Population-based differences in frequency of the transcobalamin II Pro259Arg polymorphism

Objective: A common polymorphism of the transcobalamin II (TC-II) gene, Pro250Arg, has been implicated as a possible genetic factor in population-based differences in vitamin B12 metabolism. Our objective was to determine whether the prevalence of TC-II Pro259Arg polymorphism differs significantly between Caucasian, Asian and African-American groups. Methods: Genomic DNA was available on 187 Caucasians and 43 Asians from the Toronto area, and 51 African-Americans from Northeastern United States. A mutagenically separated PCR method was employed to genotype these groups for the TC-II Pro259Arg polymorphism (776C→G). Results: The frequency of the Arg 259 allele varied significantly among the three groups studied (0.439 in Caucasian, 0.558 in Asian and 0.363 in African; P = 0.022). The Asian group had a significantly higher frequency of the Arg 259 allele compared to the Caucasian (P = 0.030) and the African-American group (P = 0.006). The frequency of the Arg 259 allele in the Caucasian and African-American groups was not significantly different (P = 0.103). Conclusion: Population-based differences in TC-II Pro259Arg frequency are significant and could be a contributor to ethnic variation in susceptibility to vitamin B12 deficiency, a common and persistent problem.