Extensive polymorphism in the extracellular domain of the mouse B cell differentiation antigen Lyb-2/CD72.
Lyb-2/CD72 is a 45-kDa mouse B cell surface protein that binds CD5 and has been shown to play a role in B cell proliferation and differentiation. Using the polymerase chain reaction we have isolated and sequenced cDNA clones encoding the serologically defined mouse Lyb-2a, Lyb-2b, and Lyb-2c alleles. We confirmed that our full length cDNA clones encode the Lyb-2a, -2b, and -2c alleles, respectively, by transfecting the isolated Lyb-2/CD72 cDNA clones into L cells and demonstrating that the transfectants bind only the appropriate allele specific anti-Lyb-2/CD72 antibodies. Sequence comparisons demonstrate that the Lyb-2/CD72 allels are highly conserved in their cytoplasmic and transmembrane domains but exhibit a high degree of polymorphism in their extracellular domains. This polymorphism in the extracellular region involves amino acid substitutions at a minimum of 20 residues and is concentrated primarily in the membrane distal region. cDNA sequence comparisons also demonstrate two distinct seven amino acid insertion/deletions among these allelic variants. A form of Lyb-2b cDNA lacking the sequence encoding the transmembrane region was isolated from a C57B1/6 mouse and a CH12.LX subline. The Lyb-2/CD72 PCR products from mRNA of mice expressing Lyb-2a and Lyb-2c contain a DNA fragment that corresponds in size to the transmembraneless form, suggesting that these mouse strains also express this mRNA.
Robinson
W H
WH
Department of Medicine, Stanford University School of Medicine, CA 94305.
Ying
H
H
Miceli
M C
MC
Parnes
J R
JR
D000818:Animals; D015703:Antigens, CD / Q000235:genetics* / Q000648:ultrastructure; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics* / Q000648:ultrastructure; D000950:Antigens, Ly / Q000235:genetics* / Q000648:ultrastructure; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005110:Extracellular Space; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D016415:Sequence Alignment; D014162:Transfection
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D000950:Antigens, Ly; C064228:CD72 protein, human; D008565:Membrane Proteins; D009838:Oligodeoxyribonucleotides; D004247:DNA