Human erythrocyte glycophorin C. Gene structure and rearrangement in genetic variants.
We have previously shown that a deletion of approximately 3 kilobases in the unique glycophorin C (GPC) gene, which encodes for the human erythrocyte glycophorins C and D, is associated with the Gerbich (Ge) blood group deficiency (Ge-2,-3 and Ge-2,+3 types) (Le van Kim, C., Colin, Y., Blanchard, D., Dahr, W., London, J. & Cartron, J.P. (1987) Eur. J. Biochem. 165, 571-579). We have now isolated and characterized the structure of the GPC gene from the common Ge+2,+3 donors and from a Ge-2,-3 variant (Ge-2,-3 gene). The GPC gene is organized in four exons distributed over 13.5-kilobase pairs (kbp) DNA and contains two directly repeated domains of 3.4 kbp in length which are likely derived from the recent duplication of a unique ancestral domain. Restriction mapping and sequence analysis indicate that a 3.4-kbp deletion within this gene, arising probably by unequal crossing over between the two repeated domains, is responsible for the formation of the Ge-2,-3 gene. The breakpoints of the deletion are located within introns 2 and 3, and therefore exon 3 is removed. The defective gene is transcribed as a mRNA with a continuous open reading frame extending over 300 nucleotides which is translated into an unusual sialoglycoprotein present on Ge-2,-3 red cells. The primary structure of this new glycoprotein has been deduced from nucleotide sequencing. It is proposed in addition, that another 3.4-kb deletion within the GPC gene eliminates exon 2 only by a similar mechanism and generates a defective gene encoding for the abnormal glycoprotein present on Ge-2,+3 erythrocytes. Interestingly, the same deletion which lead to the rare Ge-2,-3 genetic condition, occurred spontaneously and frequently in the cloned GPC gene during the propagation of the recombinant phages in Escherichia coli. From these observations we suggest that the Ge-2,-3 and Ge-2,+3 genes might represent the two allelic forms of a unique ancestral form of the GPC gene, following successive internal duplication and deletion events.
Colin
Y
Y
INSERM, Unité U76, Institut National de Transfusion Sanguine, Paris, France.
Le Van Kim
C
C
Tsapis
A
A
Clerget
M
M
d'Auriol
L
L
London
J
J
Galibert
F
F
Cartron
J P
JP
D000595:Amino Acid Sequence; D001483:Base Sequence; D001789:Blood Group Antigens; D003001:Cloning, Molecular; D005796:Genes; D006021:Glycophorins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D012333:RNA, Messenger / Q000235:genetics; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D012795:Sialoglycoproteins / Q000235:genetics*; D014158:Transcription, Genetic
D001789:Blood Group Antigens; D006021:Glycophorins; D012333:RNA, Messenger; D012795:Sialoglycoproteins