Variant Philadelphia translocations in chronic myeloid leukemia

Up to the beginning of 1986, some 327 variant Philadelphia translocations were reported in chronic myeloid leukemia. The present study represents an attempt to determine which factors (sex, age, geographic localization, etc.) influence the occurrence and chromosome involvement of these variant Philadelphia (Ph1) translocations. Clinical data indicated that band 9q34 was always rearranged in the variant Ph1 translocations and no difference existed between the hematologic and prognostic features among patients with the standard and the variant translocations. An uneven geographic distribution of the variant Ph1 translocations was found. Whether this was due to populations with different ethnic backgrounds or to environmental factors could not be determined. Twenty-eight bands were shown to be rearranged more frequently than expected (P less than 0.05); 27 of them are known to contain a fragile site and/or an oncogene and/or are rearranged more frequently than expected in other malignancies. The chromosomes involved in these variant Ph1 translocations were found to show a very particular geographic distribution, which cannot be explained at present.     

A Case of ABL-BCR Negative, Philadelphia Positive CML with t(5;9)(q13;q34)

The Philadelphia chromosome is found in more than 90 percent of chronic myeloid leukemia (CML) patients. In most cases, it results from the reciprocal t(9;22)(q34;q11), with the ABL proto-oncogene from 9q34 fused to the breakpoint cluster region (BCR) locus on 22q11. In 5 to 10 percent of patients with CML, the Ph originates from variant translocations, involving various breakpoints in addition to 9q34 and 22q11. Here we report a rare case of a Philadelphia positive CML patient carrying t(5;9)(q13;q34) and deletion of ABL/BCR on der(9) as a separate event.     

Patterns of BCR/ABL Gene Rearrangements in Chronic Myeloid Leukemia with Complex t(9;22) Using Fluorescence In Situ Hybridization (FISH)

Chronic myeloid leukemia (CML) is characterized by the reciprocal translocation t(9;22)(q34;q11.2) which fuses the ABL1 oncogene on chromosome 9 with the BCR gene on chromosome 22. It is the BCR/ABL protein that drives the neoplasm and the ABL/BCR is not necessary for the disease. In the majority of CML cases, the BCR/ABL fusion gene is cytogenetically recognizable as a small derivative chromosome 22(der 22), which is known as the Philadelphia (Ph) chromosome. However, approximately 2-10% of patients with CML involve cryptic or complex variant translocations with deletions on the der(9) and/or der(22) occuring in roughly 10-15% of CML cases. Fluorescence in situ hybridization (FISH) analysis can help identify deletions and complex or cryptic rearrangements. Various BCR/ABL FISH probes are available, which include dual color single fusion, dual color extra signal (ES), dual color dual fusion and tri color dual fusion probes. To test the utility of these probes, six patients diagnosed with CML carrying different complex variant Ph translocations were studied by G-banding and FISH analysis using the BCR/ABL ES, BCR/ABL dual color dual fusion, and BCR/ABL tricolor probes. There are differences among the probes in their ability to detect variant rearrangements, with or without accompanying chromoso me 9 and/or 22 deletions, and low level disease.     

Aberrant breakpoints in chronic myelogenous leukaemia; oncogenes and fragile sites

Summary Three hundred and twenty-five aberrant breakpoints in chronic myelogenous leukaemia (CML) with Philadelphia chromosome variant were reviewed. Eight chromosomal bands (3p21, 6p21, 7p22, 11q13, 12p13, 17p13, 17q21, and 17q25) were found to be highly involved. Apart from 17q25, all these bands correspond to oncogenes sites and/or sites involved as primary breakpoints in cancer.This work was presented in part at the Congrès National d'Hématologie et de Transfusion Sanguine, March 1985 (Nouv Rev Fr Hématol, 1985, 27:72) and at the American Association for Cancer Research Meeting (Proceeding of the AACR 1986, 27:148)     

Nonrandom distribution of exchange points in patients with structural rearrangements

High resolution studies of structural rearrangements were carried out using the G-band technique. A total of 220 breakage points were identified within individual bands from 117 unrelated cases born with a structural rearrangement. Breakage points were not evenly distributed along chromosomes in terms of G-band patterns. There was an excess involvement of light bands and a striking lack of dark bands in both reciprocal translocations and inversions. In reciprocal translocations, the middle part of a chromosome arm has less chance of being the site of an exchange than the terminal and centromeric parts. The implications of these results are briefly discussed.     

