Showing papers on "Karyotype published in 2006"

Mechanisms of chromosome number reduction in Arabidopsis thaliana and related Brassicaceae species

Abstract: Evolution of chromosome complements can be resolved by genome sequencing, comparative genetic mapping, and comparative chromosome painting. Previously, comparison of genetic maps and gene-based phylogenies suggested that the karyotypes of Arabidopsis thaliana (n = 5) and of related species with six or seven chromosome pairs were derived from an ancestral karyotype with eight chromosome pairs. To test this hypothesis, we applied multicolor chromosome painting using contiguous bacterial artificial chromosome pools of A. thaliana arranged according to the genetic maps of Arabidopsis lyrata and Capsella rubella (both n = 8) to A. thaliana, A. lyrata, Neslia paniculata, Turritis glabra, and Hornungia alpina. This approach allowed us to map the A. lyrata centromeres as a prerequisite to defining a putative ancestral karyotype (n = 8) and to elucidate the evolutionary mechanisms that shaped the karyotype of A. thaliana and its relatives. We conclude that chromosome “fusions” in A. thaliana resulted from (i) generation of acrocentric chromosomes by pericentric inversions, (ii) reciprocal translocation between two chromosomes (one or both acrocentric), and (iii) elimination of a minichromosome that arose in addition to the “fusion chromosome.” Comparative chromosome painting applied to N. paniculata (n = 7), T. glabra (n = 6), and H. alpina (n = 6), for which genetic maps are not available, revealed chromosomal colinearity between all species tested and allowed us to reconstruct the evolution of their chromosomes from a putative ancestral karyotype (n = 8). Although involving different ancestral chromosomes, chromosome number reduction followed similar routes as found within the genus Arabidopsis.

Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes

Abstract: All snake species exhibit genetic sex determination with the ZZ/ZW type of sex chromosomes. To investigate the origin and evolution of snake sex chromosomes, we constructed, by FISH, a cytogenetic map of the Japanese four-striped rat snake (Elaphe quadrivirgata) with 109 cDNA clones. Eleven of the 109 clones were localized to the Z chromosome. All human and chicken homologues of the snake Z-linked genes were located on autosomes, suggesting that the sex chromosomes of snakes, mammals, and birds were all derived from different autosomal pairs of the common ancestor. We mapped the 11 Z-linked genes of E. quadrivirgata to chromosomes of two other species, the Burmese python (Python molurus bivittatus) and the habu (Trimeresurus flavoviridis), to investigate the process of W chromosome differentiation. All and 3 of the 11 clones were localized to both the Z and W chromosomes in P. molurus and E. quadrivirgata, respectively, whereas no cDNA clones were mapped to the W chromosome in T. flavoviridis. Comparative mapping revealed that the sex chromosomes are only slightly differentiated in P. molurus, whereas they are fully differentiated in T. flavoviridis, and E. quadrivirgata is at a transitional stage of sex-chromosome differentiation. The differentiation of sex chromosomes was probably initiated from the distal region on the short arm of the protosex chromosome of the common ancestor, and then deletion and heterochromatization progressed on the sex-specific chromosome from the phylogenetically primitive boids to the more advanced viperids.

Improved methods for working with fish chromosomes with a review of metaphase chromosome banding

Abstract: Improved methods for obtaining, preparing, and staining fish chromosomes are described. Included are procedures for resolving serial or G-type bands. A brief review of various metaphase banding procedures and their use in fishes is also presented.

Identification of der(1;19)(q10;p10) in five oligodendrogliomas suggests mechanism of concurrent 1p and 19q loss.

Abstract: Deletions of portions of chromosomes 1p and 19q are closely associated with the oligodendroglioma histologic phenotype. In most cases, 1p and 19q are codeleted, yet the mechanism of dual loss is unexplained. We report 5 cases (World Health Organization grade III) in which metaphase cytogenetics identified a derivative chromosome consisting of what appears to be the whole arms of 1q and 19p forming a der(1;19)(q10;p10). Metaphase fluorescent in situ hybridization (FISH) confirmed the derivative chromosome was composed of 1q and 19p material in 3 cases; in 2 cases with few metaphases, FISH confirmed 19p material on the derivative chromosome. In all cases, interphase FISH showed net loss of 1p and 19q in 77% to 92% of cells, and microsatellite studies were consistent with 1p and 19q loss. We hypothesize the following: occurrence of a balanced whole-arm translocation between chromosomes 1 and 19 forming 2 derivative chromosomes, one composed of 1q and 19p, the other of 1p and 19q. Subsequent loss of the der(1;19)(p10;q10) then results in the simultaneous 1p and 19q loss observed in oligodendroglioma with retention of the der(1;19)(q10;p10) seen in these cases.

