Molecular Cytogenetic Techniques Research Articles

Evolutionary Dynamics of the W Chromosome in Caenophidian Snakes.

The caenophidian (assigned also as “advanced”) snakes are traditionally viewed as a group of reptiles with a limited karyotypic variation and stable ZZ/ZW sex chromosomes. The W chromosomes of the caenophidian snakes are heterochromatic, and pioneering studies demonstrated that they are rich in repetitive elements. However, a comparative study of the evolutionary dynamics of the repetitive content of the W chromosome across the whole lineage is missing. Using molecular-cytogenetic techniques, we explored the distribution of four repetitive motifs (microsatellites GATA, GACA, AG and telomeric-like sequences), which are frequently accumulated in differentiated sex chromosomes in vertebrates, in the genomes of 13 species of the caenophidian snakes covering a wide phylogenetic spectrum of the lineage. The results demonstrate a striking variability in the morphology and the repetitive content of the W chromosomes even between closely-related species, which is in contrast to the homology and long-term stability of the gene content of the caenophidian Z chromosome. We uncovered that the tested microsatellite motifs are accumulated on the degenerated, heterochromatic W chromosomes in all tested species of the caenophidian snakes with the exception of the Javan file snake representing a basal clade. On the other hand, the presence of the accumulation of the telomeric-like sequences on the caenophidian W chromosome is evolutionary much less stable. Moreover, we demonstrated that large accumulations of telomeric-like motifs on the W chromosome contribute to sexual differences in the number of copies of the telomeric and telomeric-like repeats estimated by quantitative PCR, which might be confusing and incorrectly interpreted as sexual differences in telomere length.

Harnessing Genetic Diversity of Wild Gene Pools to Enhance Wheat Crop Production and Sustainability: Challenges and Opportunities

Wild species are extremely rich resources of useful genes not available in the cultivated gene pool. For species providing staple food to mankind, such as the cultivated Triticum species, including hexaploid bread wheat (Triticum aestivum, 6x) and tetraploid durum wheat (T. durum, 4x), widening the genetic base is a priority and primary target to cope with the many challenges that the crop has to face. These include recent climate changes, as well as actual and projected demographic growth, contrasting with reduction of arable land and water reserves. All of these environmental and societal modifications pose major constraints to the required production increase in the wheat crop. A sustainable approach to address this task implies resorting to non-conventional breeding strategies, such as “chromosome engineering”. This is based on cytogenetic methodologies, which ultimately allow for the incorporation into wheat chromosomes of targeted, and ideally small, chromosomal segments from the genome of wild relatives, containing the gene(s) of interest. Chromosome engineering has been successfully applied to introduce into wheat genes/QTL for resistance to biotic and abiotic stresses, quality attributes, and even yield-related traits. In recent years, a substantial upsurge in effective alien gene exploitation for wheat improvement has come from modern technologies, including use of molecular markers, molecular cytogenetic techniques, and sequencing, which have greatly expanded our knowledge and ability to finely manipulate wheat and alien genomes. Examples will be provided of various types of stable introgressions, including pyramiding of different alien genes/QTL, into the background of bread and durum wheat genotypes, representing valuable materials for both species to respond to the needed novelty in current and future breeding programs. Challenging contexts, such as that inherent to the 4x nature of durum wheat when compared to 6x bread wheat, or created by presence of alien genes affecting segregation of wheat-alien recombinant chromosomes, will also be illustrated.

