7691
Despite this drastic effect in vivo, the in vitro immortalization of erythropoietin-dependent erythroid progenitors unexpectedly occurred at low frequency, and all four cell lines established expressed both erythrocytic (globins) and megakaryocytic markers ( glycoprotein IIb , platelet factor 4 ) as well as Spi-1 and Fli-1 transcripts at permissive temperature .
 ( cell line: cell lines, None) , ( protein: platelet factor 4, None) , ( protein: glycoprotein IIb, None) , ( protein: Spi-1, None) , ( cell type: erythropoietin-dependent erythroid progenitors, None) , ( protein: Fli-1 transcripts, 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:
 ( cell line: cell lines, None) , ( protein: platelet factor 4, None) , ( protein: glycoprotein IIb, None) , ( protein: Spi-1, None) , ( cell type: erythropoietin-dependent erythroid progenitors, None) , ( protein: Fli-1 transcripts, None) 