Klinefelter syndrome and other sex chromosomal aneuploidies

Abstract: The term Klinefelter syndrome (KS) describes a group of chromosomal disorder in which there is at least one extra X chromosome to a normal male karyotype, 46,XY. XXY aneuploidy is the most common disorder of sex chromosomes in humans, with prevalence of one in 500 males. Other sex chromosomal aneuploidies have also been described, although they are much less frequent, with 48,XXYY and 48,XXXY being present in 1 per 17,000 to 1 per 50,000 male births. The incidence of 49,XXXXY is 1 per 85,000 to 100,000 male births. In addition, 46,XX males also exist and it is caused by translocation of Y material including sex determining region (SRY) to the X chromosome during paternal meiosis. Formal cytogenetic analysis is necessary to make a definite diagnosis, and more obvious differences in physical features tend to be associated with increasing numbers of sex chromosomes. If the diagnosis is not made prenatally, 47,XXY males may present with a variety of subtle clinical signs that are age-related. In infancy, males with 47,XXY may have chromosomal evaluations done for hypospadias, small phallus or cryptorchidism, developmental delay. The school-aged child may present with language delay, learning disabilities, or behavioral problems. The older child or adolescent may be discovered during an endocrine evaluation for delayed or incomplete pubertal development with eunuchoid body habitus, gynecomastia, and small testes. Adults are often evaluated for infertility or breast malignancy. Androgen replacement therapy should begin at puberty, around age 12 years, in increasing dosage sufficient to maintain age appropriate serum concentrations of testosterone, estradiol, follicle stimulating hormone (FSH), and luteinizing hormone (LH). The effects on physical and cognitive development increase with the number of extra Xs, and each extra X is associated with an intelligence quotient (IQ) decrease of approximately 15–16 points, with language most affected, particularly expressive language skills.

Is there a relationship between sperm chromosome abnormalities and sperm morphology

Abstract: This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.

Clinical and Cytogenetic Analyses in Uveal Melanoma

Abstract: PURPOSE. Uveal melanoma is one of the most frequently occurring primary intraocular malignancies in the Western world. Cytogenetically these tumors are characterized by typical chromosomal losses and gains, such as loss of 1p, 3, and 6q and gain of 6p and 8q. Whereas most studies focus on known aberrations, in this one, cytogenetic changes were characterized and correlated with clinical and histopathologic parameters. METHODS. Karyotypes of 74 primary uveal melanomas were analyzed with respect to the presence or absence of chromosomal gains and losses. In the analysis, classic clinical and histopathologic parameters were analyzed together with the chromosomal aberrations. RESULTS. At a median follow-up of 43 months, 34 patients had died or had metastatic disease. Clonal chromosomal abnormalities were present in 59 tumors. The most frequent chromosomal abnormalities involved chromosome 8 (53%); loss of chromosome 3, p-arm (41%) and q-arm (42%); partial loss of chromosome 1, p-arm (24%); and abnormalities in chromosome 6 that resulted in gain of 6p (18%) and/or loss of 6q (28%). Less-frequent aberrations were abnormalities in chromosome 16, in particular loss of chromosome 16 q-arm (16%). In the univariate analysis, loss of chromosome 3, largest tumor diameter, gain in 8q, and mixed/epithelioid cell type in the tumor compared with tumors without these chromosomal changes or with a spindle cell type was associated with decreased disease-free survival. When corrected for confounding variables, significance of gain of 8q and cell type was decreased, whereas the significance of loss of chromosome 3p or 3q and largest tumor diameter remained the same. CONCLUSIONS. Monosomy 3 and largest tumor diameter are the most significant in determining survival of patients with uveal melanoma. Abnormalities in the q-arm of chromosome 16 are relatively common in uveal melanoma, but are not associated with survival or other cytogenetic or histopathologic