Cytogenetic study on the invasive species Gmelinoides fasciatus in the ecosystem of the Gulf of Finland

The amphipod Gmelinoides fasciatus from Lake Baikal is an example of a species being introduced into a number of water bodies in Russia, including the water system of North-west Russia, to expand food reserves of commercial fish. The interest in this crustacean has been attributed to its successful adaptation and expanding habitat area in the region. In order to assess the role of genetic mechanisms in adaptation to new conditions the frequency of chromosomal aberrations (ChA) at anaphase and telophase stages of mitosis in G. fasciatus embryos from six local populations of Lake Baikal and two invasive populations of the Gulf of Finland, originating from natural habitats were studied in two sequential years. The average level of ChA varied slightly between 0.95% in the samples collected in Lake Baikal and 2.9% in those from the Gulf of Finland. A significant increase in the frequency of ChA was found at two sites in Lake Baikal in 2015 and at two locations in the Gulf of Finland in 2016. First information on G. fasciatus chromosome number and constitution acquired by means of molecular cytogenetic techniques is presented and discussed. The results enable us to suggest this amphipod as a sensitive model to study possible mechanisms of biological adaptation and at the same time as a natural bioindicator of the environmental state.

Abstract 756: Molecular characterization of triploid and tetraploid urine FISH samples

Abstract Urothelial carcinomas (UC) are characterized, among other aberrations, by chromosome 3, 7, 17 gains and 9p21 (p16) loss. Since UC cells readily exfoliate into the urine, molecular cytogenetics techniques have been used to detect cells consistent with UC diagnosis and follow-up: a multitarget Fluorescence In Situ Hybridization (FISH) test, composed of 3, 7 and 17 centromeres and 9p21 locus multicolor probes, has been proved useful for atypical cells identification in both void urine and lower and upper urinary tract samples before morphological changes are apparent through cytological and histological examination. To date, there are no uniform criteria for urine FISH scoring though the test is commonly considered positive following the UroVysion Bladder Cancer Kit criteria (Abbott Molecular): 4 or more cells with a gain of 2 or more chromosomes (polysomy), and/or 12 or more cells with 9p21 homozygous deletion. This definition of polysomy includes trisomy and tetrasomy classes, but, as tetraploidy may represent cells at S/G2 phase, this criterion may lead to false-positives; moreover it has been described that also inflammation induces tetraploidy, and that small percentages of normal urine cells show trisomy/tetrasomy. On the other hand, triploidy and tetraploidy may have a direct role in tumorigenesis, as an intermediate state in the development of cancer aneuploidy. At the moment little is reported about the clinical correlations of urine FISH cases showing only trisomy/tetrasomy and more data are needed to clarify the diagnostic value of triploid and tetraploid urothelial cells. Aiming to better classify patients with a trisomy/tetrasomy urine FISH result, we extracted genomic DNA from 50 fixed urine cell suspensions, previously tested by urine FISH, and investigated them for the presence of fibroblast growth factor receptor 3 (FGFR3) and telomerase reverse transcriptase (TERT) promoter mutations, which constitute the most recurrent somatic alterations in BC. In particular frequent mutations in exons 7, 10 and 15 of FGFR3 characterize non-muscle invasive UC while mutations in the core promoter region of TERT gene, mainly at -124 and -146 positions from the ATG start site, have emerged as the most frequent somatic genetic alteration in both non-muscle invasive and muscle invasive UC. All specimens were subjected to PCR amplification and Sanger sequencing for FGFR3 exon 7 and 10, and for the C228T and C250T TERT promoter mutations. A preliminary analysis of 20 urine FISH cases showed 4 samples with trisomy/tetrasomy, and 1 of these 4 had a mutation of the TERT promotor. Complete results of the FGFR3 and TERT promoter molecular analysis will be presented and correlated to both FISH results and patients clinical data, in order to evaluate if the presence of FGFR3 and/or TERT promoter mutations in urine samples with FISH detected trisomy/tetrasomy may help to identify patients with a higher risk of recurrence and progression. Citation Format: Lorenza Pecciarini, Valeria De Pascali, Ilaria Francaviglia, Anna Talarico, Chiara Iacona, Massimo Freschi, Maria Giulia Cangi, Claudio Doglioni. Molecular characterization of triploid and tetraploid urine FISH samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 756. doi:10.1158/1538-7445.AM2017-756

