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PubMed2004

Telomere length heterogeneity and chromosome instability.

Chromosome aberrations are the hallmark of cancer cells. Although a few specific chromosome aberrations are frequently detected in some types of cancer, the majority of karyotypic abnormalities tend to differ between different histological types and between individuals with the same type of cancer. Recent work indicates that telomeres may be directly involved in shaping the karyotypes of tumor cells. In particular, the heterogeneity of telomere lengths within cells may have direct influence on the frequency with which chromosomes engage in telomeric fusions and in subsequent breakage-fusion-bridge cycles. Since telomere length distribution among chromosome arms is a polymorphic trait, difference in distributions between individuals may account, at least in part, for the karyotypic differences found among tumors of the same type. Conversely, if single telomere lengths happen to be inherited, the segregation of particularly short telomeres in families may increase the incidence of specific chromosome aberrations during tumor evolution, and perhaps contribute, along with other factors, to cancer pre-disposition.

Alleles↗
PubMed1986

Cytogenetic evidence for clonal evolution in B-cell chronic lymphocytic leukemia.

Sequential cytogenetic studies were performed in eight of ten patients with B-cell chronic lymphocytic leukemia presenting with trisomy 12 as the sole chromosomal abnormality. Follow-up studies of peripheral blood lymphocytes revealed that the karyotypes retained the sole abnormality of trisomy 12 in five cases, trisomy 12 converted to a normal karyotype during remission in one case, additional chromosome changes (-X,14q-) along with trisomy 12 appeared in one patient and multiple chromosome changes with or without trisomy 12 appeared in the remaining patient. The findings indicate that other chromosome changes in addition to trisomy 12 may develop as a result of clonal evolution or dedifferentiation, though the possibility that in two patients these changes may be related to chemotherapy and/or irradiation could not be ruled out entirely.

Aged↗
PubMed2004

High-speed chromosome sorting.

Structural and genetic characterization of chromosomes is necessary to understand both normal and pathologic physiology in any species. Flow cytometry and cell sorting technologies provide a means for precise measurement of chromosomal makeup as well as for the isolation of specific chromosomes for further study. Advancements in molecular biology protocols and pressures from large-scale sequencing endeavors placed increased demand on the developers of these instruments for enhanced throughput and quality of results. The ensuing improvements in sorting performance led to the development of a new generation of cytometers known as high-speed cell sorters. These machines provide superior results in less time and are cheaper and simpler to operate than their predecessors. Robust chromosome sorting can now be performed in the laboratories of individual investigators for a variety of gene- and sequence-specific studies. Resolution of the flow karyotype with increased refinement, and the development of new applications for this technology will assure that cell sorting continues to play an important role in cytogenetics, our understanding of molecular processes such as evolution and disease etiology, and ultimately serve as a launching point for predictive medicine.

Animals↗
PubMed1997

Chromosomal homeologies between human, harbor seal (Phoca vitulina) and the putative ancestral carnivore karyotype revealed by Zoo-FISH.

We report on the construction of the first comparative Zoo-FISH map of a marine mammal. Zoo-FISH with DNA probes from a human chromosome-specific library to metaphase spreads of the harbor seal (Phoca vitulina) disclosed 31 conserved syntenic segments covering the complete autosomal complement and the X chromosome. Comparison with Zoo-FISH maps of other species reveals that the harbor seal shares a high degree of karyotypic homeology with the human complement and an even higher degree with the conordinal cat complement. These findings suggest that pinniped, felid and human karyotypes have maintained conserved complements. Based on data of Zoo-FISH and comparative cytogenetics, a Zoo-FISH map of the ancestral carnivore karyotype (Z-CAR) is proposed. Flow cytometry revealed that the DNA value of the harbor seal genome is 79% that of the human genome.

Animals↗
PubMed1996

A karyotypic analysis of the lesser Malay chevrotain, Tragulus javanicus (Artiodactyla: Tragulidae).

Chevrotains are small forest-dwelling ruminants of the family Tragulidae. The chromosome number of the lesser Malay chevrotain was determined to be 2n = 32, NF = 64, G- and Q-banding allowed the identification of homologous chromosomes, and C-banding demonstrated the presence of pericentromeric, telomeric and interstitial constitutive heterochromatin. Q-band comparisons with domestic cattle revealed relatively few monobrachial chromosome band homologies. However, the smallest biarmed autosome of the chevrotain, chromosome 15, was determined to be cytogenetically homologus with the acrocentric chromosome 19 of cattle. A molecular cytogenetic analysis confirmed this putative chromosomal homology. In fact, molecular cytogenetic analyses indicate complete conservation of synteny among mouse deer chromosome 15, domestic cattle chromosome 19, domestic pig chromosome 12 and human chromosome 17. In the light of these molecular cytogenetic data and since mouse deer chromosome 15 is submetacentric and appears homologous in banding to submetacentric chromosome 12 of the domestic pig, these outgroup comparisons indicate that the acrocentric condition of cattle chromosome 19 has been derived by inversion. Since this derivative condition is present in the Antilocapridae, Bovidae, Cervidae and Giraffidae, it is a chromosomal synapomorphy that unites these advance ruminant families within the Artiodactyla.

