In this study, we investigated the mitotic and meiotic chromosomes of 11 Buthidae scorpion species, belonging to three genera (Ananteris, Rhopalurus and Tityus), to obtain detailed knowledge regarding the mechanisms underlying the intraspecific and/or interspecific diversity of chromosome number and the origin of the complex chromosome associations observed during meiosis. The chromosomes of all species did not exhibit a localised centromere region and presented synaptic and achiasmatic behaviour during meiosis I. Spermatogonial and/or oogonial metaphase cells of these buthids showed diploid numbers range from 2n = 6 to 2n = 28. In most species, multivalent chromosome associations were observed in pachytene and postpachytene nuclei. Moreover, intraspecific variability associated with the presence or absence of chromosome chains and the number of chromosomes in the complex meiotic configurations was observed in some species of these three genera. Silver-impregnated cells revealed that the number and location of nucleolar organiser regions (NORs) remained unchanged despite extensive chromosome variation; notably, two NORs located on the terminal or subterminal chromosome regions were commonly observed for all species. C-banded and fluorochrome-stained cells showed that species with conspicuous blocks of heterochromatin exhibited the lowest rate of chromosomal rearrangement. Based on the investigation of mitotic and meiotic cells...
Extensive chromosome size polymorphism in Plasmodium berghei in vivo mitotic multiplication. Size differences between homologous chromosomes mainly involve rearrangements in the subtelomeric regions while internal chromosomal regions are more conserved. Size differences are almost exclusively due to differences in the copy number of a 2.3 kb subtelomeric repeat unit. Not only deletion of 2.3 kb repeats occurs, but addition of new copies of this repeat sometimes results in the formation of enlarged chromosomes. Even chromosomes which originally lack 2.3 kb repeats, can acquire these during mitotic multiplication. In one karyotype mutant, 2.3 kb repeats were inserted within one of the original telomeres of chromosome 4, creating an internal stretch oftelomeric repeats. Chromosome translocation can contribute to chromosome size polymorphism as well We found a karyotype mutant in which chromosome 7 with a size of about 1.4 Mb is translocated to chromosome 13/14 with a size of about 3 Mb, resulting in a rearranged chromosome, which was shown to contain a junction between internal DNA sequences of chromosome 13/14 and subtelomeric 2.3 kb repeats of chromosome 7. In this mutant a new chromosome of 1.4 Mb is present which consists of part of chromosome 13/14.
A patient with a typical form of chronic myeloid leukemia was found to carry a large deletion on the derivative chromosome 9q+ and an unusual BCR-ABL transcript characterized by the insertion, between BCR exon 14 and ABL exon 2, of 126 bp derived from a region located on chromosome 9, 1.4 Mb 5′ to ABL. This sequence was contained in the bacterial artificial chromosome RP11-65J3, which in fluorescence in situ hybridization experiments on normal metaphases was found to detect, in addition to the predicted clear signal at 9q34, a faint but distinct signal at 22q11.2, where the BCR gene is located, suggesting the presence of a large region of homology between the two chromosomal regions. Indeed, blast analysis of the RP11-65J3 sequence against the entire human genome revealed the presence of a stretch of homology, about 76 kb long, located approximately 150 kb 3′ to the BCR gene, and containing the 126-bp insertion sequence. Evolutionary studies using fluorescence in situ hybridization identified the region as a duplicon, which transposed from the region orthologous to human 9q34 to chromosome 22 after the divergence of orangutan from the human-chimpanzee-gorilla common ancestor about 14 million years ago. Recent sequence analyses have disclosed an unpredicted extensive segmental duplication of our genome...
