Cell death in E13 SMA mouse skeletal muscle or spinal cord is not increased significantly.

<p><b>A</b>. Representative images of H&E-stained transverse sections of the whole body at E13 showing lumbar levels of spinal cord back from control (left) and SMA (right) littermates. Images are shown at the same scale. The areas delineated as ventral horn (VH) of spinal cord and erector spinae muscle group (ES) were analyzed. <b>B, C</b>. TUNEL (green) was performed on transverse whole body sections at E13. A separate channel (red) was used to identify anatomical landmarks and exclude autofluorescent signal (e.g. red blood cells). The total red signal was subtracted from the total green signal to show TUNEL-specific signal only. Representative images of lumbar (<b>B</b>) and cervical (<b>C</b>) spinal cord and back muscles are shown for the control (left) and SMA (right) mouse groups. Scale bar = 100 μm. <b>D</b>. TUNEL-positive structure counts in the VH of spinal cord at lumbar and cervical levels (individual counts and Mean ± SE; n = 3). <b>E</b>. TUNEL-positive structure counts in ES muscle at lumbar and cervical levels (individual counts and Mean ± SE; n = 3). There were no statistically significant differences between SMA and control groups (two-tailed t-test). <b>F</b>. Representative high-magnification images identifying TUNEL-positive structures (green) in E13 control and SMA mouse skeletal muscle as apoptotic nuclei. Hoechst (blue) was used to stain cell nuclei. Scale bar = 10 μm.