Animals↗
PubMed2005

[Karyotype and relationships of the endemic char Salvelinus krogiusae from Dal'nee Lake (Kamchatka)].

Resident (lacustrine) chars, inhabiting many lakes of Kamchatka, Chukotka, and continental coast of the Sea of Okhotsk, are of particular interest for understanding the mechanisms of speciation and evolution of Salvelinus chars. Since one of these, the char from Dal'nee Lake (Paratunka River basin, southeastern Kamchatka), is substantially different from lacustrine-riverine and anadromous chars from the Paratunka River basin in several morphological traits, hemoglobin spectrum, ecology, and reproduction, it is considered an isolated species Salvelinus krogiusae. The karyotype of the resident char from Dal'nee Lake was shown to be variable in most individuals, containing 76 to 80 chromosomes in different cells, with NF = 98. This suggests that the variability of the chromosome number in this char form is explained by Robertsonian translocations. In females and males, cells with respectively 2n = 78 and 2n = 77 prevailed. Heteromorphic sex chromosomes were not found in the karyotype of this char species. Nucleolar-organizing regions (NORs) were mostly detected in the telomeric regions of short arms of large submetacentric chromosomes. These features of the Krogius char karyotype demonstrate that this species is isolated from other Kamchatka chars, being similar to Taranetz char S. taranetzi from Chukotka Peninsula, which is in good agreement with morphological data.

Animals↗
PubMed2004

Chromosome evolution in the erythrinid fish, Erythrinus erythrinus (Teleostei: Characiformes).

The genus Erythrinus belongs to the family Erythrinidae, a neotropical fish group. This genus contains only two described species, Erythrinus erythrinus being the most widely distributed in South America. Six samples of this species from five distinct Brazilian localities and one from Argentina were studied cytogenetically. Four groups were identified on the basis of their chromosomal features. Group A comprises three samples, all with 2n = 54 chromosomes, a very similar karyotypic structure, and the absence of chromosome differentiation between males and females. One sample bears up to four supernumerary microchromosomes, which look like 'double minute chromosomes' in appearance. Groups B-D comprise the three remaining samples, all sharing an X(1)X(1)X(2)X(2)/X(1)X(2)Y sex chromosome system. Group B shows 2n = 54/53 chromosomes in females and males, respectively, and also shows up to three supernumerary microchromosomes. Groups C and D show 2n=52/51 chromosomes in females and males, respectively, but differ in the number of metacentric, subtelocentric, and acrocentric chromosomes. In these three groups (B-D), the Y is a metacentric chromosome clearly identified as the largest in the complement. The present results offer clear evidence that local samples of E. erythrinus retain exclusive and fixed chromosomal features, indicating that this species may represent a species complex.

Animals↗
PubMed2003

Chromosomal studies on sphaerodactyl lizards of genera Gonatodes and Coleodactylus (Squamata, Gekkonidae) using differential staining and fragile sites analyses.

The karyotypes of three species of sphaerodactyl gekkonid lizards are described after conventional and differential staining. Karyotypes of Gonatodeshumeralis and G. hasemani are formed by a gradual series of 32 acrocentric chromosomes, similar to those already published for other species of the genus. G. humeralis shows multiple Ag-NORs with intra-individual variability, and positive C-bands located at centromeric and telomeric regions of several chromosome pairs. Coleodactylus amazonicus, the first non-Gonatodes sphaerodactyl studied so far karyologically, exhibits 36 acrocentric/subtelocentric chromosomes and a single pair of Ag- NORs. Fragile sites were detected on two medium-sized chromosome pairs in the karyotype of G. humeralis, most of them obtained in BrdU-treated culture preparations. These sites may represent a putative fission/fusion spot involved in the differentiation of G. humeralis-like 2n = 32 and C. amazonicus-like 2n = 36 karyotypes. Our results, especially on the location of Ag-NORs and the description of fragile sites, are relevant in improving our knowledge about the events of chromosome evolution in this extremely variable and poorly known group of lizards.

Animals↗
PubMed1982

Genome evolution in pocket gophers (genus Thomomys). II. Variation in cellular DNA content.

