Karyotype Polymorphism Research Articles

P-235 Influence of female karyotype polymorphic variants on oocyte quality and embryo development

Abstract Study question Do polymorphic variants in the karyotype of women undergoing an IVF cycle directly affect oocyte and embryo laboratory parameters? Summary answer The presence of certain polymorphic variants negatively affects the oocyte survival rate and the blastocyst quality in an IVF cycle. What is known already In the recent years, there has been a growing interest in the study of polymorphic variants in infertile patients because their incidence, compared to the fertile population, is increased. However, most research has focused on the male patient study. Several studies have reported information about clinical outcomes, but the influence they may have on IVF laboratory procedures and embryo development has rarely been studied up to the blastocyst stage. In addition, it is very rare to find publications that show the study of polymorphisms according to their type or combination. Study design, size, duration Retrospective evaluation of a cohort of women who underwent autologous IVF cycles and karyotyping. The sample included 424 IVF cycles performed between July 2017-December 2021: control group (CG) with normal karyotype (211) and study group (SG) with polymorphisms (213). We studied the correlation between karyotype polymorphisms and laboratory outcomes in terms of: Number of Oocytes Retrieved, Fresh Oocyte Maturity (MII), Oocyte Survival after Thawing (TS), Fertilization (FZ), Oocyte Degeneration (OD) and Non-viable embryo rates. Participants/materials, setting, methods Analysis of the women karyotype, prior to the IVF cycle, was performed using the guidelines of the International System for Human Cytogenetic Nomenclature (ISCN). Differences between the different study groups (presence or absence of different chromosomal polymorphisms) were assessed with the appropriate statistical test according to the normality or non-normality of the variable distribution. Statistical analysis was performed using R statistical software (v.4.2.0) and SPSS (v.23.0, Chicago, IL, USA). Main results and the role of chance Average female age was 37.72 ± 3.98 (CG) and 36.73 ± 3.59 (SG). Average number of mature oocytes (MII) was: 6.45 ± 4.96(CG) and 7.59 ± 5.10 (SG). Statistically significant differences were found regarding the number of oocytes retrieved between the CG (8.14 ± 5.90) and the SG (9.53 ± 6.63) (p = 0.036), increasing when the ps+ variant was present (9.75 ± 7.21) (p = 0.045). However, no statistically significant differences were found between the presence of polymorphism (SG) and the CG in terms of: number of MII: 79.85% vs. 80.48% (p = 0.447), FZ: 73.76% vs. 70.49% (p = 0.352) and OD: 8.76% vs. 8.36% (p = 0.563) rates. In addition, the TS rate was statistically significant when there was the ps+ variant (82.95%) (p = 0.010) and/or combinations of more than one polymorphic variant (87.80%) (p = 0.044), compared to the CG (93.51%). Finally, according to embryo quality there was an increase in the non-viable embryos rate, on day 5 and/or day 6 of development, between the CG (34.17%) and the SG (43.02%) (p < 0.001), increasing when the ps+ variable was present (45.57%) (p < 0.001) and/or combinations of more than one polymorphic variant (p = 0.045). The results were corrected for confounding variables such as maternal age, oocyte origin and male factor variables, including polymorphic variants in the male karyotype. Limitations, reasons for caution Other variables that have not been analyzed may influence the outcomes. Larger prospective studies including homogeneous cohorts are needed in order to corroborate our initial results. Wider implications of the findings The polymorphic variants in the female karyotype, especially the “ps+” variant and the combination of multiple variants, could influence certain parameters in the laboratory. Therefore, it is important to request a karyotype to all patients before starting IVF treatment. Trial registration number NOT APPLICABLE

P-703 The role of maternal polymorphic karyotype variants among embryonic ploidy and mosaicism status in patients undergoing IVF treatments

