RESUMEN
We have determined the entire nucleotide sequence of the human immunoglobulin kappa locus, comprising a total of 1,010,706 nucleotides. The 76 Vkappa genes found by a hybridization-based approach and their classification in 7 families were confirmed. A Vkappa orphon located near the locus was also sequenced. In addition, we identified 55 novel Vkappa relics and truncated pseudogenes, which establish 5 new families. Among these 132 Vkappa genes, 46 have open reading frames. According to the databases and the literature, 32 unique Vkappa genes and 5 identical gene pairs form VJ-joints, 27 unique genes and 4 gene pairs are transcribed, and 25 unique genes and 4 gene pairs produce functional proteins. The Vkappa gene locus contains a 360-kb inverted duplication, which harbors 118 Vkappa genes. A comparison of the duplicated Vkappa genes suggests positive selection on the complementarity-determining regions of the duplicated genes by point mutations. The entire duplication unit was divided into 13 blocks, each of which has its distinct nucleotide sequence identity to its duplication counterpart (98.1 - 99.9 %). An inversion-mediated mechanism is suggested to generate the high-homology blocks. Based on the homology blocks and the mutation rates, the inverted duplication is assumed to have taken place approximately 5 million years ago. An orphon Vkappa gene near the kappa locus and a cluster of five Vkappa orphons on chromosome 22 have no counterparts within the kappa locus. This suggests possible mechanisms of the transposition of orphon Vkappa genes.
Asunto(s)
Evolución Molecular , Duplicación de Gen , Genes de Inmunoglobulinas/genética , Mutación de Línea Germinal/genética , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , Composición de Base , Cromosomas Humanos Par 22/genética , Bases de Datos como Asunto , Genes Duplicados/genética , Humanos , Cinética , Mutagénesis/genética , Sistemas de Lectura Abierta/genética , Filogenia , Mapeo Físico de Cromosoma , Seudogenes/genética , Secuencias Repetitivas de Ácidos Nucleicos/genética , Alineación de Secuencia , Homología de Secuencia de Ácido Nucleico , Terminología como AsuntoRESUMEN
Some aspects of the work of our group on the human and mouse immunoglobulin kappa genes are reviewed. The human kappa locus contains a large duplication: a 600 kb Ckappa-proximal copy with 40 Vkappa genes is found in the close vicinity of a 440 kb Ckappa-distal copy with 36 very similar, but not identical, Vkappa genes. The chimpanzee has only the Ckappa-proximal copy of the locus. The kappa locus of the mouse is close to 3.2 Mb in size, of which 3.1 Mb have been cloned in four contigs, leaving three small gaps of together about 90 kb; 140 Vkappa genes and pseudogenes were localized and sequenced. In parallel to the elucidation of the structure of the kappa loci, the mechanisms of the V-J rearrangement, somatic hypermutation and kappa gene expression were studied. Various polymorphisms were detected in the human population and a number of haplotypes defined. In addition to the Vkappa genes within the loci numerous Vkappa orphons were localized on different chromosomes. Comparing the kappa loci of different species allows some interesting conclusions as to the evolution of this multigene family. Finally our strategy of elucidating the structure and function of the kappa loci, which has been termed a 'cottage industry approach', is discussed in relation to the large-scale genome analysis as pursued today using automated methods.
Asunto(s)
Cadenas kappa de Inmunoglobulina/genética , Animales , Genoma , Humanos , Ratones , Pan troglodytesRESUMEN
Five contigs of the 5' part of the immunoglobulin kappa locus (F. Röschenthaler et al., Eur. J. Immunol. 1999. 29: 2065 - 2071) have been linked by cosmid clones prepared from bacterial artificial chromosomes (BACs) and by PCR. One of the previously defined contigs which contains three pseudogenes (Z7) was shown by fluorescence in situ hybridization to be located near the kappa locus on chromosome 6, but not within the locus; the three Vkappa genes are therefore now classified as orphons. A Vkappa9 / 10 gene, which was sequenced previously, was now localized within the locus, and two additional Vkappa genes were identified, a potentially functional Vkappa24 gene and a pseudogene of the Vkappa9 / 10 family. This brings the number of localized and sequenced Vkappa genes in the locus to 140; 75 of them are functional, 21 potentially functional and 44 pseudogenes. The 5' part of the kappa locus is now one contig of 1.88 megabase (Mb); it comprises 82 Vkappa genes. Other contigs of the locus are 65 kb, 105 kb and 1.04 Mb in size and contain 2, 5 and 51 Vkappa genes, respectively. The contigs are separated by three gaps of 10 - 40 kb each. Detailed restriction maps and other structural details of the kappa locus are deposted in the Internet at http://www.med. uni-muenchen.de / biochemie / zachau / kappa.htm.
