title: An experimental approach to enumerate the genes coding for immunoglobulin variable-regions.
abstract: Critical to our understanding of the immune system diversity is the determination of the number of germ line V genes. The total number of V genes is given by the product: number of subgroups x number of germ line genes per subgroup. Studies of kappa chains and of embryonic DNA indicate 5-10 V genes per subgroup. Statistical analysis of the limited sequence data of mouse kappa chains suggest about 50 V kappa subgroups. We report here a general approach for direct estimation of the number of VL and VH subgroups expressed in normal spleen, and present data for V kappa. The kappa mRNA of the spleen is a heterogeneous population where different V kappa are linked to the same C kappa, i.e. C kappa equals total V kappa. The ratio C kappa/distinct V kappa approximates the number of subgroups since V kappa of the same subgroup cross hybridize while V kappa of different subgroups do not. This ratio was determined by molecular hybridization of cloned C kappa and V kappa DNA probes with spleen mRNA. The results indicate the expression of 280 V kappa subgroups in mouse. Assuming an average of 7 genes per subgroup, we estimate about 2000 V kappa germ line genes.
mesh_terms: D000818:Animals; D001483:Base Sequence; D001666:Binding Sites, Antibody / Q000235:genetics*; D002460:Cell Line; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D051379:Mice; D009693:Nucleic Acid Hybridization; D010954:Plasmacytoma; D010957:Plasmids; D012194:RNA-Directed DNA Polymerase
chemical_list: D004274:DNA, Recombinant; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; D012194:RNA-Directed DNA Polymerase; D004262:DNA Restriction Enzymes