Microarray technology is a powerful tool for measuring RNA expression for thousands of genes at once. Various studies have been published comparing competing platforms with mixed results: some find agreement, others do not. As the number of researchers starting to use microarrays and the number of cross-platform meta-analysis studies rapidly increases, appropriate platform assessments become more important. Here we present results from a comparison study that offers important improvements over those previously described in the literature. In particular, we noticed that none of the previously published papers consider differences between labs. For this study, a consortium of ten laboratories from the Washington, DC-Baltimore, USA, area was formed to compare data obtained from three widely used platforms using identical RNA samples. We used appropriate statistical analysis to demonstrate that there are relatively large differences in data obtained in labs using the same platform, but that the results from the best-performing labs agree rather well.

Objective Duchenne muscular dystrophy (DMD) is caused by the inability to produce dystrophin protein at the myofiber membrane. A method to rescue dystrophin production by antisense oligonucleotides, termed `exon-skipping', has been reported for the mdx mouse and in four DMD patients by local intramuscular injection. We sought to test efficacy and toxicity of intravenous oligonucleotide (morpholino) induced exon skipping in the DMD dog model. Methods We tested a series of antisense drugs singly and as cocktails, both in primary cell culture, and two in vivo delivery methods (intramuscular injection, and systemic intravenous injection). The efficiency and efficacy of multi-exon skipping (exons 6-9) was tested at the mRNA, protein, histological, and clinical levels. Results Weekly or biweekly systemic intravenous injections with a three morpholino cocktail over the course of 5–22 weeks induced therapeutic levels of dystrophin expression throughout the body, with an average of about 26% normal levels. This was accompanied by reduced inflammatory signals examined by MRI and histology, improved or stabilized timed running tests and clinical symptoms. Blood tests indicated no evidence of toxicity. Interpretation This is the first report of widespread rescue of dystrophin expression to therapeutic levels in the dog model of DMD. This study also provides a proof of concept for systemic multi-exon skipping therapy. Use of cocktails of morpholinos, as shown here, allows broader application of this approach to a greater proportion of DMD patients (90%), and also offers the prospect of selecting deletions that optimize the functionality of the dystrophin protein.