NRAP (nebulin related anchoring protein) functions as a structural protein essential for myofibril organization and force transmission in cardiac and skeletal muscle. The protein localizes to specialized membrane structures including intercalated discs in cardiac muscle and myotendon junctions in skeletal muscle, where it anchors terminal actin filaments and transmits tension from myofibrils to the extracellular matrix 1. NRAP is critical for proper cardiac development and function, as evidenced by its association with severe childhood cardiomyopathies when mutated 2 3. Mutations in NRAP have been identified in patients with dilated cardiomyopathy and mixed cardiomyopathy phenotypes, often presenting with early childhood onset and autosomal recessive inheritance patterns 2 3. The protein's dysregulation is implicated in atrial fibrillation pathogenesis, where reduced NRAP synthesis leads to intercalated disc disruption 4. Additionally, NRAP protein levels are increased in various cardiac diseases, though the functional consequences of this overexpression require further investigation 5. The gene maps to human chromosome 10 and shows evolutionary conservation across species 1. Note: One abstract describes a different nucleolar protein also named 'Nrap' which appears unrelated to the muscle-associated NRAP gene 6.