Mechanisms of chromosome instability in cancers

Abstract: Most tumours arise through clonal selection and waves of expansion of a somatic cell that has acquired genetic alterations in essential genes either controlling cell death or cell proliferation. Furthermore, stability of the genome in cancer cells becomes precarious and compromised because several cancer-predisposing mutations affect genes that are responsible for maintaining the integrity and number of chromosomes during cell division. Consequently, the archetypical transformation in tumour cells results in aneuploidy. Indeed, almost all tumour cells display a host of karyotype alterations, showing translocations, gains or losses of entire or large parts of chromosomes. Cancers do not necessarily have a higher mutation rate than normal tissue at the nucleotide level, unless they have gained a mutator phenotype through exposure to environmental stress, but rather exhibit gross chromosomal changes. Therefore, it appears that the main mechanism of tumour progression stems from chromosome instability. Chromosomal instability prevailing in tumour cells arises through several different pathways and is probably controlled by hundreds of genes. Therefore, this review describes the main factors that control chromosome stability through telomere maintenance, mechanisms of cell division, and the mitotic checkpoints that govern centrosome duplication and correct chromosome segregation.

Identification of NUP98 abnormalities in acute leukemia: JARID1A (12p13) as a new partner gene

Abstract: Chromosome rearrangements are found in many acute leukemias. As a result, genes at the breakpoints can be disrupted, forming fusion genes. One of the genes involved in several chromosome aberrations in hematological malignancies is NUP98 (11p15). As NUP98 is close to the 11p telomere, small translocations might easily be missed. Using a NUP98-specific split-signal fluorescence in situ hybridization (FISH) probe combination, we analyzed 84 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia, or myelodysplastic syndrome with either normal karyotypes or 11p abnormalities to investigate whether there are unidentified 11p15 rearrangements. Neither NUP98 translocations nor deletions were identified in cases with normal karyotypes, indicating these aberrations may be very rare in this group. However, NUP98 deletions were observed in four cases with unbalanced 11p aberrations, indicating that the breakpoint is centromeric of NUP98. Rearrangements of NUP98 were identified in two patients, both showing 11p abnormalities in the diagnostic karyotype: a t(4;11)(q1?3;p15) with expression of the NUP98-RAP1GDS1 fusion product detected in a 60-year-old woman with AML-M0, and an add(11)(p15) with a der(21)t(11;21)(p15;p13) observed cytogenetically in a 1-year-old boy with AML-M7. JARID1A was identified as the fusion partner of NUP98 using 3' RACE, RT-PCR, and FISH. JARID1A, at 12p13, codes for retinoblastoma binding protein 2, a protein implicated in transcriptional regulation. This is the first report of JARID1A as a partner gene in leukemia.

High-Resolution Single-Copy Gene Fluorescence in Situ Hybridization and Its Use in the Construction of a Cytogenetic Map of Maize Chromosome 9

Abstract: High-resolution cytogenetic maps provide important biological information on genome organization and function, as they correlate genetic distance with cytological structures, and are an invaluable complement to physical sequence data. The most direct way to generate a cytogenetic map is to localize genetically mapped genes onto chromosomes by fluorescence in situ hybridization (FISH). Detection of single-copy genes on plant chromosomes has been difficult. In this study, we developed a squash FISH procedure allowing successful detection of single-copy genes on maize (Zea mays) pachytene chromosomes. Using this method, the shortest probe that can be detected is 3.1 kb, and two sequences separated by ∼100 kb can be resolved. To show the robust nature of this protocol, we localized nine genetically mapped single-copy genes on chromosome 9 in one FISH experiment. Integration of existing information from genetic maps and the BAC contig-based physical map with the cytological structure of chromosome 9 provides a comprehensive cross-referenced cytogenetic map and shows the dramatic reduction of recombination in the pericentromeric heterochromatic region. To establish a feasible mapping system for maize, we also developed a probe cocktail for unambiguous identification of the 10 maize pachytene chromosomes. These results provide a starting point toward constructing a high-resolution integrated cytogenetic map of maize.

Current status of chromosomal abnormalities in mouse embryonic stem cell lines used in Japan.

