{'fraction_non_alphanumeric': 0.020134228187919462, 'fraction_numerical': 0.008948545861297539, 'mean_word_length': 5.78030303030303, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Identification of secreted proteins during skeletal muscle development.

The differentiation program of skeletal muscle cells is exquisitely sensitive to secreted proteins. We developed a strategy to maximize the discovery of secreted proteins, using mass spectrometry-based proteomics, from cultured muscle cells, C2C12, grown in a serum-free medium. This strategy led to the identification of 80 nonredundant proteins, of which 27 were secretory proteins that were identified with a minimum of two tryptic peptides. A number of the identified secretory proteins are involved in extracellular matrix remodeling, cellular proliferation, migration, and signaling. A putative network of proteins involving matrix metalloproteinase 2, SPARC, and cystatin C that all interact with TGFbeta signaling has been postulated to contribute toward a functional role in the myogenic differentiation program.