Constitutional Robertsonian T(15;22) in Ph-positive CML

Summary Chromosome studies in a phenotypically normal 40-year-old man with Philadelphia (Ph) chromosome-positive chronic myelocytic leukemia (CML) and a constitutional Robertsonian translocation are reported. The possibility of carriers of Robertsonian translocations having an increased risk to develop Ph-positive CML is mentioned.     

T-lymphocytes with 7;14 translocations: frequency of occurrence, breakpoints, and clinical and biological significance.

Among 11,915 consecutive patients and 37 normal controls who had chromosome analysis at the Mayo Clinic between 1978 and 1984, 83 had a single sporadic metaphase with a 7;14 translocation. In 81 of the translocations, the breakpoints were at 14q11 and either 7q34 (type I) or 7p13 (type II): type I translocations occurred in 42 patients, and type II, in 39. The two other translocations had different breakpoints: one was t(7;14)(q11;q32), and the other was t(7;14)(p13;q32). All type I and type II translocations occurred in phytohemagglutinin-stimulated lymphocyte cultures; their combined incidence was 4.88 X 10(-4) per metaphase (81 of 165,991 metaphases) in such cultures. No type I or II translocation was found among 6,713 fibroblast metaphases, 33,463 amniocyte metaphases, or 68,972 bone marrow and unstimulated peripheral blood metaphases. One variant 7;14 translocation occurred in a phytohemagglutinin-stimulated culture, and the other occurred in a fibroblast culture. We did not find a correlation of sporadic 7;14 translocations with any month or season of the year or with patient age or sex. Of the 83 patients, 78 had various clinical disorders, three had ataxia-telangiectasia, one was a normal control, and one was an artificial insemination donor. Follow-up studies on 64 (77%) patients indicate that, to date, none have developed any malignant process subsequent to chromosome analysis. Except for ataxia-telangiectasia, the occurrence of types I and II translocations in lymphocyte cultures may have little, if any, clinical significance. The biological significance of these translocations may be the association of genes in chromosome bands 14q11, 7p13, and 7q34 with the normal physiology of lymphocytes such as the alpha- and beta-chains for T-cell antigen receptor.     

Analysis of spreading of inactivation in eight X autosome translocations utilizing the high resolution RBG technique

Summary Eight X autosome translocations were studied with replication banding to localize spreading of late replication into the autosomal segments. Partial spreading into the autosomal segment was seen in four translocations and no spreading of late replication was seen in four translocations. In those translocations with partial spreading of late replication into the autosomal segment, late replication did not always spread continuously from the X chromosome breakpoint throughout the autosome. Instead, it appeared to skip some bands and affect others. The data on the pattern of replication, taken to indicate also a spread of inactivation into these autosomal segments, correlated well with the clinical data in most cases and suggest that spreading of late replication is often incomplete and may be discontinuous.     

Trisomy 21 Down syndrome

Summary In a series of 374 families with Down syndrome progeny, structural chromosome rearrangements were detected in the parents of six children with regular trisomy. The aberrations were reciprocal translocations and inversions. In all three informative families, the parent who transmitted the extra chromosome was not the one with the structural rearrangement. Among the three non-informative families there was one in which both parents carried different reciprocal translocations. In two other families a chromosome aberration was detected: a triple X mother and a father with a Philadelphia chromosome. Omitting the four parents with possible biased asccrtainment, 0.4% had a chromosome rearrangement. When the parents with constitutional chromosome aberrations and those with mosaicism, described previously, are combined, the frequency of chromosomally abnormal parents lies between 1.9% and 3.2%. When correlated with parental transmission of the extra chromosome, mosaicism rather than structural rearrangements appears to be of ctiologic significance.     