Abstract: We performed chromosomal analysis on 540 mouse embryonic stem (ES) cell lines obtained during 2001 to 2004 from 20 institutions in Japan. Overall, 66.5% of the ES cell lines showed normal chromosomal numbers, but 15.9%, 9.1%, and 2.8% showed modal chromosomal numbers of 41, 42, and 39, respectively. When we karyotyped 88 ES cell lines selected arbitrarily from the 540 lines, 53 (60.2%) showed normal diploid karyotypes; the sex chromosome constitution of 52 lines was XY, with the remaining 1 being XX. Among 35 ES cell lines showing abnormal karyotypes, trisomy of chromosome 8 (41, XY, +8) was dominant (51.4%), 14.3% had trisomy 8 with loss of one sex chromosome (40, XO, +8), and 11.4% had trisomy 8 together with trisomy 11 (42, XY, +8, +11). Karyotypic abnormalities including trisomy 8 and trisomy 11 occurred in 88.6% and 17.1% of ES cell lines, respectively. The XO sex chromosome constitution was observed in 25.7% of all abnormal ES cell lines. Of the 88 selected ES cell lines, 60 lines were established from strain 129 animals, 17 from F1 progeny of C57BL/6J x CBA (called TT2 in this study), and 11 from C57BL/6J mice. Normal diploid karyotypes were observed in 58.3% of lines derived from 129, 58.8% of those from TT2, and 72.7% of C57BL/6J. The relatively high incidence of abnormalities in chromosomal number and karyotype in ES cell lines used in Japan suggests the importance of chromosomal analysis of ES cells for successful establishment of new animal models through germline transmission.

Evolution of the karyotype and sex chromosome systems in basal clades of araneomorph spiders (Araneae: Araneomorphae).

Abstract: Concepts of spider karyotype evolution are based mostly on advanced and most diversified clade, the entelegyne lineage of araneomorph spiders. Hence the typical spider karyotype is supposed to consist exclusively of acrocentric chromosomes including the multiple X chromosomes. However, our data show considerable diversity of chromosome morphology and sex chromosome systems in basal clades of araneomorphs. Karyotypes of basal araneomorphs consist of holocentric (superfamily Dysderoidea) or normal chromosomes with localized centromere. In males of basal araneomorphs the prophase of first meiotic division includes a long diffuse stage. Multiple X chromosomes are less common in basal clades. The sex chromosome system of many families includes a Y chromosome or nucleolus organizer region that occurs rarely in the entelegyne spiders. A derived X1X2Y system with an achiasmatic sex-chromosome pairing during meiosis was found in the families Drymusidae, Hypochilidae, Filistatidae, Sicariidae, and Pholcidae. This suggests a monophyletic origin of the families. In some lineages the X1X2Y system converted into an X0 system, as found in some pholcids, or into an XY system, which is typical for the family Diguetidae. The remarkable karyotype and sex chromosome system diversity allows us to distinguish four evolutionary lineages of basal araneomorphs and hypothesize about the ancestral karyotype of araneomorphs.

Mouse telocentric sequences reveal a high rate of homogenization and possible role in Robertsonian translocation

Abstract: The telomere and centromere are two specialized structures of eukaryotic chromosomes that are essential for chromosome stability and segregation. These structures are usually characterized by large tracts of tandemly repeated DNA. In mouse, the two structures are often located in close proximity to form telocentric chromosomes. To date, no detailed sequence information is available across the mouse telocentric regions. The antagonistic mechanisms for the stable maintenance of the mouse telocentric karyotype and the occurrence of whole-arm Robertsonian translocations remain enigmatic. We have identified large-insert fosmid clones that span the telomere and centromere of several mouse chromosome ends. Sequence analysis shows that the distance between the telomeric T2AG3 and centromeric minor satellite repeats range from 1.8 to 11 kb. The telocentric regions of different mouse chromosomes comprise a contiguous linear order of T2AG3 repeats, a highly conserved truncated long interspersed nucleotide element 1 repeat, and varying amounts of a recently discovered telocentric tandem repeat that shares considerable identity with, and is inverted relative to, the centromeric minor satellite DNA. The telocentric domain as a whole exhibits the same polarity and a high sequence identity of >99% between nonhomologous chromosomes. This organization reflects a mechanism of frequent recombinational exchange between nonhomologous chromosomes that should promote the stable evolutionary maintenance of a telocentric karyotype. It also provides a possible mechanism for occasional inverted mispairing and recombination between the oppositely oriented TLC and minor satellite repeats to result in Robertsonian translocations.

