Figure 7.

Birthdate tagging at TM13.5. Coronal brain sections prepared from P21 Neurog2^CreER(G2A); Cdhr1^tTA; ROSA26-TRE^mGFP (A–H) and P21 Neurog2^CreER(G2A); Cdhr1^tTA; TRE^{tdTomato-sypGFP} (I–P) mice that were given TM at E13.5. Images for mGFP reporter (A–H) and tdTomato reporter (I–P) counterstained with DAPI. A”, D’, E’, I”, L’, M’, Black and white high contrast image converted from the reporter image. A’, A”, I’, I”, High magnifications of the MOB, of which layer positions are indicated on the right-hand end. Arrows (A, A’, I, I’) indicate the internal plexiform layer that contains intrabulbar association fibers. Arrowheads (A’, A”, I’, I”) indicate cell bodies of birthdate-tagged imTCs and eTCs. Note that the basal dendrites in the upper part of the EPL are labeled. The glomerulus (GL) is encircled by a dotted line (A”, I”). The TM13.5 axons project to only anterior part of the olfactory target areas (B–H, J–P). Arrowheads (E, F, M, N) indicate axons projecting the lateral part of the OT. Arrowheads (G, O) indicate labeled axons reaching to the caudal end of the LOT. Asterisks (D, D’, E, E’, L, L’, M, M’) indicate the small domain in the anterolateral edge of the OT. D’, E’, L’, M’, Position of a cell cluster is encircled by the blue dotted line and marked with the asterisk. The curved dotted line on the left side of the cell cluster in E’, M’ depicts the lateral hook of the OT cell layer. At this TM injection stage, scattered cells in the PC express reporters (E, F, L–P). The brain illustration in the middle summarizes TM13.5 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 eight (A–F) and seven (G–L) mice. Scale bars = 100 μm (A’, A”, D’, E’, I’, I”, L’, M’) and 500 μm (A–P). CoA: cortical amygdala, GRL: granule cell layer, pD: pars dorsalis, pL: pars lateralis, TT: tenia tecta.