Figure 7. Loss of Tc-foxQ2 function leads to arrest of development of brain midline structures in the embryo.

Axonal projections are marked by acTub (red) and cell bodies are visualized by DAPI (blue). (A, A’) In WT, the primary brain commissure forms at NS13 (white arrowhead in A). (B, B’) In RNAi embryos, the primary brain commissure is slightly irregular (white arrowhead in B). The anterior epidermal aberrations reflect the loss of the labrum (compare white arrows in A and B; Kitzmann et al., 2017). (C–C’’) In WT NS15 embryo, the central brain primordium increases in size and contains more fascicles, some of which form chiasmata at the midline (white arrowhead in C). (D–D’’) In strong phenotypes, the primary commissure remains detectable along with three main branches (arrows in D). However, the structures do not expand and commissure splitting does not occur. At the same time, the brain neuropil volume is strongly reduced (compare black space between the cell bodies in C’ and D’, open arrowheads (arrows in D). (E–E’’). Weak phenotypes show some degree of splitting of the brain commissure but axonal projections are disarranged (white arrowhead in E).