Expression of Disabled 1 suppresses astroglial differentiation in neural stem cells

Abstract

Disabled 1 (Dab1), a cytoplasmic adaptor protein expressed predominantly in the CNS, transduces a Reelin-initiated signaling that controls neuronal migration and positioning during brain development. To determine the role of Dab1 in neural stem cell (NSC) differentiation, we established a culture of neurospheres derived from the embryonic forebrain of the Dab1 −/− mice, yotari. Differentiating Dab1 −/− neurospheres exhibited a higher expression of GFAP, an astrocytic marker, at the expense of neuronal markers. Under Dab1-deficient condition, the expression of NeuroD, a transcription factor for neuronal differentiation, was decreased and the JAK-STAT pathway was evidently increased during differentiation of NSC, suggesting the possible involvement of Dab1 in astrocyte differentiation via JAK-STAT pathway. Notably, expression of neural and glial markers and the level of JAK-STAT signaling molecules were not changed in differentiating NSC by Reelin treatment, indicating that differentiation of NSC is Reelin-independent. Immunohistochemical analyses showed a decrease in the number of neurons and an increase in the number of GFAP-positive cells in developing yotari brains. Our results suggest that Dab1 participates in the differentiation of NSCs into a specific cell lineage, thereby maintaining a balance between neurogenesis and gliogenesis.

Reelin sets the pace of neocortical neurogenesis

“…Together with previously published results (Hartfuss et al, 2003;Anthony et al, 2005;Keilani and Sugaya, 2008;Gaiano, 2008), they are consistent with the notion of reelin acting upstream of Notch signaling in NPCs to regulate cell fate before differentiation. Our results also emphasize the need for combined GOF and LOF approaches, as conflicting results have been obtained in two reports upon differentiation of reeler-derived neurospheres (Kwon et al, 2009;Massalini et al, 2009). The recent proposal that Dab1 suppresses astroglial differentiation, albeit independently of reelin (Kwon et al, 2009), is seemingly incompatible with previously published results showing how the lack of reelin accelerates the transition of radial glial cells to astrocytes (Hunter-Schaedle, 1997) and our own observations showing reciprocal behavior in the reelin GOF condition (supplementary material Fig.…”

Cell-Autonomous Inactivation of the Reelin Pathway Impairs Adult Neurogenesis in the Hippocampus

“…In adult reeler mice injected with BrdU to label dividing cells, the number of BrdU-labeled, GFAP-positive astrocytes is increased compared to WT mice, thereby indicating that adult neurogenesis is altered and that newly generated cells preferentially differentiate into astrocytes (Zhao et al, 2007). Furthermore, in neurospheres from the dab1 mutant mouse, yotari , and in the yotari brain in vivo , GFAP expression increases at the expense of neurons, further supporting the notion that Dab1 contributes to suppressing astroglial differentiation (Kwon et al, 2009). These results are consistent with our finding of increased labeled glia after RV-shRNA-mediated Dab1 knock-down.…”

Reelin affects chain-migration and differentiation of neural precursor cells

“…This is in agreement with a previous report (Zhao et al, 2007), describing impaired neurogenesis, but not gliogenesis, in the adult reeler dentate gyrus, one of the brain regions with ongoing postnatal neurogenesis. Recently, apparently conflicting data have been published claiming that NSC differentiation into neurons or astrocytes is independent of Reelin (Kwon et al, 2009). In that work, the authors observe that the supplementation of pCrltransfected 293T cell conditioned medium to wild type embryonic (E12.5) NSCs does not affect the differentiation into neurons or astrocytes; in addition, the differentiation of reeler embryonic NSCs, measured by Western blot of neuronal and glial markers, was not found to be different from that of analogous wild type cells.…”