Variations in chromosome size and organization in Candida albicans and Candida stellatoidea

Candida albicans and the closely related species Candida stellatoidea are medically important diploid asexual yeasts. Clinical isolates frequently show variant electrophoretic karyotypes, apparently due largely to chromosomal translocations. These translocations seem to occur at hot spots characterized by the repeated DNA sequence RSP1. A programmed karyotypic rearrangement occurs in C. stellatoidea. Karyotypic rearrangement may serve as a source of genetic variation in these asexual yeasts.     

Chromosomal abnormalities in lymphoid tumours: mechanism and role in tumour pathogenesis

Chromosomal abnormalities have been the focus of study recently, after the discovery of oncogenes at the junctions of translocations in Burkitt's lymphoma and the Philadelphia chromosome in chronic myelogenous leukaemia. Can these findings be extrapolated to other, less consistently occurring abnormalities? To analyse this question, we specifically discuss chromosomal abnormalities involving the human T-cell receptor δ/α locus. We discuss the mechanism for the formation of these chromosomal aberrations, and their possible significance for the pathogenesis of T-cell tumours. Current evidence suggests that some of these aberrations are involved in tumour pathogenesis while others are not.     

Regional mapping of two human immunoglobulin V lambda genes and analysis of the V lambda locus in chronic myeloid leukaemia.

The human immunoglobulin V lambda locus has been studied in relation to chromosomal translocations involving chromosome 22. DNA probes for two V lambda genes which belong to different subgroups and do not cross hybridize, were used to show that both V lambda genes are located on the Philadelphia chromosome in chronic myeloid leukaemia (CML). Both genes map in band 22q11 to a region that is bounded on the distal side by the breakpoints for CML 9:22 translocations and on the proximal side by the breakpoint for an X:22 translocation. We have found no evidence for rearrangements or amplification of either V lambda gene in CML, in either the chronic or acute phases of the disease. In K562 cells which are derived from the pleural effusion of a patient with Ph1-positive CML, there appears to be no rearrangement of the V lambda genes, but they are both amplified about four times. We have estimated that the minimum size for the amplification unit in K562 cells is 186 kb.     

Translocations and other karyotypic structural changes in wheat x rye hybrids regenerated from tissue culture

Summary The spontaneous occurrence of chromosome breaks, deletions, and translocations in plant tissue cultures is well documented. This study investigated the usefulness of tissue culture as a method of introgressing alien genes into wheat. Wheat X rye hybrids were regenerated from embryo scutellar calli maintained in culture for 222 days. The regenerated seedlings then were treated with colchicine to produce amphidiploids (AABBDDRR). The karyotypes of ten amphidiploids were analyzed by C-banding to determine chromosome structural changes that occurred during tissue culture. Three wheat/rye and one wheat/wheat chromosome translocations, seven deletions, and five amplifications of heterochromatin bands of rye chromosomes were identified. One amphidiploid contained a reciprocal translocation between wheat chromosome 4D and rye chromosome 1R. Non-reciprocal translocations between 2B and 3R, and between an unidentified wheat chromosome and 2R, were found independently in two amphidiploids. An additional plant had a translocation between wheat chromosomes 6B and 5A. All deletions involving rye chromosomes were noted in all 10 amphidiploids. Twelve of the 13 breakpoints in chromosomes involved in translocations and deletions occurred in heterochromatin. Amplification of heterochromatin bands on 2RL and 7RL chromosome arms also was observed in five plants. These results indicate a high degree of chromosome structural change induced by tissue culture. Therefore, tissue culture may be a useful tool in alien gene introgression and manipulation of heterochromatin in triticale improvement.Contribution No. 84-188-J, Kansas Agricultural Experiment Station, Kansas State University. Research was supported by the Science and Education Administration of the U.S. Department of Agriculture under Grant No. 59-2201-1-1-639-0 from Competitive Research Grants Office to R.G.S.     

