Materials and methods

The chromosome location of Cd39 was determined by interspecific backcross analysis using progeny derived from matings of (C57BL/6J x Mus spretus) F^ sub 1^ females and C57BL/6J male mice as described (Copeland and Jenkins, 1991). A total of 205 N^ sub 2^ mice were used to map the Cd39 locus. This interspecific backcross mapping panel has been typed for over 2500 loci that are well distributed among all the autosomes, as well as the X-chromosome (Copeland and Jenkins, 1991). C57BL/6J and M. spretus DNAs were digested with several endonucleases and analyzed by Southern blot hybridization for informative restriction fragment length polymorphisms (RFLPs) using a^ sup 32^ P-labeled probe nick-translated from a 2.3-kb EcoRI fragment of mouse Cd39 cDNA. Major fragments of 21.0, 5.6, 4.5 and 4.2 kb were detected in nnI digested C57BL/6 DNA, and major fragments of 14.0 and 9.8 kb were detected in KpnI digested M. spretus DNA. The 14.0-and 9.8-kb KpnI RFLPs from M. spretus were used to follow the segregation of the Cd39 locus in backcross mice. A description of the probes and RFLPs for the loci linked to Cd39 has been reported previously (Copeland et al., 1993). Recombination distances were calculated using Map Manager, version 2.6. 5.