Clustering of breakpoints on chromosome 11 in human B-cell neoplasms with the t(11;14) chromosome translocation

The t(11;14) (q13;q32) chromosome translocation has been reported in diffuse small and large cell lymphomas and in chronic lymphocytic leukaemia (B-CLL) and multiple myeloma. Because chromosome band 14q32 is involved in this translocation, as well as in the t(8;14) (q24;q32) translocation of the Burkitt tumour, interruption of the immunoglobulin heavy-chain locus was postulated for this rearrangement. We have cloned the chromosomal joinings between chromosomes 11 and 14 and also between chromosomes 14 and 18, in B-cell tumours carrying translocations involving these chromosomes, and suggested the existence of two translocated loci, bcl-1 and bcl-2, normally located on chromosomes 11 (band q13) and 18 (band q21) respectively, involved in the pathogenesis of human B-cell neoplasms. The results indicate that in the leukaemic cells from two different cases of CLL, the breakpoints on chromosome 11 are within 8 nucleotides of each other and on chromosome 14 involve the J4-DNA segment. Because we detected a 7mer-9mer signal-like sequence with a 12-base-long spacer on the normal chromosome 11, close to the breakpoint, we speculate that the t(11;14) chromosome translocation in CLL may be sequence specific and may involve the recombination system for immunoglobulin gene segment (V-D-J) joining.     

A chromosome 14 inversion in a T-cell lymphoma is caused by site-specific recombination between immunoglobulin and T-cell receptor loci

Specific chromosomal aberrations are associated with specific types of cancer (for review see ref. 1). The distinctiveness of each association has led to the belief that these chromosomal aberrations are clues to oncogenic events or to the state of differentiation in the malignant cell type. Malignancies of T lymphocytes demonstrate such an association characterized most frequently by structural translocations or inversions of chromosomes 7 and 14 (refs 7-9). Analyses of these chromosomally marked tumours at the molecular level may therefore provide insight into the aetiology of the cancers as well as the mechanisms by which chromosomes break and rejoin. Here we report such an analysis of the tumour cell line SUP-T1 derived from a patient with childhood T-cell lymphoma carrying an inversion of one chromosome 14 between bands q11.2 and q32.3, that is, inv(14) (q11.2; q32.2). These are the same chromosomal bands to which the T-cell receptor alpha-chain (14q11.2) and the immunoglobulin heavy-chain locus (14q32.3) have been assigned. Our analysis reveals that this morphological inversion of chromosome 14 was mediated by a site-specific recombination event between an immunoglobulin heavy-chain variable region (Ig VH) and a T-cell receptor (TCR) alpha-chain joining segment (TCR J alpha). S1 nuclease analysis shows that this hybrid gene is transcribed into poly(A)+ RNA.     

Breakpoints in the human T-cell antigen receptor alpha-chain locus in two T-cell leukaemia patients with chromosomal translocations

Specific chromosomal translocations have been observed in several human and animal tumours and are believed to be important in tumorigenesis. In many of these translocations the breakpoints lie near cellular homologues of transforming genes, suggesting that tumour development is partly due to the activation of these genes. The best-characterized example of such a translocation occurs in mouse plasmacytoma and human B-cell lymphoma, where c-myc, the cellular homologue of the viral oncogene myc, is brought into close proximity with either the light- or heavy-chain genes of the immunoglobulin loci, resulting in a change in the regulation of the myc gene. T-cell malignancies also have characteristic chromosomal abnormalities, many of which seem to involve the 14q11-14q13 region. This region has recently been found to contain the alpha-chain genes of the human T-cell antigen receptor. Here we determine more precisely the chromosome breakpoints in two patients whose leukaemic T cells contain reciprocal translocations between 11p13 and 14q13. Segregation analysis of somatic cell hybrids demonstrates that in both patients the breakpoints occur between the variable (V) and constant (C) region genes of the T-cell receptor alpha-chain locus, resulting in the translocation of the C-region gene from chromosome 14 to chromosome 11. As the 11p13 locus has been implicated in the development of Wilms' tumour, it is possible that either the Wilms' tumour gene or a yet unidentified gene in this region is involved in tumorigenesis and is altered as a result of its translocation into the T-cell receptor alpha-chain locus.     