Abstract Study question Is there a relationship between the chromosomal status of biopsied embryos and the presence of polymorphic variants in the female karyotype in IVF cycles? Summary answer The chromosomal status of biopsied embryos is prejudiced because of the presence of specific maternal polymorphic variants (qh-, qh+ and ps+) or combinations of them. What is known already Due to the increasing average age of patients who undergo IVF cycles with their own oocytes, more cycles are performed with embryo biopsy for preimplantation genetic test of aneuploidies (PGT-A). Thus, advanced maternal age has been defined as the main factor causing embryonic chromosomal abnormalities. However, few studies have established direct relationships with other factors. The prevalence of chromosomal polymorphic variants has a higher incidence in the infertile population, which is why there is a need to know the role they play in the genetic inheritance of embryos. Study design, size, duration Retrospective evaluation of a cohort of women who underwent autologous IVF cycles and karyotyping. The sample included 162 IVF cycles with embryo biopsy on D5 and/or D6 for PGT-A, performed between July 2017-December 2021: control group (CG) with normal karyotype (86) and study group (SG) with presence of polymorphisms (76). We studied the connection between maternal karyotype polymorphisms and molecular genetic outcomes in terms of euploid, mosaic, and aneuploid blastocyst rates. Participants/materials, setting, methods The analysis of the karyotype of women, prior to the IVF cycle, was performed using the guidelines of the International System for Human Cytogenetic Nomenclature (ISCN). The trophoectoderm biopsies on D5 and/or D6 blastocysts were analysed by NGS using the Illumina platform (VeriSeq Illumina®, San Diego, CA, USA). The association between the different polymorphic variants in the female karyotype and chromosomal status of embryos was analysed using R (v. 4.2.0) statistical software. Main results and the role of chance We analyzed the results of 483 embryos from 162 IVF-PGT-A cycles. Mean female age was 39.05±2.72 (CG) and 38.97±2.90 (SG). Mean number of mature oocytes (MII) was 7.16±3.94 (CG) and 8.01±5.33 (SG). Mean number of biopsied embryos was 2.97±2.15 (CG) and 2.93±1.88 (SG). No statistically significant differences were found between the CG and SG groups in terms of the rate of euploid embryos: 26.99% vs 21.50% (p = 0.3), transferable mosaic embryos: 8.90% vs 6.76% (p = 0.5), aneuploid embryos: 61.98% vs 69.96% (p = 0.12) and non-informative embryos: 2.13% vs 1.78% (p = 0.2), respectively. However, an increase in the rate of chromosomally abnormal embryos was observed when analysing each polymorphism individually. In females carrying the qh+ variant, we found a statistically significant decrease in the euploid embryo rate: 10.97% vs 26.00% found in CG (p = 0.036). Moreover, the variants qh+ and ps+ increased the rate of aneuploid embryos: 84.17% vs 63.48% in CG (p = 0.013) and 73.52% vs 61.30% in CG (p = 0.021), respectively. Furthermore, it is found that the qh- variant increased the rate of transferable mosaic embryos: 20.00% vs 8.90% in CG (p = 0.025). The results were corrected for confounding variables such as maternal age, oocyte origin and male factor variables, including polymorphic variants in the male karyotype. Limitations, reasons for caution Presence of unmeasured variables that may influence the results. Larger prospective studies including homogeneous cohorts are needed in order to corroborate our initial results. Wider implications of the findings The results show that polymorphic variants in the female karyotype may have a direct effect on the embryonic ploidy and mosaicism status. Therefore, it would be advisable for patients who undergo IVF-PGT-A cycles to have a karyotype performed and be informed of the implications that it may entail. Trial registration number Not applicable

Chromosomal polymorphism of the Ceratocystis fimbriata species complex in Brazil

Ceratocystis fimbriata is an important pathogen that causes wilt in several plant species. Despite the importance of this pathogen, knowledge about its karyotypic polymorphism and genomic architecture is limited. The main objective of this study was to investigate the karyotype of isolates of the C. fimbriata species complex from different host plants and geographical origins in Brazil. First, the identity of the isolates was confirmed conducting multilocus sequence analysis (MLSA) phylogeny using β-tubulin (TUBB), translation elongation factor 1α (TEF-1α) and mating-type (MAT1 and MAT2) gene sequences. To investigate the chromosomal polymorphism, two conditions of pulsed-field gel electrophoresis (PFGE) were used and the karyotypes of the isolates obtained. The retrotransposon-microsatellite amplified polymorphism (REMAP) molecular marker was utilized to assess the genetic variability among isolates. In the MLSA utilizing the concatenated gene sequences, Ceratocystis cacaofunesta and C. fimbriata formed separate clades, but considerable variation among C. fimbriata isolates was observed. Polymorphism in chromosome number and size was found, indicating the existence of genomic differences among isolates and occurrence of chromosomal rearrangements in the species complex. The number of chromosomes varied from seven to nine and the estimated minimum chromosome sizes were estimated to be between 2.7 and 6.0 Mbp. Small polymorphic chromosomes ranging from 1.2 to 1.8 Mbp were observed in all isolates, raising the hypothesis that they could be supernumerary chromosomes. REMAP analysis revealed a high genetic variability and that isolates from the same host tend to group together in a same cluster. Our results bring new insights into the chromosomal diversity and genome organization of the C. fimbriata complex.