Cellular DNA content (2 C-value) was measured by fluorescence flow cytometry of chromomycin-A3 stained spleen cells in 2 subgenera, 5 species, and 21 subspecies of pocket gophers (genus Thomomys). The data indicate that, in Thomomys: (1) interspecific variation is extensive but, while some congeneric species differ by as much as 230%, others are identical in C-value: (2) intraspecific differentiation can be extensive with C-values differing by as much as 35%; and (3) populations of the same subspecies with apparently similar karyotypes can differ significantly in C-value. The implications of these results for hypotheses of the "adaptive" significance of C-value variation and genome evolution are discussed.

Animals↗
PubMed2000

HSA4 and GGA4: remarkable conservation despite 300-Myr divergence.

The chicken (GGA) and human (HSA) genomes diverged around 300-350 Myr ago. Due to this large phylogenetic distance, significant synteny conservation has not been anticipated between the genomes of the two species. However, Zoo-FISH with HSA4 chromosome-specific paint on chicken metaphase chromosomes shows that the human chromosome corresponds largely to the GGA4cen-->q26 region. Comparative gene mapping data in the two species, though limited, provide strong support for these observations. The findings, together with the very recently published data on HSA9-GGAZ and HSA12-GGA1, show that some large chromosomal segments share conserved synteny in the two species. These syntenies are considerably disrupted in the mouse. This makes us believe that despite very early divergence, parts of the human and chicken genomes are more conserved than those of human and mouse, which radiated only 100-120 Myr ago. Moreover, the HSA4-GGA4q correspondence points to a "candidate" chromosome from the karyotype of a mammal-bird ancestor. The findings are thus a small but important step toward understanding the evolution of the two genomes.

Animals↗
PubMed1987

Chromosomal subclonal evolution in paroxysmal nocturnal hemoglobinuria evolving into acute megakaryoblastic leukemia.

Four cytogenetic studies were performed in the course of a paroxysmal nocturnal hemoglobinuria evolving into acute megakaryoblastic leukemia. The clonal evolution was characterized by a unique structural change (9p) at the time of diagnosis, heralding an accelerated and complex karyotypic alteration including 5q-, 12p-, +21, -5, -7. At the terminal phase, the initial population was replaced within 1 week by a new overgrowing clone with -5, +8, +17. This suggests that the paroxysmal nocturnal hemoglobinuria-associated preleukemia and leukemic states share with acute nonlymphocytic leukemia the same nonrandom chromosomal changes.

Adult↗
PubMed2004

Occurrence of a myelodysplastic syndrome (MDS) during first-line 2-chloro-deoxyadenosine (2-CDA) treatment of a low-grade gastrointestinal MALT lymphoma. Case report and review of the literature.

While myelodysplastic syndrome (MDS) and acute leukemia (AL) are well-known secondary diseases after administration of chemotherapy, particularly alkylating agents, they have only rarely been reported in the context of purine analog treatment. In all cases there was an interval of several months before onset of the secondary disease and cytogenetic analyses showed typical chromosomal aberrations. We report the case of a 68-year old male Caucasian with low-grade lymphoma who developed a MDS during ongoing first-line treatment with the purine analog 2-CDA (Cladribine). Furthermore, a normal karyotype was present initially and at all consecutive control evaluations. Thus, this case represents another rare report of an evolution of purine analog treatment-associated MDS; the absence of cytogenetic aberrations might suggest a different mechanism in the pathogenesis of this secondary disease.

Aged↗
PubMed1984

Chromosome study of Presbytis cristatus: presence of a complex Y-autosome rearrangement in the male.

The karyotypes of a female and of a male Presbytis cristatus are analysed. In the latter, there is a complex Y-autosome rearrangement. The phyletic position of this species, in relation to genus Colobus, previously studied, is proposed, considering the sequence of chromosomal rearrangements which occurred during their evolution. These rearrangements, in addition to the t(Y-autosome), are characterized by a high frequency of inversions, and above all, by several non-Robertsonian translocations which occurred very rarely during evolution of other Primates.

Animals↗
PubMed2003

Evaluation of Trypanosoma cruzi hybrid stocks based on chromosomal size variation.

