Trisomy Mapping of Olfactory Receptor and CD163 Genes to GGA16 Confirmed by FISH

Trisomy mapping using chickens naturally exhibiting two, three and four copies of GGA16 is a powerful means for assigning genes to GGA16.  MHC-Y, MHC-B and CD1 genes were all previously assigned to GGA16, a microchromosome, by trisomy mapping.  Here we used trisomy mapping combined with array comparative genomic hybridization to map two additional gene families to GGA16.  We have confirmed these assignments by FISH.  Now assigned to GGA16 are a cluster of olfactory receptor (OR) genes and CD163 genes, members of the scavenger receptor cysteine-rich (SRCR) gene superfamily.  The presence of OR genes on GGA16 is interesting in light of the hypothesis that OR genes mapping near the MHC have a role in maintenance of MHC polymorphism through odorant-based mate selection.  Not much is known about chicken CD163 gene function.  Perhaps like their counterparts in cattle, they will be found to have a role in the immune responses of γδ T cells.  Interestingly, the OR and CD163 genes map to the GGA16 p-arm away from the MHC-Y, MHC-B and CD1 genes located distally on the q-arm.