Presence Of Supernumerary Chromosomes Research Articles

The Eμ-Ret mouse is a novel model of hyperdiploid B-cell acute lymphoblastic leukemia

The presence of supernumerary chromosomes is the only abnormality shared by all patients diagnosed with high-hyperdiploid B cell acute lymphoblastic leukemia (HD-ALL). Despite being the most frequently diagnosed pediatric leukemia, the lack of clonal molecular lesions and complete absence of appropriate experimental models have impeded the elucidation of HD-ALL leukemogenesis. Here, we report that for 23 leukemia samples isolated from moribund Eμ-Ret mice, all were characterized by non-random chromosomal gains, involving combinations of trisomy 9, 12, 14, 15, and 17. With a median gain of three chromosomes, leukemia emerged after a prolonged latency from a preleukemic B cell precursor cell population displaying more diverse aneuploidy. Transition from preleukemia to overt disease in Eμ-Ret mice is associated with acquisition of heterogeneous genomic abnormalities affecting the expression of genes implicated in pediatric B-ALL. The development of abnormal centrosomes in parallel with aneuploidy renders both preleukemic and leukemic cells sensitive to inhibitors of centrosome clustering, enabling targeted in vivo depletion of leukemia-propagating cells. This study reveals the Eμ-Ret mouse to be a novel tool for investigating HD-ALL leukemogenesis, including supervision and selection of preleukemic aneuploid clones by the immune system and identification of vulnerabilities that could be targeted to prevent relapse.

Advances in understanding the evolution of fungal genome architecture.

Diversity within the fungal kingdom is evident from the wide range of morphologies fungi display as well as the various ecological roles and industrial purposes they serve. Technological advances, particularly in long-read sequencing, coupled with the increasing efficiency and decreasing costs across sequencing platforms have enabled robust characterization of fungal genomes. These sequencing efforts continue to reveal the rampant diversity in fungi at the genome level. Here, we discuss studies that have furthered our understanding of fungal genetic diversity and genomic evolution. These studies revealed the presence of both small-scale and large-scale genomic changes. In fungi, research has recently focused on many small-scale changes, such as how hypermutation and allelic transmission impact genome evolution as well as how and why a few specific genomic regions are more susceptible to rapid evolution than others. High-throughput sequencing of a diverse set of fungal genomes has also illuminated the frequency, mechanisms, and impacts of large-scale changes, which include chromosome structural variation and changes in chromosome number, such as aneuploidy, polyploidy, and the presence of supernumerary chromosomes. The studies discussed herein have provided great insight into how the architecture of the fungal genome varies within species and across the kingdom and how modern fungi may have evolved from the last common fungal ancestor and might also pave the way for understanding how genomic diversity has evolved in all domains of life.

Karyotype Diversity and Evolutionary Trends in Armored Catfish Species of the Genus Harttia (Siluriformes: Loricariidae).

Most species of the genus Harttia inhabits the headwaters of small tributaries, but some species are restricted to the main channel of some rivers. This feature, combined with limited dispersal ability, leads to the formation of small isolated populations with reduced gene flow. Currently, there are 23 taxonomically defined and recognized species, and 17 of these are found in Brazil, distributed in several hydrographic basins. Despite this diversity, few chromosomal data for the species belonging to this genus are found in the literature. Thus, this study analyzed, by classical and molecular cytogenetics methodologies, the chromosomal diversity of this genus, to discuss the processes that are involved in the evolution and karyotype differentiation of the species of the group. Seven species of Harttia were analyzed: H. kronei, H. longipinna, H. gracilis, H. punctata, H. loricariformis, H. torrenticola, and H. carvalhoi. The chromosomal diversity found in these species includes different diploid and fundamental numbers, distinct distribution of several repetitive sequences, the presence of supernumerary chromosomes in H. longipinna and multiple sex chromosome systems of the type XX/XY1Y2 in H. carvalhoi and X1X1X2X2/X1X2Y in H. punctata. Lastly, our data highlight the genus Harttia as an excellent model for evolutionary studies.

