Fig. 2. Transcriptional activity of MEF2D variants in C2C12 cells.
Luciferase activity normalised to galactosidase signal (Methods) is shown as a percentage of the wild-type (wt) control. Luciferase activity was measured in four biologically independent experiments, using three technical replicates in each with the same samples (n = 12 samples in 4 independent experiments). The points represent individual measured data, the rectangles in the box plots present the median and the 25 and 75 percentile values, while the error bars point to 1 and 99%. The luciferase signal is shown as mean ± SE, significance (* p < 0.05; ** p < 0.01; # p < 0.005; ## p < 0.001) was computed using two-sided student t-test. The different variants are grouped by their β-domain dynamics properties (Fig. 1c, Methods): var1 (gray diamond) and var2 (gray triangle) with similar β-domain dynamics; var3 (green diamond) and var4 (green triangle) with mobile β-domain; var5 (red diamond), var6 (red triangle), var7 (red circle) and var8 (red square) with rigid β-domain as compared to the wild-type. The β- variant is shown by blue diamond. a Transcriptional activity in non-differentiated C2C12 myoblasts. Variants with rigid β-domains show significantly higher transcriptional activity then the wild-type (var5 178 ± 9.6, var6 135.6 ± 9.3, var7 141.6±8.1 and var8 140.8±11.5 %), while variants with mobile β-domains show slightly increased transcription activity (var3 127.7 ± 4.9 and var4 123.9 ± 5.5 %) using n = 12 samples in 4 independent experiments. Significances (var3 p = 0.0001, var4 p = 0.0012, var5 p = 5.2*10−6, var6 p = 0.0027, var7 p = 0.0003, var8 p = 0.0044; β-minus p = 1.52*10−6) were computed using two-sided student t-test. b Transcriptional activity in differentiated C2C12 myotubes. var8 with rigid β-domain (red square) exhibits significantly higher transcriptional activity than the wild-type, while var3 (green diamond) and var4 (green triangle) with mobile β-domains, and var2 (gray triangle) with similar β-domain dynamics as the wild-type exhibit reduced transcriptional activity. (n = 12 samples in 4 independent experiments). Significances (var2 p = 2.9*10−9; var3 p = 0.008; var4 p = 1.02*10−7; var8 p = 0.0004) were computed using two-sided student t-test. c Lack of Mef2D blocks myotube formation in Mef2D knockout C2C12 cell line. Western blot images showing the lack of Mef2D, which are present endogenously in C2C12 cells. Three chosen stable KO cultures were followed through several passages to prove the stable lack of Mef2D (~70 kDa), while actin was used as inner control (~40 kDa). After 6 days of differentiation myotubes form in C2C12 cell line with endogeneous Mef2D (control, left panel), while cannot be observed in MEF2D KO cultures (right panel). Images were taken by transmitted microscopy, scale bars represent 400 µm. d Transcriptional activity in C2C12 KO cells. Rigid β-domain variants (red) have higher transcriptional activity than variants with similar dynamics to the wild-type (gray). Significances (var4 p = 0.0175, var5 p = 0.0096, var6 p = 0.0365; var7 p = 0.0022; var8 p = 0.0071) were computed using two-sided student t-test using n = 9 samples in 3 independent experiments).