Figure 7. Model for the role of the Hh signaling pathway in regulation of planarian glia.
Planarian glia are distributed throughout the nervous system and concentrated in the neuropil. if-1 and cali expression is normally repressed in these cells by high Ptc activity. A subset of these cells, however, is adjacent to Hh-secreting neurons in the medial cortex and express if-1 and cali because of inhibition of Ptc by Hh. Upon global inhibition of hh by RNAi, Ptc remains high in all cells and if-1 and cali are repressed in glia. Upon global inhibition of ptc by RNAi, expression of if-1 and cali is derepressed in glia.