The Kengyiliahirsuta karyotype polymorphisms as revealed by FISH with tandem repeats and single-gene probes.

Kengyiliahirsuta (Keng, 1959) J. L. Yang, C. Yen et B. R. Baum, 1992, a perennial hexaploidy species, is a wild relative species to wheat with great potential for wheat improvement and domestication. The genome structure and cross-species homoeology of K.hirsuta chromosomes with wheat were assayed using 14 single-gene probes covering all seven homoeologous groups, and four repetitive sequence probes 45S rDNA, 5S rDNA, pAs1, and (AAG)10 by FISH. Each chromosome of K.hirsuta was well characterized by homoeological determination and repeats distribution patterns. The synteny of chromosomes was strongly conserved in the St genome, whereas synteny of the Y and P genomes was more distorted. The collinearity of 1Y, 2Y, 3Y and 7Y might be interrupted in the Y genome. A new 5S rDNA site on 2Y might be translocated from 1Y. The short arm of 3Y might involve translocated segments from 7Y. The 7 Y was identified as involving a pericentric inversion. A reciprocal translocation between 2P and 4P, and tentative structural aberrations in the subtelomeric region of 1PL and 4PL, were observed in the P genome. Chromosome polymorphisms, which were mostly characterized by repeats amplification and deletion, varied between chromosomes, genomes, and different populations. However, two translocations involving a P genome segmental in 3YL and a non-Robertsonial reciprocal translocation between 4Y and 3P were identified in two independent populations. Moreover, the proportion of heterozygous karyotypes reached almost 35% in all materials, and almost 80% in the specific population. These results provide new insights into the genome organization of K.hirsuta and will facilitate genome dissection and germplasm utilization of this species.

Karyotyping of Fusarium oxysporum by Pulsed-Field Gel Electrophoresis and the Germ Tube Burst Method.

In fungi, karyotyping is fundamental to understanding their genome organization. It is also essential to study various genome- or chromosome-related topics such as karyotype polymorphisms and supernumerary or pathogenicity chromosomes. Here, we describe the protocols of pulsed-field gel electrophoresis and the germ tube burst method for molecular and cytological karyotyping of Fusarium oxysporum. The combined use of the two methods is valuable for determining definitive and comprehensive karyotypes of these fungi.

O-175 Impact of female chromosomal polymorphic variants on ovarian reserve markers and fertility treatments prognosis

Abstract Study question Could the presence of chromosomal polymorphisms in women undergoing fertility treatments influence ovarian reserve, oocyte preservation or IVF clinical outcomes? Summary answer Polymorphic variants of chromosomes seem to adversely influence the Anti-Müllerian Hormone (AMH) serum levels and the post-thawing oocyte survival rate. What is known already Infertile couples have been reported to have a higher incidence of karyotype abnormalities than the general population, which could lead to lower fertility rates. However, few studies have demonstrated the controversial relationship between these karyotype alterations in women and the specific involvement of these variants and their combinations in an IVF cycle. Therefore, there is a growing interest in categorizing chromosomal polymorphic variants and relating them to the subsequent evolution in ART cycles. Study design, size, duration Retrospective evaluation of a cohort of women undergoing IVF cycles in a private fertility center. The sample included 280 cycles performed between July 2017 and December 2020. The study explored the correlation between karyotype polymorphisms and IVF outcomes in terms of: Anti-Müllerian Hormone (AMH) level, Antral Follicle Count (AFC), Oocyte Maturity (MII), Oocyte Survival after Thawing (TS), Fertilization (FZ), Useful Embryos (UE), Biochemical (BP) and Clinical Pregnancy (CP), Miscarriage (M) and Live Birth (LB) rates. Participants/materials, setting, methods Women with karyotype performed before an IVF cycle. Chromosome analysis was carried out according to the International System for Human Cytogenetic Nomenclature guidelines (ISCN). Only own eggs cycles were included, and testicular sperm cycles were excluded. The normality of the distribution of the variables was assessed using the Shapiro-Wilk test. The association between IVF cycle parameters and the presence of polymorphisms was assessed by T-Student (parametric) or U-Mann-Whitney (non-parametric). Main results and the role of chance From a total of 280 IVF cycles, 198 met the inclusion criteria: Control Group (CG) with normal karyotype (94) and Study Group (SG) with presence of polymorphisms (104) were analyzed. Cycles with fresh (136) and warmed (62) oocytes were included. Mean female age was 37.66 ± 3.99 (CG) and 36.61 ± 3.72 (SG). The overall outcome rates were: 75.82% MII, 81.39% TS, 72.78% FZ, 49.07% UE on day 5, 21.82% BP, 78.18% CP, 14.53% M and 63.65% LB. Statistically significant differences were found between the presence of polymorphisms and mean AMH serum level between CG (2.36 ng/mL) and SG (1.74 ng/mL) (p = 0.04), especially when the type “qh+” was detected (1.01 ng/mL) (p = 0.02). Furthermore, statistically significant differences were found regarding oocyte thawing survival rate, which decreased in the SG (78.94%) compared to the CG (93.69%) (p = 0.02), mainly when the type “ps+” was detected (75.13%) (p < 0.01). No statistically significant differences were found between the presence of polymorphism and the AFC (p = 0.25), MII (p = 0.10), FZ (p = 0.93) or UE (p = 0.52) rate on day 5. In the same way, from 106 embryo transfers (ET) performed, no significant differences were found for BP, CP, M and LB rates (p > 0.05). Limitations, reasons for caution Larger prospective studies including homogeneous cohorts are needed in order to corroborate our initial results. Wider implications of the findings Our findings may represent a practical tool in order to advise these patients about their reproductive success, especially, in terms of post-thawing oocyte survival prognosis. Therefore, it could be provided more personalized prognostic information before embarking on IVF treatments. Trial registration number Not Applicable

