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PubMed2000

Staggered clines in a hybrid zone between two chromosome races of the harvestman Gagrellopsis nodulifera (Arachnida: Opiliones).

We analyzed a hybrid zone between two chromosome races (2n = 16 and 2n = 22) of a Japanese harvestman, Gagrellopsis nodulifera Sato and Suzuki (Arachnida: Opiliones: Phalangiidae). The hybrid zone is located in the eastern part of Tottori Prefecture, western Honshu. The width of the zone is approximately 5 to 15 km. Three independent tandem fusions/fissions seem to be the main cause of the karyotypic differences between the parental races. Ten karyotypic variants were found in the hybrid zone. They differed by numbers of diploid chromosomes and trivalents detected in meiosis. In most of the collecting sites, karyotypic heterozygotes were less common than expected. A positive correlation was found between number of trivalents in a karyotype and its deficiency rate. In some sites, the deficit of heterozygous individuals was accompanied by an excess of the intermediate homozygotes. One of the three transects across the zone was studied in detail. We found that three types of single heterozygotes (2n = 17, 2n = 19 and 2n = 21) formed a series of successive, spatially separated peaks along the transect. Two types of intermediate homozygotes (2n = 18 and 2n = 20) were also spatially separated. The most parsimonious explanation of such a structure is the staggering of clines of three tandem (or Robertsonian) fusion/fission variants that differentiate the parental races caused by selection against multiple heterozygotes. Analysis of nondisjunction in single heterozygotes demonstrated that there was a strong interindividual variation in nondisjunction rate. The mean frequency of aneuploid MII in single heterozygotes was 0.10 +/- 0.03. Crossover exchanges in some critical regions of trivalents result in abnormal chromosomal configurations: chromosomes with unequal chromatids and dicentric chromosomes. Frequency of crossover-induced chromosomal abnormalities was low in single heterozygotes (approximately equal to 4%), and was unexpectedly high in the double heterozygotes (approximately equal to 15%). Selection against karyotypic heterozygotes is considered as a main evolutionary force responsible for the structuring of the hybrid zone. A positive association between diploid chromosome number and altitude was found. The race 2n = 16 tended to occupy lower altitudes than the 2n = 22 parental race. Differences in ecological preferences may be a result of previous adaptations to different environments in allopatry. A hypothesis concerning the origin and evolution of the hybrid zone is proposed.

Animals↗
PubMed1998

ZOO-FISH analysis in insectivores: "Evolution extols the virtue of the status quo".

In evolutionary terms, insectivores are thought to be close to primates. Through ZOO-FISH analysis using human chromosome-specific painting probes, the syntenic relationship between the human and common shrew, Sorex araneus, karyotypes was studied. The human karyotype was found to be conserved in the shrew, with 32 autosomal segments of common synteny. Special arrangements, already known from similar studies on other species, were noted: fusions of HSA 16 and 19, HSA 3 and 21, and HSA 14 and 15. Only 10 breaks are necessary to transform the human karyotype into the karyotype of the common shrew. Together with known ZOO-FISH data from species belonging to other orders, this puts the human karyotype arrangement near the basis of all mammalian karyotypes. Human chromosome 2 was found to be conserved in its entirety as a single chromosome arm in the shrew. Evidence is presented that the same fusion of two original chromosomal segments formed the shrew chromosome ortholog of HSA 2 as the fusion that occurred during primate evolution to form human chromosome 2. This is a remarkable example of chromosomal coevolution.

Animals↗
PubMed2000

Morphological differentiation and possible origin of B chromosomes in natural Brazilian population of Astyanax scabripinnis (Pisces, Characidae).

Specimens of Astyanax scabripinnis from three different altitudes (1920, 1800 and 700 m) along the Ribeirão Grande stream in the Campos do Jordão region (São Paulo State, Brazil) were investigated. The same diploid number, 2n = 50, was detected in the three populations, with the following karyotypic constitution: 6M, 22SM, 10ST and 12A. The populations located at 1920 and 1800 m altitude presented a high incidence of B chromosomes varying in number (0-2), shape (meta- and submetacentrics), size (large and small) and sex-related frequency (they were more frequent among females). The two morphologically variant B chromosomes probably evolved from a metacentric macrochromosome, which is the most commonly observed B chromosome in several A. scabripinnis populations.

Altitude↗
PubMed2006

Cross-species chromosome painting unveils cytogenetic signatures for the Eulipotyphla and evidence for the polyphyly of Insectivora.

