Figure 4From: Early onset muscle weakness and disruption of muscle proteins in mouse models of spinal muscular atrophyDelayed expression of adult RyR1 mRNA splice variant in muscles from mouse models of SMA. (A) RT-PCR on RNA from hindlimb muscle from wild type mice with primers directed against ASII (+) and ASII (-). GAPDH served as a loading control to confirm equivalence of starting cDNA levels . Note that relative ratio of ASII (+) to ASII (-) increases from P2 to P21. (B) RT-PCR results demonstrated no change in the expression of ASI (+) and ASI (-) variants in control and Smn-/-;SMN2 samples at P5 (upper panel). However, there was decreased expression of ASII (+) and sustained expression of ASII (-) in muscle samples from P5 Smn-/-;SMN2 compared with controls (middle panel). GAPDH served as a loading control. N = 5 for each genotype. (C) In control P21 mice, we observed increased expression of ASI (+) transcripts relative to ASI (-) transcripts. However in Smn2B/- mice, the relative ratio of ASI (+) to ASI (-) transcripts was decreased (upper panel). Furthermore, for the ASII variant, we observed the presence of a single transcript [ASII (+)] in P21 control samples, while in Smn2B/- samples, we observed a decrease in ASII (+) transcripts compared with controls. The ASII (-) variant was also now apparent (middle panel). GAPDH served as a loading control. N = 5 for each variant. (D) Quantification of RT-PCR data show significant changes in the ASII+/ASII - ratio in Smn-/-;SMN2 samples compared with controls. The relative levels of adult and neonatal RYR1 isoforms was significantly altered for both the ASI and ASII variants in Smn2B/- animals compared with controls. (E,F) The relative levels of adult and neonatal ASII RyR1 transcript variants are not altered in P14 mice one (E) and seven (F) days post-denervation compared with sham operated mice. N = 3.Back to article page