Karyotypic polymorphism ofCrocidura tanakae(Eulipotyphla: Soricidae) and revision of the karyotype ofC. attenuatain mainland China

AbstractConventional karyotypes of Crocidura tanakae and C. attenuata collected from mainland China were examined by bone marrow and cell culture methods along with identification to species using molecular data. In contrast to C. tanakae from Taiwan, populations from mainland China were karyotypically polymorphic, varying in diploid number (2n) from 24 to 40 and fundamental number (FN) from 45 to 56. Autosomes are composed of 6–20 metacentric or submetacentric chromosomes, 0–8 subtelocentric chromosomes, and 0–24 telocentric chromosomes. These polymorphic karyotypes indicate the presence of two geographically separated races. The ancestral karyotype of C. tanakae potentially is the same as currently found on Taiwan: 2n = 40 and FN = 56. In contrast to C. tanakae, C. attenuata had a uniform karyotype (2n = 40, FN = 54) in mainland China, suggesting that previously reported karyotypic polymorphism in this species was an error due to the morphological crypsis between C. tanakae and C. attenuata in mainland China. The intricate karyotypic polymorphism of C. tanakae may be indicative of this species undergoing speciation.

Widespread Recombination Suppression Facilitates Plant Sex Chromosome Evolution.

Classical models suggest that recombination rates on sex chromosomes evolve in a stepwise manner to localize sexually antagonistic variants in the sex in which they are beneficial, thereby lowering rates of recombination between X and Y chromosomes. However, it is also possible that sex chromosome formation occurs in regions with preexisting recombination suppression. To evaluate these possibilities, we constructed linkage maps and a chromosome-scale genome assembly for the dioecious plant Rumex hastatulus. This species has a polymorphic karyotype with a young neo-sex chromosome, resulting from a Robertsonian fusion between the X chromosome and an autosome, in part of its geographic range. We identified the shared and neo-sex chromosomes using comparative genetic maps of the two cytotypes. We found that sex-linked regions of both the ancestral and the neo-sex chromosomes are embedded in large regions of low recombination. Furthermore, our comparison of the recombination landscape of the neo-sex chromosome to its autosomal homolog indicates that low recombination rates mainly preceded sex linkage. These patterns are not unique to the sex chromosomes; all chromosomes were characterized by massive regions of suppressed recombination spanning most of each chromosome. This represents an extreme case of the periphery-biased recombination seen in other systems with large chromosomes. Across all chromosomes, gene and repetitive sequence density correlated with recombination rate, with patterns of variation differing by repetitive element type. Our findings suggest that ancestrally low rates of recombination may facilitate the formation and subsequent evolution of heteromorphic sex chromosomes.

