Figure 1. Shh signalling influences polarising region proliferation.

In normal development (blue line - HBC carrier control) the percentage of polarising region cells in G1-phase of the cell cycle slightly decreases over 6 hr between HH20 and HH21 and then increases throughout wing outgrowth (Note, Shh expression terminates at HH27/28 and data and statistics taken from Chinnaiya et al., 2014; Pickering and Towers, 2016. In all cases, between 10 and 14 polarising regions were dissected and data were obtained from 5 to 10,000 cells). The inhibition of Shh signalling using cyclopamine/HBC at HH20 (red line) increases the percentage of G1-phase cells over 24 hr until HH24, then there is a sharp decrease over the next 24 hr until HH27 when Shh expression normally terminates. Over the next 24 hr until HH29, G1-phase cell numbers recover in posterior mesenchyme after Shh expression has terminated (unpaired Pearson’s χ² test **- p =< 0.01, and ****- p =< 0.0001; see Chinnaiya et al., 2014; Pickering and Towers, 2016).