Population genetics of the vitamin D binding protein (GC) subtypes in the Asian-Pacific area: description of new alleles at the GC locus.

Isoelectric focussing (IEF) in thin layer polyacrylamide gels pH range 4-6.5 has been used to analyse the GC phenotypes of 4233 individuals from 28 different population groups in the Asian, Pacific, and Australian area. Because this technique reveals subtypes of the common GC1 allele, there is almost a two-fold increase in the mean heterozygosity at the GC locus using IEF compared with conventional electrophoresis. The highest frequency (above 50%) of the GC1S allele was encountered in Indian populations, reflecting genetic affinities with Europeans. By comparison, east and south east Asians are unique offing maximum values of the GC1F allele (50%). With the exception of a few Pacific populations which show similar frequencies to east Asians, all other groups in the Pacific area, including Australia, have values of GC1F similar to GC1S ranging from 27% to 40%. The GC2 frequency in most populations varies from 20% to 30%. However, some Polynesian groups have values up to 40% and Australian Aborigines less than 10%. Among other alleles, GC1A1 is found to be widely distributed among Australian Aborigines and Melanesians and occurs sporadically in Polynesians, Micronesians, and in the Lesser Sunda Islands. Four new alleles, GC1C24, GC1C35 Aborigine, GC1A21, and GC*1A22 are described. The gene frequency data at the GC locus has been used to calculate Nei genetic distances between the populations studied.