Cloned embryonic DNA sequences flanking the mouse immunoglobulin C gamma 3 and C gamma 1 genes

To investigate the DNA surrounding genes for immunoglobulin heavy chain constant (CH) regions, we have isolated two clones bearing a C gamma 3 gene and two bearing a C gamma 1 gene from a library of mouse embryo DNA fragments. The C gamma 3 clones span 8.6 kilobase pairs (kb) on the 5' side of the gene and 6.7 kb on its 3' side, while the C gamma 1 clones together span 13 kb of 5' flanking sequence and 2.5 kb of 3' flanking sequence. Restriction mapping of the C gamma 3 gene indicates that intervening sequences divide the gene into segments of domain size, as in other CH genes. Hybridization of clone fragments to restriction digests of mouse DNA indicates that both the C gamma 1 and C gamma 3 genes probably occur as single copies in the genome. Moreover, the entire cloned sequences on the 5' side of both genes appear to be unique in the genome, indicating that no large common sequences flank CH genes. Restriction data suggest that the C gamma 3 gene is 37-40 kb 5' to the C gamma 1 gene.     

Primary structure of human gamma 3 immunoglobulin deletion mutant: gamma 3 heavy-chain disease protein Wis

The complete sequence of a gamma 3 heavy-chain disease (HCD) protein Wis is presented. The molecule is a dimer of a 289-residue chain linked by 12 disulfide bonds. Protein Wis has an unusual amino terminus, followed by a deletion of most of the VH domain. After a small stretch homologous to the VC joining region, there is a second deletion which ends at the beginning of the quadruplicated hinge. Two carbohydrate groups are linked to Asn-6 and -140. the molecule has an extra interchain disulfide bridge at position 7 in addition to the 11 normally present in the quadruplicated hinge. The previously noted homology to the gamma 1 heavy chain is striking; from positions 224 to 234, protein Wis resembles gamma 1 Nei [Ponstingl, H., & Hilschmann, N. (1976) Hoppe-Seyler's Z. Physiol. Chem. 357, 1571--1604] except for a serine which replaces Asn at position 227. The results, taken together with studies of other immunoglobulin heavy-chain deletion mutants, support the suggestion that the different domains and interdomain regions of human H chains are coded for by different gene segments and that the deleted proteins reflect alterations in the recombination of different genes and/or the splicing of heterogeneous nuclear messenger ribonucleic acid (hn mRNA).     

Cloning and complete nucleotide sequence of mouse immunoglobulin gamma 1 chain gene.

The 6.6 kb DNA fragment coding for the immunoglobulin γ1 chain was cloned from newborn mouse DNA using λgtWES·λB as the EK2 vector. The complete nucleotide sequence (1823 bases) of the γ1 chain gene was determined. The cloned gene contained the entire constant region gene sequence as well as the poly(A) addition site, but not the variable region gene. The results indicate that the variable and constant region genes of immunoglobulin heavy chain are separated in newborn mouse DNA. The constant region genes of other gamma chains (that is, γ2a, γ2b and γ3) are not present in the cloned DNA fragment. The sequence demonstrates that the γ1 chain gene is interrupted by three intervening sequences at the junction of the domains and the hinge region, as previously shown in the γ2b and α chain genes and in the γ1 chain gene cloned from myeloma. The results suggest that the intervening sequence was introduced into the heavy chain gene before divergence of the heavy chain classes, and also support the hypothesis that the splicing mechanism has facilitated the evolution of eucaryotic genes by linking duplicated domains or prototype peptides not directly adjacent to one another. Comparison of the nucleotide sequence of the γ1 chain gene around the boundaries of the coding and intervening sequences with those of other mouse genes revealed extensive divergence, although short prevalent sequences of AG-GTCAG at the 5′ border of the intervening sequence and TCTGCAG-GC at the 3′ border were deduced. A limited homology of nucleotide sequences was found among domains and between the hinge region and the 5′ portion of the CH2 domain. Comparison of 3′ untranslated sequences from the γ1 and γ2b chain genes and the mouse major β-globin gene shows significant homology and a palindrome sequence surrounding the poly(A) addition site.     