A sibship with duplication of Xq28 inherited from the mother; genomic characterization and clinical outcomes

BackgroundLoss-of-function mutations in methyl-CpG-binding protein 2 (MECP2; MIM *300005) results in the Rett syndrome, whereas gain-of-function mutations are associated with the MECP2 duplication syndrome.MethodsWe did research on a family with two brothers showing Xq28 duplication syndrome using various molecular cytogenetic techniques such as multiplex ligation-dependent probe amplification and array-based genomic hybridization.ResultsThe duplicated region had several genes including MECP2 and interleukin-1 receptor associated kinase 1 (IRAK1; MIM *300283). MECP2 and IRAK1 were associated with the neurological phenotypes in dose-sensitive and dose-critical manner. The brothers demonstrated severe intellectual disability, autistic features, generalized hypotonia, recurrent infections, epilepsy, choreiform movements such as hand-wringing movement, and moderate increased spasticity with the lower limbs. The X-inactivation test showed a complete skewed X inactivation pattern of mother. In this reason, the mother had the same loci duplication but showed significantly little neurological manifestation compared to the two sons.ConclusionsMECP2/IRAK1 duplication at Xq28 is inherited as an X-linked recessive trait and male-specific disorder associated with severe intellectual disability. We tried to analyze the information of the relationship between neuropsychiatric phenotype and the extent of duplication at Xq28 by comparing with previous reports.

A novel cytogenetic and molecular characterization of renal metanephric adenoma: Identification of partner genes involved in translocation t(9;15)(p24;q24)

Renal metanephric adenoma (MA) is a rare benign tumor frequently misclassified when microscopic features alone are applied. The correct classification of a renal tumor is critical for diagnostic, prognostic, and therapeutic purposes. Despite the advancements in cancer genomics, up until recently relatively few genetic alterations critical to MA development have been recognized. Recent data suggest that 90% of MA have BRAFV600E mutations; the genetics of the remaining 10% are unclear. To date, only one case of a chromosomal translocation, t(9;15)(p24;q24) associated with MA has been reported. However, the potential role of the KANK1 gene, which lies near the breakpoint of the short arm of chromosome 9p24, in the etiology of MA was not examined. We identified the same cytogenetic aberration utilizing molecular cytogenetic techniques in a 22-year-old female patient, and further investigated the genes involved in the translocation that might have contributed to tumorigenesis. A series of fluorescence in situ hybridization (FISH) probes identified the rearranged genes to be KANK1 on chromosome 9 (9p24.3) and NTRK3 on chromosome 15 (15q25.3). Mate-Pair genome sequencing validated the balanced translocation between 9p24.3 and 15q25.3, involving genes KANK1 and NTRK3, respectively. BRAFV600E mutational analysis was normal. Our findings indicate that gene fusions may be one mechanism by which functionally relevant genes are altered in the development of MA. Molecular and cytogenetic analyses have elucidated a novel genetic aberration, which helps to provide a better understanding of this genomic change and assist in diagnosis and classification of new subgroups/entities in metanephric adenomas.

A new method for real-time evaluation of pepsin digestion of paraffin-embedded tissue sections, prior to fluorescence in situ hybridisation

Fluorescence in situ hybridisation (FISH) is a molecular cytogenetic technique, which is regularly applied to formalin-fixed paraffin-embedded (FFPE) tissue sections of a variety of cancers to assess chromosomal aberrations. However, high-quality FISH requires optimal enzymatic digestion, and insufficient digestion is not noted until the hybridisation signals are evaluated in the fluorescence microscope. As a consequence, FISH results may be unreliable, and the experiment might have to be repeated. To solve this problem, we developed a new method for real-time evaluation of enzymatic tissue digestion. Termination of enzyme activity at the proper time facilitates successful hybridisation, and experiments do not have to be repeated. We first performed FISH on 20 FFPE samples, which had been pepsin digested for different times, and this revealed distinct morphological changes within the nucleus and perinuclear space that were detectable by light microscopy. These observations suggested that the presence of intact and clear bare nuclei, surrounded by a translucent perinuclear space, might serve as an indicator of adequate digestion. We developed a protocol for assessment of this indicator, based on morphological features, and applied this to a collection of 400 tissue samples, partly of breast cancer and partly of different types of lymphoma, prior to FISH. The FISH success rate was 99.5% (398/400), which was significantly higher than that of the conventional method. In all successful cases, morphological signs of adequate digestion were paralleled by easily interpretable FISH signals. This new method for the real-time assessment of digestion quality improved the success rate of FISH and in addition was simple and rapid.

