Anti-MYOT (aa 209-221) polyclonal antibody

Myotilin is a muscle-specific Z disk protein. Several missense mutations in the myotilin gene (MYOT) have been identified in limb girdle Muscular dystrophy (LGMD), myofibrillar myopathy, and distal myopathy patients. All previously reported pathogenic MYOT Mutations have been identified only in Exon 2. We sequenced MYOT in 138 patients diagnosed as having LGMD, myofibrillar myopathy, or distal myopathy, and identified a novel MYOT Mutation in Exon 9 encoding the second immunoglobulin-like domain in 1 patient with clinically typical LGMD. By light microscopy, there were scattered fibers with rimmed vacuoles and myofibrillary disorganization in the patient's muscle biopsy; accumulation of Z disk proteins was observed by immunohistochemistry. Immunoblot analysis demonstrated that the amount of myotilin monomer was increased in the patient Muscle, but that the myotilin homodimeric band was decreased. Functional analysis of the myotilin Mutation using a yeast 2-hybrid system revealed detective homodimerization of the Mutant myotilin and decreased interaction between mutant myotilin and alpha-actinin. The homodimerization defect was further demonstrated by immunoprecipitation. This is the first MYOT mutation outside of Exon 2 in all LGMD type 1A patient and the first MYOT mutation identified in the Japanese population. This mutation in the second immunoglobulin-like domain impairs myotilin dimerization and alters the binding between myotilin and alpha-actinin, which is known to be important for actin bundling.

Background: Protein aggregate myopathies (PAM) represent a group of familial or sporadic neuromuscular conditions with marked clinical and genetic heterogeneity that occur in children and adults. Familial PAM includes myofibrillar myopathies defined by the presence of desmin-positive protein aggregates and degenerative intermyofibrillar network changes. PAM is often caused by dysfunctional genes, such as DES, PLEC 1, CRYAB, FLNC, MYOT, ZASP, BAG3, FHL1, and DNAJB6. Objective: To retrospectively analyze genetic mutations and demographic, clinical, and morphological aspects of PAM in a French population. Methods: Forty-eight PAM patients (29 men, 19 women) were divided into two groups, those with genetically (GIM) and nongenetically identified (NGIM) mutations associated with myofibrillar myopathy. Results: Age of myopathy onset ranged from 13 to 68 years. GIM group mutations (81.25%) included DES (14), ZASP (8), FLNC (4), MYOT (4), BAG3 (1), CRYAB (2), and DNAJB6 (6). The MYOT subgroup displayed a significantly older onset age (p=0.029). Autosomal dominant inheritance was found in 74.3% of GIM and 44.4% of NGIM subjects. Overall, 22.9% had Maghrebian heritage, 72.9% Caucasian, and 4.2% Asian. The most common clinical sign was distal muscle weakness (66%) followed by simultaneous distal and proximal weakness in 49%. Eleven patients had contractures, one had a rigid spine, and five had respiratory dysfunction. GIM subjects had greater cardiac involvement (51.7%) versus the NGIM group (33.3%). The average serum creatine kinase level was 393U/L in GIM and 382U/L in NGIM subjects. Morphological analysis showed significant differences among GIM subgroups, including the number of vacuoles and regenerated fibers (ZASP), group atrophy (ZASP), and rubbed out fibers (MYOT). Ultrastructural findings showed significant differences in intranuclear rods, Z-disc thickness, and intranuclear inclusions between gene mutation subgroups. Paracrystalline inclusions were present in three patients (DNAJB6). The most frequent mutation in was in DES, followed by ZASP.Conclusions: GIM and NGIM PAM subjects showed similar results, suggesting that any unknown genes, which cause this disease have characteristics similar to those already described. Considering the complexity of clinical, morphological, and genetic data related to PAM, particularly myofibrillar myopathies, physicians should be careful when diagnosing patients with sporadic PAM.