The multi-locus H-2Dw16 region has an organization distinct from the Dd region

Genomic DNA blot analyses using probes derived from the BALB/c 3' flanking region of the Ld gene (Ld 3' fl-C) and from near the BALB/c D3d gene (50.2A) indicate that the B10.GAA37 mouse strain has a multi-locus D (Dw16) region distinct from the five-gene organization observed in the Dd and Dq regions. To isolate the Dw16 region class I genes, a genomic B10. GAA37-lambda EMBL3 library was generated and screened with probes that preferentially hybridize to K and D region class I genes. Hybridization analyses of the isolated lambda clones with Ld derived oligonucleotide probes suggested that one of the lambda clones contained the Lw16 gene, whereas several other lambda clones contained the Dw16 gene. The sequence of the Dw16 gene is most similar to that of the Dp gene, particularly in the 3' half. Furthermore, the Lw16 gene is quite similar in the 5' half and virtually identical in the 3' half to the Ld gene, indicating that Lw16, but not Dw16, is a member of the Ld gene family. Collectively, these data suggest that, through a D region recombination event, the novel Dw16 region may have been assembled from primordial counterparts of the Dp and Ld genes.