Fig. 1

Identification of a loss of function mutation in zebrafish gnl2. (A–F) Expression of the proneural bHLH transcription factor ascl1a is subtly expanded in the bw41c mutant (B) diencephalon (arrow) and hindbrain (arrowhead) at 24 hpf. At 30 hpf, the ascl1a-expressing domain is expanded in the bw41c mutant hindbrain (arrowhead in D). At 42 hpf, ascl1a expression is expanded in the midbrain (arrow), dorsal diencephalon and hindbrain (arrowhead) of bw41c mutants (F). (G and H) At 36 hpf, neuronal clusters were expanded in the bw41c mutant brain as demonstrated by the terminally differentiated neuronal marker HuC/D. (I–L) bw41c mutant phenotype at 24 (J) and 48 hpf (L). The earliest clearly visible defects in bw41c mutants (J) are the reduced forebrain (arrow), smaller eyes, thinner mid/hindbrain boundary (dashed line and arrowhead) and hyperinflated hindbrain ventricle. At 48 hpf, bw41c mutants (L) are characterized by smaller eyes, thinner mid/hindbrain boundary (dashed line and arrowhead) and severe hyperinflation of the hindbrain ventricle. (M) Schematic drawing of the Gnl2 protein with the bw41c mutation indicated by the dashed red line. (N) Phylogenetic tree of the five members of the Gnl family, Lsg-1, Gnl1, Gnl2, Gnl3/NS and Gnl3l in Drosophila melanogaster (dm), Danio rerio (dr), Mus musculus (mm) and Homo sapiens (hs). Lsg1 and Gnl1 on one hand, and Gnl2, Gnl3/NS and Gnl3l on the other hand appear to have separate common ancestors. In Drosophila and other invertebrates, there are no separate orthologs of Gnl3/NS and Gnl3l, but one common ortholog that is more similar to NS than to Gnl3l. All images are lateral view, with anterior to the left and dorsal up. di, diencephalon; e, eye; h, hindbrain; hv, hindbrain ventricle; ot, optic tectum; tg, tegmentum; t, telencephalon. Scalebar 125 μm.