The U antigen (MNS5) is one of 49 antigens belonging to the MNS blood group system (ISBT002) carried on glycophorins A (GPA) and B (GPB). U is present on the red blood cells in almost all Europeans and Asians but absent in approximately 1.0% of Black Africans. U negativity coincides with negativity for S (MNS3) and s (MNS4) on GPB, thus be called S-s-U-, and is thought to arise from homozygous deletion of GYPB. Little is known about the molecular background of these deletions. Bioinformatic analysis of the 1000 Genomes Project data revealed several candidate regions with apparent deletions in GYPB. Highly specific Gap-PCRs, only resulting in positive amplification from DNAs with deletions present, allowed for the exact genetic localization of 3 different breakpoints; 110.24-and 103.26-kb deletions were proven to be the most frequent in Black Americans and Africans. Among 157 CEPH DNAs, deletions in 6 out of 8 African ethnicities were present. Allele frequencies of the deletions within African ethnicities varied greatly and reached a cumulative 23.3% among the Mbuti Pygmy people from the Congo. Similar observations were made for U+ var alleles, known to cause strongly reduced GPB expression. The 110-and 103-kb deletional GYPB haplotypes were found to represent the most prevalent hereditary factors causative of the MNS blood group phenotype S-s-U-. Respective GYPB deletions are now accessible by molecular detection of homo-and hemizygous transmission.
Background and Aims: Only little is known about blood groups other than ABO blood groups and Rhesus factors in Arabian countries and Iran. During the last years, increased migration to Central Europe has put a focus on the question how to guarantee blood supply for patients from these countries, particularly because hemoglobinopathies with the need of regular blood support are more frequent in patients from that region. Therefore, blood group allele frequencies should be determined in individuals from Arabian countries and Iran by molecular typing and compared to a German rare donor panel. Methods: 1,111 samples including 800 individuals from Syria, 147 from Iran, 123 from the Arabian Peninsula, and 41 from Northern African countries were included in a MALDI-TOF MS assay to detect polymorphisms coding for Kk, Fy(a/b), Fy null , C w , Jk(a/b), Jo(a+/a-), Lu(a/b), Lu(8/14), Ss, Do(a/b), Co(a/b), In(a/b), Js(a/b), Kp(a/b), and variant alleles RHCE*c.697C>G and RHCE*c.733C>G. Yt(a/b), S-s-U-, Vel null , Co null , and RHCE*c.667G>T were tested by PCR-SSP. Results: Of the Arabian donors, 2% were homozy-gous for the FY*02.01N allele (Fy null), and 15.7% carried the heterozygous mutation. However, 0.8% of the German donors also carried 1 copy of the allele. 3.6% of all and 29.3% of Northern African donors were heterozygous for the RHCE*c.733C>G substitution, 0.4% of the Syrian probands were heterozygous for DO*01/DO*01.-05, a genotype that was lacking in German donors. Whereas the KEL*02.06 allele coding for the Js(a) phenotype was missing in Germans; 0.8% of the Syrian donors carried 1 copy of this allele. 1.8% of the Syrian but only 0.3% of the German donors were negative for YT*01. One donor from Northern Africa homozygously carried the GYPB*270+5g>t mutation, inducing the S-s-U+ w phenotype, and in 2 German donors a GYPB*c.161G>A exchange, which induces the Mit+ phenotype, caused a GYPB*03 allele dropout in the MALDI assay. The overall failure rate of the Arabian panel was 0.4%. Conclusions: Some blood group alleles that are largely lacking in Europeans but had been described in African individuals are present in Arabian populations at a somewhat lower frequency. In single cases, it could be challenging to provide immunized Arabian patients with compatible blood.
This study provides first evidence that aberrant trafficking of variant ABO transferases may be involved in the formation of weak ABO phenotypes.
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