Protein tyrosine kinases form a large family of signaling proteins implicated in 
both normal and malignant cell signaling. The aim of this study was to identify 
protein tyro-sine kinases that can transform hematopoietic cells to growth 
factor independent proliferation when constitutively activated by 
homodimerization. We used a modified retroviral insertion mutagenesis screen 
with a retroviral vector containing the homodimerization domain of ETV6 followed 
by an artificial splice donor site. Integration of this retroviral vector within 
a gene of the host genome would generate a fusion transcript containing the 
dimerization domain and part of the disrupted gene. Using this strategy with the 
IL3 dependent Ba/F3 cell line, we identified 8 different protein tyrosine 
kinases (Abl1, Fgfr1, Hck, Jak2, Lck, Mertk, Mst1r, Tnk1) that transformed the 
cells. These results characterize HCK, MERTK, MST1R and TNK1 as potential 
oncogenes and describe a method to identify gain-of-function fusion genes using 
a retroviral insertion screen.