Karyological and cytogenetic features of conifers in arboretums and parklands

Aim. The study of karyological and cytogenetic features of conifers growing under conditions of introduction and increased recreational pressure, to identify biodiversity and solve the problems of population and environmental genetics of representatives of this group of plants. Methods. Classical chromosome research methods with staining with acetohematoxylin were used. Results. In species, forms, and cultivars of conifers from the Pinaceae and Cupressaceae families growing in arboretums and parklands, as well as being components of green spaces in settlements of different geographical regions, variability of chromosome numbers (mixoploidy), the appearance of B chromosomes, high occurrence, and a wide range of chromosomal and meiotic anomalies are discovered. Conclusions. Karyological and cytogenetic studies have shown the presence of karyotypic polymorphism and an increase in the number of various disorders of mitosis and meiosis in conifers when introduced under growing conditions in recreational areas. Keywords: conifers, introduction, chromosome number, chromosomal rearrangements, meiosis disorders.

Chromosomal Differentiation in Genetically Isolated Populations of the Marsh-Specialist Crocidura suaveolens (Mammalia: Soricidae).

The genus Crocidura represents a remarkable model for the study of chromosome evolution. This is the case of the lesser white-toothed shrew (Crocidura suaveolens), a representative of the Palearctic group. Although continuously distributed from Siberia to Central Europe, C. suaveolens is a rare, habitat-specialist species in the southwesternmost limit of its distributional range, in the Gulf of Cádiz (Iberian Peninsula). In this area, C. suaveolens is restricted to genetically isolated populations associated to the tidal marches of five rivers (Guadiana, Piedras, Odiel, Tinto and Guadalquivir). This particular distributional range provides a unique opportunity to investigate whether genetic differentiation and habitat specialization was accompanied by chromosomal variation. In this context, the main objective of this study was to determinate the chromosomal characteristics of the habitat-specialist C. suaveolens in Southwestern Iberia, as a way to understand the evolutionary history of this species in the Iberian Peninsula. A total of 41 individuals from six different populations across the Gulf of Cádiz were collected and cytogenetically characterized. We detected four different karyotypes, with diploid numbers (2n) ranging from 2n = 40 to 2n = 43. Two of them (2n = 41 and 2n = 43) were characterized by the presence of B-chromosomes. The analysis of karyotype distribution across lineages and populations revealed an association between mtDNA population divergence and chromosomal differentiation. C. suaveolens populations in the Gulf of Cádiz provide a rare example of true karyotypic polymorphism potentially associated to genetic isolation and habitat specialization in which to investigate the evolutionary significance of chromosomal variation in mammals and their contribution to phenotypic and ecological divergence.

Karyotype and Inversion Polymorphism of Natural Populations of Glyptotendipes glaucus (Meigen, 1818) (Diptera, Chironomidae) from Small Water Bodies of Kaliningrad

New data on chromosome polymorphism of one of the phytophilous species of chyronomids Glyptotendipes glaucus (Meigen, 1818) from five water bodies of Kaliningrad are presented. It is established that G. glaucus in the water bodies of Kaliningrad is characterized by an inversion type polymorphism. The level of natural inversion polymorphism for each population is determined. The inversion polymorphism is compared with earlier data for the Saratov, Bryansk, and Kaliningrad regions. The persistence of the distribution trend and prevalence of homo- and heterozygous inversions glaB1.2 and glaB2.2 and the fixation of the band sequence glaA2 in the heterozygous state in populations from the Karasevka and Chistyi ponds are noted. Typical of earlier studies of Glyptotendipes glaucus populations of Kaliningrad. The presence of inversion sequences glaG4 and glaD2 of Glyptotendipes glaucus populations in Kaliningrad typical for earlier undertaken studies persists.

Evidence for Karyotype Polymorphism in the Free-Living Flatworm, Macrostomum lignano, a Model Organism for Evolutionary and Developmental Biology.