De novo balanced chromosome rearrangements and extra marker chromosomes identified at prenatal diagnosis: clinical significance and distribution of breakpoints.

A questionnaire sent to major cytogenetics laboratories in the United States and Canada over a 10-year period collected data on the frequency and outcome of cases with either apparently balanced de novo rearrangements or de novo supernumerary marker chromosomes detected at amniocentesis. Of 377,357 reported amniocenteses, approximately 1/2,000 had a de novo reciprocal translocation, 1/9,000 a Robertsonian translocation, 1/10,000 a de novo inversion, and 1/2,500 an extra structurally abnormal chromosome of unidentifiable origin. The risk of a serious congenital anomaly was estimated to be 6.1% (n = 163) for de novo reciprocal translocations, 3.7% (n = 51) for Robertsonian translocations, and 9.4% (n = 32) for inversions. The combined risk for reciprocal translocations and inversions was 6.7% (95% confidence limits 3.1%-10.3%). The risk of abnormality for extra nonsatellited marker chromosomes was 14.7% (n = 68), and that for satellited marker chromosomes was 10.9% (n = 55). In non-Robertsonian rearrangements, distribution of breakpoints among chromosomes was not as would be expected strictly on the basis of length. Most breaks were stated to occur within G-negative bands, but there was little evidence of particular hot spots among these bands. Nevertheless, there did appear to be a correlation between those bands in which breakage was observed most often and those bands where common or rare fragile sites have been described.     

DNA profiling of cattle using micro- and minisatellite core probes

We have evaluated 15 different micro- and minisatellite core probes for use in identity and paternity testing in cattle, based on Southern blot hybridization analysis. The core probes were tested in animals of different breeds and by analysis of seven two-generation pedigrees. Of the 15 core probes tested, seven were able to detect on average seven variant bands per individual animal. Segregation analysis showed that on average two out of 3 6 variant bands scored per core probe were genetically linked while two out of 12 variant bands correspond to the same allelic pair. The results obtained demonstrate the effectiveness of multilocus core probes for determining identity and paternity in cattle.     

ABL/BCR gene variant with two-step mechanism: Unusual localization and rare/novel chromosomal rearrangements in CML patients

Aims: Variant translocations involving 9q, 22q and at least one additional genomic locus occur in 5-10% of the patients with chronic myeloid leukemia (CML). The mechanisms for the formation of these variant translocations are not fully characterized. Here we report CML cases presenting a variant translocation indicating two-step mechanism with rare/novel chromosomal rearrangement. Methods: Karyotype analysis was performed on metaphases obtained through short-term cultures of bone marrow and blood. Detection of BCR-ABL fusion gene was performed using dual-color dual-fusion (D-FISH) and extra signal (ES) translocation probes. BAC-FISH was also carried out. Results: In Patient 1, the third partner chromosome was der(11)(p15) with a 2F2G1R signal pattern, which is an unusual signal pattern with the two-step mechanism. Patients 2 and 3 showed typical positive (2F1G1R) signal pattern. In Patient 2, both the chromosome 22s were involved in variant formation. The second fusion was observed below the BCR gene of the second homologue. In Patient 3 the third chromosome was der(13)(q14). The fourth patient showed a variant pattern with BCR/ABL-ES probe involving der(X)(q13) region. Conclusion: The presence of different rearrangements of both 9q34 and 22q11 regions highlights the genetic heterogeneity of this subgroup of CML. In each case with variants, further studies with FISH, BAC-FISH or more advanced technique such as microarray should be performed. Future studies should be performed to confirm the presence of true breakpoint hot spots and assess their implications in CML with variant Ph.     