Origin of B chromosomes in Characidium alipioi (Characiformes, Crenuchidae) and its relationship with supernumerary chromosomes in other Characidium species.

B chromosomes are apparently dispensable components found in the genomes of many species that are mainly composed of repetitive DNA sequences. Among the numerous questions concerning B chromosomes, the origin of these elements has been widely studied. To date, supernumerary chromosomes have been identified in approximately 60 species of fish, including species of the genus Characidium Reinhardt, 1867 in which these elements appear to have independently originated. In this study, we used molecular cytogenetic techniques to investigate the origin of B chromosomes in a population of Characidium alipioi Travassos, 1955 and determine their relationship with the extra chromosomes of other species of the genus. The results showed that the B chromosomes of Characidium alipioi had an intraspecific origin, apparently originated independently in relation to the B chromosomes of Characidium gomesi Travassos, 1956 Characidium pterostictum Gomes, 1947 and Characidium oiticicai Travassos, 1967, since they do not share specific DNA sequences, as well as their possible ancestral chromosomes and belong to different phylogenetic clades. The shared sequences between the supernumerary chromosomes and the autosommal sm pair indicate the origin of these chromosomes.

A Rare Familial Paracentric Inversion in the Long Arm of Chromosome 8: Case Report and Review of the Literature

Background/Aim: The incidence of paracentric inversions (PAI)in the general population ranges from 0.09-0.49/1,000 and PAIs involving a relatively short chromosome segment, are generally considered to be harmless. However, PAI carriers have a very low risk to give rise to a viable zygote (3.8%).To present a rare case of a healthy individual, carrier of an 8q paracentric inversion. Methods: A 37-year-old man and his 30-year-old wife were referred for karyotypic analysis due to a previous miscarriage at 33 weeksof gestation. Cytogenetic analysis was performed on peripheralblood lymphocytes by GTG banding. Molecular karyotype analysis performed using Agilent G3 4x180 K CGH+SNP microarray platform. Results: The wife had a normal karyotype 46,XX but the man’s karyotype was 46,XY,inv(8)(q23.1q24.2). Karyotypic analysis ofhis parents revealed that his mother carried the same inversion.Molecular analysis reported no duplication or loss in or near the inverted region. Conclusions: Review of the literature revealed the rarity ofchromosome 8 paracentric inversions and showed that although the risk of a carrier to have an abnormal offspring is low, in cases of large inversions or previous abortions prenatal diagnosis should be offered by conventional and molecular cytogenetic techniques.

Molecular cytogenetic techniques for identification of copy-number variations

In the latter decades, the conventional cytogenetics techniques have experienced significant advancement into molecular cytogenetics technologies. The limitations of conventional cytogenetics techniques have largely been overcome by these new technologies. Molecular cytogenetics techniques are basic

Application of Genomic In Situ Hybridization in Horticultural Science.