Over the past decade, the free-living flatworm Macrostomum lignano has been successfully used in many areas of biology, including embryology, stem cells, sexual selection, bioadhesion and aging. The increased use of this powerful laboratory model, including the establishment of genomic resources and tools, makes it essential to have a detailed description of the chromosome organization of this species, previously suggested to have a karyotype with 2n = 8 and one pair of large and three pairs of small metacentric chromosomes. We performed cytogenetic analyses for chromosomes of one commonly used inbred line of M. lignano (called DV1) and uncovered unexpected chromosome number variation in the form of aneuploidies of the largest chromosomes. These results prompted us to perform karyotypic studies in individual specimens of this and other lines of M. lignano reared under laboratory conditions, as well as in freshly field-collected specimens from different natural populations. Our analyses revealed a high frequency of aneuploids and in some cases other numerical and structural chromosome abnormalities in laboratory-reared lines of M. lignano, and some cases of aneuploidy were also found in freshly field-collected specimens. Moreover, karyological analyses were performed in specimens of three further species: Macrostomum sp. 8 (a close relative of M. lignano), M. spirale and M. hystrix. Macrostomum sp. 8 showed a karyotype that was similar to that of M. lignano, with tetrasomy for its largest chromosome being the most common karyotype, while the other two species showed a simpler karyotype that is more typical of the genus Macrostomum. These findings suggest that M. lignano and Macrostomum sp. 8 can be used as new models for studying processes of partial genome duplication in genome evolution.

Reproductive outcome and fetal karyotype of couples with recurrent miscarriages

Purpose: The purpose of this study was to evaluate the relationship between fetal karyotype and parental chromosomal abnormalities, and assess the long-term reproductive outcomes in couples with recurrent miscarriages (RM). Materials and Methods: The reproductive outcomes of 34 couples with abnormal karyotypes and RM were investigated. Ultrasound examinations were performed during pregnancy, fetal karyotypes were determined following miscarriages, and successful pregnancy outcomes were recorded. Results: Of the 34 couples, 20 individuals presented with chromosomal abnormalities, specifically in nine females and 11 males (45% vs 55%, χ2 = 0.2833, p > 0.05). Fifteen couples (44.1%) possessed karyotype polymorphisms, of which the most common variant was a long Y chromosome in males. The reproductive outcomes of subsequent pregnancies consisted of 25 live births of phenotypically normal infants (73.5%), one infant with multiple malformations (2.9%), and eight RM (23.6%). With regards to karyotypes, 69.2% (9/13) of couples had inversions and 73.3% (11/15) had karyotype polymorphisms that resulted in live births of phenotypically normal babies. Fetal karyotyping was performed in a total of 29 cases. Normal karyotypes were present in 48.3% (14/29) of cases, whereas 41.4% (12/29) had abnormalities (either numerical or structural), and 10.3% (3/29) has a karyotype polymorphism. Conclusions: There is a positive correlation between chromosomal abnormalities and spontaneous miscarriages. A complete evaluation and special treatment should be provided to couples with a history of recurrent miscarriage(s) during a subsequent pregnancy, particularly when one partner is a carrier of chromosome abnormalities (i.e., inversions of chromosome 9 and long Y chromosome in males). Prenatal diagnosis is necessary in carrier couples suffering from more than two miscarriages.

Meiotic abnormalities in metaphase I human spermatocytes from infertile males: frequencies, chromosomes involved, and the relationships with polymorphic karyotype and seminal parameters.

The aim of this study was to look in depth at the relationship between meiotic anomalies and male infertility, such as the determination of the chromosomes involved or the correlation with patient features. For this purpose, a total of 31 testicular tissue samples from individuals consulting for fertility problems were analyzed. Metaphase I cells were evaluated using a sequential methodology combining Leishman stained procedures and multiplex fluorescence in situ hybridization protocols. The number of chromosomal units and chiasmata count per bivalent were established and a hierarchical cluster analysis of the individuals was performed. The relationship of the seminogram and the karyotype over recombination were evaluated using Poisson regression models. Results obtained in this study show a significant percentage of infertile individuals with altered meiotic behavior, mostly specified as a reduction in chiasmata count in medium and large chromosomes, the presence of univalents, and the observation of tetraploid metaphases. Moreover, the number and the type of anomalies were found to be different between cells of the same individual, suggesting the coexistence of cell lines with normal meiotic behavior and cell lines with abnormalities. In addition, chromosomal abnormalities in metaphase I are significantly associated with oligozoospermia and/or polymorphic karyotype variants.