Asunto(s)
Mapeo Cromosómico , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , Animales , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BLRESUMEN
At the present state of analysis the central part of the kappa locus comprises four contigs of together 1.2 Mb and contains 55 Vkappa genes. It is flanked by the 3' part of the locus with 22 Vkappa genes in 0.4 Mb (T. Kirschbaum et al., Eur. J. Immunol. 1998. 28: 1458-1466) and the 5' part with 63 Vkappa genes in six contigs of together 1.5 Mb (F. Röschenthaler et al., accompanying report). The 5' and the central regions have one large contig in common. A part of the central region is linked to the 3' region resulting in a 1.1-Mb contig. The structure of the contigs was established mainly by the analysis of overlapping cosmid clones derived from genomic DNA and yeast and bacterial artificial chromosomes (YACs and BACs) and by PCR techniques. Pulsed-field gel electrophoresis of YAC digests indicated that three gaps between the contigs of the central region are 10-40 kb in size, comprising together about 90 kb. Internal duplications in this part of the locus and rearranged YACs were the major problems of the structural work. Structural details are to be found on the Internet at http://www.med.uni-muenchen.de/biochemie/zach au/kappa.htm. In a concluding section of the report the mouse kappa locus is compared to the human one and some aspects of the evolution of the kappa locus are discussed.
Asunto(s)
Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Animales , Cromosomas Artificiales de Levadura/genética , Cromosomas Bacterianos/genética , Mapeo Contig , Cósmidos , Evolución Molecular , Humanos , Ratones , Familia de Multigenes , Reacción en Cadena de la Polimerasa , Mapeo RestrictivoRESUMEN
The 5' region of the mouse kappa locus comprises 63 Vkappa genes in six contigs of together 1.5 Mb, including one which links the region to the central part of the locus. The structures of the contigs were established by detailed restriction mapping of cosmid clones prepared from libraries of mouse C57BL/6 DNA and of yeast and bacterial artificial chromosomes (YACs, BACs with mouse DNA inserts). Pulsed-field gel electrophoresis of yeast artificial chromosome digests indicated that the gaps between the contigs were 10 to 60 kb, comprising together about 160 kb. The region of the kappa locus described here contains Vkappa1, Vkappa2, Vkappa9/10, Vkappa11, Vkappa12/13, Vkappa20, Vkappa24, Vkappa32, Vkappa33/34 and Vkappa38C genes as well as the VkappaRF gene and, towards the center of the locus, a number of Vkappa4/5 genes. Near the 5' end of the locus interspersed alpha-tubulin gene-like sequences were found. At its 3' side the region borders on the Vkappa4/5 contigs of the central region of the locus which is described in the accompanying report (Eur. J. Immunol. 1999. 29: 2057-2064). Structural details are to be found in the Internet at http://www.med.uni-muenchen.de/biochemie/zach au/kappa.htm. In a concluding section the main features of the structure of the mouse kappa locus are summarized.
Asunto(s)
Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Animales , Secuencia de Bases , Cromosomas Artificiales de Levadura/genética , Cromosomas Bacterianos/genética , Mapeo Contig , Cartilla de ADN/genética , Ratones , Datos de Secuencia Molecular , Familia de Multigenes , Mapeo RestrictivoRESUMEN
In this report 118 mouse Vkappa genes are described which, together with the 22 Vkappa genes reported previously (T. Kirschbaum et al., Eur. J. Immunol. 1998. 28: 1458-1466) amount to 140 genes that had been cloned and sequenced in our laboratory. For 73 of them cDNAs are known, i. e. they have to be considered functional genes, although 10 genes of this group have 1-bp deviations from the canonical promoter, splice site or heptanucleotide recombination signal sequences. Twenty Vkappa genes have been defined as only potentially functional since they do not contain any defect, but no cDNAs have been found (yet) for them. Of the 140 Vkappa genes 47 are pseudogenes. There are indications that two to five Vkappa genes or pseudogenes exist in the kappa locus which we have not yet been able to clone. The 140 Vkappa genes and pseudogenes were assigned to 18 gene families, 4 of them being one-member families. This differs from previous enumerations of the families only by the combination of the Vkappa9 and Vkappa10 families and by the addition of the Vkappa dv gene as a new separate family. Sequence identity usually was 80% or above within the gene families and 55-80% between genes of different families. Many of the mouse Vkappa gene families show significant homologies to the human ones, indicating that in evolution Vkappa gene diversification predated the divergence of the primate and rodent clades.
