Figure 8.

Birthdate tagging at TM15.5. Coronal brain sections prepared from P22 Neurog2^CreER(G2A); Cdhr1^tTA; ROSA26-TRE^mGFP (A–F) and P21 Neurog2^CreER(G2A); Cdhr1^tTA; TRE^{tdTomato-sypGFP} (G–L) mice that were given TM at E15.5. Images for mGFP reporter (A–F) and tdTomato reporter (G–L) counterstained with DAPI. A”, D’, E’, G”, J’, K’, Black and white high contrast image converted from the reporter image. A’, A”, G’, G”, High magnifications of the MOB, of which layer positions are indicated on the right-hand end. Arrows (A, A’, G, G’) indicate the internal plexiform layer that contains intrabulbar association fibers. Arrowheads (A’, A”, G’, G”) indicate cell bodies of birthdate-tagged eTCs, whose basal dendrites horizontally extend in the upper part of the EPL. The glomerulus (GL) is encircled by a dotted line (A”, G”). The TM15.5 axons only project to the pE (B, H) and the small domain in the anterolateral edge of the OT (asterisks in D, D’, E, E’, J, J’, K, K’). This domain contains a cell cluster, which is encircled by the yellow dotted line and marked with the asterisk (D’, E’, J’, K’). The curved dotted line on the left of the cell cluster in E’, K’ depicts the lateral hook of the OT cell layer. The brain illustration summarizes TM15.5 axon projections and indicates the levels at which individual sections were prepared. The pie chart shows the proportion of neuron subtypes tagged at this TM stage in each reporter line. Representative images from five (A–F) and nine (G–L) mice. Scale bars = 100 μm (A’, A”, D’, E’, G’, G”, J’, K’) and 500 μm (A–L). GRL: granule cell layer, pD: pars dorsalis, pL: pars lateralis, TT: tenia tecta.