The proposal deals with studies at both protein and DNA levels of variants of alpha and delta glycophorins (Glycophorins A and B) of the human erythrocyte membrane. These proteins constitute a family of closely homologous glycoproteins that specify the antigens for the MNSsU blood group system. Serologically variant phenotypes occur in the human population and are often associated with structurally variant glycophorin molecules. Several variant glycophorins are hybrid molecules, products of hybrid genes; they appear to constitute another family of proteins where mechanisms of human gene rearrangements and expression of variant proteins can now be studied. The variant glycophorins exhibit extensive polymorphism, of high incidence in selected human populations and non-human primates. The long-term objectives of this research are to gain insight into the mechanisms of gene rearrangements and phenotypic expression of gene products that result in the high degree of polymorphism observed in the glycophorin family of proteins. This may provide a basis for understanding the diversity of the MNSsU blood group system and of other blood groups.
Specific aims are as follows: 1) To carry out protein and carbohydrate structural studies of glycophorin variants, to provide a structural correlation of the expression of these glycoproteins on the cell surface and indicate the range of structures that may exist in different populations. This includes isolation of variant proteins and determination of polypeptide sequence and carbohydrate structures and attachment sites. 2) To carry out parallel studies of genomic organization of variant genes. First, oligonucleotide mapping, sequencing of variant sites by amplification through polymerase chain reaction, and finally partial library cloning sequencing. 3) To clone alpha, delta and the third glycophorin genes to understand the organization of this gene cluster and to provide a framework for understanding of variant genes. 4) To study the organization of this gene cluster and to provide a framework for understanding of variant genes. 4) To study the organization of glycophorin genes in higher primates where extensive polymorphism among single individuals may provide further insight into the diversity of this system. In summary, this project will investigate the molecular basis for the diversity of a family of cell surface glycoproteins that are the MNSsU blood group antigens. This is one of the first blood group systems to undergo such an investigation. More generally, it will provide clues on some mechanisms of human gene rearrangements resulting in human variants. As a side benefit, it will provide information relevant to the national project of mapping and sequencing of the human genome.
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