Pericentromeric location of the telomeric DNA sequences on the European grayling chromosomes

The chromosomal characteristics, locations and variations of the C-band positive heterochromatin and telomeric DNA sequences were studied in the European grayling karyotype (Thymallus thymallus, Salmonidae) using conventional C-banding, endonucleases digestion banding, silver nitrate (AgNO3), chromomycin A3 and 4′,6-diamidino-2-phenylindole staining techniques as well as fluorescence in situ hybridization (FISH) and primed in situ labelling. Original data on the chromosomal distribution of segments resistant to AluI restriction endonuclease and identification of the C-banded heterochromatin presented here have been used to characterize the grayling karyotype polymorphism. Structural and length polymorphism of the chromosome 21 showing a conspicuous heterochromatin block adjacent to the centromere seems to be the result of the deletion and inversion. Two pairs of nuclear organizer regions (NOR)-bearing chromosomes were found to be polymorphic in size and displaying several distinct forms. FISH with telomeric peptide nucleic acid probe enabled recognition of the conservative telomeric DNA sequences. The karyotype of the thymallid fish is thought to experienced numerous pericentric inversions and internal telomeric sites (ITSs) observed at the pericentromeric regions of the six European grayling metacentric chromosomes are likely relics of the these rearrangements. None of the ITS sites matched either chromosome 21 or NOR bearing chromosomes.

The Polymorphism of Cytogenetic Markers in the Farm and Wild-Living Raccoon Dog (Nyctereutes Procyonoides) / Polimorfizm Markerów Cytogenetycznych U Jenota (Nyctereutes Procyonoides) W Populacjach Hodowlanych I Dziko Żyjących

Abstract The raccoon dog (Nyctereutes procyonoides) is a mammalian species that belongs to Canidae family, order Carnivora. This species represents both animals living in the wild and farm animals used in the fur industry. Raccoon dogs have the most ‘primitive’ karyotype among Canidae family. The Chinese raccoon dog (Nyctereutes procyonoides procyonoides) is characterised by a variable number of chromosomes (2n = 54 + 0-4 B). B chromosomes are supernumerary chromosomes occurring in addition to the basic set of A chromosomes in the cells of many organisms. The function and origin of these additional chromosomes is not clear. The aim of this work was to determine possible karyotypic differences between wild-living and farm populations, using methods of classical and molecular cytogenetics. The most useful cytogenetic markers to analyse karyotype polymorphism of canine are the number of B chromosomes and nucleolar organizer regions. A variation was identified in the number of B chromosomes and nucleolar organizer regions (NORs) in cells between wild-living and breeding populations.

Evaluation of the taxonomic status of populations assigned to Phyllomedusa hypochondrialis (Anura, Hylidae, Phyllomedusinae) based on molecular, chromosomal, and morphological approach.

BackgroundThe taxonomic and phylogenetic relationships of the genus Phyllomedusa have been amply discussed. The marked morphological similarities among some species hamper the reliable identification of specimens and may often lead to their incorrect taxonomic classification on the sole basis of morphological traits. Phenotypic variation was observed among populations assigned to either P. azurea or P. hypochondrialis. In order to evaluate whether the variation observed in populations assigned to P. hypochondrialis is related to that in genotypes, a cytogenetic analysis was combined with phylogenetic inferences based on mitochondrial and nuclear sequences.ResultsThe inter- and intra-population variation in the external morphology observed among the specimens analyzed in the present study do not reflect the phylogenetic relationships among populations. A monophyletic clade was recovered, grouping all the specimens identified as P. hypochondrialis and specimens assigned P. azurea from Minas Gerais state. This clade is characterized by conserved chromosomal morphology and a common C-banding pattern. Extensive variation in the nucleolar organizing region (NOR) was observed among populations, with four distinct NOR positions being recognized in the karyotypes. Intra-population polymorphism of the additional rDNA clusters observed in specimens from Barreiras, Bahia state, also highlights the marked genomic instability of the rDNA in the genome of this group. Based on the topology obtained in the phylogenetic analyses, the re-evaluation of the taxonomic status of the specimens from the southernmost population known in Brazil is recommended.ConclusionsThe results of this study support the need for a thorough revision of the phenotypic features used to discriminate P. azurea and P. hypochondrialis. The phylogenetic data presented here also contribute to an extension of the geographic range of P. hypochondrialis, which is known to occur in the Amazon basin and neighboring areas of the Cerrado savanna, where it may be sympatric with P. azurea, within contact zones. The misidentification of specimens may have led to inconsistencies in the original definition of the geographic range of P. azurea. The variability observed in the NOR of P. hypochondrialis reinforces the conclusion that these sites represent hotspots of rearrangement. Intraspecific variation in the location of these sites is the result of constant rearrangements that are not detected by classical cytogenetic methods or are traits of an ancestral, polymorphic karyotype, which would not be phylogenetically informative for this group.

