Fig. 4: Sun1 loss in Lmna^F/F:mcm/Sun1^–/– hearts inhibits changes in nuclear morphology and organization caused by Lmna loss.

A Heart extracts from Lmna^F/F:mcm/Sun1^+/+ and Lmna^F/F:mcm/Sun1^−/− confirmed the absence of Sun1 in the Sun1^−/− hearts (red). GAPDH was used as a loading control (green). A representative blot is shown for the number of animals (N) per genotype is indicated below the image. Markers are in kDa (B) Immunofluorescence imaging of CMs isolated from 2-month-old Lmna^F/F:mcm/Sun1^+/+ and Lmna^F/F:mcm/Sun1^−/− mice. Absence of Sun1 results in the redistribution of Nesprin1 to the poles of the nuclei indicated by the yellow arrows. Note that the two nuclei in each cardiomyocyte are positioned closer to each other and are elongated. Images are representative for N = 3 per genotype shown. Hoechst staining is shown in blue, sarcomeric α-actinin is magenta, (scale bar 10 μm). C Immunostaining of CM nuclei in sections through the left heart ventricle 25 days after Cre induction (Tmx). CM nuclei with redistributed or absent Lamin A/C expression are indicated by yellow arrowheads (Ci, Cii). CM nuclei still expressing Lamin A/C are indicated by red arrowheads (Cii, Ciii and iv). Intensity staining and quantification of Lamin A/C levels in nuclei of cardiomyocytes shows a reduction after Cre-induction (***P = 0.0008; ****P < 0.0001; unpaired two-tailed T-test, mean ± SD) (lower panel). Data are analysed of nuclei from Lmna^FF:mcm/Sun1^+/+ Tmx (n = 400), Lmna^FF:mcm/Sun1^+/+ CTL (n = 384), Lmna^FF:mcm/Sun1^−/− Tmx (n = 328) and Lmna^FF:mcm/Sun1^−/− CTL (n = 399). Scale bar 10 μm. D Lmna^F/F:mcm/Sun1^+/+ CM nuclear morphologies are distorted with indentations (red arrowheads) at the nuclear periphery and DAPI intense foci localizing to the tips of the nuclei (yellow arrowheads). In the absence of Sun1, Lmna^F/F:mcm/Sun^−/− CMs show no nuclear indentations or chromatin redistribution. 70% of CM nuclei in Lmna^F/F:mcm/Sun1^+/+ hearts had NE ruptures/distortions or were misshapen compared to less than 1% of CM nuclei in Lmna^F/F:mcm/Sun^−/− Cre-induced mice (lower panel). Data are analysed were of nuclei from 2 animals per genotype Lmna^FF:mcm/Sun1^+/+ Tmx (n = 206), Lmna^FF:mcm/Sun1^+/+ CTL (n = 152), Lmna^FF:mcm/Sun1^−/− Tmx (n = 131) and Lmna^FF:mcm/Sun1^−/− CTL (n = 150), Lmna^Wt/Wt/Sun1^−/− Tmx (n = 144) (No statistical analysis was performed). Source data are provided as a Source Data file.