A complex translocation at the murine kappa light-chain locus.

We have previously reported that a segment of DNA from a murine plasmacytoma comprises DNA from three chromosomes, the immunoglobulin kappa light-chain locus on chromosome 6, the S mu locus on chromosome 12, and a region on chromosome 15. We now report that the reciprocal product contains DNA from only the kappa locus and chromosome 15 and not from S mu. We conclude that a complex series of events, including both a transposition of DNA and a translocation between chromosomes, generated these imperfect reciprocal products.     

Mapping of the c-myc, pvt-1 and immunoglobulin kappa genes in relation to the mouse plasmacytoma-associated variant (6;15) translocation breakpoint.

A variant mouse plasmacytoma (MPC)-associated translocation chromosome has arisen by pericentric inversion and exchange of the distal segments of a Robertsonian 6;15 fusion chromosome in the CAK TEPC 1198 mouse plasmacytoma, as described earlier. In situ hybridization was performed on the normal and the inverted Rb chromosomes, using myc and kappa probes. On the normal Rb chromosome, myc was in the 15 D2/3 region, whereas kappa hybridized in the 6 C2 area, as expected. On the inverted Rb chromosome, myc remains on the centrometric side of the translocation breakpoint on the chromosome 15-derived portion, whereas kappa has moved to the chromosome 6-derived segment that joined the same breakpoint on the telomeric side. Taken together with our recent demonstration that the murine c-myc locus is oriented 'head up' on chromosome 15, and with the results of Cory and co-workers concerning the relationship between the kappa gene and the associated pvt-1 region in the CAK TEPC 1198 tumor, the following conclusions can be drawn: (i) in the variant translocation of the CAK TEPC 1198 MPC, the breakage occurs 3' of the c-myc gene, as in the human Burkitt lymphoma-associated variant translocations; (ii) the pvt-1 gene on chromosome 15 is distal to the myc gene; (iii) the kappa light chain locus is oriented 'head up' on mouse chromosome 6 and faces pvt-1 and, beyond it, c-myc, in a head-to-tail configuration.     

Variant (6;15) translocations in murine plasmacytomas involve a chromosome 15 locus at least 72 kb from the c-myc oncogene.

The variant (6;15) translocations in murine plasmacytomas join the myc oncogene-bearing band of chromosome 15 and the immunoglobulin kappa band of chromosome 6. We recently cloned a region from chromosome 15 linked to C kappa and have now used probes from that region to define the major locus of plasmacytoma variant translocations, which we denote pvt-1. In five of nine plasmacytomas we analysed, the 6;15 translocation resulted from reciprocal recombination between the C kappa locus and a 4.5-kb region of pvt-1. Moreover, nearby we located the region shown by others to have undergone a complex (15;12;6) translocation in plasmacytoma PC7183. All the chromosome 6 breakpoints fell between 1 and 3 kb 5' to C kappa but only two were near J kappa genes. Thus the J kappa -C kappa region appears to be a recombination 'hot spot' in lymphocytes, but the breaks are unlikely to be mediated via V/J recombination enzymes. Comparison of a cloned 108-kb region across pvt-1 and another of 52 kb across c-myc established that the pvt-1 breakpoints lie at least 72 kb from the c-myc promoters. Since c-myc is expressed at a substantial level, the 6;15 translocation apparently activates c-myc. Activation may occur directly, at a remarkable distance along the chromosome, or indirectly, via a putative pvt-1 gene product.     

c-myc and immunoglobulin kappa light chain constant genes are on the 8q+ chromosome of three Burkitt lymphoma lines with t(2;8) translocations.

