DMPK is a serine/threonine protein kinase primarily expressed in skeletal, cardiac, and smooth muscle that maintains muscle structure and function through multiple mechanisms. The protein regulates myosin phosphorylation by phosphorylating PPP1R12A to inhibit myosin phosphatase activity, and phosphorylates PLN to regulate sarcoplasmic reticulum calcium uptake and cardiac contractility 1. DMPK also modulates nuclear envelope integrity and muscle-specific gene expression during myocyte differentiation [UniProt annotation]. DMPK mutations cause myotonic dystrophy type 1 (DM1), the most prevalent adult-onset muscular dystrophy, through CTG trinucleotide repeat expansion in the DMPK 3' untranslated region 2. This expansion triggers a toxic RNA gain-of-function mechanism rather than simple protein loss, disrupting RNA splicing through MBNL1 protein sequestration and causing widespread cellular dysfunction 3. DM1 manifests as a multisystem disorder affecting skeletal and cardiac muscle, the central nervous system, and other organs, with phenotypic variability including myotonia, cataracts, cardiac arrhythmias, and testicular atrophy 1. Recent therapeutic advances targeting miR-23b and miR-218 to restore MBNL1 expression show promise in correcting DM1 cellular defects across varying repeat sizes 4, while optical genome mapping now enables accurate repeat expansion measurement for improved diagnosis 5.