THE 3 GENES OF THE HUMAN FCGR1 GENE FAMILY ENCODING FC-GAMMA-RI FLANKTHE CENTROMERE OF CHROMOSOME-1 AT 1P12 AND 1Q21

The high-affinity receptor for immunoglobulin G, Fc gamma RI (FCGR1), is encoded by a family of three genes within humans that share over 98 % of DNA sequence homology. Efforts to define the location of the FCGR 1 genes within chromosome 1 have been made to determine if they are ti ghtly linked to the five other FCGR genes present at 1q23. Our results , obtained through both fluorescence in situ hybridization analysis of human cells and Southern analysis of cell lines containing Ip and Iq, show instead that the three genes flank the centromere of chromosome 1 at bands 1p12 and 1q21. FCGR1B was found at 1p12, whereas both FCGR1 A and FCGR1C were localized to 1q21. This places the FCGR1 gene family within a large pericentric linkage group which is conserved between h umans and mice. We hypothesize that the three FCGR1 genes were separat ed by a pericentric inversion, known to have occurred on human chromos ome 1, which relocated FCGR1A and FCGR1C to the long arm and left FCGR 1B positioned on the short arm. We have also performed FCGR1 gene copy number experiments which indicate the existence of three FCGR1 genes within the human genome.