Although all classical lines of evidence point to the fact that Trypanosoma cruzi has a predominantly clonal evolution, accumulating data show that some T. cruzi stocks are the result of hybridisation events. We evaluated whether chromosomal polymorphism would give evolutionary information on hybrid isolates. Twenty-three coding sequences were mapped on the chromosomes of nine parasite stocks, four of which are putative hybrids (CL Brener and rDNA group 1/2). Phenetic analyses of karyotype data were based on the absolute chromosomal size difference index (aCSDI), a method that assumes that the genomic distance between two organisms is the sum of the size differences between their homologous chromosomes. aCSDI-based dendrograms obtained from a variable number of probes (3-18 probes) defined in all the cases three clusters: two corresponding, respectively, to T. cruzi I and T. cruzi II groups; and a third one, to rDNA group 1/2. CL Brener was alternatively positioned in T. cruzi II or rDNA group 1/2 clusters. Three clusters were also observed in the dendrogram constructed with restriction fragment length polymorphism (RFLP) data from 18 probes. The topology of the chromosome and RFLP dendrograms is similar, with a significant correlation coefficient (r=0.86062; P<0.0001), supporting a strong structuring of the clusters. This study also revealed that hybrid stocks have a larger proportion of two different-sized homologous chromosomes, as compared with non-hybrid strains. Overall, our results show that chromosomes are valuable characters for identification of evolutionary groups, in particular, T. cruzi hybrid organisms.

Animals↗
PubMed2005

Comparative genome analyses of Arabidopsis spp.: inferring chromosomal rearrangement events in the evolutionary history of A. thaliana.

Comparative genome analysis is a powerful tool that can facilitate the reconstruction of the evolutionary history of the genomes of modern-day species. The model plant Arabidopsis thaliana with its n = 5 genome is thought to be derived from an ancestral n = 8 genome. Pairwise comparative genome analyses of A. thaliana with polyploid and diploid Brassicaceae species have suggested that rapid genome evolution, manifested by chromosomal rearrangements and duplications, characterizes the polyploid, but not the diploid, lineages of this family. In this study, we constructed a low-density genetic linkage map of Arabidopsis lyrata ssp. lyrata (A. l. lyrata; n = 8, diploid), the closest known relative of A. thaliana (MRCA approximately 5 Mya), using A. thaliana-specific markers that resolve into the expected eight linkage groups. We then performed comparative Bayesian analyses using raw mapping data from this study and from a Capsella study to infer the number and nature of rearrangements that distinguish the n = 8 genomes of A. l. lyrata and Capsella from the n = 5 genome of A. thaliana. We conclude that there is strong statistical support in favor of the parsimony scenarios of 10 major chromosomal rearrangements separating these n = 8 genomes from A. thaliana. These chromosomal rearrangement events contribute to a rate of chromosomal evolution higher than previously reported in this lineage. We infer that at least seven of these events, common to both sets of data, are responsible for the change in karyotype and underlie genome reduction in A. thaliana.

Arabidopsis↗
PubMed2003

Cytogenetic analysis of four species of the genus Alsodes (Anura: Leptodactylidae) with comments about the karyological evolution of the genus.

A comparative cytogenetic analysis of Alsodes pehuenche, A. vanzolinii, A. verrucosus and A. aff. vittatus show that all four species share the same diploid number 2n = 26; the fundamental number is 50 in A. vanzolinii and 52 in A. aff. vittatus, A. pehuenche and A. verrucosus. The karyotypes of A. pehuenche and A. aff. vittatus are described for the first time; the C-band patterns, the NOR locations and Q-band patterns are also described for the first time for the four species. C-band patterns are species specific and useful to identify the taxa. The usefulness of the chromosomal data in taxonomy and systematics of Alsodes species is discussed. Transformation of euchromatin into heterochromatin and centric fissions and translocations are proposed as the main mechanisms that govern the chromosomal evolution of the frog genus Alsodes.

Animals↗
PubMed1994

Clonality and karyotype studies in polycythemia vera.

The molecular determination of the monoclonal or non-clonal nature of polycythemia cases is now possible in all or almost all females by study of the methylation pattern of several polymorphic X-linked loci. However, the techniques used are sophisticated and costly and the results do not clarify all cases. Karyotypic studies of PV, despite the number of cases reported thus far, remain insufficient. The natural history of cytogenetic events and their mechanisms of occurrence are still poorly known. Unsuccessful examinations are around 10-15%. The proportion of patients with clonal anomalies, 10-15% at diagnosis, increases with time, myelo-ablative treatments and evolution to myelofibrosis/myeloid metaplasia, so as to be close to 100% in cases with myelodysplasia/acute transformation. A few of the most frequently found non-random anomalies among which in particular trisomy 8 and 9, double trisomy 8+9, 20q- and trisomy of part or totality of 1q have some degree of specificity. Other recurring aberrations, such as 13q- mainly occur in late stages of PV, in which complex, unstable karyotypes are found. Finally none of those anomalies can be considered as a primary lesion. The frequency of clonal evolution is a matter of discussion. Despite their theoretical interest, PV cytogenetic results are of little diagnostic value, and as regards prognosis, they are statistically significant, but are of poor value in most individual patients. In conclusion, it is felt that clonality and karyotype studies should be pursued in PV, completed by "interphase cytogenetics" and molecular biology investigations, with theoretical aims rather than for immediate practical reasons.

Cloning, Molecular↗