The T-cell receptor (TCR) alpha/delta chain locus on chromosome 14q11 is nonrandomly involved in translocations and inversions in human T-cell neoplasms. We have analyzed three acute T-lymphoblastic leukemia samples carrying a t(10;14)(q24;q11) chromosome translocation by means of somatic cell hybrids and molecular cloning. In all cases studied the translocation splits the TCR delta chain locus. Somatic cell hybrids containing the human 10q+ chromosome resulting from the translocation retain the human terminal deoxynucleotidyltransferase gene mapped at 10q23-q24 and the diversity and joining, D delta 2-J delta 1, regions of the TCR delta chain, but not the V alpha region (variable region of the TCR alpha chain), demonstrating that the split occurred within the V alpha-D delta 2 region. Molecular cloning of the breakpoint junctions revealed that the TCR delta chain sequences involved are made from the D delta 2 segment. The chromosome breakpoints are clustered within a region of approximately 263 base pairs of chromosome 10. The results suggest that the translocation of the TCR delta chain locus to a locus on 10q, which we have designated TCL3, results in deregulation of this putative oncogene, leading to acute T-cell leukemia.
Human leukemic T cells carrying a t(10;14)(q24;q11) chromosome translocation were fused with mouse leukemic T cells, and the hybrids were examined for genetic markers of human chromosomes 10 and 14. Hybrids containing the human 10q+ chromosome had the human genes for terminal deoxynucleotidyltransferase that has been mapped at 10q23-q25 and for C alpha [the constant region of TCRA (the alpha-chain locus of the T-cell antigen receptor gene)], but not for V alpha (the variable region of TCRA). Hybrids containing the human 14q- chromosome retained the V alpha genes. Thus the 14q11 breakpoint in the t(10;14) chromosome translocation directly involves TCRA, splitting the locus in a region between the V alpha and the C alpha genes. These results suggest that the translocation of the C alpha locus to a putative cellular protooncogene located proximal to the breakpoint at 10q24, for which we propose the name TCL3, results in its deregulation, leading to T-cell leukemia. Since hybrids with the 10q+ chromosome also retained the human terminal deoxynucleotidyltransferase gene, it is further concluded that the terminal deoxynucleotidyltransferase locus is proximal to the TCL3 gene, at band 10q23-q24.
We describe a chromosome translocation in a karyotype mutant of the rodent malarial parasite Plasmodium berghei. In this mutant (named EP) a small chromosome (chromosome 7), which has exhibited a size range between 0.9 and 1.4 Mb in other clones of P. berghei, is translocated to chromosome 13 or 14 with a size of about 3 Mb. By comparison of Apa-I restriction fragments of the chromosomes from mutant EP and from a reference clone (named HP) of P. berghei, we found evidence for a junction of subtelomeric chromosome 7 sequences and internal chromosome 13/14 sequences. In addition, a new chromosome of 1.4 Mb (named EP7) is present in mutant EP, which is (mainly) composed of sequences of chromosome 13/14. EP7 contains one telomeric region derived from chromosome 13/14. We found evidence that internal sequences of chromosome 13/14 are joined to telomeric sequences in the other telomeric region of EP7. The karyotype of mutant EP was stable during asexual and sexual multiplication and we found no indications for phenotypic changes.
Somatic cell hybrids have been constructed between a thymidine kinase-deficient mouse cell line and blood leukocytes from a patient with acute promyelocytic leukemia showing the 15q+;17q- chromosome translocation frequently associated with this disease. One hybrid contains the 15q+ translocation chromosome and very little other human material. We have shown that the c-fes oncogene, which has been mapped to chromosome 15, is not present in this hybrid and, therefore, probably is translocated to the 17q- chromosome. Analysis of the genetic markers present in this hybrid has enabled a more precise localization of the translocation breakpoints on chromosomes 15 and 17. Our experiments also have enabled an ordering and more precise mapping of several genetic markers on chromosomes 15 and 17.
We have established a cell line, which we named 380, from a young male with acute lymphoblastic leukemia (FAB type L2). Karyologic analysis of this cell line indicates that it carries an 8;14 and a 14;18 chromosome translocation, which are characteristic of Burkitt lymphoma and of follicular lymphoma, respectively. This cell line is Epstein-Barr virus antigen-negative, reacts with monoclonal antibodies specific for B cells, and contains rearranged immunoglobulin heavy and light chain genes, but does not express human immunoglobulins. In this cell line, both mu heavy chain constant (C mu) loci are rearranged within the joining (JH) DNA segment. One of the JH segments on one of the 14q+ chromosomes is rearranged with a segment of chromosome 8, where the c-myc oncogene resides, while the other is rearranged with a segment of chromosome 18 where a putative oncogene, which we have called bcl-2, is located. The c-myc oncogene, which is translocated to one of the 14q+ chromosomes, is in its germ-line configuration more than 14 kilobases away from both the JH segment and the heavy chain enhancer that is located between the JH and mu switch region. Based on these findings, we propose a model of some aspects of B-cell oncogenesis according to which B-cell neoplasms carrying translocations involving the heavy chain loci on both human chromosomes 14 are the result of a multiple step process.
