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Results for “karyotype evolution”

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PubMed2001

NUP98 gene rearrangements and the clonal evolution of chronic myelogenous leukemia.

The role of the BCR-ABL fusion gene in the pathogenesis of the chronic phase of chronic myelogenous leukemia (CML) has been well established. Several additional genetic changes have been reported to occur, at varying frequencies, during disease progression to "accelerated" and "blast crisis" phases. The NUP98 gene localized to chromosome band 11p15 has been found at the breakpoints of several distinct chromosomal translocations in patients with both de novo and therapy-related myelodysplastic syndromes (MDS) and acute myelogenous leukemia (AML). Using combined cytogenetic and molecular analyses, we have found rearrangements of the NUP98 gene in the leukemic cells of two patients with Philadelphia chromosome-positive CML, during disease evolution. As expected, analysis of the t(7;11)(p15;p15) from one of the patients showed an in-frame NUP98-HOXA9 fusion. The fusion points were similar to previously reported NUP98-HOXA9 fusion points from patients with MDS/AML. Our results indicate that the NUP98 gene is an additional, albeit infrequent, genetic target during clonal evolution of CML.

Chromosome Breakage↗
PubMed1975

Q-, C-, and G-banding patterns in the germ-line and somatic chromosomes of Miastor sp. (Diptera: Cecidomyidae).

Q-, C-, and G-banding patterns are described for the germ-line and somatic chromosomes of Miastor sp. The chromosome number in the germ line is 36, which is 3 less than that previously reported for the same cultured line 18 years ago. There are 8 chromosome groups: 8 large acrocentrics, 11 large and medium submetacentrics, 4 medium metacentrics, 4 medium subtelocentrics, 6 medium telocentrics, one medium acrocentric, one small submetacentric, and one small telocentric. All 8 large acrocentrics have a Q-band and an interstitial C-band in the short arm, suggesting that these chromosomes are at least partially homologous (or homeologous) and that the germ line originally was polyploid. Only one other germ-line chromosome, the small submetacentric, has a Q-band and an interstitial C-band. In somatic cells there are 8 chromosomes, 28 chromosomes having been eliminated during early cleavage. Three of the four pairs of somatic chromosomes are heteromorphic, despite the indications of a polyploid origin of the germ-line chromosomes and despite the presence of somatic pairing. Furthermore, there is a great deal of restriction on which chromosomes are retained in somatic cells, and it may be that the same 8 chromosomes are retained by all embryos. The G-banding pattern is not as clear as the other two banding patterns. The findings are discussed in relation to observations in other cecidomyids, and a model for the evolution of the chromosome system of Miastor is presented.

Animals↗
PubMed2004

The chicken genome and the developmental biologist.

Recently the initial draft sequence of the chicken genome was released. The reasons for sequencing the chicken were to boost research and applications in agriculture and medicine, through its use as a model of vertebrate development. In addition, the sequence of the chicken would provide an important anchor species in the phylogenetic study of genome evolution. The chicken genome project has its roots in a decade of map building by genetic and physical mapping methods. Chicken genetic markers for map building have generally depended on labour intensive screening procedures. In recent years this has all changed with the availability of over 450,000 EST sequences, a draft sequence of the entire chicken genome and a map of over 1 million SNPs. Clearly, the future for the chicken genome and developmental biology is an exciting one. Through the integration of these resources, it will be possible to solve challenging scientific questions exploiting the power of a chicken model. In this paper we review progress in chicken genomics and discuss how the new tools and information on the chicken genome can help the developmental biologists now and in the future.

Animals↗
PubMed1997

Molecular analysis of the cyclin-dependent kinase inhibitor genes, p15, p16, p18 and p19 in the myelodysplastic syndromes.

The myelodysplastic syndromes (MDS) are a heterogeneous group of clonal blood disorders characterized by dyshematopoiesis with a frequent evolution to acute leukemia. Chromosomal deletions rather than translocations are the predominant karyotypic abnormalities in MDS, suggesting a recessive mechanism in the pathogenesis of MDS, such as inactivation of tumor suppressor genes. A group of cyclin-dependent kinase inhibitors, p15 (INK4B), p16 (INK4A), p18 (INK4C) and p19 (INK4D), are candidate tumor suppressor genes. To determine whether genetic alterations of these genes play an important role in the development and/or progression of MDS, we examined 46 samples from MDS patients by Southern blotting, single-strand-conformation polymorphism (SSCP) using polymerase chain reaction (PCR) and sequencing of DNA. These samples included 13 refractory anemias (RA), four refractory anemias with ringed sideroblasts (RARS), 16 refractory anemias with an excess of blasts (RAEB), eight refractory anemias with an excess of blasts in transformation (RAEB-T) and five chronic myelomonocytic leukemia (CMMoL) samples. Except for allelic polymorphisms or silent point mutations, no alterations of coding regions of these four CDKI genes were identified. In summary, genetic abnormalities of the p15, p16, p18 and p19 genes are rare events in the development and/or progression of MDS.

Blotting, Southern↗
PubMed2000

Towards the minimal eukaryotic parasitic genome.

