Molecular analysis of FY and RH alleles in the population of Rosario, Argentina

COTORRUELO C; FIORI S; DI MÓNACO R

El Cairo

Congreso; XIXth Regional Congress of the International Society of Blood Transfusion, Eastern Mediterranean and Europe; 2009

Background: advances in molecular genetics have contributed to establishing the structure of the genes from most of the 29 blood group systems presently known, making possible the development of high-throughput platforms for molecular blood group typing. To make DNA typing reliable, the analysis of the polymorphism and allele distribution of genes under study is needed since genetic variability is observed among different ethnic groups. Urban populations of Argentina are assumed to have a white Caucasian European genetic component. However, historical and biological data account for the influence of other ethnic groups. Aim: the purpose of this study was to analyse, in the population of Rosario, the third largest city of Argentina, the presence of FY*BES and RH*es alleles, attributed to Africans. Methods: blood samples from 275 self-identified white blood donors were studied. FY genotyping was performed by PCR strategies using primers designed with the allele-differentiating base at the 3? position. Two PCRs, each containing a forward primer (nucleotide -33T at the 3? end) to target the normal FY alleles? promoter region paired with reverse primers specific to anneal FY*A and FY*B (C125 and T125 at the 3? end) alleles respectively were set up. The FY*BES allele was detected with a forward primer that anneal the mutated promoter region (-33C at the 3? end) paired with the FY*B specific primer. RH*es genotyping was carried out detecting the 733C>G mutation in the RHCE gene. Two separate PCRs were performed using a forward primer specific for intron 4 of the RHCE gene and reverse primers complementary to RH exon 5 containing at their 3? ends the polymorphic nucleotides 733G (to anneal in RHCE exon 5) or 733C (to anneal in RHD exon 5) in each reaction. Results: PCRs studies revealed the presence of FY*BES in 21 samples of the 275 individuals studied (allele frequency: 0.0382). Twelve individuals of the 275 donors carried the RH*es allele (allele frequency: 0.0218). We found 4 individuals with both FY*BES and RH*es alleles. The number of individuals with a concomitant occurrence of both alleles was significantly higher than that expected by chance (p: 0.0001, hypothesis test concerning the rate parameter of a Poisson distribution). We found that 4.68% of the present gene pool is composed by alleles primarily associated with African ancestry and about 12% of the individuals carried at least one RH or FY allele that is predominantly observed among African populations. Fourteen percent of Fy(b-) subjects were FY*A/FY*BES. Conclusions: these findings reflect the contribution of African alleles to the genetic pool of the population under study and will help to estimate its genetic admixture. The identification of Fy(b-) patients carrying the FY*A/FY*BES genotype makes possible to transfuse them with Fy(b+) blood units with no risk of alloimmunization since they express normal levels of the FY*B product in other body tissues. FY genotyping allow increasing the pool of compatible units, mainly benefiting those patients that require chronic transfusions. The detection of the RH*es allele suggest the VS antigen has a frequency of 4.36% in the population analysed. Since this antigen is immunogenic and is not on commercially available panels red blood cells, we propose to test sera suspected to have alloantibodies with VS+ erythrocytes so that anti-VS may not go undetected.