Comparative cytogenetics between two species of the family Pseudopimelodidae (Siluriformes): occurrence of natural triploidy and supernumerary chromosomes

The Pseudopimelodidae family comprises 35 species however, cytogenetic studies have been performed in only six species. This study uncovered karyotypic data on Pseudopimelodus pulcher and Microglanis cottoides. Both species possessed 2n=54, with 20m+16sm+10st+8a and FN=100 for P. pulcher and 30m+14sm+6st+4a and FN=104 for M. cottoides. A female of M. cottoides with 45m+21sm+9st+6a (2n=81) plus two extra small chromosomes was found, indicating a natural triploidy with supernumerary chromosomes. The formation of the polyploid individual seems to have come from a diploid female gamete, due to the presence of a marker chromosome pair partially heterochromatic presents only in females and common to that exemplar. This triploid female showed three chromosomes with nitrate staining (AgNOR), 18S rDNA probe and chromomycin A3 (CMA3) staining. AgNORs were observed on pairs 12 and 23 in P. pulcher and pair 24 in M. cottoides, results that were confirmed with an 18S rDNA probe and CMA3 fluorochrome. These are the first chromosomal data for P. pulcher and provide the first description of natural triploidy with the presence of supernumerary chromosomes in this family and emphasizing well the chromosomal rearrangements diversification between this species.

Chromosomal Evolution in the Brazilian Geckos of the Genus Gymnodactylus (Squamata, Phyllodactylidae) from the Biomes of Cerrado, Caatinga and Atlantic Rain Forest: Evidence of Robertsonian Fusion Events and Supernumerary Chromosomes

Chromosomes of the South American geckos Gymnodactylus amarali and G. geckoides from open and dry areas of the Cerrado and Caatinga biomes in Brazil, respectively, were studied for the first time, after conventional and AgNOR staining, CBG- and RBG-banding, and FISH with telomeric sequences. Comparative analyses between the karyotypes of open areas and the previously studied Atlantic forest species G. darwinii were also performed. The chromosomal polymorphisms detected in populations of G. amarali from the states of Goiás and Tocantins is the result of centric fusions (2n = 38, 39 and 40), suggesting a differentiation from a 2n = 40 ancestral karyotype and the presence of supernumerary chromosomes. The CBG- and RBG-banding patterns of the Bs are described. G. geckoides has 40 chromosomes with gradually decreasing sizes, but it is distinct from the 2n = 40 karyotypes of G. amarali and G. darwinii due to occurrence of pericentric inversions or centromere repositioning. NOR location seems to be a marker for Gymnodactylus, as G. amarali and G. geckoides share a medium-sized subtelocentric NOR-bearing pair, while G. darwinii has NORs at the secondary constriction of the long arm of pair 1. The comparative analyses indicate a non-random nature of the Robertsonian rearrangements in the genus Gymnodactylus.

Comparative chromosomal analyses in species of the genus Pimelodella (Siluriformes, Heptapteridae): occurrence of structural and numerical polymorphisms

Cytogenetic analyses were carried out in fispecies of Pimelodella from the main sub-basins of Up- per Parana River and Paraiba do Sul River. The diploid number ranged from 2n = 46 to 2n = 58 chromosomes, and all populations differed in the karyotype constitution. The presence of supernumerary chromosomes as well as the occurrence of a XX/XY sex chromosome system and heterochromatin polymorphisms were detected. The 18S rDNA FISH confi rmed the presence of single NORs and revealed additional sites on supernumerary chromosomes. The number and location of 5S rDNA sites were variable. Aspects related to the karyotypic evo- lution within the genus are discussed.

Modulation of gene expression in drug resistant Leishmania is associated with gene amplification, gene deletion and chromosome aneuploidy

Gene expression and DNA copy number analyses using full genome oligonucleotide microarrays of Leishmania reveal molecular mechanisms of methotrexate resistance.

Geographic Variation in Meiotic Instability in <I>Eucheira socialis</I> (Lepidoptera: Pieridae)

We studied four populations of the pierid butterfly Eucheira socialis Westwood, located in the Mexican states of Sinaloa, Durango, Mexico, and Oaxaca. We found extreme geographic variation in spermatogenic abnormalities, including a variable number of chromosomes, irregular pairing of chromosomes, lagging chromosomes in metaphase I, lagging chromosomes in anaphase I, the production of micronuclei, and the failure of some spermatids to condense before maturation. We also present evidence suggesting the production of aneuploid sperm. These abnormalities correlate with previously reported male biases in the primary sex ratio of two of these populations. The population with the greatest bias in sex ratio also exhibited the highest frequencies of spermatogenic abnormalities. Because butterflies have female heterogamety and Eucheira females are XO, a possible mechanism linking the sex ratio biases and these abnormalities is nondisjunction of the X chromosomes during spermatogenesis, yielding disomic X sperm. We conclude that the most parsimonious explanation for the meiotic abnormalities in E. socialis is the presence of supernumerary chromosomes, which are associated with sex ratio biases in other systems.

