MNSs Blood Groups and Major Glycophorins

Importance of extended blood group genotyping in multiply transfused patients

“…However, caution in performing this test and interpreting the results must be exercised as the PCR-based amplification assays are prone to be contaminated and the genotype determination may not be associated with the antigen expression on the RBCs membrane. Such situations include the detection of genes with a silencing mutation in a location other than that being analysed (point mutation in the GATA box), a gene that is silenced by an alteration of a gene encoding protein with a modifying effect (Rhmod and Rhnull) or the failure to detect hybrid genes (particularly in the Rh and MN blood group systems) (Avent & Reid, 2000;Cartron et al, 1998;Cheng-Han Huang & Blumenfeld, 1995;Huang, 1997;Tournamille, Colin, Cartron, & Le Van Kim, 1995).…”

MNS Blood Group System

“…So the ' pseudoexon ' is spliced out of GYPB mRNA, together with the regions homologous to the second and third introns of GYPA [52] . The exons are numbered according to the system used by Huang and Blumenfeld [18] in which pseudoexons are numbered so that homologous exons maintain the same number in all three genes. GYPA cDNA from this library was then isolated with mixed oligonucleotides representing the central region of GPA.…”

“…The GYPB pseudoexon may be translated in rare phenotypes where a functional acceptor splice site is transplanted into GYPB from GYPA by gene conversion [18] (see Section 3.11 ). Many anti -M and homologous to amino acid residues 27 -58 of GPA.…”

“…M g phenotype results from Thr4Asn (23) of GPA.N [253,256 -258] , the result of 68C > A in GYPA.N [50] , possibly arising from a GYPA.N allele with a small GYPB insertion and untemplated mutations [18] (see Section 3.9 ). This asparagine residue is not glycosylated and the amino acid substitution also prevents, or at least grossly reduces, glycosylation of Ser2 and Thr3, a total reduction of three O -glycans responsible for a degree of sialic acid defi ciency (Table 3.5 ).…”

“…M c was determined [256,270] . GYP * M c ( GYP * 08 ) represents GYPA.N with 59T > C, which could arise from a GYPA.M allele with a small GYPB insertion [18] (see Section 3.9 ). Residues 2, 3, and 4 have normal glycosylation.…”