Asunto(s)
Genes de Inmunoglobulinas , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , Familia de Multigenes , Animales , Secuencia de Bases , Clonación Molecular , ADN Complementario/genética , Humanos , Ratones , Datos de Secuencia Molecular , SeudogenesRESUMEN
A detailed restriction map of a 430-kb contig comprising the single Ckappa, the 5 Jkappa and the adjoining 22 Vkappa gene segments is presented. The first 12 Vkappa genes following the JkappaCkappa region belong to the Vkappa21 family, the subsequent ones to the closely related families Vkappa8 and Vkappal 9/ 28. Previous difficulties in cloning all Vkappa21 genes can now be explained by the presence of a duplicated region in this part of the locus. The structure was established by analysis of yeast artificial chromosome, bacterial artificial chromosome and cosmid clones and by the so-called long template PCR technique. The distance between Ckappa and the proximal Vkappa21 gene is 22 kb and the average distances between the Vkappa genes are about 20 kb. Of the 12 Vkappa21 genes 5 were sequenced for the first time and 8 of the 12 genes were found to be expressed. Of the 10 Vkappa8 and Vkappa19/28 germline genes 9 are new; expression products of 8 of the 10 genes were known. The known 5', 3' polarities allow to specify for the 22 Vkappa genes whether they are rearranged to the JkappaCkappa element by a deletion or an inversion mechanism. Also the formation of interesting rearrangement products in classical cell lines as MPC11, MOPC41 and PC 7043 can be explained now. The non-Vkappa sequence L10 whose rearrangement by inversion has been described earlier (Hoechtl and Zachau, Nature 1983. 302: 260-263) was now localized downstream of JkappaCkappa.
Asunto(s)
Genes de Inmunoglobulinas , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , Secuencia de Aminoácidos , Animales , Cromosomas Artificiales de Levadura , Cromosomas Bacterianos , Clonación Molecular , Cósmidos , Reordenamiento Génico de Linfocito B , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Familia de Multigenes/inmunología , Mapeo Restrictivo , Células Tumorales CultivadasRESUMEN
The human immunoglobulin kappa locus is a duplicated structure. Contigs of 600 kb with 40 Vkappa genes and 440 kb with 36 Vkappa genes had been established for the Ckappa proximal (p) and distal (d) copies, respectively. In addition the human genome contains more than 24 dispersed Vkappa genes, called orphons. In the present study, 22 kappa-locus derived YACs were analyzed in detail, while 30 orphon-derived YACs were characterized only with respect to some parameters. The kappa-locus derived YACs allowed three gaps to be closed which previously could not be bridged by cosmid and phage lambda cloning. At the 5' side, the p contig was extended in the YACs by 50 kb and the d contig by 16 kb. At the 3'side, the d contig was extended by 11.5 kb. Beyond the 3' end of the d contig a new Vkappa gene was found, which is located, according to pulsed field gel electrophoresis (PFGE) experiments, at a distance of at least 140 kb from the last Vkappa gene of the contig. This Vkappa gene, which was termed Z0, occurred on three YACs, albeit at distances smaller than 140 kb; this was probably due to deletions in the YACs caused by abundant repetitive sequences at the borders of the locus. According to its sequence and to the restriction map of its surroundings, Z0 is an orphon gene of the so-called Z family, of which several members are known to be dispersed throughout the genome. The possibility that Z0 has been the parent of the other Z orphons is discussed.
