Fv2 encodes a truncated form of the Stk receptor tyrosine kinase

The Friend virus susceptibility 2 ( Fv2 ) locus encodes a dominant host factor that confers susceptibility to Friend virus-induced erythroleukaemia in mice. We mapped Fv2 to a 1.0-Mb interval that also contained the gene ( Ron ) encoding the stem cell kinase receptor (Stk). A truncated form of Stk (Sf-stk), which was the most abundant form of Stk in Fv2 -sensitive ( Fv2 ss ) erythroid cells, was not expressed in Fv2 resistant ( Fv2 rr ) cells. Enforced expression of Sf-stk conferred susceptibility to Friend disease, whereas targeted disruption of Ron caused resistance. We conclude that the Fv2 locus encodes Ron , and that a naturally expressed, truncated form of Stk confers susceptibility to Friend virus-induced erythroleukaemia.