Cytogenetic Analysis Did Not Reveal Differentiated Sex Chromosomes in Ten Species of Boas and Pythons (Reptilia: Serpentes)

Homologous and differentiated ZZ/ZW sex chromosomes (or derived multiple neo-sex chromosomes) were often described in caenophidian snakes, but sex chromosomes were unknown until recently in non-caenophidian snakes. Previous studies revealed that two species of boas (Boa imperator, B. constrictor) and one species of python (Python bivittatus) independently evolved XX/XY sex chromosomes. In addition, heteromorphic ZZ/ZW sex chromosomes were recently revealed in the Madagascar boa (Acrantophis sp. cf. dumerili) and putatively also in the blind snake Myriopholis macrorhyncha. Since the evolution of sex chromosomes in non-caenophidian snakes seems to be more complex than previously thought, we examined ten species of pythons and boas representing the families Boidae, Calabariidae, Candoiidae, Charinidae, Pythonidae, and Sanziniidae by conventional and molecular cytogenetic methods, aiming to reveal their sex chromosomes. Our results show that all examined species do not possess sex-specific differences in their genomes detectable by the applied cytogenetic methods, indicating the presence of poorly differentiated sex chromosomes or even the absence of sex chromosomes. Interestingly, fluorescence in situ hybridization with telomeric repeats revealed extensive distribution of interstitial telomeric repeats in eight species, which are likely a consequence of intra-chromosomal rearrangements.

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Interstitial Telomeric Repeats Are Rare in Turtles

Genes ◽

10.3390/genes11060657 ◽

2020 ◽

Vol 11 (6) ◽

pp. 657 ◽

Cited By ~ 2

Author(s):

Lorenzo Clemente ◽

Sofia Mazzoleni ◽

Eleonora Pensabene Bellavia ◽

Barbora Augstenová ◽

Markus Auer ◽

...

Keyword(s):

In Situ Hybridization ◽

Karyotype Evolution ◽

Chromosomal Rearrangements ◽

Telomeric Repeats ◽

Squamate Reptiles ◽

Nucleoprotein Complexes ◽

Interstitial Telomeric Repeats ◽

Eukaryotic Organisms ◽

Genomic Regions

Telomeres are nucleoprotein complexes protecting chromosome ends in most eukaryotic organisms. In addition to chromosome ends, telomeric-like motifs can be accumulated in centromeric, pericentromeric and intermediate (i.e., between centromeres and telomeres) positions as so-called interstitial telomeric repeats (ITRs). We mapped the distribution of (TTAGGG)n repeats in the karyotypes of 30 species from nine families of turtles using fluorescence in situ hybridization. All examined species showed the expected terminal topology of telomeric motifs at the edges of chromosomes. We detected ITRs in only five species from three families. Combining our and literature data, we inferred seven independent origins of ITRs among turtles. ITRs occurred in turtles in centromeric positions, often in several chromosomal pairs, in a given species. Their distribution does not correspond directly to interchromosomal rearrangements. Our findings support that centromeres and non-recombining parts of sex chromosomes are very dynamic genomic regions, even in turtles, a group generally thought to be slowly evolving. However, in contrast to squamate reptiles (lizards and snakes), where ITRs were found in more than half of the examined species, and birds, the presence of ITRs is generally rare in turtles, which agrees with the expected low rates of chromosomal rearrangements and rather slow karyotype evolution in this group.

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Use of meiotic FISH for identification of a new monosome in Gossypium hirsutum L.

Genome ◽

10.1139/g97-005 ◽

1997 ◽

Vol 40 (1) ◽

pp. 34-40 ◽

Cited By ~ 15

Author(s):

Yuanfu Ji ◽

Dwaine A. Raska ◽

M. Nurul Islam-Faridi ◽

Charles F. Crane ◽

Michael S. Zwick ◽

...