We have determined the localization of c-myc and the immunoglobulin kappa light chain genes on the 8q+/2p- chromosomes of the three Burkitt lymphoma lines BL21, LY66 and LY91 with t(2;8) translocation by in situ hybridization. BL21 is characterized by a complex translocation in which a piece of chromosome 9 appears to be located between the fragments of chromosome 8 and 2 on the 8q+ chromosome. Our data indicate that in all three cell lines the c-myc gene is located on the 8q+ chromosome proximal to the breakpoint in band 8q24. In all cell lines examined the cluster of kappa variable genes has remained on the 2p- chromosome. In LY91 cells the major part of the joining region remained on 2p-, while the joining region has moved to 8q+ in the cell lines BL21 and LY66. In all three cell lines the constant kappa light chain gene was found on the 8q+ chromosome. The fact that an essentially identical pattern was found in the cell line BL21, with the complex translocation, suggests that the insertion of the piece of chromosome 9 into the 8q+ chromosome might be a secondary event. Our present data fit into the concept that in all Burkitt lymphoma lines investigated so far, including cases with t(8;14) and the variant translocations t(2;8) and t(8;22), the c-myc gene becomes situated at the 5' side of an immunoglobulin constant gene. This may have implications for the generation of somatic mutations in the coding and non-coding part of the c-myc gene.     

Myc oncogene activation in B and T lymphoid tumours

The chromosome translocations characteristic of certain B lymphoid tumours associate the myc oncogene and immunoglobulin loci. The typical t(12;15) in murine plasmacytomas and analogous t(14;8) in Burkitt lymphomas couple the myc coding region to one of the switch recombination regions within the immunoglobulin heavy (H) chain locus; hence the switch machinery may promote some translocations. Significantly, translocation induces constitutive myc expression, the untranslocated myc allele remaining silent. The predilection for breakpoints near the 5' end of the c-myc gene may reflect selection for altered myc regulation. In most tumours, the stimulatory effect of the H locus context is not understood, but an H locus enhancer participates in some tumours, including one displaying a novel transposition. The variant (6;15) translocations found in about 15% of plasmacytomas involve the myc band and the region of chromosome 6 where the kappa locus lies. The t(6;15) is shown here to represent an exchange between C kappa and a chromosome 15 locus (designated pvt-1) which lies unexpectedly far from c-myc. The association of myc expression with pvt-1 alterations suggest that myc can be activated at a distance. Myc has also been implicated in some T lymphomas by detection of proviral inserts near myc and also, surprisingly, within the pvt-1 locus. Inserts near myc appear to activate its expression via the retroviral enhancer.     

Familial reciprocal translocation t(17;19) (q11.2;q13.2) associated with neurofibromatosis type 1, including one patient with non-Hodgkin lymphoma and an additional t(14;20) in B lymphocytes

The cosegregation of a reciprocal translocation t(17;19) (q11.2;13.2) with neurofibromatosis type 1 in three generations suggested that the breakpoint on chromosome 17 involved the NF1 gene. In order to map the breakpoint, we analysed DNAs of patients using parts of the NF1 gene as probes. Southern analysis revealed that the chromosome 17 breakpoint lies within intron 23 of the NF1 gene. One of the patients of the family developed a non-Hodgkin lymphoma. An additional translocation t(14;20) (q32;13.1) in his B lymphocytes points to a gene on chromosome 20 that is juxtaposed to the IGH locus on 14q32, and that may be of relevance for the development of this tumor type.     

Molecular analysis of a t(7;14)(q35;q32) chromosome translocation in a T cell leukemia of a patient with ataxia telangiectasia

Molecular analysis of somatic cell hybrids derived from T cells carrying a t(7;14)(q35;q32) chromosomal translocation from a patient with ataxia telangiectasia and T cell leukemia indicates that the breakpoint on chromosome 14 is proximal to the IgH locus and to the D14S1 locus, while the breakpoint on chromosome 7 involves the T cell receptor beta chain locus immediately 5' to J beta 1.5 on chromosome 7. The separation of V beta and C beta observed in somatic cell hybrids defined the orientation of the T cell receptor beta chain locus on chromosome 7 where the V beta genes are centromeric and the C beta genes are telomeric. A novel chromosomal alteration, undetected cytogenetically, was revealed as being an inversion with duplication of the distal band of chromosome 14q32. The importance of the 14q32 region in the leukemogenic process is discussed.     

Isolation of DNA markers from a region between incontinentia pigmenti 1 (IP1) X-chromosomal translocation breakpoints by a comparative PCR analysis of a radiation hybrid subclone mapping panel.