Molecular cytogenetic techniques, such as in situ hybridization methods, are admirable tools to analyze the genomic structure and function, chromosome constituents, recombination patterns, alien gene introgression, genome evolution, aneuploidy, and polyploidy and also genome constitution visualization and chromosome discrimination from different genomes in allopolyploids of various horticultural crops. Using GISH advancement as multicolor detection is a significant approach to analyze the small and numerous chromosomes in fruit species, for example, Diospyros hybrids. This analytical technique has proved to be the most exact and effective way for hybrid status confirmation and helps remarkably to distinguish donor parental genomes in hybrids such as Clivia, Rhododendron, and Lycoris ornamental hybrids. The genome characterization facilitates in hybrid selection having potential desirable characteristics during the early hybridization breeding, as this technique expedites to detect introgressed sequence chromosomes. This review study epitomizes applications and advancements of genomic in situ hybridization (GISH) techniques in horticultural plants.

Erratum to: A de novo 3p13 deletion induced by a complex chromosomal rearrangement combined with a pericentric inversion of chromosome 3, inv(3)(p13q12), and a translocation between chromosome 3 and 8, t(3;8)(q13.1;q24.2), in a child with developmental delay

A de novo complex chromosomal rearrangement is very rare but likely to be present in a child with developmental disabilities and physical alterations. A child presented in this study showed global developmental delay and some typical phenotypes. Initial karyotyping and FISH analysis in the patient showed an apparently de novo balanced translocation between chromosome 3 and 8, t(3;8)(q13.1;q24.2). Further analysis using multiplex ligation-dependent probe amplification and array-based comparative genomic hybridization revealed a cryptic microdeletion on 3p13 region. Nearly one-third of balanced rearrangements are reported to involve cryptic disruptions at breakpoints, however, the microdeletion of the proposita was present in non-translocated region of the chromosome 3. After careful reevaluation of the results, a pericentric inversion, inv(3)(p13q13.1) that induced deletion was revealed. The clinical features of developmental delay in cognition, language, and motor function and facial and physical phenotype of the proposita were similar to those found in the children with 3p13 deletion. This case shows that combined molecular cytogenetic techniques with routine karyotyping are very useful to identify subtle genomic changes associated with abnormal phenotypes.

The Novel Translocation t(4;15)(q31;q22) in AML Is Associated with a Proliferative Phenotype in the Presence of All-Trans Retinoic Acid (ATRA)

Introduction: We describe for the first time, a novel chromosomal translocation in AML. The cells bearing this translocation proliferated rapidly following stimulation with ATRA in vitro. A 30-year old woman presented with monocytic AML. Karyotype revealed: 46,XX,t(9;11)(p22;q23)[13]/46,XX[7]. Mutational analysis showed an activating mutation in NRAS (c.34G>A; p.G12S). She achieved remission with standard induction therapy followed by cytarabine consolidation in the absence of an optimal donor. Following a disease free interval of 8 months, she relapsed. Karyotype at relapse: 46,XX,t(4;15)(q31;q22),t(9;11)(p22;q23)[20] (Figure 1). Mutational analysis revealed no new mutations. In the setting of chemotherapy refractory disease, she was enrolled on a phase I clinical trial combining escalating doses of TCP (tranylcypromine, Parnate¨) with fixed doses of ATRA (NCT02273102). The patient died from rapid disease progression shortly after her first cycle of therapy. Unexpectedly, we observed a rapid proliferation in the patient’s blasts following treatment with ATRA in vitro. We hypothesized that the novel t(4;15) translocation was involved in the regulation of retinoic acid (RA) signaling, and may have contributed to the rapid disease progression observed in this patient when she was treated with ATRA. To this end, we fully characterized the fusion gene and created a cell line bearing the translocation. Using these cells, we will further elucidate the mechanisms accounting for a rare and potentially clinically relevant effect of ATRA, in vitro.Methods: Cytogenetics and molecular-cytogenetic techniques, next generation sequencing (WES), RNA-seq, RT-PCR, and direct Sanger sequencing were used to map the chromosomal translocation. Cell proliferation and Annexin V apoptosis assays were used to test the effects of ATRA and various retinoic acid receptor (RAR) agonists and antagonists in vitro. Cells were treated with ATRA, RARα, and RARγ agonists and antagonists for 72 h and cell proliferation and apoptosis were measured with CellTiter-Glow (Promega)¨ luminescence viability assay and Annexin V/PI staining (FACS), respectively.Results: We mapped the t(4;15)(q31;q22) at the single nucleotide level, and discovered a novel fusion of TMEM154 (4q31.3) and RASGRF1 (15q24.2) genes at both the DNA and RNA level. The fusion protein included exons 1-6 from TMEM154 and exons 15-24 from RASGRF1. RASGRF1 (Ras protein specific nucleotide releasing factor 1) activates Ras by catalyzing the exchange of Ras-bound GDP for GTP. We determined that TMEM154 (transmembrane protein 154) is regulated by RA based on gene expression profiling. This particular translocation appears to result in a proliferative advantage in AML cells treated with RAR agonists such as ATRA, even at physiological levels (10 nM) (Figure 2). In MLL-rearranged cell lines without t(4;15), ATRA has a neutral or anti-proliferative effect, suggesting that the t(4;15) product interacts with the RA pathway to induce proliferation of AML blasts. We hypothesize that by increasing expression of TMEM154-RASGRF1, ATRA drives proliferation through Ras signaling. Of note, RAR antagonists inhibited proliferation and induced cell death (Figure 2). Also, treating the cells with MAP Kinase and Ras inhibitors consistently diminished the proliferative effect of ATRA. Updated studies shedding light on the mechanism of interaction between RA signaling and the TMEM154-RASGRF1 fusion protein will be presented.Conclusions: Our study for the first time identifies t(4;15) as a novel and pathogenic translocation in AML. This rare event may confer a proliferative advantage in the presence of ATRA and caution is advised should patients with this lesion be considered for treatment with ATRA. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Pallister–Killian syndrome: Cytogenetics and molecular investigations of mosaic tetrasomy 12p in prenatal chorionic villus and in amniocytes. Strategy of prenatal diagnosis