Asunto(s)
Cromosomas Artificiales de Levadura/genética , Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Mapeo Cromosómico , Clonación Molecular , Cósmidos/genética , Cartilla de ADN , Electroforesis en Gel de Campo Pulsado , Biblioteca de Genes , Humanos , Región Variable de Inmunoglobulina/genética , Reacción en Cadena de la Polimerasa , Mapeo RestrictivoRESUMEN
A single contig spanning the entire mouse immunoglobulin kappa light chain (Igk) locus on chromosome 6 has been established using yeast and bacterial artificial chromosome clones. Detailed mapping of the Igk locus indicates that a member of the Igk-V2 gene family, located about 3.5 megabases upstream of the Igk-J-C complex, is the most distal functional Igk-V gene. Sequence analyses of Igk-V genes and anonymous DNA segments provide indications for internal duplications at the 5' end of the Igk-V locus and identify the likely origin of Igk-V orphon gene clusters located elsewhere in the mouse genome.
Asunto(s)
Mapeo Cromosómico , Cromosomas Artificiales de Levadura , Cadenas kappa de Inmunoglobulina/genética , Animales , Secuencia de Bases , Cricetinae , ADN , Elementos Transponibles de ADN , Células Híbridas , Ratones , Datos de Secuencia Molecular , Familia de MultigenesRESUMEN
In continuation of our efforts to elucidate the immunoglobulin kappa locus of the mouse we analyzed 46 yeast artificial chromosomes (YACs) containing V kappa, J kappa and C kappa genes. The YACs, which were derived from DNA of C57BL/6 and C3H mice, ranged from 0.3-1.9 Mb in size. On the basis of hybridization with probes specific for the V kappa gene families a group of 13 YACs was selected for detailed analysis. The V kappa genes of the YACs were then characterized by hybridization to the family-specific probes and by the sizes of the EcoRI fragments on which they were found. This way evidence was obtained for 140 different V kappa gene signals on the YACs. Of these 63 had been characterized before on clones from a cosmid library of total mouse DNA (I. Zocher et al., Eur. J. Immunol. 1995. 25: 3326-3331) and 22 others were found now on cosmid clones derived from the YACs. Six V kappa genes of the previous study which were not found on the YACs are probably located outside of the kappa locus. The YACs were arrayed in a unique order establishing a YACs panel which most likely contains the whole kappa locus. The cosmid contigs and solitary cosmid clones which contain the 63 plus 22 V kappa gene signals mentioned above comprise about 2.0 Mb. Assuming that the remaining 55 V kappa genes are spaced at the same average distance of 24 kb, one may extrapolate to a locus size of 3.3 Mb.
Asunto(s)
Genes de Inmunoglobulinas , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , Animales , Secuencia de Bases , Cromosomas Fúngicos/inmunología , Biblioteca de Genes , Regiones Constantes de Inmunoglobulina/genética , Regiones Constantes de Inmunoglobulina/aislamiento & purificación , Región Variable de Inmunoglobulina/aislamiento & purificación , Cadenas kappa de Inmunoglobulina/aislamiento & purificación , Ratones , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Familia de Multigenes/inmunologíaRESUMEN
Although numerous solitary germ-line V kappa genes and two small V kappa contiguously cloned gene regions (contigs) are known, no attempts to systematically elucidate the structure of the kappa locus of the mouse have been reported so far. As a first step to this aim we screened a cosmid library of C57BL/6J mouse DNA with 18 probes that are more or less specific for the different V kappa gene families. Ninety-one V kappa gene-containing cosmid clones were characterized by detailed restriction mapping and hybridizations. Several contigs were constructed from overlapping clones. The contigs and the still unlinked cosmid clones cover 1.6 Mb. Many of the cosmid clones were localized on chromosome 6 where the kappa locus is known to reside; no evidence for the existence of dispersed V kappa genes (orphons) was obtained. Eighty-five strong hybridization signals were assigned to distinct V kappa gene families, while for 11 weak signals the assignment was less definite. As to the distribution of gene families within the locus the following situation emerged: there are both, groups of genes which belong to one V kappa gene family ("clusters") and groups in which genes of different families are interspersed. The interspersion of gene families seems to be more pronounced than has been assumed so far. Additional V kappa genes which are known to exist will have to be isolated from other gene libraries of the same mouse Ig kappa haplotype.
