Fifteen loci and 12 genes, encoding proteins of different cellular compartments, have been identified to be involved in autosomal-dominant FDCM with pure DCM. 8-Sarcoglycan, encoded by SGCD, is one of the four (a, p, 8, and g) proteins forming the sarcoglycan complex—a component of the glycoprotein transmembrane complex (DCG) in the plasma membrane. DES and VCL encode cytoskeletal proteins, desmin, an intermediate filament, and metavinculin, respectively. PLN encodes phospholamban in the sarcoplasmic reticulum, a major substrate for cAMP-dependent protein kinase in cardiac muscles. It is an inhibitor of cardiac muscle sarcoplasmic reticulum Ca2+-ATPase. Mutations have been identified in sarcomeric proteins: actin encoded by ACTC, cardiac troponin T encoded by TNNT2, cardiac myosin-binding protein C encoded by MYBPC3, p-myosin heavy chain encoded by MYH7, a-tropomyosin encoded by TPM1, and titin encoded by TTN. Telethonin/TCap is encoded by TCAP and is a substrate of titin. TCap interacts and colocalizes with the muscle limb protein (MLP), which is a Z-disc protein encoded by CSPR3. Recently, MLP mutations have been identified in DCM families.
Four disease loci have been related to autosomal-dominant FDCM with a conduction defect. The only gene identified is LMNA encoding lamins A and C, components of the nuclear envelope, produced by alternative splicing. LMNA mutations have been found in FDCM associated with atrial fibrillation and in FDCM with LV apical aneurysm. For autosomal-dominant FDCM with skeletal myopathy and conduction defect, the only identified disease gene is again LMNA. Mutations are associated with autosomal-dominant Emery-Dreifuss muscular dystrophy (AD-EDMD) and limb girdle muscular dystrophy type 1B (LGMD1B), and were recently described in a myopathy specifically affecting the quadriceps muscle.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.