ERK pathway inhibition by U0126 induces a significant increase in SMN expression in the motor neurons of severe SMA-like mice and in myogenic cells of severe-type SMA patients. A, B, Western blot analysis and quantification of SMN protein expression in the ventral lumbar spinal cord of vehicle- and U0126-treated control mice at 2 and 6 d of age, vehicle-treated SMA-like mice at 2 d of age, and U0126-treated SMA-like mice at 2 and 6 d of age (n = 3). C, D, Western blot analysis and quantification of SMN protein expression in brain, heart, kidneys, lungs, liver, diaphragm, and tibialis of U0126-treated SMA-like mice at 2 d of age (n = 3). E–I, Immunodetection of gems in ChAT-positive motor neurons in the lumbar spinal cord (L1–L5) of vehicle-treated (E) and U0126-treated control (F) mice at 6 d of age, vehicle-treated SMA-like mice at 2 d of age (G), and U0126-treated SMA-like mice at 6 d of age (H). Scale bar, 25 μm. Quantitative analysis of gems per motor neuron (I). J, K, Western blot analysis and quantification of SMN protein expression in vehicle- and U0126-treated human SMA cultured myotubes from two type 2 SMA patients (n = 3 each patient). L, M, Western blot analysis and quantification of SMN protein expression in vehicle- and U0126-treated human SMA cultured myotubes and myoblasts from a type 2 SMA patient (n = 3). N, O, Quantification by real-time RT-PCR of exon 7–exon 8 (E7-E8) segment containing SMN transcripts normalized either by exon 4–exon 5 (E4-E5) segment containing SMN transcripts (N) or by 18S transcripts (O) in the ventral lumbar spinal cord of vehicle- and U0126-treated control and SMA-like mice at 2 d of age (n = 9). Data are displayed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.