Asunto(s)
Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Familia de Multigenes/inmunología , Animales , Secuencia de Bases , Clonación Molecular , Cósmidos/inmunología , Biblioteca de Genes , Región Variable de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/aislamiento & purificación , Cadenas kappa de Inmunoglobulina/aislamiento & purificación , Hígado/química , Ratones , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Mapeo RestrictivoAsunto(s)
Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Alelos , ADN Complementario/genética , Regulación de la Expresión Génica , Reordenamiento Génico de Linfocito B , Humanos , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/biosíntesis , MutaciónRESUMEN
The 76 V kappa (variable) gene segments of the human immunoglobulin kappa locus (Ig kappa) were cloned in two contigs. Within each contig the distances between the genes range from a few hundred bp to 31 kb. We have now studied the question of whether transcripts are produced from intergenic regions, from regions near the kappa locus or from V kappa orphon regions. RNAs from several cell lines were converted to cDNAs which were then hybridized to the cosmid and phage lambda clones of the locus and of the orphon regions; the conditions were chosen such that the hybridization of transcripts with repetitive elements was minimized. The expression of a rearranged V kappa gene in a lymphoid cell line was readily detected. Also, a region 46 kb downstream from C kappa (constant) and a cDNA clone from a non-lymphoid cell line hybridizing to this region were studied in some detail. No transcripts were found, however, to be derived from the intergenic regions of the germ-line kappa locus which is in keeping with current ideas on the evolution of the V kappa multigene family.
Asunto(s)
Genes de Inmunoglobulinas/genética , Región Variable de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/genética , ARN Mensajero/genética , Secuencia de Aminoácidos , Clonación Molecular , ADN Complementario/genética , Humanos , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Mapeo Restrictivo , Transcripción GenéticaRESUMEN
Fluorescence in situ hybridization (FISH) of cosmid clones of human V kappa gene regions to human and primate chromosomes contributed to the dating of chromosome reorganizations in evolution. A clone from the kappa locus at 2p11-p12 (cos 106) hybridized to the assumed homologous chromosome bands in the chimpanzees Pan troglodytes (PTR) and P. paniscus (PPA), the Gorilla gorilla (GGO), and the orangutan Pongo pygmaeus (PPY). Human and both chimpanzees differed from gorilla and orangutan by the mapping of cos 170, a clone derived from chromosome 2cen-q11.2; the transposition of this orphon to the other side of the centromere can, therefore, be dated after the human/chimpanzee and gorilla divergence. Hybridization to homologous bands was also found with a cosmid clone containing a V kappa I orphon located on chromosome 1 (cos 115, main signal at 1q31-q32), although the probe is not fully unique. Also, a clone derived from the orphon V kappa region on chromosome 22q11 (cos 121) hybridized to the homologous bands in the great apes. This indicates that the orphons on human chromosomes 1 and 22 had been translocated early in primate evolution.
Asunto(s)
Mapeo Cromosómico , Hominidae/genética , Cadenas kappa de Inmunoglobulina/genética , Animales , Evolución Biológica , Cromosomas Humanos Par 1/genética , Cromosomas Humanos Par 2/genética , Cromosomas Humanos Par 22/genética , Gorilla gorilla , Humanos , Hibridación Fluorescente in Situ , Pan troglodytes , Pongo pygmaeusRESUMEN
The immunoglobulin kappa genes of nonhuman primates were studied by using sequence information and hybridization probes derived from the human kappa gene regions. The following results were obtained: (1) V kappa gene probes of the three major human kappa subgroups hybridized to restriction nuclease digests of DNA from the chimpanzees Pan troglodytes (PTR) and Pan paniscus (PPA), the gorilla Gorilla gorilla (GGO), the orangutan Pongo pygmaeus (PPY), the macaque Macaca mulatta (MMU), the marmoset Callithrix geoffrei (CGE), and the bushbaby Galago demidovii (GDE), yielding patterns of decreasing similarity to the patterns of the human V kappa multigene family. (2) The C kappa gene segments of PTR, GGO, and PPY were 99.6, 97, and 93%, respectively, identical in sequence to the human C kappa gene. A V kappa gene in PTR, GGO, PPY, and MMU was 98, 96, 96, and 95%, respectively, identical to the most C kappa proximal V kappa gene, called B3. The other two J kappa-C kappa proximal V kappa genes in human, B1 and B2, hybridize to restriction fragments of sizes identical to that of DNA from humans and great apes. (3) The long-range restriction maps of the human (HSA), PTR, and GGO kappa loci as established by pulsed-field gel electrophoresis (PFGE) are quite homologous. According to the maps, however, and to hybridization studies with 11 duplication-differentiating probes, there is only one copy of the locus in PTR and GGO. This means that the duplication of large parts of the kappa locus as found in humans occurred after the branch-point of human and great ape evolution.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Cadenas kappa de Inmunoglobulina/genética , Primates/genética , Animales , Secuencia de Bases , Línea Celular , ADN , Cartilla de ADN , Humanos , Regiones Constantes de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/genética , Sondas Moleculares , Datos de Secuencia Molecular , Familia de Multigenes , Mapeo RestrictivoRESUMEN
An amplicon that is highly homologous to a part of the human kappa locus was found at the 3' or telomeric side of C kappa at a distance of about 1.5 Mb. From analysis of sequence divergence, it is concluded that the amplicon was formed after the duplication of the kappa locus, which may have taken place about 1 million years ago. A V kappa gene of subgroup III within the amplicon turned out to have no defects in its sequence and to have a 5'-3' orientation opposite to the one of J kappa C kappa. Theoretically, a functional V kappa-J kappa-C kappa gene could be formed by an inversion mechanism, but no rearrangement products were observed so far.