In many mouse plasmacytomas, the active c-myc gene has been truncated by chromosome translocation with the resultant severance of the protein-coding sequence from the normal promoter. Transcripts of such truncated c-myc genes were analyzed by Northern blotting, nuclease S1 mapping, primer extension assays and cDNA cloning. We conclude that transcription originates from multiple initiation sites on both c-myc coding and non-coding strands with the two-sets of transcripts derived from adjacent but essentially non-overlapping regions located greater than 1 kb from the translocation junction. In X63Ag8, where c-myc is translocated to the immunoglobulin C gamma 2b gene, the c-myc non-coding strand transcripts include the translocation junction and then splice directly into the gamma 2b CH1 exon. We propose that chromosome translocation activates a cryptic promoter in the first intron and that the heterogeneously initiated, bipolar transcription reflects the absence of a suitably placed TATA box element.
Cytogenetic analysis was carried out on peripheral blood cultures from seven patients with acute promyelocytic leukaemia (APL-M3). A reciprocal 15;17 chromosome translocation, t(15q+;17q-), was found in all cases, and the breakpoints estimated to be 15q22 and 17q12-21. In addition to the t(15q+;17q-), trisomy 10 was found in 50% of cells analysed in one case. These results suggest that the 15;17 chromosome translocation may be observed in most cases of APL where the leukaemic cells are cultured before cytogenetic analysis is performed. The use of conditioned media in the culture of leukaemic cells is also described.
In prokaryotes, the transfer of DNA between cellular compartments is essential for the segregation and exchange of genetic material. SpoIIIE and FtsK are AAA+ ATPases responsible for intercompartmental chromosome translocation in bacteria. Despite functional and sequence similarities, these motors were proposed to use drastically different mechanisms: SpoIIIE was suggested to be a unidirectional DNA transporter that exports DNA from the compartment in which it assembles, whereas FtsK was shown to establish translocation directionality by interacting with highly skewed chromosomal sequences. Here we use a combination of single-molecule, bioinformatics and in vivo fluorescence methodologies to study the properties of DNA translocation by SpoIIIE in vitro and in vivo. These data allow us to propose a sequence-directed DNA exporter model that reconciles previously proposed models for SpoIIIE and FtsK, constituting a unified model for directional DNA transport by the SpoIIIE/FtsK family of AAA+ ring ATPases.
More than 50% of adult patients with acute myeloid leukemia (AML) carry chromosome abnormalities, like t(8;21)(q22;q22), t(15;17), t(8;21)inv(16) or t(16;16). t(10;17) translocation was very rare in AML. There are only 10 such cases reported in the literature. Here, we describe a case of acute myeloid leukemia with t(10;17)(p13;q12) chromosome translocation, who had complete remission after one course of chemotherapy.
Many recurrent chromosome translocations in cancer result in the generation of fusion genes that are directly implicated in the tumorigenic process. Precise modeling of the effects of cancer fusion genes in mice has been inaccurate, as constructs of fusion genes often completely or partially lack the correct regulatory sequences. The reciprocal t(2;13)(q36.1;q14.1) in human alveolar rhabdomyosarcoma (A-RMS) creates a pathognomonic PAX3-FOXO1 fusion gene. In vivo mimicking of this translocation in mice is complicated by the fact that Pax3 and Foxo1 are in opposite orientation on their respective chromosomes, precluding formation of a functional Pax3-Foxo1 fusion via a simple translocation. To circumvent this problem, we irreversibly inverted the orientation of a 4.9 Mb syntenic fragment on chromosome 3, encompassing Foxo1, by using Cre-mediated recombination of two pairs of unrelated oppositely oriented LoxP sites situated at the borders of the syntenic region. We tested if spatial proximity of the Pax3 and Foxo1 loci in myoblasts of mice homozygous for the inversion facilitated Pax3-Foxo1 fusion gene formation upon induction of targeted CRISPR-Cas9 nuclease-induced DNA double strand breaks in Pax3 and Foxo1. Fluorescent in situ hybridization indicated that fore limb myoblasts show a higher frequency of Pax3/Foxo1 co-localization than hind limb myoblasts. Indeed...
