Figure 6. NK1R-Expressing Neurons of the Parafacial Respiratory Group/Retrotrapezoid, Paratrigeminal, and Parabrachial Nuclei Require Math1.

(A) Sagittal model of the hindbrain showing the PB, motor nuclei V, VII, and X (all gray), and the ventral respiratory nuclei (black).

(B) Sagittal model of ventral medullary nuclei magnified from rectangle in (A).

(C–D) Magnified regions from E18.5 WT and Math1-null hindbrains corresponding to the upper and middle dashed boxes in (A), and showing loss of NK1R (red) in the (C) parabrachial nucleus and (D) ventral paratrigeminal region in the Math1-null hindbrain (V is labeled by Vacht, green).

(E–J) Magnified regions from E18.5 (E–I) WT and (F–J) Math1-null hindbrains corresponding to the model in (B) and labeled with (E,F) Vacht (blue) and NK1R (red), (G,H) Sst (green), Phox2b (red), and Lbx1 (blue), and (I,J) Vglut2 (white). Horizontal brackets indicate approximate rostral-caudal extent of nuclei such as the RTN (yellow arrows) and preBötC (yellow dotted ovals). NK1R and Phox2b were lost from the RTN in the Math1-null while NK1R and Sst were retained in the preBötC (compare (E) to (F) and (G) to (H)). Vglut2 was decreased in the Math1-null (compare (I) to (J)).

(K–N) Coronal sections through the facial nucleus of E16.5 Math1^LacZ/+ and Math1^LacZ/LacZ null hindbrains at approximate levels 1 and 2 indicated in (B), showing expression of Phox2b (red), Lbx1 (blue), and βgal (LacZ protein, green). Ventral gal cells (yellow arrowheads) were more laterally restricted in the Math1-null hindbrain (compare (K) to (M)) and almost absent from the caudal pFRG/RTN (compare (L) to (N)).

(O,P) Magnifications from the yellow boxed regions in (L) and (N) show co-expression of gal with Phox2b and Lbx1 in both the (O) Math1^LacZ/+ and (P) Math1^LacZ/LacZ null hindbrains.

(Q,R) Magnifications from adjacent sections to (O,P) showing loss of NK1R (red) co-expression in the misplaced pFRG/RTN neurons of the Math1-null hindbrain (compare Q to R).

Rostral is to the left in (A–J) and lateral is to the left in (K–R). Note that unlike GFP, gal forms aggregates, which appear as green puncta in (K–R).

Abbreviations: ambiguus (X), Bötzinger complex (BötC), facial motor (VII), lateral reticular (LRt), parafacial respiratory group/retrotrapezoid (pFRG/RTN), pre-Bötzinger complex (preBötC), rostral ventral respiratory group (rVRG), and the trigeminal motor (V) nuclei. Scale bar, 130 μm (C), 330 μm (D), 180 μm (E–J), 45 μm (K–N), 8 μm (O–R).