Figure 6.

SCN is derived from a distinct progenitor domain. Representative images of Six3 and Lhx1 (A), Rx, Six6, and Dlx2 (B), and Fzd5 and SHH (C) mRNA expression (columns) in SCN progenitor domain from E10.5 to E13.5 (rows). Leftmost column shows entire coronal section, with dotted box indicating approximate region of enlarged images in corresponding row to the right. Dotted black lines in enlarged Six3 images indicate hypothesized early SCN margins outlined by Six3 expression from E11.5 to E13.5. Note at E10.5 that the region that will give rise to SCN neurons expresses a combination of Six3, Rx, and Fzd5. By E11.5, Rx expression is lost and Six6 expression begins. Also note the E11.5 onset of Lhx1 (black arrow) and Dlx2 on the most ventral aspects of tissue beneath the third ventricle. Scale bar, 500 μm. D, Rostrocaudal location of SCN progenitor domain. ISH images depict patterns of Six3, Lhx1, Six6, Dlx2, and Fzd5 mRNA expression (rows) in transverse plane from rostral eye fields to caudal developing pituitary at E11.5 and E13.5. Open bars above indicate the developing SCN within the rostrocaudal axis. Note that, although expression of Six3 and Six6 is consistent along the ventral surface from rostral eye fields to the early pituitary, Lhx1 and Dlx2 mark discrete zones within this region at both E11.5 and E13.5. Please note in D that E11.5 depicts same transverse images as shown in A–C, and E13.5 shows the same Six6 and Fzd5 images shown in A–C now within the rostrocaudal context of the developing brain. Scale bar, 500 μm.