ObjectivePallister–Killian syndrome (PKS) is a rare, sporadic genetic disorder caused by mosaic tetrasomy of the short arm of chromosome 12 (12p). Clinically, PKS is characterized by several systemic abnormalities, such as intellectual impairment, hearing loss, epilepsy, hypotonia, craniofacial dysmorphism, pigmentary skin anomalies, epilepsy, and a variety of congenital malformations. Prenatally, PKS can be suspected in the presence of ultrasound anomalies: diaphragmatic hernia, rhizomelic micromelia, hydrops fetalis, fetal overweight, ventriculomegaly in the central nervous system, congenital heart defects, or absent visualization of the stomach. In all these cases, a detailed genetic study is required. PKS is diagnosed by prenatal genetic analysis through chorionic villus sampling, genetic amniocentesis, and cordocentesis. Case ReportWe report two cases of PKS with prenatal diagnosis of isochromosome 12p made by cytogenetic studies. The first case is of a 36-year-old pregnant woman who underwent genetic chorionic villus sampling at 13th weeks of gestation after 1st trimester prenatal ultrasound revealed clinical features of PKS: flat nasal bridge and fetal hydrops. The second case is of a 32-year-old pregnant woman with genetic amniocentesis at 17th weeks of gestation that showed mos46,XX[21]/47,XX,+i(12p) associated to PKS. ConclusionNew molecular cytogenetic techniques array comparative genomic hybridization and fluorescence in-situ hybridization in association with conventional karyotype are pivotal innovative tools to search for chromosomic anomalies and for a complete prenatal diagnosis, especially in cases such as PKS where array comparative genomic hybridization analysis alone could not show mosaicism of i(12p).

Идентификация маркеров профессионального сочетанного облучения молекулярно-цитогенетическим методом mFISH

Идентификация маркеров профессионального сочетанного облучения молекулярно-цитогенетическим методом mFISH

Identification of small marker chromosomes using microarray comparative genomic hybridization and multicolor fluorescent in situ hybridization.