A strategy based on the use of human-specific interspersed repetitive sequence (IRS)-PCR amplification was used to isolate regional DNA markers in the vicinity of the incontinentia pigmenti 1 (IP1) locus. A radiation hybrid (RH) resulting from a fusion of an irradiated X-only somatic cell hybrid (C12D) and a thymidine kinase deficient (TK-) hamster cell line (a23) was identified as containing multiple X chromosome fragments, including DNA markers spanning IP1 X-chromosomal translocation breakpoints within region Xp11.21. From this RH, a panel of subclones was constructed and analyzed by IRS-PCR amplification to (a) identify subclones containing a reduced number of X chromosome fragments spanning the IP1 breakpoints and (b) construct a mapping panel to assist in identifying regional DNA markers in the vicinity of the IP1 locus. By using this strategy, we have isolated three different IRS-PCR amplification products that map to a region between IP1 X chromosome translocation breakpoints. A total of nine DNA sequences have now been mapped to this region; using these DNA markers for PFGE analyses, we obtained a probe order DXS14-DXS422-MTHFDL1-DXS705. These DNA markers provide a starting point for identifying overlapping genomic sequences spanning the IP1 translocation breakpoints; the availability of IP1 translocation breakpoints should assist the molecular analysis of this locus.     

The human T cell antigen Leu-2 (T8) is encoded on chromosome 2

Summary The locus encoding the human T lymphocyte cell surface antigen Leu-2 has been assigned to chromosome 2 with a DNA mapping panel derived from somatic cell hybrids. The two genomic components identified by a cDNA clone for Leu-2 segregated with human chromosome 2 in all 24 independent hybrid clones examined. The cosegregation of the Leu-2 and immunoglobulin kappa (IgK) loci in hybrids with spontaneous rearrangements of chromosome 2 is consistent with the possibility that the Leu-2 locus is on proximal human 2p near IgK. In the mouse, a locus for a T lymphocyte cell surface antigen with properties similar to Leu-2 is closely linked to the IgK locus on mouse chromosome 6. Hence the syntenic relationship of a gene implicated in T cell killing with the immunoglobulin kappa locus would then be conserved in the mouse and human genomes.     

Human T-cell tumours containing chromosome 14 inversion or translocation with breakpoints proximal to immunoglobulin joining regions at 14q32.

T-cell tumours are frequently found to carry an inversion of chromosome 14 (inv(14)) (q11;q32) or more rarely a chromosome 14 translocation t(14;14) with the same cytogenetic breakpoints (q11;q32). We have examined the molecular junctions of an inv(14) and a translocation t(14;14) using T-cell receptor (TCR) alpha joining (J) region probes. Both of these chromosomal abnormalities have breakpoints within the TCR J alpha locus at 14q11 and both have breakpoints which are proximal (i.e. on the centromeric side) to the immunoglobulin heavy chain JH region at 14q32. The cloned segments corresponding to the junctions at 14q32 are not associated with obvious immunoglobulin-like sequences. This contrasts to the previously described inv(14) in the cell line SUP-T1 and places a potential cluster of chromosome 14 breakpoints downstream of the Ig JH locus. The possible role of the varying breakpoints in the development of these tumours is discussed.     

(11; 14) translocation in three boys with acute lymphoblastic leukemia of T-cell immunophenotype

Three boys, 12, 15 and 5 years old are presented with acute lymphoblastic leukemia resp. Non-Hodgkin's lymphoma with leukemic transformation. Blast cells could be characterized as being of T-cell origin. Hand mirror variant was the predominant morphologic feature of the blast cells in two patients. Chromosome analysis of the leukemic blast cells revealed a pseudodiploid (modal chromosome number = 46) karyotype in two patients and a pseudotetraploid (modal chromosome number = 92) in one patient. A chromosome translocation (11; 14) with breakpoints at (p 13; q 13) (within the human T-cell receptor alpha chain locus!) was found in the leukemic cells of all three cases plus an additional t (7; 9) (q 22; p 13) in one patient.     