Insectivore-like animals are traditionally believed among the first eutherian mammals that have appeared on the earth. The modern insectivores are thus crucial for understanding the systematics and phylogeny of eutherian mammals as a whole. Here cross-species chromosome painting, with probes derived from flow-sorted chromosomes of human, was used to delimit the homologous chromosomal segments in two Soricidae species, the common shrew (Sorex araneus, 2n = 20/21), and Asiatic short-tailed shrew (Blarinella griselda, 2n = 44), and one Erinaceidae species, the shrew-hedgehog (Neotetracus sinensis, 2n = 32), and human. We report herewith the first comparative maps for the Asiatic short-tailed shrew and the shrew-hedgehog, in addition to a refined comparative map for the common shrew. In total, the 22 human autosomal paints detected 40, 51 and 58 evolutionarily conserved segments in the genomes of common shrew, Asiatic short-tailed shrew, and shrew-hedgehog, respectively, demonstrating that the common shrew has retained a conserved genome organization while the Asiatic short-tailed shrew and shrew-hedgehog have relatively rearranged genomes. In addition to confirming the existence of such ancestral human segmental combinations as HSA 3/21, 12/22, 14/15 and 7/16 that are shared by most eutherian mammals, our study reveals a shared human segmental combination, HSA 4/20, that could phylogenetically unite the Eulipotyphlan (i.e., the core insectivores) species. Our results provide cytogenetic evidence for the polyphyly of the order Insectivora and additional data for the eventual reconstruction of the ancestral eutherian karyotype.

Animals↗
PubMed2003

Multicolor karyotyping and clinicopathological analysis of three intravascular lymphoma cases.

Intravascular lymphoma (IVL) is a rare neoplastic disease characterized by the presence of large malignant lymphoid cells in small vessels. It is often diagnosed at autopsy. Clinical manifestations are typically neurologic and dermatologic. Karyotypic abnormalities have been described in a small number of cases and have revealed complex alterations in the majority of cases. We have identified three cases of IVL with varied clinicopathological findings. Karyotypic analysis was undertaken by standard G-banding and supplemented by multi-colored karyotyping (M-FISH) to decipher the chromosomal content of marker chromosomes and undefined additions. M-FISH clarified the chromosomal abnormalities in two cases and unveiled cryptic translocations der(10)t(10;22), der(17)t(17;22), and balanced t(11;14). Comparison with previously published karyotypes revealed prominent involvement of chromosomes 1, 3, 6, 11, 14, and 18, similar to the pattern of clonal evolution in other B-cell lymphomas. The most frequent alterations seen were -6 or 6q- and +18 or dup(18q), with a minimally deleted region located at 6q21-q23 and a commonly amplified region located at 18q13-q23, respectively. Few differences between the classical and Asian variant of this disease were apparent at the karyotypic level. Cytogenetic analysis of additional cases supplemented by multicolor karyotyping may help identify the full spectrum of genetic alterations associated with IVL and assist in the delineation of the critical mutations associated with initiation and progression of this disease.

Aged↗
PubMed1988

Cytogenetics of chronic myelogenous leukemia.

The fundamental pathogenetic significance of the Ph chromosome abnormality in CML has been clarified by molecular studies. However, this balanced reciprocal t(9;22) is probably not the primary event in the pathogenesis of this disease, at least at a cytogenetic level. The cause of Ph variants in +/- 5% of patients is still unknown. Improvements in cytogenetic techniques and molecular studies in a limited number of cases indicate that simple variants do not exist: Region 9q34 appears to be involved in all types of Ph variants. There is tentative evidence that these variants may in fact represent a clonal evolution from a standard t(9;22). The types of additional secondary abnormalities found in Ph variants are the same as those commonly found in standard cases. Ph negative CML represents a heterogeneous group of myeloproliferative/myelodysplastic disorders. The various mechanisms that could lead to Ph negativity are discussed. Some karyotypically normal cases and those showing a chromosome abnormality other than the Ph during the chronic phase have shown the same molecular changes as found in Ph positive CML. The types of clonal changes accompanying transformation to an acute phase are similar to those seen in myeloid disorders as a whole. The prognostic karyotypic factors in predicting imminent metamorphosis to the acute stage and during the acute phase are discussed. The extent of clonal evolution, the type of secondary abnormalities, and their relationship to the hematopoietic lineage of blast cells should be assessed. The nonrandom clonal changes found in 80% of cases are +Ph, +8, i(17q), +19, and loss of the Y. The significance of +Ph is possibly related to amplification of the bcr/abl fusion gene product, but the reason for the other persistent nonrandom changes is still speculative. Recent cytogenetic data indicate that the specific changes observed in various types of ANLL may be seen in corresponding types of MT, such as t(15;17) in promyelocytic transformations and abnormalities of 3q21-3q26 in megakaryoblastic transformations. Patients with LT usually have an early precursor B phenotype associated with a better prognosis. They tend to have either normal or hypodiploid karyotypes. An i(17q) is never seen and +8 and +19 are absent in most series. Duplication of the Ph and loss of the Y are common to both MT and LT. Data relating 14q+ abnormalities to LT are presently ambiguous.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromosome Aberrations↗
PubMed2001

