3982
The key role of erythropoietin ( Epo ) for colony formation by early erythroid progenitors ( burst-forming units-erythroid [ BFU-E ]) has been confirmed.
 ( protein: Epo, None) , ( cell type: early erythroid progenitors, None) , ( protein: erythropoietin, None) , ( cell type: burst-forming units-erythroid, None) , ( cell type: BFU-E, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: Epo, None) , ( cell type: early erythroid progenitors, None) , ( protein: erythropoietin, None) , ( cell type: burst-forming units-erythroid, None) , ( cell type: BFU-E, None) 