Integrative mapping of Gossypium hirsutum L. by meiotic fluorescent in situ hybridization of a tandemly repetitive sequence (B77)

We determined the relative positions of the tandem-repeat molecular cytogenetic marker B77, translocation breakpoints, and telosome arms in Gossypium hirsutum cytogenetic stocks by fluorescence in situ hybridization (FISH) analysis of meiotic quadrivalents in 16 single and 2 double translocation heterozygotes and five monotelodisomics. Results delimited the B77 FISH locus to the right arm of the D-subgenome chromosome 14 (14R) and the short arm (14sh), respectively. By equating 14R with 14sh and 14L (left) with 14Lo (long), the findings established a unified nomenclature for the arms of chromosome 14. Previously reported chromosome 14 arm locations were confirmed for four of the five translocations involving chromosome 14, namely NT1L-14L (2780), NT2R-14R (2B-1), NT14L-23R (2777), and NT14R-24R (2781), whereas the location of breakpoint T6L-14L was not confirmed and was reassigned to arm 14R. When used as a probe on Southern blots, the B77 signal was associated with a terminus of the D-subgenome RFLP linkage group (LG) D04 by linkage analysis of an interspecific F(2) population, now known to be chromosome 20. However, additional codominant DNA marker information in the affected region excluded the B77 polymorphism detected by Southern blot hybridization from chromosome 20 and, indeed, from the remainder of the genome.     

Unbalanced 1q whole-arm translocation resulting in der(14)t(1;14)(q11-12;p11) in myelodysplastic syndrome

Unbalanced whole-arm translocations (WATs) of the long arm of chromosome 1, resulting in complete trisomy 1q, are chromosomal abnormalities detectable in both solid tumors and hematologic neoplasms. Among the WATs of 1q to acrocentric chromosomes, a few patients with der(1;15) described as a dicentric chromosome have been reported so far, whereas cases of der(1;14) are much rarer. We report on a case of der(1;14) detected as single anomaly in a patient with myelodysplastic syndrome. The aim of our work was to investigate the breakpoints of the (1;14) translocation leading to the der(1;14). Fluorescence in situ hybridization (FISH) experiments have been performed on chromosome preparations from bone marrow aspirate, using specific centromeric probes of both chromosomes, as well as a probe mapping to 1q11 band. FISH results showed that in our patient the derivative chromosome was monocentric with a unique centromere derived from chromosome 14. The breakpoints of the translocation were located in the short arm of chromosome 14 and in the long arm of chromosome 1, between the alphoid D1Z5 and the satellite II domains. The 1q breakpoint was within the pericentromeric region of chromosome 1, which is notoriously an unstable chromosomal region, involved in different chromosomal rearrangements.     

The chromosome breakpoint at 14q32 in an ataxia telangiectasia t(14;14) T cell clone is different from the 14q32 breakpoint in Burkitts and an inv(14) T cell lymphoma

Summary The T cell receptor chain gene locus and the immunoglobulin heavy chain gene locus (IgH) have previously been mapped to the q11 and q32 positions respectively of the human chromosome 14. Both of these sites are also common breakpoints in lymphocytes from ataxia telangiectasia (A-T) patients. Using in situ hybridisation we show that the 14q32 breakpoint in an A-t non-leukaemic T cell clone with t(14;14) translocation, lies outside the IgH locus and proximal to it with respect to the centromere. The 14q11-14qter segment of the homologous chromosome 14 carrying the constant gene region of the chain locus is translocated to this 14q32 position.     

Immunohistochemical comparison of CD5, lambda,and kappa expression in primary and recurrent buccal Mucosa-associated lymphoid tissue (MALT) lymphomas

Mucosa-associated lymphoid tissue (MALT) lymphoma is a type of extranodal marginal zone B-cell lymphoma and is a distinct subtype of non-Hodgkin's lymphoma.Primary MALT lymphomas can also occur in the oral cavity, although their appearance in this location is rare. The neoplastic cells of which MALT lymphomas are composed express B-cell antigens and show monotypic immunoglobulin expression with light-chain restriction.Although neoplastic MALT lymphoma cells do not express CD5, previous studies have shown that CD5 positive MALT lymphomas are more prone to dissemination than those that do not express CD5. Moreover, there are some reports that describe kappa- and lambda- dual light chain expression in B cell malignant neoplasms.A 66-year-old Japanese woman with swelling of the right buccal mucosa was referred to our hospital. The lesion was excised and was pathologically diagnosed as a MALT lymphoma tumor with a t(11;18)(q21;q21) chromosome translocation.Swelling of the right buccal mucosa recurred 2 years later. The recurrent tumor was then excised and pathologically diagnosed as MALT lymphoma.Immunohistochemical examination of CD5, lambda, and kappa expressions revealed that the primary tumor was positive for CD5, kappa, and lambda, but the recurrent tumor was weakly positive for CD5 and kappa.With respect to lambda positivity, the recurrent tumor showed negativity.Our study suggests that immunohistochemical expression of CD5, kappa, and lambda in oral MALT lymphoma have the risk of recurrence.We first described the recurrence of CD5 positive MALT lymphoma in the oral cavity and compared the immunohistochemical expressions of CD5, lambda, and kappa between the primary and recurrent tumors.     

