Additional file 4: Video S1. of Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes

Depolarization-induced contraction in mature human iPSC-derived skeletal myocytes. Membrane depolarization was triggered by 50 mM K+ in an extracellular medium devoid of Ca2+ ions. A typical Fura2 image sequence is first presented as 340/380 fluorescence ratio to reflect the increase in intracellular Ca2+ (from blue to red color) then as raw images captured using 380 nm excitation wavelength from which myocyte contractions can be more readily followed. To obtain a video file, Fura2 images (obtained in a property locked format, Aquacoscomos, Hamamatsu) were first converted into universal Tiff format using a screen capture software (Gadwin Systems Ltd). Tiff images sequence was then converted into a video file (.avi) with ImageJ software (NIH). (AVI 38635 kb

Additional file 2: Figure S2. of Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes

Alpha-actinin immunofluorescence and ultrastructure of human iPSC-derived skeletal myocytes on day 3 post-differentiation in culture. A Immunofluorescence labeling of α-actinin in one of the few elongated cells at this very early stage of differentiation. Note the punctuate labeling along the periphery of the cell. B 1–3 Electron micrographs shown at increasing magnification to disclose structural details of the early cytoskeleton remodeling. The area occupied by nascent myofilaments is relatively limited and mainly localized at the periphery of the cell. Note the presence of many undifferentiated cells surrounding this early myocyte. (TIFF 3844 kb

Additional file 1: Figure S1. of Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes

Bright field photomicrographs of human iPSC-derived skeletal myocytes differentiating in culture. A Proliferating myogenic progenitors. B–F Cells photographed at different times (from 3 to 22 days; d = days) following the switch to differentiation conditions, (scale:100 μm). Notice the rapid elongation of the cells within the first week post-differentiation and the high density of mature skeletal myocytes on day 22. (TIFF 3627 kb

Additional file 5: Video S2. of Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes

Spontaneous contractions of 10-day-old human iPSC-derived skeletal myocytes. Live cell imaging on day 10 post-differentiation using time-sequence microphotography (61 frames at 100 ms interval converted to mp4 video format). Images were acquired with ×20 lens objective on a phase contrast TE2000 Nikon inverted microscope. Cells were bathed in standard culture medium, and images were captured at room temperature (~ 21 °C). (MP4 1740 kb

Additional file 3: Figure S3. of Development of the excitation-contraction coupling machinery and its relation to myofibrillogenesis in human iPSC-derived skeletal myocytes

Developing myofibrils in a 5-day-old human iPSC-derived skeletal myocyte. Nascent sarcomeres found at the center of the cell appear relatively more organized than those located at the periphery. Electron microphotographs were taken at low (upper image) and high (lower image) magnification from two different skeletal myocytes, 5 days after the switch to differentiation conditions. (TIFF 7644 kb

Baseline clinical and physical characteristics and of enrolled patients.

<p>Baseline clinical and physical characteristics and of enrolled patients.</p

Pulmonary function in SMA type 2 and 3 patients.

<p>Pulmonary function in SMA type 2 and 3 patients.</p

Electrophysiologic assessment of SMA type 2 and 3 patients.

<p>Electrophysiologic assessment of SMA type 2 and 3 patients.</p

Motor function in SMA type 2 and 3 patients.

<p>Motor function in SMA type 2 and 3 patients.</p

Muscle MRI imaging of SMA type 2 and 3 patients.

<p>Muscle MRI imaging of SMA type 2 and 3 patients.</p