Three members of the human cystatin gene superfamily, AHSG, HRG, and KNG, map within one megabase of genomic DNA at 3q27.

While constructing a contig in the human chromosome region 3q27, we identified two YAC clones that were positive for the polymorphic marker D3S1602. One of these clones was also positive for a sequence-tagged site derived from the kininogen (KNG) gene. Because of the known evolutionary and structural relationship of KNG to other members of the cystatin gene superfamily, we tested the physical linkage of the genes encoding alpha-2HS-glycoprotein (AHSG), KNG, and histidine-rich glycoprotein (HRG), all of which were previously mapped to the long arm of chromosome 3. Our results show the colocalization of the three genes in two independent, partially overlapping YAC clones. The genomic inserts of the two clones were 1 Mb and 1.3 Mb in size, indicating that the three genes map within 1 Mb of DNA. The largest YAC was also positive for the polymorphic marker D3S1262, substantiating previously reported data of genetic linkage between this marker and HRG. Fluorescence in situ hybridization localized the two YAC clones to chromosome band 3q27.