Cytogenetic and molecular analysis of an unbalanced translocation (X;7) (q28;p15) in a dysmorphic girl

Summary A severely retarded and dysmorphic girl, carrying an unbalanced X/7 translocation with breakpoints at Xq28 and 7p14, was analyzed by cytogenetic, biochemical and molecular techniques. The X/7 translocated chromosome was found to replicate consistently late in the 105 metaphases analyzed. In 83 of these cells, late replication was limited to the X portion of the abnormal chromosome, whereas in 22 cells incomplete spreading into the autosomal fragment was observed. Southern blot and in situ hybridization experiments with probe G80 (locus D7S373) (previously localized to 7p13–15) and G98 (localized to 7p14–15) assigns the former to 7p15 and the latter to 7p14, thus suggesting the order 7ter-G80-G98-cen. The activity of the enzyme phosphoserine phosphatase localized to 7pter p14 was increased. Southern blotting experiments with 19 probes spanning the entire X chromosome demonstrated that the translocated chromosome had lost a portion of Xq28 (locus DXS51) but still retained part of Xq27 (F9 locus). The results confirm that the proband is trisomic for the region 7p15-pter and monosomic for the region Xq28-qter. Comparing her phenotype with those of other cases of partial trisomy or monosomy 7p, we confirm that band 7p21 is probably involved in skull development.     

Localization of the rhabdomyosarcoma t(2;13) breakpoint on a physical map of chromosome 13.

Previous investigations of the pediatric soft tissue tumor alveolar rhabdomyosarcoma have identified a characteristic translocation t(2;13)(q35;q14). We have employed a physical mapping strategy to localize the site of this translocation breakpoint on chromosome 13. Using a panel of somatic cell hybrid and lymphoblast cell lines with deletions and unbalanced translocations involving chromosome 13, we have mapped numerous probes from the 13q12-q14 region and demonstrate that this region is divisible into five physical intervals. These probes were then mapped with respect to the t(2;13) rhabdomyosarcoma breakpoint by quantitative Southern blot analysis of an alveolar rhabdomyosarcoma cell line with two copies of the derivative chromosome 13 and one copy of the derivative chromosome 2. Our findings demonstrate that the t(2;13) breakpoint is localized within a map interval delimited by the proximal deletion breakpoints in lymphoblast lines GM01484 and GM07312. Furthermore, the breakpoint is most closely flanked by loci D13S29 and TUBBP2 within this map interval. These findings will facilitate chromosomal walking strategies for cloning the regions disrupted by the alveolar rhabdomyosarcoma translocation. In addition, this physical map will permit rapid determination of the proximity of new cloned sequences to the translocation breakpoint.     

Translocation (X;13)(p11.21;q12.3) in a girl with incontinentia pigmenti and bilateral retinoblastoma

A de novo t(X;13)(p11.21;q12.3) translocation is described in an 19-month-old girl with incontinentia pigmenti (IP) and bilateral retinoblastoma. Based on previously reported two girls and this patient, each with a structural X chromosome abnormality and IP, it was assumed that the locus for IP is at Xp11.21. Q-banding analysis revealed that the translocated chromosomes were of paternal origin. The derivative X chromosome was late-replicating in 9% of cultured peripheral blood lymphocytes and in 1% of skin fibroblasts. The erythrocyte esterase D activity in the patient was normal. Several possibilities were considered for possible causative relationship between the X/13 translocation and the development of retinoblastoma. One possibility involved functional monosomy of 13q14 in a minority of retinoblasts due to the spreading of inactivation of the translocated X chromosome segment.