High temperature (HT, heat) stress is detrimental to wheat (Triticum aestivum L.) production. Wild relatives of bread wheat may offer sources of HT stress tolerance genes because they grow in stressed habitats. Wheat chromosome translocation lines, produced by introgressing small segments of chromosome from wild relatives to bread wheat, were evaluated for tolerance to HT stress during the grain filling stage. Sixteen translocation lines and four wheat cultivars were grown at optimum temperature (OT) of 22/14°C (day/night). Ten days after anthesis, half of the plants were exposed to HT stress of 34/26°C for 16 d, and other half remained at OT. Results showed that HT stress decreased grain yield by 43% compared with OT. Decrease in individual grain weight (by 44%) was the main reason for yield decline at HT. High temperature stress had adverse effects on leaf chlorophyll content and Fv/Fm; and a significant decrease in Fv/Fm was associated with a decline in individual grain weight. Based on the heat response (heat susceptibility indices, HSIs) of physiological and yield traits to each other and to yield HSI, TA5594, TA5617, and TA5088 were highly tolerant and TA5637 and TA5640 were highly susceptible to HT stress. Our results suggest that change in Fv/Fm is a highly useful trait in screening genotypes for HT stress tolerance. This study showed that there is genetic variability among wheat chromosome translocation lines for HT stress tolerance at the grain filling stage and we suggest further screening of a larger set of translocation lines.
Faithful chromosome segregation is essential for all living organisms. Bacterial chromosome segregation utilizes highly conserved directional SpoIIIE/FtsK translocases to move large DNA molecules between spatially separated compartments. These translocases employ an accessory DNA-interacting domain (gamma) that dictates the direction of DNA transport by recognizing specific DNA sequences. To date it remains unclear how these translocases use DNA sequence information as a trigger to expend chemical energy (ATP turnover) and thereby power mechanical work (DNA movement). In this thesis, I undertook a mechanistic study of directional DNA movement by SpoIIIE from the Gram-positive model bacterium Bacillus subtilis. Specifically, I was interested in understanding the information transfer within the protein from sequence recognition, to ATP turnover, and ultimately to chromosome translocation. How do DNA sequences trigger directional chromosome movement?
Although exceptions may be readily identified, two
generalizations concerning genetic differences among species may
be drawn from the available allozyme and chromosome data.
First, structural gene differences among species vary widely.
In many cases, species pairs do not differ more than intraspecific
populations. This suggests that either very few or no gene substitutions
are required to produce barriers to reproduction
(Avise 1976). Second, chromosome form and/or number differs
among even closely related species (White 1963; 1978; Fredga 1977;
Wright 1970). Many of the observed chromosomal differences involve
translocational rearrangements; these produce severe fitness depression
in heterozygotes and were, thus, long considered unlikely candidates
for the fixation required of genetic changes leading to
speciation (Wright 1977). Nonetheless, the fact that species
differences are frequently translocational argues convincingly
for their fixation despite prejudices to the contrary.
