Fig. 7. Nkx6.1 is necessary for the development of 5-HT neurons in r1. (A,B) Whole-mount in situ hybridization of chick hindbrain 3 days after electroporation with morpholino-modified antisense oligonucleotides targeted against Nkx6.1 (6.1 MO), for (A) Gata2 and Gata3, or (B) Gata (purple) and Nkx2.2 (orange). Arrows indicate the loss of Gata expression of the electroporated side. The midbrain (MB) and mid-hindbrain boundary (MHB, arrow) are indicated (A). (C-E) Immunofluorescence on thin (10-12 µm) sections through the ventral neural tube in r1 of the hindbrain three days after electroporation with 6.1 MO (D, red), with antibodies against 5-HT (C,D, green; E, red) or Nkx2.2 (E, green). The location and absence of 5-HT neurons is indicated by arrows; the floor plate (fp) is marked.