Fig. S1

The neurogenetic gradient. Markers of progressive glutamatergic neurogenesis are expressed in a wave from posterior to anterior in the developing thalamus. The neurogenetic marker deltaA (dla) starts in the ventro-posterior sector of the thalamus (marked by irx1b), and gradually fills the thalamus by 30 hpf (a, d, and g, arrows). This wave of expression is followed by that of the terminal neuronal marker vglut2.1, again on the background of the pan-thalamic marker irx1b (b, e, and h). Wnt8b is one of the earliest markers of the MDO and its broad expression at the 20-somite stage (c) is refined to a small band located at theMDOat 24 hpf (f) and 36 hpf (i). At 48 hpf (long-pec stage), her6 is expressed in the PTh, shh positive MDO, and the rTh. The expression domain of neurog1 marks the cTh and is not expressed in the rTh (k). Similar to her6 and complementary to neurog1, the expression domain of ascl1a in the PTh, in the rTh including a lateral part (l), which will give rise to the reticular nucleus) and a medial part [m, which will give rise to parts of the anterior thalamic nucleus; Mueller T, Guo S (2009) The distribution ofGAD67-mRNAin the adult zebrafish (teleost) forebrain reveals a prosomeric pattern and suggests previously unidentified homologies to tetrapods. J Comp Neurol 516:553–568] and in the pretectum at 48 hpf (l). Embryos are shown laterally (a–i), whereas embryos were sectioned horizontally and displayed dorsally in (j–l). White double-headed arrows marks the width of the caudal thalamus (a, b, d, e, g, and h) and the shrinking domain of the rostral thalamus marked by her6 in (c, f, and i). cTh, caudal thalamus; MDO, mid-diencephalic organizer; PTec, pretectum; PTh, prethalamus; rTh, rostral thalamus.