GAA deficiency in Pompe disease is alleviated by exon inclusion in iPS cell-derived skeletal muscle cells. Homo sapiens

While there are many human skeletal muscle disorders, very few therapies have been developed. It has not been possible to generate large amounts of purified skeletal muscle cells from pluripotent stem cells, and to test therapies quantitatively. We therefore devised conditions for generating and expanding purified human myogenic progenitors from induced pluripotent stem (iPS) cells. The progenitors retained the capacity to differentiate into multinucleated myotubes and showed a normal karyotype throughout the expansion phase. We applied this method to Pompe disease, a metabolic myopathy caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). In a screen, we identified sequences that suppressed aberrant GAA exon 2 splicing caused by the frequent c.-32-13T>G (IVS1) GAA variant. Antisense oligonucleotides (AONs) that blocked these sequences promoted exon 2 inclusion in patient-derived myotubes. As this raised GAA enzymatic activity above the disease threshold, AON-mediated splicing correction may provide a treatment option for Pompe disease. Overall design: RNA samples to be analyzed by microarrays were prepared using RNeasy columns with on-column DNA digestion (Qiagen). 300 ng of total RNA per sample was used as input into a linear amplification protocol (Ambion), which involved synthesis of T7-linked double-stranded cDNA and 12 hours of in vitro transcription incorporating biotin-labelled nucleotides. Purified and labeled cRNA was then hybridized for 18h onto HumanHT-12 v4 expression BeadChips (Illumina) following the manufacturer's instructions. After recommended washing, chips were stained with streptavidin-Cy3 (GE Healthcare) and scanned using the iScan reader (Illumina) and accompanying software. Samples were exclusively hybridized as biological replicates. The bead intensities were mapped to gene information using BeadStudio 3.2 (Illumina). Background correction was performed using the Affymetrix Robust Multi-array Analysis (RMA) background correction model. Variance stabilization was performed using the log2 scaling and gene expression normalization was calculated with the method implemented in the lumi package of R-Bioconductor. Data postprocessing and graphics was performed with in-house developed functions in Matlab. Hierarchical clustering of genes and samples was performed with one minus correlation metric and the unweighted average distance (UPGMA) (also known as group average) linkage method. 6 samples were analyzed: F134, Human fibroblast line F134, 1 replicate 237iPS, Human induced reprogrammed cells (iPSCs) from patient 1, 1 replicate 75iPS, Human induced reprogrammed cells (iPSCs) from patient 2, 1 replicate 1981iPS, Human induced reprogrammed cells (iPSCs) from patient 1, 1 replicate H1, Human Embryonic Stem Cell (ESC) H1, 1 replicate H9, Human Embryonic Stem Cell (ESC) H9, 1 replicate