DMPK and myotonic dystrophy type 1: Using an independent biochemical approach, RNA-IP with an anti-MBNL1 antibody clearly shows the pull down of mutant DMPK transcripts from extracts made from DM1 cells and from skeletal muscles of transgenic mice expressing the EGFP-DMPK 3′ UTR (CTG)>200 transgene (Fig. 2).