An XX/XY sex microchromosome system in a freshwater turtle, Chelodina longicollis (Testudines: Chelidae) with genetic sex determination

Abstract: Heteromorphic sex chromosomes are rare in turtles, having been described in only four species. Like many turtle species, the Australian freshwater turtle Chelodina longicollis has genetic sex determination, but no distinguishable (heteromorphic) sex chromosomes were identified in a previous karyotyping study. We used comparative genomic hybridization (CGH) to show that C. longicollis has an XX/XY system of chromosomal sex determination, involving a pair of microchromosomes. C-banding and reverse fluorescent staining also distinguished microchromosomes with different banding patterns in males and females in ∼70% cells examined. GTG-banding did not reveal any heteromorphic chromosomes, and no replication asynchrony on the X or Y microchromosomes was observed using replication banding. We conclude that there is a very small sequence difference between X and Y chromosomes in this species, a difference that is consistently detectable only by high-resolution molecular cytogenetic techniques, such as CGH. This is the first time a pair of microchromosomes has been identified as the sex chromosomes in a turtle species.

Phylogenetic conservation of chromosome numbers in Actinopterygiian fishes.

Abstract: The genomes of ray-finned fishes (Actinopterygii) are well known for their evolutionary dynamism as reflected by drastic alterations in DNA content often via regional and whole-genome duplications, differential patterns of gene silencing or loss, shifts in the insertion-to-deletion ratios of genomic segments, and major re-patternings of chromosomes via non-homologous recombination. In sharp contrast, chromosome numbers in somatic karyotypes have been highly conserved over vast evolutionary timescales - a histogram of available counts is strongly leptokurtic with more than 50% of surveyed species displaying either 48 or 50 chromosomes. Here we employ comparative phylogenetic analyses to examine the evolutionary history of alterations in fish chromosome numbers. The most parsimonious ancestral state for major actinopterygiian clades is 48 chromosomes. When interpreted in a phylogenetic context, chromosome numbers evidence many recent instances of polyploidization in various lineages but there is no clear indication of a singular polyploidization event that has been hypothesized to have immediately preceded the teleost radiation. After factoring out evident polyploidizations, a correlation between chromosome numbers and genome sizes across the Actinopterygii is marginally statistically significant (p = 0.012) but exceedingly weak (R (2) = 0.0096). Overall, our phylogenetic analysis indicates a mosaic evolutionary pattern in which the forces that govern labile features of fish genomes must operate largely independently of those that operate to conserve chromosome numbers.

Premeiotic endomitosis produces diploid eggs in the natural clone loach, Misgurnus anguillicaudatus (Teleostei: Cobitidae).

Abstract: The natural clone loach produces unreduced eggs genetically identical to somatic cells of the mother fish and such diploid eggs normally develop as a clone without genetic contribution of sperm. Following the identification of clonal nature and diploidy of eggs, we conducted cytological studies to determine the mechanisms responsible for this unusual oogenesis. Cytolological observation of full-grown oocytes cultured in vitro revealed that oocytes of both the clone and the control loach underwent two successive meiotic divisions: formation of a bipolar spindle and metaphase in meiosis I and equal segregation of chromosomes, extrusion of the first polar body and the appearance of metaphase of meiosis II. However, spindle size of the clone was larger than that of the control. Bivalent chromosome number of germinal vesicle of oocytes was 25 in the control diploid, whereas 50 in the clone. The results suggest that chromosomes are duplicated by mitosis without cytokinesis before meiosis, i.e. premeiotic endomitosis and then oocytes differentiated from tetraploid oogonia undergo a quasinormal meiosis followed by two successive divisions to produce diploid eggs.