Concerted evolution of the mouse immunoglobulin gamma chain genes

The nucleotide sequences of the immunoglobulin heavy-chain constant region genes of mouse, C gamma 3, C gamma 1, C gamma 2b and C gamma 2a, together with that of a human equivalent C gamma 4 were compared. All the six pairs of genes within the mouse C gamma gene family contain DNA segments that exhibit marked homology, whereas no such segmental homology was found in interspecies comparisons. This result indicates that the four C gamma genes of the mouse evolved concertedly by exchanging parts of their genetic information with each other either by gene conversion or by double unequal crossing-over. Another example of such concerted evolution was found in gene regions encoding membrane domains of the mouse C gamma chains. We also searched for such segmental homologies in other mammalian C gamma gene families and found at least two more examples in man and guinea-pig. In the mouse C gamma gene family, the silent positions of an exon encoding the third domain of C gamma chains show much greater divergence in sequence than other regions, indicating that the genetic information encoded by this gene region was least scrambled during recent evolution. A phylogenetic tree constructed from the nucleotide differences of this exon demonstrates that at least two C gamma genes had already existed before mammalian radiation. Based on these results, evolution of mammalian C gamma gene families is discussed.     

Structure of immunoglobulin gamma 2b heavy chain gene cloned from mouse embryo gene library.

A mouse DNA clone containing the constant part of the immunoglobulin gamma 2b heavy chain was isolated from a mouse gene library. The library was constructed in Charon 4A from a partial EcoRI digest of mouse embryo DNA and was screened with a plasmid (p gamma (11)7) containing a cDNA insert of the heavy chain constant region of the plasmacytoma MPC-11 (1). The Charon 4A clone contains a 14 kb insert which is cleaved by EcoRI into a 6.8 kb and 7.2 kb fragments, of which only the 6.8 kb contains the sequence for gamma 2b heavy chain. Restriction analysis and partial sequence of the insert in p gamma (11) 7 enabled us to obtain three fragments corresponding to the 5' (amino acid 161-302) middle (amino acid 302-443) and 3' (mostly non coding 107 bp) regions of the constant region. Restriction analysis of the Charon 4A clone and hybridisation to these nick translated fragments revealed that the gamma 2b constant region gene contains about 1.5 kb and has three intervening sequences.     

Gene segments encoding membrane domains of the human immunoglobulin gamma 3 and alpha chains

The carboxyterminal region of the heavy chains, according to its hydrophilic or hydrophobic properties, determines whether the immunoglobulin will be secreted or membrane-bound. We have determined the nucleotide sequences of the human IGHG3, IGHA1, and IGHA2 membrane exons isolated from genomic DNA libraries. The IGHG3 M1 and M2 exons are separated by a long intron of 2.1 kilobases (kb) containing an highly repeated motif of 34 base pairs (bp). The IGHA1 and IGHA2 genes, like the mouse Igh-A gene, have a single exon encoding the extracellular, transmembrane, and cytoplasmic regions. For each class of immunoglobulins, the sequences of membrane exons are highly conserved between human and mouse, but no alignment is possible for the flanking regions. In contrast, for a same species, the sequences of the heavy chain membrane exons differ from one class to another. While the hydrophobic profile of the membrane core is well conserved, the cytoplasmic region differs in length and in composition. None of the intracellular domains presents the sequence implied in signal transduction, implying that membrane immunoglobulins need other proteins, which probably interact with the constant or membrane domain, to transmit signals leading to B-cell activation.The nucleotide sequence data reported in this paper have been submitted to the EMBL nucleotide sequence database and have been assigned the accession numbers M35288-91. Address correspondence and offprint requests to: M.-P. Lefranc.     

Evolution of the rat immunoglobulin gamma heavy-chain gene family

The sequences of the four immunoglobulin gamma heavy chains of the rat (gamma 1, gamma 2a, gamma 2b, gamma 2c) have been determined. These sequences reveal that the rat genes have evolved differently from the closely related mouse gamma genes (gamma 1, gamma 2a, gamma 2b, gamma 3): in rat two of the four genes (gamma 2a and gamma 1) are 94% homologous to each other and best resemble the single mouse gamma 1 gene. Rat gamma 2b is equivalent to the mouse gamma 2a/gamma 2b pair as regards both nucleotide sequence and antibody effector functions whilst rat gamma 2c resembles mouse gamma 3. In evolutionary terms this suggests the existence of a set of three common C gamma genes before separation of rat and mouse as individual species. In addition, two independent duplication events must have occurred after species separation affecting different constant regions; this yielded rat gamma 2a and gamma 1 as a recently evolved pair and mouse gamma 2a and gamma 2b as a different pair. Furthermore, the sequence comparisons reveal several other features of interest; rat IgG2b lacks two amino acids in CH1 which are conserved in all other sequenced gamma chains. Residues believed to be essential for monocyte interaction (FcRI) are retained only in rat gamma 2b and not in the other rat gamma genes whilst a particular motif involved in C1q interaction shows a variation in both rat IgG1 and rat IgG2a which has not been observed previously.     

