Figure 7. Ascl1 lineage in the trigeminal sensory system in the brainstem.
(A) Diagram of an E12.5 embryo depicting section planes in hindbrain regions shown in (B–D). (B) Ascl1 is restricted to the ventricular zone around the fourth ventricle whereas β-gal marked Ascl1 lineage cells from E12.5 in Ascl1-CreER™;R26R-stop-lacZ embryos are found in the mantle zone by E13.5. (E–I) YFP+ Ascl1 lineage cells in Ascl1-CreER™;R26R-stop-YFP treated with tamoxifen at E10.5 and harvested at E11.5 are dB3 neurons as indicated by co-expression with Tlx3 (H) and Lmx1b (G), but not Pax2 (H) or Lhx1/5 (I). (J) Summary of neuronal subtypes and transcription factors for early (dA1–dB4) and late (dBLa and dBLb) neurogenesis in rhombomere 7 (Sieber et al., 2007). (K–N’) In Ascl1-CreER™;R26R-stop-lacZ embryos, tamoxifen was administered at E10.5 (K–N) and E12.5 (K’–N’), and harvested 24 hours later (K, K’) or at E18.5 (L–N’). (O) Diagram depicting E18.5 embryo brainstem with section plane used in panels (L–N’) shown. (L”–N”) Diagrams of coronal sections of hindbrain showing precerebellar nuclei. 4v, fourth ventricle; CN, cochlear nucleus; ECN, external cuneate nucleus; Gi, gigantocellular reticular nucleus; ION, inferior olive nucleus; LPGi, lateral paragigantocellular nucleus; LRL, lower rhombic lip; LRt, lateral reticular nucleus; MZ, mantle zone; Sp5, spinal trigeminal nucleus; PCRtA, parvicellular reticular nucleus, alpha part; PN, pontine nuclei; Pr5, the primary sensory trigeminal nucleus; Rtgn, reticulotegmental nucleus; URL, upper rhombic lip; VM, medial vestibular nucleus; Vsp, spinal vestibular nucleus; VZ, ventricular zone. Scale bars = 20µm for B, E–I, 200µm for C, K–N’.