Correlation between immunoglobulin light chain expression and variant translocation in Burkitt's lymphoma

Burkitt's-type lymphomas-leukaemias (BL) are monoclonal proliferations of malignant B lymphocytes. Irrespective of whether they carry the Epstein-Barr virus (EBV) genome, these tumour cells have been shown consistently to have one of the specific reciprocal chromosome translocations, t(8; 14), t(2; 8) or t(8; 22), involving the long arm of chromosome 8 (on 8q24) and chromosome 14, 2 or 22 (on 14q32, 2p12 and 22q11, respectively). The latter chromosomes have been shown recently to carry genes for immunoglobulin (Ig) heavy chains, and kappa and lambda light chains, respectively. Furthermore, the localization of kappa light chains within 2pcen-2p13 encompasses the breakpoint observed in Burkitt's translocation (2p12). It was therefore considered of interest to determine whether the expression of immunoglobulin chains in BL cells is related to the type of chromosomal anomalies observed. We report here that there is a direct relationship between expression of immunoglobulin light chains and specific type of translocation: BL cells with t(8; 22) express lambda chains, whereas those with t(2; 8) express kappa chains.     

The DNA sequence of human chromosome 21

Chromosome 21 is the smallest human autosome. An extra copy of chromosome 21 causes Down syndrome, the most frequent genetic cause of significant mental retardation, which affects up to 1 in 700 live births. Several anonymous loci for monogenic disorders and predispositions for common complex disorders have also been mapped to this chromosome, and loss of heterozygosity has been observed in regions associated with solid tumours. Here we report the sequence and gene catalogue of the long arm of chromosome 21. We have sequenced 33,546,361 base pairs (bp) of DNA with very high accuracy, the largest contig being 25,491,867 bp. Only three small clone gaps and seven sequencing gaps remain, comprising about 100 kilobases. Thus, we achieved 99.7% coverage of 21q. We also sequenced 281,116 bp from the short arm. The structural features identified include duplications that are probably involved in chromosomal abnormalities and repeat structures in the telomeric and pericentromeric regions. Analysis of the chromosome revealed 127 known genes, 98 predicted genes and 59 pseudogenes.     

The DNA sequence and analysis of human chromosome 14

Chromosome 14 is one of five acrocentric chromosomes in the human genome. These chromosomes are characterized by a heterochromatic short arm that contains essentially ribosomal RNA genes, and a euchromatic long arm in which most, if not all, of the protein-coding genes are located. The finished sequence of human chromosome 14 comprises 87,410,661 base pairs, representing 100% of its euchromatic portion, in a single continuous segment covering the entire long arm with no gaps. Two loci of crucial importance for the immune system, as well as more than 60 disease genes, have been localized so far on chromosome 14. We identified 1,050 genes and gene fragments, and 393 pseudogenes. On the basis of comparisons with other vertebrate genomes, we estimate that more than 96% of the chromosome 14 genes have been annotated. From an analysis of the CpG island occurrences, we estimate that 70% of these annotated genes are complete at their 5' end.     

Loss of alleles of loci on the short arm of chromosome 3 in renal cell carcinoma

Loss of genes at specific chromosomal loci is a characteristic of retinoblastoma, Wilms' tumour, transitional cell carcinoma of the bladder, embryonal tumours and small cell carcinoma of the lung. The significance of nonrandom gene loss in these neoplasms is that gene loss on one chromosome may uncover null mutations at corresponding loci of the homologous chromosome. Loss of specific gene products from somatic cells may be critical in the origin or evolution of certain human tumours. Clues to identification of new loci of gene loss in common adult solid tumours may be found in literature that describes chromosomal abnormalities in rare heritable cancers. Karyotypes of tumours in two families with hereditary renal carcinoma showed translocations involving the short arm of chromosome 3 (refs 10 and 11). We have examined tumours from 18 patients with non-hereditary renal cell carcinomas and found loss of alleles at loci on the short arm of chromosome 3 in all eleven of the patients who could be evaluated.     

