Fig. 3: lin-39 over-expression induces excess SM proliferation.

(A) Expression pattern of the endogenous zh120(lin-39::zf1::gfp) reporter in the SMs at different stages of larval development (see Supplementary Movie S1). DIC images overlaid with the LIN-39::ZF1::GFP (green), with the separate GFP channel below. Animals were between the 1-cell (early L3) and the 8-cell stage (L4.4) after completion of the SM divisions. For each stage, z-sections of the left and right body sides are shown. Black and yellow arrowheads indicate the SM nuclei. At least 15 animals were examined for each of the stages shown. (B) Schematic drawings of the transgenes used for SM expression (top). Images show the SMs in zhEx678[pbx-hlh-8p>lin-39::mCherry] and zhEx690[pbx-hlh-8p>nls::mCherry] control larvae at the L4 stage. Mid-sagittal DIC images overlaid with the NLS::mCherry or LIN-39::mCherry signals (magenta) are shown, with the separate and merged fluorescence signals below (SM > GFP, green). Panels show maximum intensity z-projections of the fluorescent signals in the left and right body halves, respectively. The 16 SM nuclei are indicated with black and white arrowheads and the extra SM > GFP, LIN-39::mCherry double-positive cells with yellow arrowheads. (B’) Quantification of SM numbers in L4 larvae. Bars show the average numbers of SMs, error bars the standard deviation and dots the individual values. Two independent lines each for pbx-hlh-8p>lin-39::mCherry (zhEx678.1 & 672.2) and pbx-hlh-8p>nls::mCherry (zhEx690.1 & 690.2) transgenes were scored. The numbers of animals scored are indicated in brackets. Statistical significance was determined with a two-tailed Mann-Whitney non-parametric test and is indicated with ** for p = 0,0017. Scale bars are 20 µm. Source data are provided as a Source Data file.