Keyword(s):

In Situ Hybridization ◽

Gossypium Hirsutum ◽

Fluorescence In Situ Hybridization ◽

Molecular Cytogenetics ◽

Clinical Diagnostics ◽

Identification System ◽

Gossypium Hirsutum L ◽

Molecular Cytogenetic ◽

Cytogenetic Methods

The extensive use of molecular cytogenetics in human genetics and clinical diagnostics indicates that analogous applications in plants are highly feasible. One sort of application would be the identification of new aneuploids, which traditionally involves either direct karyotypic identification, which is feasible in only a few plant species, or tests with markers (cytogenetic, genetic, or molecular), which require sexual hybridization and at least one subsequent seed or plant generation. We have used meiotic fluorescence in situ hybridization (FISH) to analyze a new monosome of cotton (Gossypium hirsutum L., 2n = 4x = 52, 2(AD)1) that had a phenotype which seemed to be distinct from monosomes in the Cotton Cytogenetic Collection. Painting with A2-genome DNA revealed the monosome's D-subgenome origin. DAPI–PI staining showed that the monosome carries a major NOR, delimiting it to the major NOR-bearing chromosomes of the D-subgenome, i.e., 16 or 23. Dual-color FISH with 5S and 18S–28S rDNAs indicated that the monosome contains separate major clusters of each of these two tandemly repeated rDNA elements, thus delimiting the monosome to chromosome 23, for which the Cotton Cytogenetic Collection has previously been devoid of any sort of deficiency. Of the 26 chromosomes in the cotton genome, the Collection now provides coverage for 16 (70%) in the form of monosomy, and 20 (77%) in the form of monosomy and (or) telosomy. Use of molecular cytogenetic methods to identify a new plant aneuploid in cotton exemplifies the fact that a physicochemical karyotypic chromosome identification system is not required a priori for application of new molecular cytogenetic methods, thus indicating their potential applicability to nearly all plant species.Key words: fluorescence in situ hybridization, monosome, aneuploid, Gossypium hirsutum.

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Cytogenetically Elusive Sex Chromosomes in Scincoidean Lizards

International Journal of Molecular Sciences ◽

10.3390/ijms22168670 ◽

2021 ◽

Vol 22 (16) ◽

pp. 8670

Author(s):

Alexander Kostmann ◽

Barbora Augstenová ◽

Daniel Frynta ◽

Lukáš Kratochvíl ◽

Michail Rovatsos

Keyword(s):

Sex Chromosomes ◽

Chromosome Morphology ◽

Comparative Genomic ◽

Morphological Divergence ◽

Telomeric Sequences ◽

Molecular Cytogenetic ◽

Interstitial Telomeric Sequences ◽

Rdna Loci ◽

Cytogenetic Methods

The lizards of the species-rich clade Scincoidea including cordylids, gerrhosaurids, skinks, and xantusiids, show an almost cosmopolitan geographical distribution and a remarkable ecological and morphological divergence. However, previous studies revealed limited variability in cytogenetic traits. The sex determination mode was revealed only in a handful of gerrhosaurid, skink, and xantusiid species, which demonstrated either ZZ/ZW or XX/XY sex chromosomes. In this study, we explored the karyotypes of six species of skinks, two species of cordylids, and one gerrhosaurid. We applied conventional and molecular cytogenetic methods, including C-banding, fluorescence in situ hybridization with probes specific for telomeric motifs and rDNA loci, and comparative genomic hybridization. The diploid chromosome numbers are rather conserved among these species, but the chromosome morphology, the presence of interstitial telomeric sequences, and the topology of rDNA loci vary significantly. Notably, XX/XY sex chromosomes were identified only in Tiliqua scincoides, where, in contrast to the X chromosome, the Y chromosome lacks accumulations of rDNA loci. We confirm that within the lizards of the scincoidean clade, sex chromosomes remained in a generally poor stage of differentiation.

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Insight into the Chromosome Structure of the Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) by a Combined Use of GISH and FISH Techniques

Plants ◽

10.3390/plants9040542 ◽

2020 ◽

Vol 9 (4) ◽

pp. 542

Author(s):

Egizia Falistocco

Keyword(s):