Loss of genes on the short arm of chromosome 11 in bladder cancer

Recent studies have shown that normal cellular sequences on chromosome 13 are lost during the development of retinoblastomas and that sequences on chromosome 11 are similarly lost during the development of Wilms' kidney tumours and embryonal tumours. Cells from these tumors have been found to contain either the paternal or maternal copies of loci on the affected chromosome, but not both. Thus, the somatic loss of heterozygosity for sequences on chromosome 13 or 11 is hypothesized to result in homozygosity for a recessive mutant allele on these chromosomes, and in this way the chromosomal loss may contribute to the development of these tumours. We sought to investigate whether similar losses of heterozygosity for chromosome 11 sequences occurred in a common adult tumour. We chose to analyse bladder cancers, since such cancers are common in the adult population and are derived from urogenital tissue, as are Wilms' tumours. We examined constitutional and tumour genotypes at loci on the short arm of chromosome 11 (11p) in 12 patients with transitional cell carcinomas. In five tumours, we observed the somatic loss of genes on 11p resulting in homozygosity or hemizygosity of the non-deleted alleles in the tumour cells. Our results show that the frequency of loss of 11p sequences in bladder cancer approaches that seen in Wilms' tumour (42% compared with 55%), and suggest that recessive genetic changes involving sequences on 11p may contribute to the development of bladder neoplasms.     

Loss of heterozygosity of chromosome 3p markers in small-cell lung cancer

Specific chromosomal deletions sometimes associated with tumours such as retinoblastoma (chromosome 13q14) and Wilm's tumour (chromosome 11p13) have led to the hypothesis that recessive genes may be involved in tumorigenesis. This hypothesis is supported by demonstration of allele loss specific for these regions using polymorphic DNA markers and by the isolation of a complementary DNA clone for the retinoblastoma gene. A cytogenetic deletion in chromosome 3 (p14-p23) was reported in small-cell lung cancer (SCLC) by Whang-Peng et al. At least one homologue of chromosome 3 was affected in the majority of SCLC tumours; however, the multiple chromosomal changes seen presented the possibility that chromosome 3 was rearranged, not deleted. We used polymorphic DNA probes for chromosome 3p and compared tumour and constitutional genotypes of nine SCLC patients. Our data show loss of alleles of chromosome 3p markers in tumour DNA of all nine patients supporting the hypothesis that this region contributes to tumorigenesis in SCLC.     

No linkage of chromosome 5q11-q13 markers to schizophrenia in Scottish families

Recent work suggests that an autosomal dominant gene for schizophrenia may be located on the 5q11-q13 region of chromosome 5 (refs 1 and 2): a report of schizophrenia associated with trisomy 5q11-q13 in two members of a family of Chinese origin prompted the discovery of linkage with markers p105-599Ha and p105-153Ra in five Icelandic and two English schizophrenic families. The strongest linkage was observed when the phenotype was broadly defined to include minor psychiatric diagnoses not traditionally considered part of the schizophrenia spectrum. By contrast, no evidence was found of linkage in a single multiplex Swedish schizophrenic pedigree. To determine whether these conflicting results arise from genetic and/or uncertainties in defining the schizophrenic phenotype, we examined fifteen Scottish schizophrenic families with restriction fragment length polymorphisms that span this region. We found no evidence for linkage, regardless of how broadly or narrowly the schizophrenic phenotype is defined, and conclude that a susceptibility locus, whose presence awaits confirmation, on the proximal portion of the long arm of chromosome 5 can be responsible for only a minority of cases of familial schizophrenia.     