Chromosomes of some argentine angiosperms and their taxonomic significance

Abstract Meiotic or mitotic chromosomes of eleven species of angiosperms native in Argentina, belonging to seven families, were studied in order to be used in cytotaxonomic studies and gain some insights on the evolutive relationships of the different groups. Most of our data were the first cytological information for the species. The genus Alvaradoa Liebm. was investigated cytologically for the first time. The novel karyologically studied species, all diploid, were: Bomarea macrocephala Pax and Bomarea stans Kränz. 2n = 18, Loasa bergii Hieron. 2n = 26, Alvaradoa subovata Cronquist 2n = 16, Schizanthus grahamii Gillies 2n = 20, Viola montagnei Gay and Viola roigii Rossow 2n = 14. The same numbers to the ones previously reported in the literature were found from different populations of Cajophora chuquitensis (Meyen) Urb. & Gilg. 2n = 18, Ramorinoa girolae Speg. 2n = 20, and Schizanthus grahamii Gillies 2n = 20. The presence of supernumerary chromosomes, 0 to 6, in Ligaria cuneifolia (Ruiz & Pav.) Tiegh., 2n = 20, was recorded. Data are compared with previously published results and chromosome figures of all studied species are provided.

Chiasma Frequency in Frogs of the Genus Leiopelma (Amphibia; Anura) and a Test of the Hypothesis of Inducible Recombination

The rate of recombination in three species of Leiopelma (Leiopelmatidae, Anura) from New Zealand was estimated by measuring chiasma frequency in spermatocyte bivalents. Both the mean and intra-individual variance of excess chiasmata frequency differed among the three species (L. hochsletteri = 13.17 5 2.96 SD, L. harnilroni = 9.69 + 1.16 SD; L. archeyi = 10.71 1.1 1 SD). L. hochstetteri has one of the highest rates of intra-individual variation in chiasma frequency found in frogs. The presence of supernumerary chromosomes in L. hochsretteri was used to test the theory of inducible recombination. If supernumeraries are parasites, then they will be associated with an increase in either chiasma frequency or an increase in within-individual variance. However, this was not found in L. hochsferteri, Nevertheless, the high variance in chiasma frequency associated with these putative genomic parasites in L. hochstetteri makes it impossible to rule out the Red Queen hypothesis as an explanation.

B Chromosomes and Natural Triploidy in <i>Rhamdia</i> sp. (Pisces, Siluriformes, Heptapteridae)

Cytogenetical studies were carried out on 13 specimens of Rhamdia sp. from Grande stream (Paraiba do Sul river basin, Mantiqueira hills, Brazil). It was evidenced a standard diploid number 2n=58 chromosomes (46M/SM and 12ST), plus 1 to 4 B chromosomes, found in 10 specimens. One individual presented natural triploidy, lacking B chromosomes. Fluorescent in situ hybridization with 5S and 18S rDNA probes was employed to improve the conventional karyotypical analyses. Inferences about the presence of supernumerary chromosomes within the genus Rhamdia, based on the karyotypical evolutionary pattern of this group, as well as the reoccurrence of natural triploidy in fish at Mantiqueira hills are discussed.

Comparative cytogenetics and supernumerary chromosomes in the Brazilian lizard genus Enyalius (Squamata, Polychrotidae).

Cytogenetical analyses based on conventional and differential staining were performed for the first time on five species of the Brazilian lizard genus Enyalius: E. bibronii, E. bilineatus, E. iheringii, E. leechii, and E. perditus. The species share a similar 2n = 36 (12M + 24m) karyotype, comprised of 12 metacentric or submetacentric macrochromosomes, except for an acrocentric pair 6 that characterizes E. bibronii. The 24 microchromosomes were acrocentrics, but in E. perditus two meta/submetacentric microchromosome pairs were unambiguously identified. Karyotypes with 2n = 37 and 2n = 37/38 chromosomes were also observed in some specimens of E. bilineatus as a result of the presence of supernumerary chromosomes (Bs). Ag-NORs were always located at the distal region of the long arm of the submetacentric pair 2. The constitutive heterochromatin was mostly restricted to the pericentromeric regions of some macrochromosomes and microchromosomes. A XX:XY mechanism of sex determination with a dot-like Y microchromosome occurs in E. bilineatus, E. leechii, and E. perditus.

The genus Ornithogalum L. (Hyacinthaceae) in Italy. XIII. Ornithogalum adalgisae Groves

Summary Omithogalum adalgisae Groves was described in 1877 and it had not been found since then. Recently it was been rediscovered in Apulia (South Italy), in the surroundings of Lecce and Bari. O. adalgisae has been studied from morphological and caryological points of view. It is a polyploid endemic with 2n = 5x = 45 and In = 6x = 54 chromosomes. The presence of supernumerary chromosomes has been observed too.