Small chromosomes among Danish Candida glabrata isolates originated through different mechanisms

We analyzed 192 strains of the pathogenic yeast Candida glabrata from patients, mainly suffering from systemic infection, at Danish hospitals during 1985–1999. Our analysis showed that these strains were closely related but exhibited large karyotype polymorphism. Nine strains contained small chromosomes, which were smaller than 0.5 Mb. Regarding the year, patient and hospital, these C. glabrata strains had independent origin and the analyzed small chromosomes were structurally not related to each other (i.e. they contained different sets of genes). We suggest that at least two mechanisms could participate in their origin: (i) through a segmental duplication which covered the centromeric region, or (ii) by a translocation event moving a larger chromosome arm to another chromosome that leaves the centromere part with the shorter arm. The first type of small chromosomes carrying duplicated genes exhibited mitotic instability, while the second type, which contained the corresponding genes in only one copy in the genome, was mitotically stable. Apparently, in patients C. glabrata chromosomes are frequently reshuffled resulting in new genetic configurations, including appearance of small chromosomes, and some of these resulting “mutant” strains can have increased fitness in a certain patient “environment”.Electronic supplementary materialThe online version of this article (doi:10.1007/s10482-013-9931-3) contains supplementary material, which is available to authorized users.

Interclonal Variations in the Molecular Karyotype of Trypanosoma cruzi: Chromosome Rearrangements in a Single Cell-Derived Clone of the G Strain

Trypanosoma cruzi comprises a pool of populations which are genetically diverse in terms of DNA content, growth and infectivity. Inter- and intra-strain karyotype heterogeneities have been reported, suggesting that chromosomal rearrangements occurred during the evolution of this parasite. Clone D11 is a single-cell-derived clone of the T. cruzi G strain selected by the minimal dilution method and by infecting Vero cells with metacyclic trypomastigotes. Here we report that the karyotype of clone D11 differs from that of the G strain in both number and size of chromosomal bands. Large chromosomal rearrangement was observed in the chromosomes carrying the tubulin loci. However, most of the chromosome length polymorphisms were of small amplitude, and the absence of one band in clone D11 in relation to its reference position in the G strain could be correlated to the presence of a novel band migrating above or below this position. Despite the presence of chromosomal polymorphism, large syntenic groups were conserved between the isolates. The appearance of new chromosomal bands in clone D11 could be explained by chromosome fusion followed by a chromosome break or interchromosomal exchange of large DNA segments. Our results also suggest that telomeric regions are involved in this process. The variant represented by clone D11 could have been induced by the stress of the cloning procedure or could, as has been suggested for Leishmania infantum, have emerged from a multiclonal, mosaic parasite population submitted to frequent DNA amplification/deletion events, leading to a 'mosaic' structure with different individuals having differently sized versions of the same chromosomes. If this is the case, the variant represented by clone D11 would be better adapted to survive the stress induced by cloning, which includes intracellular development in the mammalian cell. Karyotype polymorphism could be part of the T. cruzi arsenal for responding to environmental pressure.

Molecular Cytogenetic Identification and Characterization of Robertsonian Chromosomes in the Large Japanese Field Mouse (Apodemus speciosus) Using FISH

Robertsonian (Rb) karyotypic polymorphism in Apodemus speciosus has interested many researchers with particular referece to the genetic divergence between Rb and non-Rb populations. Failure to find morphologic, biochemical, or genetic differences in previous studies reveals the necessity of focusing on loci on Rb chromosomes, which can be characterized by FISH mapping with DNA probes. In an Rb heterozygote, DNA probes from laboratory mouse chromosomes (MMUs) 1 and 10 were simultaneously hybridized to the long arm of a metacentric and a medium-sized acrocentric chromosome and to the short arm of the metacentric and a small acrocentric chromosome, respectively. Four additional probes derived from each of MMUs 1 and 10 were mapped to the long and short arms, respectively, of the Rb chromosome identified by the above markers. Homologies between the long arm of the Rb chromosome and MMU 1 and between the short arm and MMU 10 were supported by all ten markers, which were dispersed along nearly the entire lengths of the Rb chromosomes. These results indicate that the long and short arms of the Rb chromosomes are homologous to Apodemus speciosus chromosomes 12 and 19 (defined in a previous study), respectively. This ten-marker series can be useful for detecting chromosome-specific divergence between the two karyotypic populations at the gene level.