Figure 4

Co-culture of prechordal and epichordal neural explants results in ZLI induction. (A) Explanted brain regions are schematically shown in a stage HH14 chick brain stained by in situ hybridisation for the expression of Lfng (anterior to the left, dorsal to the top): 1, telencephalon; 2, pro-Pth; 3, pro-ZLI; 4, pro-Th; 5, midbrain; 6, hindbrain. (B) Explants from brain regions as indicated in (A) were cultured in isolation (left two columns) or in combination (right column) for 24 hours and analysed for the expression of Shh by in situ hybridisation. Note induction of Shh at the interface of co-cultured pro-Pth + pro-Th, pro-Pth + midbrain and telencephalon + pro-Th tissue, but not after co-culture of pro-Th + pro-Th or telencephalon + hindbrain. The yellow broken line in panel '2 + 4' indicates the interface between pro-Pth and pro-Th tissue. (C) Explants from brain regions as indicated in (A) were cultured in isolation (left two columns) or in combination (right column) for 24 hours and analysed for the expression of Lfng, Dmbx1, Foxg1 (all in blue) and Shh (red) by in situ hybridisation. Note gap of Lfng expression in '2 + 4' explants (red arrow) and induction of Shh in '1 + 5' explants (red arrowheads).