stem cells (Morshead et al, 1994;Garcia-Verdugo et al, 1998). Neuroblasts in the SVZ travel the rostral migratory stream to the olfactory bulb where they differentiate into granule and periglomerular neurons throughout adult life (Morshead et al, 1994;Garcia-Verdugo et al, 1998;Luskin, 1998). Migrating neuroblasts express doublecortin (DCX) and b-III tubulin (TuJ1). Using DCXenhanced green fluorescent protein (DCX-EGFP) transgenic mice and immunostaining with antibodies against Tuj1 in wild-type mice, two groups have characterized biophysical properties and current profiles of migrating neuroblasts in acute brain slices (Bolteus and Bordey, 2004;Walker et al, 2007). DCX-EGFP cells in the SVZ and the dentate gyrus exhibit electrophysiological characteristics of immature and mature neurons, respectively, suggesting that DCXexpressing cells are a heterogeneous cell population (Walker et al, 2007).Focal cerebral ischemia promotes neurogenesis in the SVZ and induces SVZ neuroblast migration toward the ischemic boundary (Parent et al, 2002;Zhang et al, 2001Zhang et al, , 2004Arvidsson et al, 2002;Jin et al, 2003). It is unknown whether ischemia affects electrophysiological properties of migrating neuroblasts. Moreover, gene profiles of m...

Human neural stem cell intracerebral grafts show spontaneous early neuronal differentiation after several weeks

“…S5). This is further strengthened by our electrophysiological pattern developments which are similar to earlier patch-clamp characterization of doublecortin-expressing cells in the subventricular zone after ischemic stroke [36].…”

Patterns and Dynamics of Subventricular Zone Neuroblast Migration in the Ischemic Striatum of the Adult Mouse

“…Neuroblasts in the SVZ are a heterogeneous population derived from different neural stem cells (Willaime-Morawek et al , 2006; Merkle et al , 2007; Ventura and Goldman, 2007; Young et al , 2007). Stroke induces changes in gene profiles of neuroblasts localized to the SVZ (Liu et al , 2009). Whether neuroblasts emigrating laterally from the SVZ to the ischemic striatum comprise a subgroup of neuroblasts remains to be determined.…”

Oligodendrogenesis after cerebral ischemia

“…Demyelination in the corpus callosum produced by lysolecithin induces SVZ generated doublecortin (DCX) lineage neuroblasts to differentiate into OPCs (Jablonska et al, 2010). However, DCX lineage OPCs were not detected in adult ischemic brain, although stroke greatly increases DCX lineage neuroblasts (Liu et al, 2009; Zhang et al, 2009). These data indicate that stroke induces oligodendrogenesis by recruiting resident OPCs in white and gray matter and OPCs generated by SVZ neural progenitor cells and that new oligodendrocytes generated after stroke become mature myelinating oligodendrocytes.…”