Two Tandem Fusions and Supernumerary Chromosomes inNectomys Squamipes(Cricetidae, Rodentia)

SUMMARYIn Nectomys squamipes collected in different regions of Brazil, two basic chromosomal entities with 2n = 52 and 56 chromosomes occurred. Both entities are characterized by variations in the diploid numbers due to the presence of supernumerary chromosomes (2n = 52, 53, 54, 55 and 2n = 56, 57, 58, 59). Two tandem fusions have been recognized as the mechanism involved in the differentiation of the two basic karyotypes (2n = 52 and 2n = 56). G- and C-band patterns, localization of the nucleolus organizer regions (NOR's) and R-banding obtained after 5-BrdU incorporation are presented. The supernumerary chromosomes, the Y and the short arm of the X chromosome are late replicating.

Supernumerary Chromosomes in Saxifraga virginiensis (Saxifragaceae)

Acetocarmine squashes of root tips have demonstrated that 2n = 20 and 38 in Saxifraga virginiensis. These contrast with the earlier reported count of 2n = 28 for this species. In several populations supernumerary chromosomes were detected. Both intrapopulational and interpopulational variation in supernumerary chromosome number were detected, with the largest number of supernumerary chromosomes observed being six. Because these supernumerary chromosomes are equal in size to many of the smaller A chromosomes during mitotic metaphase, the presence of supernumerary chromosomes in this species could not be ascertained by analysis of mitotic metaphase preparations alone. During mitotic prophase, however, the supernumerary chromosomes of S. virginiensis are highly heterochromatic, appearing more densely coiled and darkly stained than the A chromosomes. This characteristic facilitated the recognition of supernumerary chromosomes in this species. The similarity in size of A and supernumerary chromosomes during mitotic metaphase and the observation of six supernumerary chromosomes in one population suggest that the count of 2n = 28 reported earlier for S. virginiensis may actually be a misinterpretation of 2n = 20 plus 8 supernumerary chromosomes. Furthermore, these findings and the observation of this same supernumerary chromosome phenomenon in other species of Saxifraga raise the possibility that some of the many disparate chromosome counts attributed to aneuploidy in the large genus Saxifraga may also be the result of misinterpretations of supernumerary chromosomes as A chromosomes.

SUPERNUMERARY CHROMOSOMES IN SAXIFRAGA VIRGINIENSIS (SAXIFRAGACEAE)

Acetocarmine squashes of root tips have demonstrated that 2n = 20 and 38 in Saxifraga virginiensis. These contrast with the earlier reported count of 2n = 28 for this species. In several populations supernumerary chromosomes were detected. Both intrapopulational and interpopulational variation in supernumerary chromosome number were detected, with the largest number of supernumerary chromosomes observed being six. Because these supernumerary chromosomes are equal in size to many of the smaller A chromosomes during mitotic metaphase, the presence of supernumerary chromosomes in this species could not be ascertained by analysis of mitotic metaphase preparations alone. During mitotic prophase, however, the supernumerary chromosomes of S. virginiensis are highly heterochromatic, appearing more densely coiled and darkly stained than the A chromosomes. This characteristic facilitated the recognition of supernumerary chromosomes in this species. The similarity in size of A and supernumerary chromosomes during mitotic metaphase and the observation of six supernumerary chromosomes in one population suggest that the count of 2n = 28 reported earlier for S. virginiensis may actually be a misinterpretation of 2n = 20 plus 8 supernumerary chromosomes. Furthermore, these findings and the observation of this same supernumerary chromosome phenomenon in other species of Saxifraga raise the possibility that some of the many disparate chromosome counts attributed to aneuploidy in the large genus Saxifraga may also be the result of misinterpretations of supernumerary chromosomes as A chromosomes.

Morpho‐karyological Types of Dugesia (Turbellaria, Tricladida) in Israel and Their Distribution Patterns

AbstractPopulations of Dugesia in Israel have been classified on morphological and karyological criteria into 5 types. Two of these are morphologically similar to the Dugesia lugubris group (n = 4) but differ karyologically (Types 1 and 2: n=8), and three types are morphologically similar to the Dugesia gonocephala group (n= 8) but two differ karyologically (Types 4 and 5: n= 9). The three ‘gonocephala’ types are distributed in three distinct areas of Israel with little overlap, while the two ‘lugubris’ types are found in springs of one of these areas, The Rift Valley, where special localised conditions prevail. Possible relationships between Types 3, 4 and 5 are discussed with particular reference to their karyotypes and the presence of supernumerary chromosomes in Type 5.