Fig. 1

βgal from Zic3-lacZ marks the septal primordia and OB cells originating from septum. (a-d) βgal was enriched in the E15.5 and E18.5 septum and co-localized with Gsx2 within VZ progenitors (b, d). Insets in (b) and (d) show high magnification views of septum (b’) and (d’). Inset in (c) shows βgal staining in the E18.5 striatum was found in axons ascending from diencephalon as evidenced by co-labeling with neurofilament (c’). (e-g) βgal from Zic3-lacZ displayed a dorsal to ventral gradient, similar to Zic proteins stained by panZic antibody, in the E18.5 septum. Boxes in (e) represent high magnification views in (f) and (g). (h, i) Horizontal section of E18.5 brain showed βgal⁺ cells migrating to the OB along the RMS and expressing Sp8 on the medial side (indicated by arrows) in a pattern similar to endogenous Zic3 gene expression shown in the inset (h’), whereas very few βgal⁺ cells were on the lateral side despite the presence of migrating Sp8⁺ cells (indicated by arrowheads). (J-L) Many βgal⁺ and Zic⁺ cells were found in the E18.5 OB in regions including the forming GL (k) and the germinal zone (l). Boxes in (j) represent high magnification views in (k) and (l). Most βgal⁺ cells were Zic⁺, while many Zic⁺ cells were βgal⁻. (m-o) Many βgal⁺ cells in the forming GL (n) and germinal zone (o) of the OB co-expressed Sp8, constituting a subpopulation of Sp8⁺ interneurons. Boxes in (m) represent high magnification views in (n) and (o). (p) Mef2c⁺ granule cells in the E18.5 OB did not express βgal