912
Thus , this study provides evidence that a novel , ubiquitous factor ( HF - 1a ) and a muscle factor ( HF - 1b / MEF - 2 ) can form a novel , E - box - independent pathway for muscle - specific expression in ventricular cardiac muscle cells .
 HF - 1a, HF - 1b, MEF - 2
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 HF - 1a, HF - 1b, MEF - 2