Asunto(s)
Mapeo Cromosómico , Genes de Inmunoglobulinas , Cadenas kappa de Inmunoglobulina/genética , Secuencia de Bases , Evolución Biológica , Clonación Molecular , ADN/genética , Elementos Transponibles de ADN , Humanos , Datos de Secuencia Molecular , Familia de MultigenesRESUMEN
The human kappa locus contains 25 pseudogenes. After seven of them were described earlier the structures of the remaining 18 are reported now, thus completing the description of all human V kappa genes and pseudogenes. Most of the pseudogenes carry several defects each. Alignments of the pseudogene sequences and comparison with the consensus sequences of the potentially functional V kappa genes indicate that, on PCR amplification of genomic DNA aimed at certain genes of the latter class, also some of the pseudogenes would be coamplified. Unique sequences, which qualify as sequence tagged sites (STS), were defined across the locus. The occurrence of 15 repetitive elements of the LINE1 type in the locus is described. The 15 sequenced Alu elements were assigned to the known Alu subfamilies of different evolutionary age. One of the Alu elements was found only in one of the copies of the kappa locus. It must, therefore, have been inserted after the duplication step which may have taken place about one million years ago. This element belongs to an Alu subfamily known to have been mobile until recently. Some aspects of the evolution of the V kappa pseudogenes and orphons (i.e. V kappa genes located outside the kappa locus) are also discussed.
Asunto(s)
Cadenas kappa de Inmunoglobulina/genética , Seudogenes/fisiología , Secuencias Repetitivas de Ácidos Nucleicos/fisiología , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , ADN/análisis , Electroforesis en Gel de Poliacrilamida , Genes/fisiología , Humanos , Datos de Secuencia Molecular , Mutación , Hibridación de Ácido Nucleico , Mapeo Restrictivo , Análisis de Secuencia de ADNRESUMEN
The immunoglobulin kappa locus and its immediate surroundings, which are described in the present report, comprise 3 Mb of DNA, i.e., 0.1% or one per mill of the 3000 Mb of the human genome. Based on the work of our group during the past 12 years, we can now (1) depict in much detail the structure of the kappa locus with its 76 V kappa genes and pseudo genes, five J kappa elements and one C kappa gene; (2) specify the size of the germ-line repertoire of kappa light chains, which is one of the sources of the practically unlimited antibody diversity; (3) assign the known transcription products (studied as cDNAs) and kappa proteins to certain germ-line V kappa genes and attribute the differences in sequences to hypermutation and, to a lesser extent, to allelic variation; (4) analyze the hypermutation patterns which may contribute to the understanding of this enigmatic process; (5) describe the V kappa-J kappa rearrangements for half of the V kappa genes by a deletion mechanism and for the other half by a mechanism involving inversions of Mb-sized (i.e., 0.5 mm long) DNA fragments; (6) define various regulatory and other conserved sequence elements; (7) get clues as to the variation of the structure of the kappa locus in different individuals and populations, including a haplotype with only half the number of V kappa genes; (8) interpret many aspects of the evolution of the kappa locus in terms of duplications, insertions, deletions and gene conversions; (9) attribute the formation of the 24 V kappa orphons (i.e., genes outside the locus), whose sequences were determined, to pericentric inversions and other transposition processes; (10) answer a series of questions of biomedical interest; and (11) contribute 12.5 Mb of restriction maps, 1.8 Mb of clones and 250 kb of sequences to the elucidation of the human genome.