Microsporidia are well-known to infect immunocompromised patients and are also responsible for clinical syndromes in immunocompetent individuals. In recent years, evidence has been obtained in support of a very close relationship between Microsporidia and Fungi. In some species, the compaction of the genome and genes is remarkable. Thus, a systematic sequencing project has been initiated for the 2.9 Mbp genome of Encephalitozoon cuniculi, which will be useful for future comparative genomic studies.

Animals↗
PubMed2000

Frequency increase and mitotic stabilization of a B chromosome in the fish Prochilodus lineatus.

Six populations of the fish Prochilodus lineatus were analysed for B chromosome frequency. A study of spermatogenesis revealed the absence of B accumulation during the stages analysed. In one of the populations, from the Mogi-Guaçu river where samples have been analysed over a ten-year period, B chromosome frequency doubled between 1979-80 and 1987 89, whereas no additional changes were noticed in samples collected in 1991-92. The analysis of B chromosome mitotic instability, manifested by intraindividual variation in B chromosome number, indicated a very significant decrease during this time period. This suggests that, in the 1980s, this population was in the final stage of B chromosome invasion, and that there was a possible causal relationship between B mitotic instability and the accumulation mechanism that caused its frequency increase. Mitotic stabilization might thus be a way by which a mitotically unstable B chromosome may become neutralized.

Animals↗
PubMed2003

Tertiary trisomics in the garden pea as a model of B chromosome evolution in plants.

It is hypothesized that, in plants, genetically empty B chromosomes may originate from the extra chromosome (E) of tertiary trisomics if (i) the region of basic chromosomes homologous to the E (H-region) harbors a sporophytic lethal covered by the wild-type allele in E, and (ii) crossing-over between E and the H-region is suppressed. Under these conditions, most loss-of-function mutations occurring in the H-region are deleterious for haploid gametophytes, whereas those occurring in E are neutral or advantageous for hyperploid (n+1) gametophytes. As a result, natural selection at the gametophyte level can lead to the degeneration of E, leaving the H-region intact. Using Hammarlund translocation T(3-6)a, we synthesized two trisomic lines of the garden pea (Pisum sativum L.), where E was composed of the short arms of chromosomes 3 and 6 and the H-region carried recessive markers. In the trisomic line TRIS, we found few crossovers between E and the H-region. In the trisomic line TRUST, obtained after a change of basic chromosome constitution, recombination in this region was completely suppressed. After induction in the H-region of TRUST of a recessive sporophytic mutation rmv, two 15-chromosome lines of stable trisomics were established. One of them passed 11 generations, having produced more than 6000 individuals, all of them trisomic, and E remained present as a single element with no pairing partners. No tetrasomics were detected in these lines. If such trisomics occurred in nature, their extra chromosomes are likely to become a B chromosome.

Chromosomes, Plant↗
PubMed2004

Chromosome inheritance in triploid Pacific oyster Crassostrea gigas Thunberg.

Reproduction and chromosome inheritance in triploid Pacific oyster (Crassostrea gigas Thunberg) were studied in diploid female x triploid male (DT) and reciprocal (TD) crosses. Relative fecundity of triploid females was 13.4% of normal diploids. Cumulative survival from fertilized eggs to spat stage was 0.007% for DT crosses and 0.314% for TD crosses. Chromosome number analysis was conducted on surviving progeny from DT and TD crosses at 1 and 4 years of age. At Year 1, oysters from DT crosses consisted of 15% diploids (2n=20) and 85% aneuploids. In contrast, oysters from TD crosses consisted of 57.2% diploids, 30.9% triploids (3n=30) and only 11.9% aneuploids, suggesting that triploid females produced more euploid gametes and viable progeny than triploid males. Viable aneuploid chromosome numbers included 2n+1, 2n+2, 2n+3, 3n-2 and 3n-1. There was little change over time in the overall frequency of diploids, triploids and aneuploids. Among aneuploids, oysters with 2n+3 and 3n-2 chromosomes were observed at Year 1, but absent at Year 4. Triploid progeny were significantly larger than diploids by 79% in whole body weight and 98% in meat weight at 4 years of age. Aneuploids were significantly smaller than normal diploids. This study suggests that triploid Pacific oyster is not completely sterile and cannot offer complete containment of cultured populations.

Animals↗
PubMed2004

Evolutionary dynamics of a B chromosome invasion in island populations of the grasshopper Eyprepocnemis plorans.

Four natural populations of the grasshopper Eyprepocnemis plorans in the Mallorca island were analysed for several years revealing the recent invasion of the B1 chromosome from the south-west part of the island (Palma region) towards the north and to the east. In only 10 years, the mean number of Bs in the northern population at Pollença increased from 0.053 to 0.692. Therefore, B chromosome invasion seems to be very rapid and has recently arrived to the north of the island. The south-west (close to Palma) is the most likely point at which B invasion started in the Mallorca Island. Finally, the number of B chromosomes was significantly associated to an increase in chiasma frequency (and thus recombination) in A chromosomes.

Analysis of Variance↗