The Distribution and Spreading of Rare Variants in the Histone Multigene Family of Drosophila Melanogaster

We surveyed the distribution of rare variant restriction sites within and among histone gene arrays of Drosophila melanogaster using restriction fragment length polymorphism (RFLP) analysis. Seventy-three naturally occurring arrays were digested with restriction enzymes that had no recognition sites in the published histone sequence. Of the arrays surveyed, 68.5% had at least two nonconsensus restriction sites present as indicated by the presence of a small band or bands on the autoradiographs. These bands were almost always the length of a single repeat in the histone multigene family or a multiple of this length. In arrays with more than one band, intensity of the bands almost always decreased with increasing size. This shows that within these arrays variant restriction sites were predominantly located on adjacent repeats. If these bands are caused by spreading of variant sites, as is most likely, then variants spread along the array as an inverse function of distance. Overall, if a sequence spread it had a 92% probability of ending up in its nearest neighbor. This pattern may result from the noncontiguous nature of the histone family.     

Structural studies on individual components of bovine transferrin

The single-banding components of bovine transferrin from animals homozygous for the four transferrin variants found in the U.K. were isolated. Sedimentation equilibrium ultracentrifugation and sodium dodecyl sulphate-polyacrylamide-gel electrophoresis showed that the bands of a single variant have molecular weights of 77500 and 73300 respectively. The different bands of a single variant and single bands of different variants show no evidence of size heterogeneity or of low-molecular-weight peptides being split off after reduction in 6m-guanidine hydrochloride. The two slower bands of a single variant, which both contain 2 molecules of sialic acid/molecule of protein, have the same molecular weight and amino acid composition, and give identical peptide ;maps', although differences in composition and peptide ;maps' occur between the different variants. The results support the concept that bovine transferrin is essentially a single polypeptide chain, but they do not explain differences in electrophoretic mobility between bands of the same variant which are not produced by differing sialic acid content.     

Chronology of the replication of sex chromosome bands in lymphocytes of normal subjects and patients]

The replication sequence of the bands carried by chromosomes X and Y has been studied in normal individuals and in patients with structural abnormalities of the X. By comparing the segment with that of the autosomal bands (which had been previously studied), it was shown that the normal early X replicates in early X-phase for its R-bands and in late S-phase for its Q bands. The late X replicates entirely in late S-phase, and the sequence of band replication is not as stringent as for the early X and the autosomes. The study of fourteen cases of anomalies of chromosome X in females showed the following: in balanced reciprocal X-autosome translocations the rearranged X most often replicates early and the normal X late. Both show a normal replication sequence of their bands. In non-balanced X-autosome translocations, inactivation of the autosome fragment attached to the AUTOSOME FRAGMENT ATTACHED TO THE X may take place. In Xq- or in ter rea (X;X) (pter;pter), band p22 has a delayed replication. In iso-Xor Xp-, the long-arm-band sequence of replication shows a variation comparable to that of the late X in fibroblasts. These replication modifications are likely to induce partial inactivations or changes in activity which correspond to the so-called position effect in Drosophila.     

Rearrangements of chromosome 9 in different hematological neoplasias

In the present article the frequency of anomalies in chromosome 9 among children with hematological neoplasias amounted to 25/112 in acute lymphoblastic leukemia (ALL), 10/83 in acute myeloid leukemia (AML), and 3/20 in myelodysplastic syndrome (MDS). In ALL, deletions are encountered more often than translocations. Deletions are found in both single anomalies and as an element in complex karyotypes. The rearrangements involve the bands 9q34 and 9q22 the most often. The translocation t(9;22)(q34; q11) is encountered in 7.1% of all cases of ALL. In AML, translocation are found more often than deletions. Structural rearrangements most often involved the long arm, at bands 9q22 and 9q34. Deletions, duplications, and translocations were recorded in MDS. No relationship with the initial hematological indicators, including blastosis, were found. The studies attest to different directions of the clinical prognosis in the course of acute leukemia (AL) where there are deletions. Multidrug resistance and the continuing progress of the disease in the course of chemotherapy is found in t(9;22)(q34; q11).