Development of homozygosity for chromosome 11p markers in Wilms' tumour

Somatic alterations in the genome are found in many human tumours. Chromosome rearrangements or base substitutions that activate cellular oncogenes appear to act dominantly. In contrast, recessive alleles apparently contribute to childhood retinoblastoma, as homozygosity (or hemizygosity ) for chromosome 13 is often established in tumours, by either mitotic nondisjunction or recombination. Parallels exist between retinoblastoma and childhood Wilms' tumour (WT). Retinoblastoma is often inherited and accompanied by a deletion of chromosome 13 (band q14), while WT is occasionally associated with aniridia and deletion of chromosome 11 band p13. Most Wilms' tumours are sporadic and not accompanied by these findings, although interstitial deletion of chromosome 11 in tumour, but not normal, cells has been reported. In view of these parallels, we compared constitutional and tumour DNAs from WT patients by using chromosome 11p DNA probes. We report here that although heterozygosity in constitutional DNAs was often preserved in tumour DNAs, one case developed homozygosity for chromosome 11p markers in tumour cells, implying the involvement of chromosomal events in revealing a recessive WT locus. This observation suggests the action of such general mechanisms in a tumour other than retinoblastoma.     

Evidence against linkage of schizophrenia to markers on chromosome 5 in a northern Swedish pedigree

Schizophrenia is a severe mental illness with a typically chronic course affecting nearly 1% of the human population. It is generally accepted that genetic factors have an important pathogenic role in a substantial portion of schizophrenia cases; however, despite decades of family studies, there is no agreed-upon mode of inheritance. The discovery of genetic aetiologic factors and resolution of the inheritance pattern(s) will undoubtably emerge from genetic linkage studies. With these objectives in mind, we undertook a linkage project, starting in 1985, in a previously well-documented kindred from north Sweden. Multipoint linkage analyses were used to screen the proximal long arm of chromosome 5 using restriction fragment length polymorphism (RFLP) markers at five loci and the distal long arm using RFLPs at two loci, one of which was the locus for the glucocorticoid receptor. We found strong evidence against linkage between schizophrenia and the seven loci. These results, together with the positive evidence for linkage of schizophrenia with markers in the proximal long arm of chromosome 5 lead us to conclude that the genetic factors underlying schizophrenia are heterogeneous.     

Somatic deletion and duplication of genes on chromosome 11 in Wilms' tumours

One of the most provocative findings in tumour biology is the relationship between chromosomal changes and embryonal cancers in children. For example, children with the rare paediatric syndrome AGR triad (aniridia, genito-urinary abnormalities and mental retardation) often develop Wilms' tumours at a very early age and carry a germ-line deletion on the short arm of chromosome 11 (11p13). It has been suggested that the germ-line deletion 11p is the first of two or more steps to cancer in AGR children. If this were true, one might expect a similar deletion to arise somatically in the far more common isolated Wilms' tumours of children without AGR, as suggested by Knudson from epidemiological data. However, a chromosomal deletion on 11p was observed in only two of five such cases, while it was absent or seen inconsistently in others. We have now used a molecular genetic approach to determine whether Wilms' tumour cells possess somatic alterations at 11p loci. We have found somatic deletions of specific genes in four of six Wilms' tumours. Surprisingly, in all four cases, the deletions were associated with duplications leading to homozygosity of the non-deleted alleles in the tumour cells. As analogous observations were recently reported in retinoblastoma, the genetic events reported here may underlie the development of many such embryonal tumours in children.     

Chromosome 5 allele loss in human colorectal carcinomas

That the sporadic and inherited forms of a particular cancer could both result from mutations in the same gene was first proposed by Knudson. He further proposed that these mutations act recessively at the cellular level, and that both copies of the gene must be lost for the cancer to develop. In sporadic cases both events occur somatically whereas in dominant familial cases susceptibility is inherited through a germline mutation and the cancer develops after a somatic change in the homologous allele. This model has since been substantiated in the case of retinoblastoma, Wilms tumour, acoustic neuroma and several other tumours, in which loss of heterozygosity was shown in tumour material compared to normal tissue from the same patient. The dominantly inherited disorder, familial adenomatous polyposis (FAP, also called familial polyposis coli), which gives rise to multiple adenomatous polyps in the colon that have a relatively high probability of progressing to a malignant adenocarcinoma, provides a basis for studying recessive genes in the far more common colorectal carcinomas using this approach. Following a clue as to the location of the FAP gene given by a case report of an individual with an interstitial deletion of chromosome 5q, who had FAP and multiple developmental abnormalities, we have examined sporadic colorectal adenocarcinomas for loss of alleles on chromosome 5. Using a highly polymorphic 'minisatellite' probe which maps to chromosome 5q we have shown that at least 20% of this highly heterogeneous set of tumours lose one of the alleles present in matched normal tissue. This parallels the assignment of the FAP gene to chromosome 5 (see accompanying paper) and suggests that becoming recessive for this gene may be a critical step in the progression of a relatively high proportion of colorectal cancers.     