Cytogenetics of eight Neotropical species of Chauliognathus Henzt, 1830: implications on the ancestral karyotype in Cantharidae (Coleoptera).

Meiotic chromosomes of eight Neotropical species of the genus Chauliognathus occurring in Southern Brazil were analysed from testis cells. The meioformula of all the species was n = 6 + X (with six pairs of autosomes and one X chromosome). This meioformula is also present in C. scriptus plus two other species of other genera of Cantharidae, suggesting an evolutionary tendency towards the compaction of the karyotype starting from the ancestral Polyphagan meioformula n = 9 + Xy(p). The presence of an XO sex chromosome mechanism in all cantharid species studied to date indicates that the reduction of the number of autosomes was probably paralleled by the loss of the small typical Polyphagan yp heterosome. Thus the meioformula n = 6 + X seems to be an apomorphy for Cantharidae and may have evolved soon after the separation of the ancestral cantharid from the other families of Polyphaga.

Animals↗
PubMed1992

The chromosomes of Leishmania.

Chromosome size polymorphisms occur in Leishmania such that each strain of a given species has a distinctive molecular karyotype. Despite this variability, the chromosomal similarities among closely related strains of Leishmania are sufficiently characteristic to permit classification of unidentified clinical isolates. Mechanisms generating chromosome size polymorphisms are related to chromosomal evolution. In this review, Geoffrey Lighthall and Suzanne Giannini explain that the chromosomal profiles of members of different species may be diverging from a conserved 'consensus' karyotype at different rates, and present a current understanding of the genomic organization of Leishmania with emphasis on chromosomal elements.

Journal Article↗
PubMed1997

Assignment of TCF1, TGM1, CALM1, CKB, THBS1, B2M, and FES in Ateles paniscus chamek (Platyrrhini, Primates).

Regional assignment of five markers to chromosome 2 of Ateles paniscus chamek (APC) confirmed a syntenic association similar to human (HSA) 12q + 14q + 15q. TCF1 was allocated to a shortest region of overlap (SRO) in APC 2p and found to be syntenic to PEPB, while TGM1, CALM1, THBS1, and B2M were assigned to APC 2q, being syntenic to NP, HEXA, and MPI. Conversely, markers close to HSA 14qter (CKB) and HSA 15qter (FES-IDH2) were relocated to other Ateles syntenic groups. Karyotypic comparisons showed an evident homoeology between APC 2p and HSA 12q, whereas APC 2q was similar to an HSA 14qter::HSA 15qter fusion product.

Animals↗
PubMed1993

Chromosome analysis of 20 breast carcinomas: cytogenetic multiclonality and karyotypic-pathologic correlations.

Short-term cultures from 20 breast carcinomas were analyzed cytogenetically. A normal female chromosome complement was found in 4 cases. Clonal chromosome aberrations were detected in 16 tumors. In 10 tumors, multiple cytogenetic clones were found; in 2 cancers the clones were related, reflecting clonal evolution, but in the remaining 8 tumors the clones were cytogenetically unrelated, indicating clonal heterogeneity in the origin of the tumor parenchyma. Correlation analysis between karyotypic and pathologic parameters indicated that cases with complex karyotypes and/or cytogenetically unrelated clones, when compared with cases with a single simple karyotypic abnormality, were generally of higher histologic malignancy grade, had more mitoses in the histologic sections, and also more often had carcinoma in situ lesions in the same breast.

Aneuploidy↗
PubMed1999

Stepwise chromosome evolution in Drosophila albomicans.

