Figure 2

Spatiotemporal expression of Lrrn1 in the early embryo. Lrrn1 expression seen in whole-mount in situ hybridization specimens of (a-f) chick and (g, h) mouse embryos. (a'-d') Transverse vibratome sections of similar specimens to those in (a-d), respectively (plane and position of section indicated by a horizontal black line). Embryonic stage is indicated in the bottom left corner of each panel. (a) In the early chick, strong expression is seen throughout the neural plate in the epiblast layer (E in (a')) but not in the hypoblast (H) or primative streak (PS). (b) Downregulation in the prechordal mesendoderm of the head process (PM). (c) Strong expression in the neural plate but marked downregulation in the ventral midline. (d) Downregulation becomes evident at the mid-hindbrain boundary (MHB). Note the presence of expression in the unsegmented presomitic mesoderm (PSM) and in the myotomal component of the somites (M in (d')). (e) Downregulation in the isthmocerebellar region (white bracket), diencephalon and optic stalk (black and white arrowheads, respectively). (f) Strong expression in the hindbrain (HB), midbrain (MB), pretectum (PT), telencephalon (Tel) and at the prethalamus at the anterior margin of the ZLI (black arrowhead). Note the absence of expression posterior to this in the ZLI and dorsal thalamus. (g) Strong expression of mouse Lrrn1 in the hindbrain (HB) and dorsal telencephalon (Tel) at e9.5. Weak expression is seen in the pretectum (black arrowhead). (h) This pattern remains unchanged at e10.5. (a', d') 4×; (b', c') 10×. Scale bars in (a', b') = 200 μm.