Haldane's rule states that in the F of interspecific crosses,
the heterogametic sex is absent or sterile in the preponderance
of cases (Haldane 1932). This rule definitely applies in the genus
Dr°sophila (Ehrman 1962). Sex chromosome translocations do
not impose a fitness depression as severe as that imposed by autosomal
The 15;12 chromosome translocation in murine plasmacytomas and the 8;14 in human Burkitt lymphomas often link the cellular myc oncogene to the locus for constant regions of immunoglobulin heavy chains (CH locus). To clarify how and why c-myc translocation occurs, we have sequenced the mouse and human c-myc genes and correlated c-myc transcription with c-myc rearrangement. Both genes comprise three exons; the second and third encode the myc polypeptide, which is conserved between mammals and birds, particularly in its more basic C-terminal half. Southern blots showed that four of 12 Burkitt lines have c-myc linked near CH switch regions and two near the joining region (JH) locus. Hence, immunoglobulin recombination machinery may participate in translocation, although the common myc breakpoint region around exon 1 does not resemble a switch region. Tumours with breakpoints just 5' to exon 1, or distant from c-myc, had normal c-myc mRNAs of 2.25 and 2.4 kb, which differ at their 5' ends, while tumours with breakpoints within exon 1 or intron 1 had altered c-myc mRNAs (2.1-2.7 kb in Burkitt lines), initiated within intron 1. Both types of mRNAs probably yield the same polypeptide. Since the untranslocated c-myc allele was generally silent...
Recent molecular analyses of Burkitt lymphomas carrying the t(8;14) chromosome translocation have indicated that a dichotomy exists regarding the molecular mechanisms by which the translocations occur. Most sporadic Burkitt tumors carry translocations that apparently arise due to mistakes in the immunoglobulin isotype-switching process. In contrast, there is evidence that the translocations of most endemic Burkitt lymphomas occur as a consequence of aberrant V-D-J recombination of variable, diversity, and joining gene segments, catalyzed by the recombinase enzymes. This phenomenon was first noted in follicular lymphomas and chronic lymphocytic leukemias of the B-cell lineage and has been described in T-cell malignancies as well. In each of these cases, analysis of the nucleotide sequence at chromosome breakpoints demonstrated the involvement of immunoglobulin heavy chain JH or T-cell-receptor alpha-chain J alpha gene segments in the translocation. We now have cloned and sequenced both the 8q- and 14q+ translocation breakpoints deriving from the t(8;14) translocation of the endemic Burkitt lymphoma line Daudi. Our data show that the translocation resulted from a reciprocal exchange between the DH region on chromosome 14 and sequences far 5' of the MYC protooncogene on chromosome 8. Features of the nucleotide sequences surrounding the breakpoint further implicate the V-D-J joining machinery in the genesis of chromosome translocations in endemic Burkitt lymphomas and...
This is the final version of the article. It was first published by Wiley at http://doi.org/10.1002/cjp2.10; A proportion of MYC translocation positive diffuse large B-cell lymphomas (DLBCL) harbour a BCL2 and/or BCL6 translocation, known as double-hit DLBCL, and are clinically aggressive. It is unknown whether there are other genetic abnormalities that cooperate with MYC translocation and form double-hit DLBCL, and whether there is a difference in clinical outcome between the double-hit DLBCL and those with an isolated MYC translocation. We investigated TP53 gene mutations along with BCL2 and BCL6 translocations in a total of 234 cases of DLBCL, including 81 with MYC translocation. TP53 mutations were investigated by PCR and sequencing, while BCL2 and BCL6 translocation was studied by interphase fluorescence in situ hybridization. The majority of MYC translocation positive DLBCLs (60/81=74%) had at least one additional genetic hit. In MYC translocation positive DLBCL treated by R-CHOP (n=67), TP53 mutation and BCL2, but not BCL6 translocation had an adverse effect on patient overall survival. In comparison with DLBCL with an isolated MYC translocation, cases with MYC/TP53 double-hits had the worst overall survival, followed by those with MYC/BCL2 double-hits. In MYC translocation negative DLBCL treated by R-CHOP (n=101)...
The duck-billed platypus is an extraordinary mammal. Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species. In this paper, we review the evolution and formation of meiotic multiples in plants and invertebrates to try to gain insights into the origin of the platypus meiotic multiple. We describe the meiotic hurdles that translocated mammalian chromosomes face, which make longer chains disadvantageous in mammals, and we discuss how sex chromosomes and dosage compensation might have affected the evolution of sex-linked meiotic multiples. We conclude that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species. We discuss alternative evolutionary models, which fall broadly into two categories: either the chain is the result of a sequence of translocation events from an ancestral pair of sex chromosomes (Model I) or the entire chain came into being at once by hybridization of two populations with different chromosomal rearrangements sharing monobrachial homology (Model II).