Structural polymorphism of mouse complement C2 detected by microscale peptide mapping: linkage to H-2

A gene locus controlling a serum protein migrating electrophoretically in the beta region of mice and detected by using a strain derived from the Japanese wild mouse (Mus musculus molossinus)

Antigenic specificities of serum proteins from the MOL-ANJ strain of mice (a strain derived from Japanese wild mice, Mus musculus molossinus) were studied by gel precipitation with alloantisera produced by reciprocal alloimmunization between MOL-ANJ and BALB/c mice. An alloantigen which migrates immunoelectrophoretically in the beta region of serum proteins has been identified. Evidence indicates that this antigenic specificity is controlled by a co-dominant autosomal gene locus designated by the symbol Sas-2. The evidence also suggests that Sas-2 is genetically different from the previously described Sas-1 which controls a serum protein in the mouse. Sas-2 was located by linkage analysis between Idh-1 locus and Akp-1 locus on chromosome 1.

Antigenic polymorphism of a serum protein migrating electrophoretically in the alpha region detected by using a strain derived from the Japanese wild mouse (Mus musculus molossinus)

Antigenic specificities of a serum protein from the mouse Mol-A strain (a strain derived from the Japanese wild mouse, Mus musculus molossinus) was studied by gel precipitation with alloantisera produced by reciprocal alloimmunization between Mol-A and BALB/c mice. Alloantigens which migrate immunoelectrophoretically in the alpha region of serum proteins have also been identified. The evidence indicated that this antigenic specificity is controlled by a codominant autosomal locus designated Aph-1. The evidence also suggests that the Aph-1 locus is linked to the alpha locus on chromosome 2.

The molecular genetics of components of complement

Rapid progress has been made in establishing linkages and in chromosome allocation of the genes of some 9 complement components. In the MHC, C2, Factor B, and two C4 or C4 related genes have been placed in some detail in both man and mouse. The gene coding for the cytochrome P-450 21-hydroxylase has been shown to be duplicated and immediately 3' to the two C4 genes, though it appears to be functionally and structurally unrelated to the complement components. Thus six genes have been mapped to this region where particular haplotypes are associated with increased susceptibility to a number of diseases, some of which are autoimmune in character. The complete gene structure of Factor B has been solved in man and rapid progress is being made with the C2 and C4 genes. The structural basis of the polymorphisms of these genes is being established. In C4, the polymorphism is exceptionally complex with varying numbers of loci and probably more than 50 allotypes occurring in man. A structural basis has also been found for the big differences in the biological activity of some of the C4 allotypes in man. Apart from the genes in the MHC, linkage has been found between the genes coding for C4bp, CR1, and Factor H. Remarkably there are sequence homologies between these proteins and C2 and Factor B, probably related to the ability to bind to one or other of the structurally similar proteins C3b and C4b. The complete cDNA sequences of C3 and C4 in mouse and man have given much information on the many posttranslational modifications of these proteins. A partial structure has been obtained for the C3 gene and the homology shown between C3, C4, C5, alpha 2-macroglobulin, and pregnancy zone protein. Although the amount of detailed information in the molecular genetics of complement components is accumulating rapidly, there appears to be a reasonable prospect that linkages and homologies will classify the data into a comprehensible form.

Genetic polymorphism of the sixth component of complement (C6) in mice

Immunofixation after isoelectric focusing revealed two forms of mouse C6, C6A and C6M, both of which consist of two major protein bands and one or more acidic minor bands. They were distinguishable by their different isoelectric point (pI) ranges: C6M has more acidic pI ranges (pH less than 6.2) than C6A (pH less than 6.3). C6A was found in common inbred mice of Mus musculus domesticus, while C6M was found in inbred and wild mice of M. m. molossinus (Japanese wild mice, an Asian subspecies). Breeding experiments showed that these two forms of C6 were controlled by a single codominant autosomal locus. We propose the designation C-6 for this locus with two alleles, C-6a and C-6m, which encode for C6A and C6M, respectively. Linkage analysis indicated that the locus is not closely linked to the following loci: Idh-1, agouti, Amy-1, brown, Gpd-1, Mup-1, Pgm-2, Pgm-1, albino, Hbb, Es-1, Mod-1, Sep-1, Es-3, Igh-1, beige, Es-10, Sod-1, and C-3.