Anti-MYOD1 monoclonal antibody, clone 6.9B

Rhabdomyosarcoma (RMS) is a primitive embryonal mesenchymal neoplasm demonstrating skeletal muscle differentiation. Diagnosis of RMS remains difficult due to the diversity of clinical features, pathological forms, and lesion's locations. Immunohistochemistry and Fluorescence in Situ Hybridization are common methods used to aid RMS diagnosis. In this research we tested protein expression of Desmin (Clone MX046), MyoD1 (Clone MX049), MyoD1 (Clone 5.8A), MyoD1 (Clone EP212), Myogenin (Clone F5D), and cytogenetic features in 21 RMS cases, with following results: positive rates of Desmin (Clone MX046), MyoD1 (Clone MX049), MyoD1 (Clone 5.8A), MyoD1 (Clone EP212) and Myogenin (Clone F5D) were 100.00%, 100.00%, 90.48%, 95.24% and 85.71%, respectively, with cytoplasmic stains of MyoD1 (Clone 5.8A) in 38.10% (8/21) cases and only nuclear stains of MyoD1 (Clone EP212), MyoD1 (Clone MX049) in all positive cases. FOX01 gene was detected apart in 9 alveolar RMS samples, where MyoD1 (Clone MX049), MyoD1 (Clone 5.8A) and MyoD1 (Clone EP212) were 100% positive but MyoD1 (Clone 5.8A) only 44.44% (4/9). Thus we believe MyoD1 (Clone MX049) performs more sensitive and specific than MyoD1 (Clone 5.8A) and MyoD1 (Clone EP212).

Pluripotent stem cells (PSC) hold great promise for the treatment of human skeletal muscle diseases. However, it remains challenging to convert PSC to skeletal muscle cells, and the mechanisms by which the master regulatory transcription factor, Pax7, promotes muscle stem (satellite) cell identity are not yet understood. We have taken advantage of PSC-derived skeletal muscle precursor cells (iPax7), wherein the induced expression of Pax7 robustly initiates the muscle program and enables the in vitro generation of precursors that seed the satellite cell compartment upon transplantation. Remarkably, we found that chromatin accessibility in myogenic precursors pre-figures subsequent activation of myogenic differentiation genes. We also found that Pax7 binding is generally restricted to euchromatic regions and excluded from H3K27 tri-methylated regions in muscle cells, suggesting that recruitment of this factor is circumscribed by chromatin state. Further, we show that Pax7 binding induces dramatic, localized remodeling of chromatin characterized by the acquisition of histone marks associated with enhancer activity and induction of chromatin accessibility in both muscle precursors and lineage-committed myoblasts. Conversely, removal of Pax7 leads to rapid reversal of these features on a subset of enhancers. Interestingly, another cluster of Pax7 binding sites is associated with a durably accessible and remodeled chromatin state after removal of Pax7, and persistent enhancer accessibility is associated with subsequent, proximal binding by the muscle regulatory factors, MyoD1 and myogenin. Our studies provide new insights into the epigenetic landscape of skeletal muscle stem cells and precursors and the role of Pax7 in satellite cell specification.