Immunoglobulin allotypes in Southwest Asia: populations at the crossroads

Southwest Asia has a long history of contact with Central Asian and with Sub-Saharan African populations. Is the genetic structure of these populations reflective of these historical facts? To study this, data was generated on the immunoglobulin heavy chain (GM) and light chain (KM) allotypes from seven Arab and three non-Arab populations in SW Asia to examine the relationship of these populations to SE European, NW Indian, Sub-Saharan African, and Central Asian populations. Like mtDNA and Y chromosome markers, the GM haplotypes are largely continent specific making them an excellent tool for the detection of gene flow whereas the KM markers are less informative. Six of the nine GM haplotypes detected in SW Asians are Indo-European, Sub-Saharan African, or East Asian specific. The allotype results indicate variable but significantly higher Sub-Saharan African gene flow in Arab populations (average 26.9%; 15.0-61.6%) vs. the non-Arab populations (average 7.3%; 9.0-13.4%), but higher levels of Central Asian gene flow in the non-Arab populations (average 28.8%; 10.5-48.8%) vs. the Arab populations (average 9.0%; 0.0-26.4%). Principal components analysis and hierarchical cluster analysis based on the immunoglobulin allotypes are consistent with the historical population contacts of this part of the world and reflect the power of the GM haplotypes in dissecting population relationships. However, the KM*1 frequencies were only correlated with the degree of African gene flow (Pearson r = 0.69, P = 0.026) in SW Asian populations.