Changes in motor nuclei of cranial nerves in Nkx2.2^-/-; Nkx2.9^-/- double-deficient mouse mutants.

<p><i>In situ</i> hybridizations were performed with digoxigenin-labeled <i>peripherin</i> riboprobe on serial cross-sections of hindbrain from E15.5 wild type (A-D), single Nkx.2.2 (E-H) and Nkx2.9 (I-L), and double mutant (M-T) mouse embryos. Note the strong reduction of motor nuclei for the facial nerve (nVII) and the almost complete loss of nuclei for the vagal nerve (dmnX, filled arrowhead) as well as the nucleus ambiguus (dotted circle) in hindbrains of Nkx2.2^-/-; Nkx2.9^-/- double-deficient embryos. In contrast, the branchiovisceral motor nucleus of the trigeminal nerve (nV) was basically unaltered and the somatic motor nuclei of the hypoglossal (nXII) and abducens (nVI) nerves appeared augmented in double mutant mice with additional ectopic <i>peripherin</i>-expressing cells next to the motor nucleus of the abducens nerve (open arrowhead in P and T). Scale bars correspond to 100 μm.