A 'stepwise chromosome evolution model' is proposed to elaborate the two stages of the sex chromosome evolution of Drosophila albomicans. To explain the occurrence of both a 3-X and a 3-Y in this species it is proposed that these chromosomes evolved sequentially. The selection forces acting in the two stages are different. The genic composition in the first fused sex chromosome of D. albomicans was supposed to be selectively superior to the primitive unfused chromosomes, thus the fused chromosome could overcome the meiotic structural incompatibility and be maintained in the population during the first stage. When the second fusion occurred, the newly fused sex chromosome was preferentially selected, as it could provide a meiotic pairing partner for the first fusion. The fused sex chromosomes were eventually fixed in the population. Based on this model, we tried to determine which fused chromosome, 3-X or 3-Y, established first. The karyotyping result of four experimental hybrid populations showed that the fused 3-X, as opposed to 3-Y, chromosome has higher fitness values. However, without the coexistence of 3-X, 3-Y is excluded rapidly. Therefore, 3-X is likely to be the first fused chromosome in the stepwise chromosome evolution model. The formation and fixation of the fused 3-Y chromosome occurred subsequently.

Animals↗
PubMed1989

Geographical patterns of karyotype polymorphism in Italian populations of Ornithogalum montanum (Liliaceae).

The geographical patterns of quinacrine banding polymorphism at 20 sites, and of numbers of accessory (B) chromosomes, were studied in nine Italian populations of Ornithogalum montanum Cyr. ex Ten. (Liliaceae). Eight banding sites appear monomorphic. The standardized gene frequency variance, Fst, is heterogeneous among the remaining 12 sites; variation is greatest for four polymorphisms whose frequency is correlated with the winter temperature of the localities studied. A strong negative association is apparent between numbers of B chromosomes and Q bands. Spatial autocorrelation shows three distinct modes of geographical variation: (i) random distributions; (ii) patterns with positive short-range autocorrelation; (iii) patterns with negative intermediate-range autocorrelation. Some microevolutionary implications of these findings are discussed.

Biological Evolution↗
PubMed1996

Shared synteny of human chromosome 17 loci in Canids.

Canids are unusual among mammals in the large degree to which their karyotypes have diverged during speciation. In many instances, chromosome segments from different species share cytogenetic homology, and a presumed phylogenetic tree of Canid evolution can be constructed based on the relative shuffling of chromosomal elements. In this study, four gene probes (myeloperoxidase [MPO], Miller-Dieker [MDCR], ERBB2, and retinoic acid receptor alpha [RARA]) from human chromosome 17 were used in fluorescence in situ hybridizations with chromosomes of three different Canids: two subspecies of the Asiatic raccoon dog (Nyctereutes) and the domestic dog (Canis familiaris). The Nyctereutes subspecies have widely diverged karyotypes (2n = 38 versus 2n = 54) and Canis familiaris has a large number (2n = 78) of chromosomes. This study confirms the identity of two shared chromosomes of Nyctereutes. The Japanese raccoon dog chromosome 13 shares linkage with the Chinese raccoon dog chromosome 5. Both of these Nyctereutes chromosomes share synteny with human chromosome 17. Human chromosome 17 shares linkage with Canis familiaris chromosome 23. The relative order and spacing of the genes mapped in these species suggests the occurrence of chromosome rearrangements, most notably inversions, during the evolution of these animals.

Animals↗
PubMed1998

Prognostic value of cytogenetics in multiple myeloma.

Karyotypic studies of bone marrow were conducted in 79 previously untreated patients with multiple myeloma who received a standard programme of chemotherapy. An abnormal karyotype was observed in 46% of patients, virtually all showing multiple abnormalities consistent with a long period of preclinical clonal evolution. Patients with an abnormal pattern showed various aberrations with hyperdiploidy in 64%, pseudodiploidy in 5% and hypodiploidy in 31%. The number of chromosomes affected ranged from two to 19 (median 10), with at least one trisomy in 83%, one monosomy in 75%, and one translocation in 42% of patients. Lymphoma-like karyotypes were present in 17% of patients with an abnormality but were not associated with atypical clinical features, such as an extramedullary mass, leukaemia, or increased serum lactate dehydrogenase. Monosomy or deletion of chromosome 13 was present in 47% of patients with an abnormal pattern, who lived for a shorter duration (median 10 months) than patients with other abnormalities (median 34 months) or with diploidy (median 35 months). The cause of the short survival of patients with monosomy or deletion of chromosome 13 was not clear, but further studies on the relationship with specific oncogenes are indicated.

Bone Marrow Cells↗
PubMed1986

Shifts in blast cell phenotype and karyotype at relapse of childhood lymphoblastic leukemia.