BackgroundMarker chromosomes are small supernumerary chromosomes that cannot be unambiguously identified by chromosome banding techniques alone. However, the precise characterization of marker chromosomes is important for prenatal diagnosis and proper genetic counseling. In this study, we evaluated the chromosomal origin of marker chromosomes using a combination of banding cytogenetics and molecular cytogenetic techniques including diverse fluorescence in situ hybridization (FISH) assays and array comparative genomic hybridization (array CGH).ResultsIn a series of 2871 patients for whom cytogenetic analysis was requested, 14 cases with small supernumerary marker chromosomes (sSMCs) were identified. Nine sSMCs were mosaic, and five nonmosaic. Of the nine cases with known parental origins, four were identified as de novo, and four and one were maternally and paternally inherited, respectively. Six sSMCs were identified by FISH using centromeric probes; three sSMCs were derived from chromosome 15, including two heterochromatic sSMC(15)s and a large sSMC(15) spanning 15q11.1q13.1, and three sSMCs originated from chromosome 14 or 22. Array CGH revealed two cases with derivatives of chromosome 2 and whole chromosome painting multicolor-FISH (M-FISH) identified three cases with derivatives of chromosome 6, 16, and 19, respectively. One maker chromosome in Turner syndrome was characterized as sSMC(X) by preferential application of a centromeric probe for X-chromosome. In addition, one sSMC composed of genomic materials from chromosomes 12 and 18 was identified in parallel with parental karyotype analysis that revealed the reciprocal balanced translocation.ConclusionsThis report is the largest study on sSMCs in Korea and expands the spectrum of sSMCs that are molecularly characterized.Electronic supplementary materialThe online version of this article (doi:10.1186/s13039-016-0273-5) contains supplementary material, which is available to authorized users.

Cytogenetics of the Thorny Catfish Trachydoras paraguayensis (Eigenmann & Ward, 1907), (Siluriformes, Doradidae): Evidence of Pericentric Inversions and Chromosomal Fusion

The karyotype and chromosomal characteristics of Trachydorasparaguayensis, a representative of the South American catfish family Doradidae, were analyzed by conventional (Giemsa staining, silver staining, C-banding) and molecular (FISH with rDNA and telomeric probes) cytogenetic techniques. The diploid chromosome number was 2n = 56, with 36 metacentric, 16 submetacentric, and 4 subtelocentric chromosomes in both sexes; however, a remarkable heteromorphism in pair 22 (submetacentric and metacentric elements) was detected in 6 individuals. Compared to other representatives of Doradidae which mostly have 58 chromosomes, the karyotype of T. paraguayensis suggests a reduction in 2n due to chromosomal fusion, as could be deduced from the presence of an interstitial telomere sequence in the submetacentric pair 19. Pale heterochromatic blocks were present in the terminal regions of some chromosomes, very similar to other species of Doradidae. The interstitial position of the NORs observed in the karyotype of T. paraguayensis differs from those reported for most Doradidae species, indicating that it is a derived character. FISH with 5S rDNA revealed 2 interstitial fluorescent signals in the submetacentric pair 22, and the polymorphism of these sites likely resulted from a pericentric inversion.

Rapid diagnosis of pseudomosaicism in a case of Level II mosaicism for trisomy 5 in a single colony from an in situ culture of amniocytes and a review of mosaic trisomy 5 at amniocentesis

