(A–C) Time course of Isl1 (A), FoxP1 (B), and Etv1 (C) expression in the developing hindbrain. Whole mount ISH, hindbrain ventral views. Asterisks indicate the r4 FMN germinal zone; white-filled arrows mark the final FMN settling position at E11.5 and E12.5; black-filled arrows indicate FoxP1-expressing I (B) and Etv1-expressing DL (C) subnuclei at E13.5 and E15.5; open arrowheads in (A) and (C) mark a subpopulation of Etv1-expressing FMNs occupying M positions within the E15.5 facial subnucleus.
(D–F) Immunofluorescence staining for FOXP1/ISLl (D), ETV1/ISL1 (E), and ETV1/FOXP1 (F) on coronal cryosections through r5/6 (E11.5 and E12.5) and r6 (E13.5 and E15.5). Dashed white lines outline the dorsal and ventral surfaces of the hindbrain; thick solid white lines in (D) and (E) outline DL and I facial motor subnuclei, respectively; thin gray lines in (F) outline the FMN migratory stream and nascent facial nucleus. Representative images, n = 3 embryos per time point.
(G–L) ETV1 (G and J) and FOXP1 (H and K) expression in control (G and H) and Cdk5−/−(J and K) FMNs at E16.5. Coronal planes of section indicated in (I) and (L), n = 1 Cdk5−/−, n = 1 wild-type littermate control.
Scale bars: 500 μm in (A)–(C) and 100 μm in (D)–(F), (G), (H), (J), and (K).
See also Figure S2.