Shh signaling is reduced in MZjek. (A,B) shh is expressed in the notochord and floorplate (arrowhead) of wildtype (A, N=30) and MZjek at 24 hpf (B, N=40). Insets show transverse sections of shh in the spinal cord (A',B' N=28,39). (C–H) Class II genes patched1, nkx2.2a, and olig2 are reduced in MZjek. patched1 expression is reduced in MZjek (D, N=26) as compared to wildtype embryos (C, N=18). Most notably, patched1 expression is severely reduced in the ZLI (arrowheads C,D). Insets show close up of head region, highlighting expression in the ZLI (arrowheads C′,D′). nkx2.2a is absent in prethalamic (anterior arrowhead) and thalamic (posterior arrowhead) areas surrounding the ZLI in MZjek mutants (E,E',F,F' N=25,37). olig2 expression is reduced in the forebrain (G,H arrowhead; N=12,17) and ventral spinal cord (arrow in insets G'H') in MZjek embryos. Boxed region in G,H shown at higher magnification in G′,H′. (I–L) Class I genes pax3a and dbx1a show increased expression in MZjek. pax3a expression is expanded in the dorsal spinal cord (bars) in MZjek embryos (I,I',J,J' N=23,34). Boxed region in I,J shown at higher magnification in I',J'. dbx1a expression is also expanded in the thalamic areas posterior to the ZLI (arrowheads K,K′,L,'' N=8,10).