ObjectiveWe present prenatal diagnosis of pseudomosaicism for trisomy 5 and a review of the literature of mosaic trisomy 5 at amniocentesis. Case ReportA 39-year-old woman underwent amniocentesis at 17 weeks of gestation, which revealed a karyotype of 47,XY,+5[1]/46,XY[20]. The single colony with trisomy 5 had five metaphase cells, and all five cells had the karyotype of 47,XY,+5. Repeat amniocentesis performed at 20 weeks of gestation revealed a karyotype of 46,XY in 27/27 colonies. Simultaneously, interphase fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH), and quantitative fluorescent polymerase chain reaction (QF-PCR) were performed on uncultured amniocytes. Interphase FISH revealed no trisomy 5 in 100 uncultured amniocytes. aCGH revealed no genomic imbalance. QF-PCR excluded uniparental disomy 5. A healthy 3662-g male baby was delivered with a normal karyotype in cord blood and 3.75% (3/80 cells) of trisomy 5 cells in uncultured urinary cells compared with 0.95% (1/105 cells) of trisomy 5 cells in normal control examined by FISH at 1.5 months of age. A review of seven cases with mosaic trisomy 5 at amniocentesis shows that 4/7 had clinically normal outcome, 3/7 had structural defects, mainly the heart, 6/6 had normal karyotype in blood, and 2/3 had mosaic trisomy 5 in the fetal tissues. ConclusionPrenatal diagnosis of mosaic trisomy 5 should alert the possibility of fetal structural abnormalities, especially the heart, and culture artifacts. We suggest that the application of molecular cytogenetic techniques such as aCGH, interphase FISH, and QF-PCR on uncultured amniocytes is useful in our understanding of the mosaic status at repeat amniocentesis.

Distribution of Telomeric Sequences (TTAGGG)n in Rearranged Chromosomes of Phyllotine Rodents (Cricetidae, Sigmodontinae)

Phyllotines are sigmodontine rodents endemic to South America with broad genetic variability, Robertsonian polymorphisms being the most frequent. Moreover, this taxon includes a species with multiple sex chromosomes, which is infrequent in mammals. However, molecular cytogenetic techniques have never been applied to phyllotines to elucidate their karyotypic evolution. We studied the chromosomes of 4 phyllotine species using FISH with a pantelomeric probe (TTAGGG)_n. Graomys griseoflavus, Eligmodontia puerulus, and E. morgani are polymorphic for Robertsonian translocations, whereas Salinomys delicatus possesses XX/ XY₁Y₂ sex chromosomes. Telomeric signals were detected at both ends of all chromosomes of the studied species. In S. delicatus interstitial telomeric sequences (ITS) were observed in the 3 major chromosome pairs, which are equidistant from one of the telomeres in these chromosomes. These results suggest that ITS are important in the reshuffling of the highly derived karyotype of S. delicatus. Considering the phylogeny of phyllotines, the Robertsonian rearrangements of G. griseoflavus, E. puerulus, and E. morgani possibly represent chromosome fusions which have occurred independently. The pericentromeric regions of the biarmed chromosomes of these species do not contain telomeric sequences characteristic for strict fusions of recent origin, suggesting a common pattern of telomeric repeat loss during chromosomal evolution of these rodents.

Genomic Organization Under Different Environmental Conditions: Hoplosternum Littorale as a Model.

The Amazon has abundant rivers, streams, and floodplains in both polluted and nonpolluted environments, which show great adaptability. Thus, the goal of this study was to map repetitive DNA sequences in both mitotic chromosomes and erythrocyte micronuclei of tamoatás from polluted and nonpolluted environments and to assess the possible genotoxic effects of these environments. Individuals were collected in Manaus, Amazonas (AM), and submitted to classical and molecular cytogenetic techniques, as well as to a blood micronucleus test. Diploid number equal to 60 chromosomes are present in all individuals, with 18S ribosomal DNA sites present in one chromosome pair and no interstitial telomeric sites on chromosomes. The micronucleus test showed no significant differences in pairwise comparisons between environments or collection sites, but the Rex3 retroelement was dispersed on the chromosomes of individuals from unpolluted environments and compartmentalized in individuals from polluted environments. Divergent numbers of 5S rDNA sites are present in individuals from unpolluted and polluted environments. The mapping of repetitive sequences revealed that micronuclei have different compositions both intra- and interindividually that suggests different regions are lost in the formation of micronuclei, and no single fragile region undergoes breaks, although repetitive DNA elements are involved in this process.