Figure 7. Selective removal of Atoh1 in RTN precursors produces a ventral to dorsal shift of periVII neurons.

(A) Combined Phox2b (red) and YFP (green) staining on a transverse section of an E12.5 P2b::CreBAC1;R26^YFP (Srinivas et al., 2001) hindbrain showing efficient recombination of the reporter allele in dB2 progenitors. In the dA3 domain, where Phox2b and Cre are switched on postmitotically, newly born cells are still YFP⁻ but express it during their ventral migration. (B and C) Combined Atoh1 ISH with a CDS probe of Atoh1 and Phox2b IHC on coronal hindbrain sections of P2b::CreBAC1;Atoh1^lox/+ (B) or P2b::CreBAC1;Atoh1^lox/lox embryos (C) at E15.5 or E12.5 as indicated. Cre recombinase expressed from the Phox2b promoter removes Atoh1 message in the RTN precursors but not in the rhombic lip (RL) or the cells of the anterior extramural stream (AES) of Atoh1^lox/lox embryos. Higher magnifications of the boxed areas are shown below. (D and E) Immunofluorescence for Lbx1 (red) and Phox2b (green) on coronal E15.5 hindbrain sections of the indicated genotypes (dorsal at top, lateral on the left). The double-labeled periVII cells are in yellow, the insets show close ups corresponding to the boxed areas. The Lbx1⁺/Phox2b⁺ cells accumulate dorso-laterally of nVII in P2b::CreBAC1;Atoh1^lox/lox mutants. (F) Quantification of the Lbx1⁺/Phox2b⁺ periVII cells at E15.5 located ventrally (Vent) or dorsally (Dors) of nVII. In P2b::CreBAC1;Atoh1^lox/+ controls, 25 ± 2.3% of the periVII neurons are located dorso-laterally of nVII vs 75 ± 2.6% in P2b::CreBac1;Atoh1^lox/lox mutants.

DOI: http://dx.doi.org/10.7554/eLife.07051.010