In Situ Hybridization ◽

Medicago Sativa ◽

Tandem Repeats ◽

Chromosome Structure ◽

Substantial Part ◽

Telomeric Repeats ◽

Evolutionary Pathway ◽

Suitable Material ◽

Interstitial Telomeric Repeats

Cytogenetic research in Medicago sativa subsp. sativa L., the cultivated tetraploid alfalfa (2n = 4x = 32), has lagged behind other crops mostly due to the small size and the uniform morphology of its chromosomes. However, in the last decades, the development of molecular cytogenetic techniques based on in situ hybridization has largely contributed to overcoming these limitations. The purpose of this study was to extend our knowledge about the chromosome structure of alfalfa by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) techniques. The results of self-GISH (sGISH) suggested that a substantial part of the repetitive fraction of the genome of subsp. sativa is constituted by tandem repeats typical of satellite DNA. The coincidence of sGISH and C-banding patterns supported this assumption. The FISH mapping of the Arabidopsis-type TTTAGGG telomeric repeats demonstrated, for the first time, that the alfalfa telomeres consist of this type of sequence and revealed a massive presence of interstitial telomeric repeats (ITRs). In the light of this finding M. sativa appears to be a suitable material for studying the origin and function of such extra telomeric repeats. To further exploit this result, investigation will be extended to the diploid subspp. coerulea and falcata in order to explore possible connections between the distribution of ITRs, the ploidy level, and the evolutionary pathway of the taxa.

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Cytogenetic Evidence for Sex Chromosomes and Karyotype Evolution in Anguimorphan Lizards

Cells ◽

10.3390/cells10071612 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1612

Author(s):

Barbora Augstenová ◽

Eleonora Pensabene ◽

Lukáš Kratochvíl ◽

Michail Rovatsos

Keyword(s):

Sex Determination ◽

Sex Chromosomes ◽

Comparative Genome Hybridization ◽

Squamate Reptiles ◽

Cytogenetic Evidence ◽

Poorly Differentiated ◽

Cytogenetic Methods ◽

Variable Group

Anguimorphan lizards are a morphologically variable group of squamate reptiles with a wide geographical distribution. In spite of their importance, they have been cytogenetically understudied. Here, we present the results of the cytogenetic examination of 23 species from five anguimorphan families (Anguidae, Helodermatidae, Shinisauridae, Varanidae and Xenosauridae). We applied both conventional (Giemsa staining and C-banding) and molecular cytogenetic methods (fluorescence in situ hybridization with probes for the telomeric motifs and rDNA loci, comparative genome hybridization), intending to describe the karyotypes of previously unstudied species, to uncover the sex determination mode, and to reveal the distribution of variability in cytogenetic characteristics among anguimorphan lizards. We documented that karyotypes are generally quite variable across anguimorphan lineages, with anguids being the most varying. However, the derived chromosome number of 2n = 40 exhibits a notable long-term evolutionary stasis in monitors. Differentiated ZZ/ZW sex chromosomes were documented in monitors and helodermatids, as well as in the anguids Abronia lythrochila, and preliminary also in Celestus warreni and Gerrhonotus liocephalus. Several other anguimorphan species have likely poorly differentiated sex chromosomes, which cannot be detected by the applied cytogenetic methods, although the presence of environmental sex determination cannot be excluded. In addition, we uncovered a rare case of spontaneous triploidy in a fully grown Varanus primordius.

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Cytogenetic Analysis of the Asian Box Turtles of the Genus Cuora (Testudines, Geoemydidae)

Genes ◽

10.3390/genes12020156 ◽

2021 ◽

Vol 12 (2) ◽

pp. 156

Author(s):

Lorenzo Clemente ◽

Sofia Mazzoleni ◽

Eleonora Pensabene ◽

Tomáš Protiva ◽

Philipp Wagner ◽

...

Keyword(s):