Chromosome arrangement and nuclear architecture but not centromeric sequences are conserved between Arabidopsis thaliana and Arabidopsis lyrata

Abstract: In contrast to the situation described for mammals and Drosophila, chromosome territory (CT) arrangement and somatic homologous pairing in interphase nuclei of Arabidopsis thaliana (n = 5) are predominantly random except for a more frequent association of the chromosomes bearing a homologous nucleolus organizer region. To find out whether this chromosome arrangement is also characteristic for other species of the genus Arabidopsis, we investigated Arabidopsis lyrata ssp. lyrata (n = 8), one of the closest relatives of A. thaliana. First, we determined the size of each chromosome and chromosome arm, the sequence type of centromeric repeats and their distribution between individual centromeres and the position of the 5S/45S rDNA arrays in A. lyrata. Then we demonstrated that CT arrangement, homologous pairing and sister chromatid alignment of distinct euchromatic and/or heterochromatic regions within A. lyrata interphase nuclei are similar to that in A. thaliana nuclei. Thus, the arrangement of interphase chromosomes appears to be conserved between both taxa that diverged about 5 million years ago. Since the chromosomes of A. lyrata resemble those of the presumed ancestral karyotype, a similar arrangement of interphase chromosomes is also to be expected for other closely related diploid species of the Brassicaceae family.

Y chromosome microdeletions in azoospermic patients with Klinefelter's syndrome.

Abstract: Aim: To study the occurrence of Y chromosome microdeletions in azoospermic patients with Klinefelter's syndrome (KFS). Methods: Blood and semen samples were collected from azoospermic patients with KFS (n= 14) and a control group of men of proven fertility (n= 13). Semen analysis was done according to World Health Organization (WHO) guidelines. Blood samples were processed for karyotyping, fluorescent in situ hybridization (FISH) and measurement of plasma follicle stimulating hormone (FSH) by radioimmunoassay. To determine Y chromosome microdeletions, polymerase chain reaction (PCR) of 16 sequence tagged sites (STS) and three genes (DFFRY, XKRY and RBM1Y) was performed on isolated genomic DNA. Testicular fine needle aspiration cytology (FNAC) was done in selected cases. Results: Y chromosome microdeletions spanning the azoospermia factor (AZF)a and AZFb loci were found in four of the 14 azoospermic patients with KFS. Karyotype and FISH analysis revealed that, of the four cases showing Y chromosome microdeletion, three cases had a 47,XXY/ 46,XY chromosomal pattern and one case had a 46,XY/ 47,XXY/ 48,XXXY/ 48,XXYY chromosomal pattern. The testicular FNAC of one sample with Y chromosome microdeletion revealed Sertoli cell-only type of morphology. However, no Y chromosome microdeletions were observed in any of the 13 fertile men. All patients with KFS had elevated plasma FSH levels. Conclusion: Patients with KFS may harbor Y chromosome microdeletions and screening for these should be a part of their diagnostic work-up, particularly in those considering assisted reproductive techniques.

Array comparative genomic hybridization analysis in first-trimester spontaneous abortions with 'normal' karyotypes.

Abstract: Array comparative genomic hybridization (array CGH) analysis was conducted in chorionic villous samples from 20 first-trimester spontaneous abortions with G-banding normal chromosomes. A microarray, containing 2,173 BAC clones and covering the whole genome with a 1.5-Mb resolution, was constructed and used in the analysis. Two deletions were identified: a 1.4-Mb deletion at 3p26.2-p26.3 and a 13.7-Mb deletion at 13q32.3-qter. Reexamination of chromosome preparations from the sample with the 13.7-Mb deletion documented a mixture of cells with the 13q- chromosome and those with 46,XX chromosomes, the latter of which are likely to have been derived from contaminating decidual cells. This left the 1.4-Mb 3p deletion as the only instance with submicroscopic imbalance detected, giving a frequency of 1 in 19 (5%) G-banding normal abortions.

Phenotypic variability in isodicentric Y patients: study of nine cases.

Abstract: Isodicentric chromosomes are the most commonly reported aberrations of the human Y chromosome. As they are unstable during cell division and can generate various types of cell lines, most reported patients are chromosomal mosaics, generally including a 45,X cell line. Phenotypes depend on the location of the breakpoints as well as on the proportion of each cell line and vary from male to abnormal female or individual with ambiguous genitalia. Although phenotypic variability is known to also depend on the degree of mosaicism in the various tissues, gonads are rarely studied. We report nine cases of isodicentric Y chromosomes studied by conventional and molecular cytogenetic: three males, five females, and one individual with sexual ambiguity. Two males had a non-mosaic karyotype, while the third male was a mosaic with a predominant 46,XY cell line. Three of the females had a major 45,X cell line, while the last two females and the patient with ambiguous genitalia had a major 46,X,idic(Y) cell line. Analyses of gonadal tissues from the individual with sexual ambiguity and of three of the five female patients gave results concordant with their phenotype, allowing us to better understand the sexual differentiation of these patients.

