MOLECULAR-GENETICS OF THE GLYCOPHORIN GENE FAMILY, THE ANTIGENS FOR MNSS BLOOD-GROUPS - MULTIPLE GENE REARRANGEMENTS AND MODULATIONS OF SPLICE-SITE USAGE RESULT IN EXTENSIVE DIVERSIFICATION
Oo. Blumenfeld et Ch. Huang, MOLECULAR-GENETICS OF THE GLYCOPHORIN GENE FAMILY, THE ANTIGENS FOR MNSS BLOOD-GROUPS - MULTIPLE GENE REARRANGEMENTS AND MODULATIONS OF SPLICE-SITE USAGE RESULT IN EXTENSIVE DIVERSIFICATION, Human mutation, 6(3), 1995, pp. 199-209
The purpose of the review is to describe a system of human erythrocyte
membrane glycoproteins exhibiting extensive diversity, Glycophorins A
and B (GPA and GPB) are the antigens of the MNSs blood groups; thus i
ndividuals bearing variant glycophorins can be readily identified by s
erological typing. Examination of the wide array of variants of these
antigens showed that they include many forms, possibly made evident by
lack of constraints due to the apparent dispensability of the parent
molecules. This article reviews the molecular genetics of 25 variants
of the glycophorin gene family, whose common denominator is that they
arise from unequal gene recombinations or gene conversions coupled to
splice site mutations. Most rearrangements occurred within a 2-kb regi
on mainly within GPA and GPB of the gene family and only rarely within
the third member, GPE. The key feature is the shuffling of sequences
within two specific exons (one of which is silent), homologous in the
two parent genes. This has resulted in expression of a mosaic of seque
nces within this region, leading to polymorphism. The common pattern o
f recombinations coupled to pre-mRNA splicing was the predominant mech
anism of the origin of glycophorin diversity, Thus far this mechanism
appears to be unique among human gene families. It could have occurred
by chance rearrangements among closely linked genes and been driven b
y a biological advantage, not as yet identified. This remains to be es
tablished. Nevertheless, gene rearrangements observed here are akin to
those reported for the major histocompatibility complex (MHC). In the
glycophorin family the small size of the region within which gene int
eractions have occurred and the participation of essentially only two
alleles makes this relatively simpler system more focused and easier t
o dissect and describe molecularly. (C) 1995 Wiley-Liss, Inc.