Figure 8.

Smed-runt-like1 is induced during regeneration and controls patterning of photoreceptor neurons in the eye. (a) qRT-PCR analysis of smed-runt-like1 expression in regenerating planarians at different time points of regeneration. Expression levels are normalized to intact levels. Error bars represent standard deviations of the mean of three biological replicates. (b, c) In situ hybridization analysis of smed-runt-like1 mRNA in intact animals (b) and (left to right) regenerating head, trunk, and tail fragments at 5 days after dissection (c). Note that smed-runt-like1 is not detected in intact animals, but it is induced in cells in proximity to the regenerating brain. Arrows point to regions of smed-runt-like1 expression. Anterior is left. Scale bar is approximately 2 mm. (d-j) Effect of smed-runt-like1 RNAi on the regenerating visual system. (d) Schematic drawing of the planarian visual system. Bipolar photoreceptor cells cluster to form a rhabdomeric structure on one end, and axonal projections, which reach out to the brain in a contra- or ipsilateral manner, on the other end. (e-i) Immunofluorescence analysis of photoreceptor neurons, 14 days after decapitation, in control (e, f) and smed-runt-like1 RNAi (g-i) animals stained with an anti-Arrestin antibody (kindly provided by H Orii). The regions depicted are indicated in (d). Note that RNAi animals show a variety of patterning defects, such as mispositioning of photoreceptor cells (g), abnormal rhabdomere morphology (h), and axon guidance defects (i). Arrowheads point to mispositioned cells, white arrow to a malformed rhabdomere, yellow arrow to a misrouted axon. c, optic chiasm; cb, cell bodies; r, rhabdomere. Scale bars = 10 mm in (e, g, h), 50 mm in (e, i). (j) Summary of smed-runt-like1 RNAi phenotypes. The number of animals scored is indicated in parentheses.