Fig. 1.

Novel early-forming Math1 lineages in the medulla and caudal pons. (A) Time course (E10.5–16.5) of LacZ expression in the medulla of Math1^LacZ/+ mice (approximately level 5 in B′). An early migration (yellow arrows) from the cRL is seen several days before the PES (black arrowheads), giving rise to novel Math1 lineages (yellow arrowheads). (Inset) cRL and migrating cells (yellow arrow) at E10.5. (B) Brainstem schematic. Lines 1–6 indicate coronal hemisection levels shown in (B′) depicting nuclei that contain new (dark blue) and known (light blue) Math1 lineages. (C–F) Side views of whole-mount E18.5 Math1^Cre*PR/+;ROSA^LacZ/+ hindbrains induced on E9.5, E10.5, E12.5, or E13.5, showing LacZ-labeled cell somas (blue) of new (yellow arrowheads) and known (black arrowheads) lineages. (G) A Math1^Cre*PR/−;ROSA^LacZ/+ (Math1-null) hindbrain induced daily (E9.5 to E17.5) had staining mainly at the cRL (yellow arrowhead). (Some background fourth-ventricle staining was visible due to tissue clearing). (C′–G′) Ventral surfaces of C–G. (H and I) Coronal sections from E18.5 Math1^Cre*PR/+; ROSA^EYFP/+ (H) and Math1^Cre*PR/−; ROSA^EYFP/+ (I) null hindbrains induced at E10.5, showing loss of most staining from the medulla in the Math1-null. (H′ and I′) Magnified boxed regions in H and I, from slightly more rostral positions, show primarily labeled DC neurons in Math1^Cre*PR/+ and CP cells in Math1^Cre*PR/− (yellow arrowhead), adjacent to the cRL. Lateral to left in A and B′ and H–I′; rostral to left in B and C–G; rostral up in C′–G′. Abbreviations: cRL, caudal rhombic lip; CP, choroid plexus. See Table 1 for other abbreviations. (Scale bar: A, 290 μm; A Inset, 60 μm; C–G, 1,000 μm; C′–G′, 900 μm; H and I, 400 μm; H′ and I′, 100 μm.)