Sex Determination ◽

Sex Chromosomes ◽

Wide Distribution ◽

Iucn Red List ◽

Telomeric Repeats ◽

Rdna Loci ◽

Box Turtles ◽

Genotypic Sex Determination ◽

Poorly Differentiated ◽

Almost All

The Asian box turtle genus Cuora currently comprises 13 species with a wide distribution in Southeast Asia, including China and the islands of Indonesia and Philippines. The populations of these species are rapidly declining due to human pressure, including pollution, habitat loss, and harvesting for food consumption. Notably, the IUCN Red List identifies almost all species of the genus Cuora as Endangered (EN) or Critically Endangered (CR). In this study, we explore the karyotypes of 10 Cuora species with conventional (Giemsa staining, C-banding, karyogram reconstruction) and molecular cytogenetic methods (in situ hybridization with probes for rDNA loci and telomeric repeats). Our study reveals a diploid chromosome number of 2n = 52 chromosomes in all studied species, with karyotypes of similar chromosomal morphology. In all examined species, rDNA loci are detected at a single medium-sized chromosome pair and the telomeric repeats are restricted to the expected terminal position across all chromosomes. In contrast to a previous report, sex chromosomes are neither detected in Cuoragalbinifrons nor in any other species. Therefore, we assume that these turtles have either environmental sex determination or genotypic sex determination with poorly differentiated sex chromosomes. The conservation of genome organization could explain the numerous observed cases of interspecific hybridization both within the genus Cuora and across geoemydid turtles.

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New Data on Organization and Spatial Localization of B-Chromosomes in Cell Nuclei of the Yellow-Necked Mouse Apodemus flavicollis

Cells ◽

10.3390/cells10071819 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1819

Author(s):

Tatyana Karamysheva ◽

Svetlana Romanenko ◽

Alexey Makunin ◽

Marija Rajičić ◽

Alexey Bogdanov ◽

...

Keyword(s):

In Situ Hybridization ◽

Sex Chromosomes ◽

Interphase Nucleus ◽

Spatial Organization ◽

Three Dimensional ◽

Dna Probes ◽

B Chromosomes ◽

Apodemus Flavicollis ◽

Yellow Necked Mouse

The gene composition, function and evolution of B-chromosomes (Bs) have been actively discussed in recent years. However, the additional genomic elements are still enigmatic. One of Bs mysteries is their spatial organization in the interphase nucleus. It is known that heterochromatic compartments are not randomly localized in a nucleus. The purpose of this work was to study the organization and three-dimensional spatial arrangement of Bs in the interphase nucleus. Using microdissection of Bs and autosome centromeric heterochromatic regions of the yellow-necked mouse (Apodemus flavicollis) we obtained DNA probes for further two-dimensional (2D)- and three-dimensional (3D)- fluorescence in situ hybridization (FISH) studies. Simultaneous in situ hybridization of obtained here B-specific DNA probes and autosomal C-positive pericentromeric region-specific probes further corroborated the previously stated hypothesis about the pseudoautosomal origin of the additional chromosomes of this species. Analysis of the spatial organization of the Bs demonstrated the peripheral location of B-specific chromatin within the interphase nucleus and feasible contact with the nuclear envelope (similarly to pericentromeric regions of autosomes and sex chromosomes). It is assumed that such interaction is essential for the regulation of nuclear architecture. It also points out that Bs may follow the same mechanism as sex chromosomes to avoid a meiotic checkpoint.

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Application of the FISH Technique to Visualize Sex Chromosomes in Domestic Cat Spermatozoa

Animals ◽

10.3390/ani11072106 ◽

2021 ◽

Vol 11 (7) ◽

pp. 2106

Author(s):

Barbara Kij-Mitka ◽

Halina Cernohorska ◽

Svatava Kubickova ◽

Sylwia Prochowska ◽

Wojciech Niżański ◽

...

Keyword(s):

In Situ Hybridization ◽

Fluorescence In Situ Hybridization ◽

Sex Chromosomes ◽

Chromosomal Abnormalities ◽

Molecular Cytogenetics ◽

Molecular Probes ◽

Domestic Cat ◽

Fish Technique ◽

Y Chromosomes

Fluorescence in situ hybridization is a molecular cytogenetics technique that enables the visualization of chromosomes in cells via fluorescently labeled molecular probes specific to selected chromosomes. Despite difficulties in carrying out the FISH technique on sperm, related to the need for proper nuclear chromatin decondensation, this technique has already been used to visualize chromosomes in human, mouse, cattle, swine, horse, and dog spermatozoa. Until now, FISH has not been performed on domestic cat sperm; therefore, the aim of this study was to visualize sex chromosomes in domestic cat sperm. The results showed the presence of X and Y chromosomes in feline spermatozoa. The procedure used for sperm decondensation and fluorescence in situ hybridization was adequate to visualize chromosomes in domestic cat spermatozoa and, in the future, it may be used to determine the degree of chromosomal abnormalities in these gametes.

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