Localization of gene for human p53 tumour antigen to band 17p13

Recently the gene for the cellular tumour antigen p53, a phosphoprotein found in increased concentration in a variety of human cells, had been mapped to region 17q22 by in situ hybridization techniques and has been shown to translocate to the chromosome carrying the translocation [t(15; 17)] associated with acute promyelocytic leukaemia (APL). Based on this finding it has been postulated that this gene has a role in the pathogenesis of APL. Here we present evidence that the gene for p53 is not located on the long arm of chromosome 17, but maps to band 17p13. We therefore suggest that this gene is not directly involved in the chromosome translocation observed in APL.     

The RNA component of telomerase is mutated in autosomal dominant dyskeratosis congenita

Dyskeratosis congenita is a progressive bone-marrow failure syndrome that is characterized by abnormal skin pigmentation, leukoplakia and nail dystrophy. X-linked, autosomal recessive and autosomal dominant inheritance have been found in different pedigrees. The X-linked form of the disease is due to mutations in the gene DKC1 in band 2, sub-band 8 of the long arm of the X chromosome (ref. 3). The affected protein, dyskerin, is a nucleolar protein that is found associated with the H/ACA class of small nucleolar RNAs and is involved in pseudo-uridylation of specific residues of ribosomal RNA. Dyskerin is also associated with telomerase RNA (hTR), which contains a H/ACA consensus sequence. Here we map the gene responsible for dyskeratosis congenita in a large pedigree with autosomal dominant inheritance. Affected members of this family have an 821-base-pair deletion on chromosome 3q that removes the 3' 74 bases of hTR. Mutations in hTR were found in two other families with autosomal dominant dyskeratosis congenita.     

Hereditary spherocytosis associated with deletion of human erythrocyte ankyrin gene on chromosome 8

Hereditary spherocytosis (HS) is one of the most common hereditary haemolytic anaemias. HS red cells from both autosound dominant and recessive variants are spectrin-deficient, which correlates with the severity of the disease. Some patients with recessive HS have a mutation in the spectrin alpha-2 domain (S.L.M. et al., unpublished observations), and a few dominant HS patients have an unstable beta-spectrin that is easily oxidized, which damages the protein 4.1 binding site and weakens spectrin-actin interactions. In most patients, however, the cause of spectrin deficiency is unknown. The alpha- and beta-spectrin loci are on chromosomes 1 and 14 respectively. The only other genetic locus for HS is SPH2, on the short arm of chromosome 8 (8p11). This does not correspond to any of the known loci of genes for red cell membrane proteins including protein 4.1 (1p36.2-p34), the anion exchange protein (AE1, band 3; 17q21-qter), glycophorin C (2q14-q21), and beta-actin (7pter-q22). Human erythrocyte ankyrin, which links beta-spectrin to the anion exchange protein, has recently been cloned. We now show that the ankyrin gene maps to chromosome 8p11.2, and that one copy is missing from DNA of two unrelated children with severe HS and heterozygous deletions of chromosome 8 (del(8)(p11-p21.1)). Affected red cells are also ankyrin-deficient. The data suggest that defects or deficiency or ankyrin are responsible for HS at the SPH2 locus.     

新近发现的恶性肿瘤的染色体异常

作者报告一组新近发现的恶性肿瘤的染色体异常,均属少见的染色体变异.系采用淋巴结或骨髓直接法制备染色体标本.恶性淋巴瘤核型为14q~+t(2;14);慢性粒细胞白血病核型为pht(2;22).讨论了癌基因与染色体易位的关系.