Fig. 1. Nkx6.1 expression in the developing mouse hindbrain. In situ hybridization with a Nkx6.1 probe on flat-mounted hindbrains at different embryonic stages (A,B,E,F) and on coronal hindbrain sections at E12.5 (G-L). Rhombomeric positions are indicated (r2 to r6). At E8.5 (A), Nkx6.1 is expressed in ventral progenitor cells. At E10.5 (B), Nkx6.1 expression spans the entire length of the ventral hindbrain. At E10.5, immunofluorescence detection of Nkx6.1 (red in C,D) with Nkx2.2 (green in C) or Isl1 (green in D) shows co-expression of Nkx6.1 with both Nkx2.2 and Isl1 (yellow appearing cells in C,D). At E11.5 (E), Nkx6.1 expression is detected in the trigeminal (nV), and in migrating facial branchio-motor (fbm) neurons (nVII) from r4 to r6, as well as in a lateral column representing the motor nuclei of the inner ear efferents (IEE), the superior (nSS) and inferior (nIS) salivatory nucleus and nucleus ambiguous (nA). At E12.5 (F), Nkx6.1 marks the entire stream of migrating fbm neurons from r4 into the dorsal half of r6, and is also detected in the oculomotor (nIII) (G), trochlear (nIV) (H), trigeminal (nV) (I), abducens (nVI) (J), facial nuclei (nVII) (K,J), the nucleus ambiguous (nA) (L), the dorsal motor nucleus of the vagal nerve (dmnX) (L) and the hypoglossal nucleus (nXII) (L). Nkx6.1 is also detected in the raphe nuclei (nRP) (K,L).