Analyses of bone marrow blast cells collected at diagnosis and relapse from 68 children with acute lymphoblastic leukemia (ALL) demonstrated changes in the expression of cell markers in one-fourth of the patients. Loss of the common ALL antigen (CALLA) was a frequent change, occurring in 8 of the 51 cases initially classified as common or pre-B ALL. The HLA-DR antigen was either acquired or lost in 5 of the 68 cases, terminal deoxynucleotidyl transferase was lost in 6 of 25 cases, and reactivity of the T10 antigen with monoclonal antibodies was increased in 6 of 17 cases of non-T cell ALL. Conversion to acute nonlymphoblastic leukemia, so-called lineage switch, was noted in two cases of common ALL and one of pre-B ALL, coinciding with the loss of CALLA. Results of chromosomal analyses in cases with a loss of CALLA implicated several mechanisms in the observed phenotypic changes. In six cases, including each instance of lineage switch, the original karyotype had been replaced by an entirely different abnormal karyotype, suggesting clonal selection or induction of a second malignancy. In another case, the evidence suggested clonal evolution. Our findings demonstrate that sequential phenotypic and cytogenetic studies may yield valuable insights into the mechanisms of leukemic recurrence and may have implications for treatment selection.

Adolescent↗
PubMed2006

Chromosome plasticity in Ctenomys (Rodentia Octodontidae): chromosome 1 evolution and heterochromatin variation.

A chromosome 1 (Cr1) pericentric inversion is described in six of seven species in the genus Ctenomys (tuco-tucos) from Uruguay. The inversion was inferred from G-band analyses of subtelocentric Cr1 hypothesised to be derived from the ancestral metacentric condition. Cr1 varies across species in heterochromatin amount and localisation including a metacentric chromosome without positive C-bands in C. torquatus, a subtelocentric chromosome with heterochromatic short arms in C. rionegrensis, and a subtelocentric chromosome negative after C-banding in five of the species analysed here. Pachytene chromosomes from C. rionegrensis, a species with the highest heterochromatin content, and C. torquatus, one of the species with the lowest heterochromatin content, were analysed in order to assess possible mechanisms of heterochromatin evolution. This analysis revealed the presence of three heterochromatic chromocenters in C. rionegrensis where bivalents converge, while in C. torquatus only one chromocenter was observed. In both species, highly repetitive DNA was observed, localised in chromocenters after "in situ" hybridisation. Heterochromatin associated protein M31 was localised in chromocenters of both species after immuno-detection. The spread of heterochromatin in Ctenomys chromosomes could be produced by chromatin exchanges at the chromocenter level. We propose the exchange of this DNA associated proteins between non-homologous chromosomes in pachytene to be the responsible for the spread of heterochromatin through the karyotypes of species like C. rionegrensis.

Animals↗
PubMed1994

Some evidence of incipient speciation in Drosophila kikkawai.

Altogether 11 geographic populations of Drosophila kikkawai were analysed from the viewpoint of karyotypic variation, inversion polymorphism and sexual isolation. The results revealed that of all the populations, the New Guinea population was the most genetically diverged, characterized by its distinct karyotype, possession of a fixed inversion, and its females exhibiting sexual isolation at the level of preferential mating. Based on these findings it was inferred that incipient speciation has proceeded in D. kikkawai and its New Guinea population is on its way to speciation.

Animals↗
PubMed2004

Hotspots of mammalian chromosomal evolution.

BACKGROUND: Chromosomal evolution is thought to occur through a random process of breakage and rearrangement that leads to karyotype differences and disruption of gene order. With the availability of both the human and mouse genomic sequences, detailed analysis of the sequence properties underlying these breakpoints is now possible. RESULTS: We report an abundance of primate-specific segmental duplications at the breakpoints of syntenic blocks in the human genome. Using conservative criteria, we find that 25% (122/461) of all breakpoints contain > or = 10 kb of duplicated sequence. This association is highly significant (p < 0.0001) when compared to a simulated random-breakage model. The significance is robust under a variety of parameters, multiple sets of conserved synteny data, and for orthologous breakpoints between and within chromosomes. A comparison of mouse lineage-specific breakpoints since the divergence of rat and mouse showed a similar association with regions associated with segmental duplications in the primate genome. CONCLUSION: These results indicate that segmental duplications are associated with syntenic rearrangements, even when pericentromeric and subtelomeric regions are excluded. However, segmental duplications are not necessarily the cause of the rearrangements. Rather, our analysis supports a nonrandom model of chromosomal evolution that implicates specific regions within the mammalian genome as having been predisposed to both recurrent small-scale duplication and large-scale evolutionary rearrangements.

Animals↗