The CAR1 Gene Encoding a Cellular Receptor Specific for Subgroup B and D Avian Leukosis Viruses Maps to the Chicken tvb Locus

Host susceptibility to subgroup B, D, and E avian leukosis viruses (ALV) is determined by specific alleles of the chicken tvb locus. Recently, a chicken gene that encodes a cellular receptor, designated CAR1, specific for subgroups B and D ALV was cloned, and it was proposed that this gene was the s3 allele of tvb (J. Brojatsch, J. Naughton, M. M. Rolls, K. Zingler, and J. A. T. Young, Cell 87:845–855, 1996). We now report that in a backcross derived from an F₁ (Jungle Fowl × White Leghorn [WL]) male mated with inbred WL females, the cloned ALV receptor gene cosegregated with two markers linked to tvb. The two markers used were a tvb^s1-specific antigen recognized by the chicken R2 alloantiserum and restriction fragment length polymorphisms associated with the expressed sequence tag com152e. With all three markers, no crossovers were observed among 52 backcross progeny tested and LOD linkage scores of 15.7 were obtained. These data demonstrate that CAR1 is the subgroup B and D ALV susceptibility gene located at tvb^s3.