The nucleotide sequence of a human immunoglobulin C gamma1 gene

We report the nucleotide sequence of a gene encoding the constant region of a human immunoglobulin gamma 1 heavy chain (C gamma 1). A comparison of this sequence with those of the C gamma 2 and C gamma 4 genes reveals that these three human C gamma genes share considerable homology in both coding and noncoding regions. The nucleotide sequence differences indicate that these genes diverged from one another approximately 608 million years ago. An examination of hinge exons shows that these coding regions have evolved more rapidly than any other areas of the C gamma genes in terms of both base substitution and deletion/insertion events. Coding sequence diversity also is observed in areas of CH domains which border the hinge.     

Nucleotide sequence and properties of the murine gamma 3 immunoglobulin heavy chain gene switch region: implications for successive C gamma gene switching

During B lymphocyte differentiation, immunoglobulin heavy chain constant region (CH) genes undergo a unique series of DNA recombination events culminating in the CH class switch. CH switch (S) regions are located 2 kb 5' of each CH gene except delta (i.e. mu, gamma 3, gamma 1, gamma 2b, gamma 2a, epsilon and alpha). We describe the structural features of the gamma 3 switch region. Hybridization experiments show that S gamma 3 has remarkable homology to both S mu and other S gamma regions while S mu possesses limited homology to the other S gamma sequences. However, S mu possesses extensive sequence homology with S epsilon and S alpha. The nucleotide sequence of S gamma 3 reveals higher densities of S mu repetitive sequences (GAGCT and GGGGT) and another S region common sequence (YAGGTTG) than observed for S gamma 1, S gamma 2b or S gamma 2a. In addition, the conservation of S mu like repetitive sequences in S gamma regions is correlated with the 5' leads to 3' gamma gene order (i.e. S gamma 3 greater than S gamma 1 greater than S gamma 2b greater than S gamma 2a). A model is presented which suggests that the unique features of S gamma 3 may allow for successive switches from C mu to any C gamma gene.     

Gene conversion and polymorphism: generation of mouse immunoglobulin gamma 2a chain alleles by differential gene conversion by gamma 2b chain gene

We have determined the complete nucleotide sequence of the C57BL/6 allele of the mouse immunoglobulin gamma 2a chain gene. A comparison with the BALB/c gamma 2a gene for 1912 nucleotides reveals that the two alleles exhibit extensive divergence, since there are 138 single-base-pair differences and 8 insertions or deletions. We have compared the two gamma 2a alleles with the two corresponding gamma 2b alleles, which differ in only 12 positions. It appears that among the 134 differences between the two gamma 2a alleles, 70 are at positions where gamma 2a and gamma 2b are identical in the BALB/c haplotype and 54 are at positions where gamma 2a and gamma 2b are identical in the C57BL/6 haplotype. All these results suggest that nonreciprocal gene conversion between nonallelic genes can introduce sequence homogeneity in linked genes and can generate extensive divergence and polymorphism in allelic genes. We suggest that the gamma 2a and gamma 2b gene ancestors freely diverged after duplication, and that the conversion events were promoted by a deletion shortening the distance between the two loci.     

Duplication of the human immunoglobulin heavy chain gamma 2 gene.

The five C gamma genes in the human immunoglobulin heavy chain region show nonrandom association and segregation as haplotypes. From the study of genetic variation in C gamma genes of 58 healthy Caucasian volunteers, we have identified a haplotype that involves a duplication of C gamma 2. This haplotype contains both the 13.5-kilobase (kb) and 25-kb BamHI fragment alleles of C gamma 2. In addition, the patterns and relative intensity of BamHI fragments containing C gamma genes were those expected for genomic DNA containing three copies of C gamma 2 for every two copies of the four other C gamma genes. A new EcoRI polymorphism in C gamma 4 was useful in defining the haplotype containing the duplication. Alleles of the C gamma genes in the duplication haplotype, including Gm markers of C gamma 1 and C gamma 3 and DNA polymorphisms of C psi gamma, C gamma 2, and C gamma 4, were consistent with its origin from an unequal crossover between the two common C gamma haplotypes, H1 and H2. This recombinant haplotype, which has been designated H2;1(gamma 2 dup) to reflect its origin, occurred with a frequency of .043 in a random sample of 116 chromosomes.     

