Chromosomal locations of mouse immunoglobulin genes.

Abstract

The A comparison of karyotypic data with hybridization data has limited the possible locations of the Ig genes to only a few chromosomes.In the mouse, as in other mammals, the chromosomal locations of the genes coding for antibody heavy and light chain structures have not been clearly identified. From genetic studies it has been inferred that these genes are located on different autosomes (1), and it has been suggested on the basis of a variable region marker that the mouse K locus may be on chromosome 6 (2). However, owing to the lack of a demonstrable linkage between heavy or light chain constant-region genes and other loci and to the possible existence of regulatory loci affecting the expression of the immunoglobulin structural genes (3, 4), a more definitive study is called for. We have therefore attempted to solve this problem by use of the molecular hybridization techniques. In these experiments, cDNA probes representing the constant regions of mouse K and AI light chain mRNAs and a, 72h and M heavy chain mRNAs were annealed to a large excess of DNA from a series of mouse-human hybrid cell lines that are deficient for various mouse chromosomes (5). A similar approach using hybrids segregating human chromosomes has shown that the structural gene for human a-globin is on chromosome 16 (6). The results of our studies demonstrate clearly that genes CA, CK, and CH are autosomal and not linked. Moreover, a comparison of karyotypic and hybridization data has limited the possible locations of these genes to only a few chromosomes. Interestingly, our results indicate that the chromosome containing the CK gene is probably not chromosome 6. 55-14, 55-54, and 55-91 were derived from three independent fusions of HT-1080-6TG human fibrosarcoma cells with BALB/c mouse peritoneal macrophages; the hybrid line 55-84 was derived from a fusion of HT-1080-6TG cells with OTT6050 mouse teratocarcinoma cells (5). The F numbers refer to different flasks in which hybrids were formed following the initial fusion event, and Cl numbers refer to different clonal isolates from the initial hybrid cell cultures. Line VII is an early sample of the 55-14 F7 culture that was kept frozen until its cultivation for the present series of experiments. Karyotype analyses were carried out by using the trypsin-Giemsa banding technique (5). MATERIALS AND METHODSDNAcDNA Annealing Experiments. The cDNA probes were synthesized from highly purified heavy and light chain mRNAs isolated from various mouse plasmacytomas. The tumors used as sources of the particular mRNAs were: AI, H2020

Linkage analyses of murine immunoglobulin heavy chain and serum prealbumin genes establish their location on chromosome 12 proximal to the T (5;12) 31H breakpoint in band 12F1.

“…The map position of Igh-1 established by these data conflicts with the results obtained by using specific cDNA probes (13) which une4uivocally identify structural genes. A possible explanation is that the observations of Valbuena et al are contingent on the particular cell hybrids examined and therefore lack general validity.…”

“…Recently, conflicting reports have been published on the assignment of the Igh genes. The results obtained by renaturing specific cDNA transcripts with chromosomal DNA preparations from human fibrosarcoma-mouse macrophage cell hybrids led Valbuena et al (13) to conclude that the most probable location of the Igh-C genes was on mouse chromosome 15. In contrast, Hengartner et al (14), analyzing the immunoglobulin production of intraspecific cell hybrids, have tentatively assigned the Igh-V and Igh-C group to mouse chromosome 12, which was clearly excluded in the former study.…”

“…Interestingly, both assignments failed to match with the probable locations inferred from negative linkage data. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], whereas the sex chromosome and chromosome 19 remain structurally unmarked. The inbred strains C57BL/6J, LP/J, and BALB/cJ were purchased from the Jackson Laboratory, whereas all other mice were from the colonies maintained at the Medical Research Council Radiobiology Unit, Harwell.…”

Ef2: a new LY-3-linked light-chain marker expressed in normal mouse serum immunoglobulin.

“…A second implication of the structural gene hypothesis is that the genes coding for mouse V~ sequences must reside on Chromosome 6. The Chromosome-6 location of the V~-structural genes, however, is currently a subject of controversy, because conflicting reports have appeared (11,27). Interpretation of the results as due to differences in V~-structural genes also has implications for the recently proposed gene rearrangement model (23).…”

The mouse immunoglobulin kappa light-chain genes are located in early- and late-replicating regions of chromosome 6.

“…The kappa constant region (CK) and variable region (VK) genes reside on mouse chromosome 6 (30,69). The J region genes are clustered within a 1.7-kb genomic segment (46,62) and are located 2.4 kb from the CK gene (46,47) on the same EcoRI segment (43).…”