Myotonic dystrophy type 1 (DM1) can be an RNA dominant disease in which mutant transcripts containing an expanded CUG repeat (CUGexp) cause muscle dysfunction by interfering with biogenesis of other mRNAs. mechanisms for dysregulation we performed global mRNA profiling in transgenic mice that express CUGexp RNA when compared with IgG2a/IgG2b antibody (FITC/PE) knockout and null mice. We found that the majority of Y-33075 changes induced by CUGexp RNA in skeletal muscle can be explained by reduced activity of Mbnl1 including many changes that are secondary to myotonia. The pathway most affected comprises genes involved Y-33075 in calcium signaling and homeostasis. Some effects of CUGexp RNA on gene expression are caused by abnormal alternative splicing or downregulation of Mbnl1-interacting mRNAs. However several of the most highly dysregulated genes showed altered transcription as indicated by parallel changes of the corresponding pre-mRNAs. These results support the idea that mRNA contains a highly expanded CUG repeat (CUGexp) and is retained in nuclear foci (2-4). Accumulation of this transcript in the nucleus leads to RNA dominant disease by interfering with the regulated expression of other genes (reviewed in 5). Expression of CUGexp RNA in transgenic mice or RNA containing an interrupted CUG repeat reproduces features of DM1 such as repetitive actions potentials (myotonia) and degenerative adjustments in skeletal muscle tissue (6 7 The mutant mRNA can be believed to influence gene manifestation through several specific Y-33075 mechanisms. The 1st indicator of mRNA on polyadenylation (8). Splicing regulators in the Muscleblind-like (MBNL) family members such as for example MBNL1 were proven to bind to CUGexp RNA with high affinity and be sequestered in nuclear foci (9-11). Decreased MBNL1 activity qualified prospects to abnormal rules of substitute splicing for a number of genes indicated in skeletal muscle tissue and center (10 12 MBNL protein could also regulate mRNA localization (13) nonetheless it can be unclear whether this activity can be affected in DM1. Furthermore to results on MBNL proteins DM1 can be connected with upregulation of two extra RNA binding proteins CUGBP1 and hnRNP H (14-16). These protein regulate substitute splicing balance and translation for a group of muscle-expressed transcripts some of which are also regulated by Mbnl1 (17-19). Moreover CUGexp hairpins are processed by Dicer resulting in short poly(CUG) RNAs that may induce posttranscriptional silencing of genes that contain CAG repeats (20). Finally CUGexp RNA may influence transcription by activating signaling proteins such as protein kinase C or the dsRNA-dependent protein kinase PKR or by leaching transcription factors from chromatin (15 21 22 A mRNA. This leads to a shift of the reading frame truncation of the Clcn1 protein loss of channel function repetitive action potentials and delay of muscle relaxation (myotonia) (23-26). A similar derangement exists in human DM1 (23 27 Myotonic discharges are known to influence gene expression in skeletal muscle (28-31) but the full spectrum of genes responding to muscle hyperactivity has not been determined. To identify genes and pathways impacted by CUGexp RNA we used oligonucleotide microarrays to examine gene expression in (null mice that have severe myotonia. To determine which changes in CUGexp-expressing mice may result from Mbnl1 sequestration results were compared with knockout mice (12). We also used RNA immunoprecipitation to identify Mbnl1-interacting mRNAs whose expression may be affected by Mbnl1 sequestration. Our results indicate that gene expression abnormalities in DM1 may result from effects on transcription processing and stability of RNA and point to pathways impacted by this disease. RESULTS Effects of CUGexp RNA on gene expression in skeletal muscle To determine global effects of CUGexp RNA on gene expression we used Affymetrix Mouse Genome 430 microarrays to compare two founder lines of = 6 per group). Of ～45 000 probe sets on the expression arrays ～23 000 showed detectable gene expression in muscle (see Materials and Methods). Among the muscle-expressed transcripts 269 were dysregulated either in transgenic line = 252) than in line = 75) and the Y-33075 fold-change was generally greater (< 0.001 for paired < 0.01 in line encoding a Ca2+ Y-33075 binding protein involved in membrane trafficking and encoding.