Introduction of human gamma 1 immunoglobulin genes into fertilized mouse eggs

A rearranged human gamma 1 immunoglobulin gene was introduced into fertilized mouse eggs. The phage Ch4A-VCE-gamma 1 was constructed by ligating an EcoRI and BglII fragment of pBR322-CESSV(CE-1) containing the VDJ region with an EcoRI and BamHI fragment of Ch4A-HIg gamma 1-10 containing the gamma 1 constant region. About 200 copies of Ch4A-VCE-gamma 1 genes were introduced into fertilized mouse eggs. Of 489 eggs injected with these genes, 319 survived and were transferred to oviducts of foster mothers. Thirtyeight mice were born and were screened for the presence of human gamma 1 immunoglobulin genes by Southern blot hybridization. Five of these 38 mice had integrated human gamma 1 immunoglobulin genes. None of the human gamma 1 copies in each mouse had undergone deletions or rearrangements as judged by the Southern blotting patterns for several restriction enzymes. Human gamma 1 gene was present in several different tissues. All the mice tested so far transmit the human gamma 1 gene to a fraction of their offspring in an autosomal dominant manner. Spleen cells from transgenic mice were analyzed for immunoglobulin production by reverse plaque assay or immunofluorescence staining of cytoplasmic immunoglobulin, but synthesis and secretion of human gamma 1 chains could not be detected. No human gamma 1 immunoglobulin mRNA was detected in the liver and spleen of a transgenic mouse. The presence of the human gamma 1 immunoglobulin gene appeared to have no effect on the expression of endogenous mouse immunoglobulin genes.     

The gamma S-crystallin gene is mutated in autosomal recessive cataract in mouse

We established a recessive cataract model from a spontaneous mutation in the KUNMING outbred mice. Lens opacity appears 11 days after birth. Slit lamp examination reveals that the opacity mainly localizes to the nuclear region of the lens. Histological analysis shows a severe degeneration of the epithelial cells underneath the anterior lens capsule, whereas those cells in the equatorial region display an excessive proliferation and migration. Within the cortical area underneath the posterior lens capsule, both vacuoles and morgagnian-like bodies are seen. Blue-stained spherical bodies are observed in the embryonic nucleus, forming a Y-like pattern. We mapped the disease locus and found a homozygous G to A nucleotide conversion at position 489 of Crygs in mutant mice, leading to a truncated gene product (Trp163Stop). This finding suggests that CRYGS is not only a lens structural protein, but is also likely to be involved in epithelial cell proliferation, apoptosis, and migration.     

Sequence of a human immunoglobulin gamma 3 heavy chain constant region gene: comparison with the other human C gamma genes.

We report the first and complete nucleotide sequence of a human gamma 3 heavy chain constant region gene (C gamma 3). This gene displays the same organization than the others C gamma genes and exhibits normal RNA splice and polyadenylation sites. A comparison of its primary sequence with those of C gamma 1, C gamma 2 and C gamma 4 genes confirms the high degree of homology (95%) of the human family in both coding and non-coding regions, and the divergence of the hinge region. The C gamma 3 gene we sequenced codes for a Gm(b) gamma 3 chain (EZZ). Comparison with other known protein sequences reveals that only two specific aminoacids are involved in the Gm(b) and Gm(g) allotypes, which suggests an important part of the spatial configuration in the allotypic specificities.     

The expression and chromatin structure of the chicken glyceraldehyde-3-phosphate dehydrogenase gene in mouse cells

Chicken glyceraldehyde-3-phosphate dehydrogenase gene (GAPD) and thymidine kinase gene (TK) were co-transfected into mouse LMTK- cells by the calcium phosphate precipitation technique. Four of the eight hypoxanthine/aminopterin/thymidine-containing medium-resistant, TK+ transfectants were shown to produce different amounts of chicken glyceraldehyde-3-phosphate dehydrogenase by zymogram analysis. Subcloning and further analysis revealed that the chicken GAPD was stably inherited and that its enzyme subunits randomly combined with mouse subunits in heterotetramers. Although the contribution of chicken enzyme varied from approximately 30 to approximately 90% of the total glyceraldehyde-3-phosphate dehydrogenase activity with a proportional increase in total activity in the different subclones, it did not appear to affect the expression of mouse endogenous glycolytic enzymes since there was no distinct change in the levels of either mouse glyceraldehyde-3-phosphate dehydrogenase mRNA nor mouse phosphoglycerate kinase enzyme activity. The levels of chicken GAPD copy number, mRNA, and enzyme apparently were generally correlated in the different subclones, suggesting that the chicken GAPD in the mouse cells were expressed constitutively. In situ hybridization revealed that the transfected genes were integrated into mouse chromosomes in one cluster, and the locations of these clusters were different in different clones. Chromatin structure analyses of the chicken GAPD in four different transfectants revealed three DNase I-hypersensitive sites located around 0.2, 2.0, and 3.4 kilobases upstream from the 5' side of the gene. These sites are also present in the same locations in chicken lymphoblastoid cells (Kuo, M. T., Iyer, B., and Schwartz, R. J. (1982) Nucleic Acids Res 10, 4565-4579), indicating the dominant transmission of DNase I-hypersensitive cleavage sites in the transfected gene.