Immortalization of a human colorectal adenoma cell line by continuous in vitro passage: possible involvement of chromosome 1 in tumour progression.

Abstract: A non-tumorigenic epithelial cell line designated PC/AA, derived from a large pre-malignant colorectal adenoma from a patient with familial polyposis coli (also referred to as hereditary adenomatosis of the colon and rectum) has became immortal in vitro. PC/AA has been passaged in vitro continuously for over A years and shows no signs of senescence. At early passage, PC/AA has a normal diploid karyotype but with late passage is showing signs of progression, becoming aneuploid and displaying signs of morphological transformation. Every cell examined of late-passage PC/AA has an isochro-mosome (Iq), and one other marker chromosome which is probably derived from an additional chromosome 8. The majority of cells examined have 48 chromosomes. Despite showing signs of progression in vitro, late-passage PC/AA has remained non-tumorigenic in athymic nude mice and retained morphological differentiation characteristics of colonic cells, in particular the ability to synthesize and secrete mucin. Two other cell lines derived from small adenomas did not become immortal in vitro and were also non-tumorigenic in athymic nude mice. The isolation of an immortal pre-malignant human epithelial cell line could prove invaluable in studies on human careinogenests and tumour progression. Our results, showing that only a large adenoma and no small adenomas have given rise to immortal cell lines, raise the possibility that the acquisition of in vitro immortality is associated with a relatively late stage in the adenoma-carcinoma sequence. The possible involvement of chromosome I in tumour progression is discussed.

Karyotype differentiation of four Cestrum species (Solanaceae) based on the physical mapping of repetitive DNA

Abstract: We studied the karyotypes of four Brazilian Cestrum species (C. amictum, C. intermedium, C. sendtnerianum and C. strigilatum) using conventional Feulgen staining, C-Giemsa and C-CMA3/DAPI banding, induction of cold-sensitive regions (CSRs) and fluorescent in situ hybridization (FISH) with rDNA probes. We found that the karyotypes of all four species was 2n = 2x = 16, with, except for the eighth acrocentric pair, a predominance of meta- and submetacentric chromosomes and various heterochromatin classes. Heterochromatic types previously unreported in Cestrum as neutral C-CMA30/DAPI0 bands, CMA3+ bands not associated with NORs, and C-Giemsa/CSR/DAPI- bands were found. The heterochromatic blocks varied in size, number, position and composition. The 45S rDNA probe preferentially located in the terminal and subterminal regions of some chromosomes, while 5S rDNA appeared close to the centromere of the long arm of pair 8. These results suggest that karyotype differentiation can occur mainly due to changes in repetitive DNA, with little modification in the general composition of the conventionally stained karyotype.

Factors affecting flow karyotype resolution.

Abstract: Background: One of the major factors which influences the chromosome purity achievable particularly during high speed sorting is the analytical resolution of individual chromosome peaks in the flow karyotype, as well as the amount of debris and fragmented chromosomes. We have investigated the factors involved in the preparation of chromosome suspensions that influence karyotype resolution. Methods: Chromosomes were isolated from various human and animal cell types using a series of polyamine buffer isolation protocols modified with respect to pH, salt concentration, and chromosome staining time. Each preparation was analyzed on a MoFlo sorter (DAKO) configured for high speed sorting and the resolution of the flow karyotypes compared. Results: High resolution flow cytometric data was obtained with chromosomes optimally isolated using hypotonic solution buffered at pH 8.0 and polyamine isolation buffer (with NaCl excluded) between pH 7.50 and 8.0. Extending staining time to more than 8 h with chromosome suspensions isolated from cell lines subjected to sufficient metaphase arrest times gave the best result with the lowest percentage of debris generated, tighter chromosome peaks with overall lower coefficients of variation, and a 1- to 5-fold increase in the yield of isolated chromosomes. Conclusions: Optimization of buffer pH and the length of staining improved karyotype resolution particularly for larger chromosomes and reduced the presence of chromosome fragments (debris). However, the most interesting and surprising finding was that the exclusion of NaCl in PAB buffer improved the yield and resolution of larger chromosomes. q 2006 International Society for Analytical Cytology