Chameleons are well-known lizards with unique morphology and physiology, but their sex determination has remained poorly studied. Madagascan chameleons of the genus Furcifer have cytogenetically distinct Z and W sex chromosomes and occasionally Z1Z1Z2Z2/Z1Z2W multiple neo-sex chromosomes. To identify the gene content of their sex chromosomes, we microdissected and sequenced the sex chromosomes of F. oustaleti (ZZ/ZW) and F. pardalis (Z1Z1Z2Z2/Z1Z2W). In addition, we sequenced the genomes of a male and a female of F. lateralis (ZZ/ZW) and F. pardalis and performed a comparative coverage analysis between the sexes. Despite the notable heteromorphy and distinctiveness in heterochromatin content, the Z and W sex chromosomes share approximately 90% of their gene content. This finding demonstrates poor correlation of the degree of differentiation of sex chromosomes at the cytogenetic and gene level. The test of homology based on the comparison of gene copy number variation revealed that female heterogamety with differentiated sex chromosomes remained stable in the genus Furcifer for at least 20 million years. These chameleons co-opted for the role of sex chromosomes the same genomic region as viviparous mammals, lacertids and geckos of the genus Paroedura, which makes these groups excellent model for studies of convergent and divergent evolution of sex chromosomes.

• Keywords
• Chameleons, Homology, Karyotypes, Microdissection, Sex chromosomes, qPCR,
• MeSH
• Lizards * genetics   MeSH
• Evolution, Molecular MeSH
• Sex Chromosomes genetics   MeSH
• Sex Determination Processes genetics   MeSH
• Mammals genetics   MeSH
• Base Sequence MeSH
• DNA Copy Number Variations * MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Geckos are an excellent group to study the evolution of sex determination, as they possess a remarkable variability ranging from a complete absence of sex chromosomes to highly differentiated sex chromosomes. We explored sex determination in the Madagascar leaf-tail geckos of the genus Uroplatus. The cytogenetic analyses revealed highly heterochromatic W chromosomes in all three examined species (Uroplatus henkeli, U. alluaudi, U. sikorae). The comparative gene coverage analysis between sexes in U. henkeli uncovered an extensive Z-specific region, with a gene content shared with the chicken chromosomes 8, 20, 26 and 28. The genomic region homologous to chicken chromosome 28 has been independently co-opted for the role of sex chromosomes in several vertebrate lineages, including monitors, beaded lizards and monotremes, perhaps because it contains the amh gene, whose homologs were repeatedly recruited as a sex-determining locus. We demonstrate that all tested species of leaf-tail geckos share homologous sex chromosomes despite the differences in shape and size of their W chromosomes, which are not homologous to the sex chromosomes of other closely related genera. The rather old (at least 40 million years), highly differentiated sex chromosomes of Uroplatus geckos can serve as a great system to study the convergence of sex chromosomes evolved from the same genomic region.

• Keywords
• DNA-seq, cytogenetics, evolution, genomics, qPCR, reptiles, sex chromosomes, sex determination,
• MeSH
• Phylogeny MeSH
• Lizards * genetics   MeSH
• Sex Chromosomes genetics   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Madagascar MeSH

The recent discovery of two independently evolved XX/XY sex determination systems in the snake genera Python and Boa sparked a new drive to study the evolution of sex chromosomes in poorly studied lineages of snakes, where female heterogamety was previously assumed. Therefore, we examined seven species from the genera Eryx, Cylindrophis, Python, and Tropidophis by conventional and molecular cytogenetic methods. Despite the fact that these species have similar karyotypes in terms of chromosome number and morphology, we detected variability in the distribution of heterochromatin, telomeric repeats, and rDNA loci. Heterochromatic blocks were mainly detected in the centromeric regions in all species, although accumulations were detected in pericentromeric and telomeric regions in a few macrochromosomes in several of the studied species. All species show the expected topology of telomeric repeats at the edge of all chromosomes, with the exception of Eryx muelleri, where additional accumulations were detected in the centromeres of three pairs of macrochromosomes. The rDNA loci accumulate in one pair of microchromosomes in all Eryx species and in Cylindrophis ruffus, in one macrochromosome pair in Tropidophis melanurus and in two pairs of microchromosomes in Python regius. Sex-specific differences were not detected, suggesting that these species likely have homomorphic, poorly differentiated sex chromosomes.

• Keywords
• C-banding, CGH, FISH, boa, evolution, heterochromatin, karyotype, python, rDNA, sex chromosomes, telomeres,
• MeSH
• Boidae * genetics   MeSH
• Cytogenetic Analysis MeSH
• Evolution, Molecular MeSH
• Sex Chromosomes MeSH
• DNA, Ribosomal genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Ribosomal MeSH

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.

• Keywords
• CGH, FISH, comparative genome hybridization, evolution, fluorescence in situ hybridization, heterochromatin, karyotype, rDNA, reptiles, sex chromosomes, sex determination, telomeres,
• MeSH
• Cytogenetic Analysis methods   MeSH
• Diploidy MeSH
• In Situ Hybridization, Fluorescence MeSH
• Lizards classification   genetics   MeSH
• Karyotyping MeSH
• Evolution, Molecular MeSH
• Sex Chromosomes genetics   MeSH
• Sex Determination Processes MeSH
• DNA, Ribosomal genetics   MeSH
• Comparative Genomic Hybridization MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA, Ribosomal MeSH

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.

• Keywords
• CGH, FISH, evolution, karyotype, rDNA, sex chromosomes, telomeres,
• MeSH
• Cytogenetic Analysis * MeSH
• Phylogeny MeSH
• Lizards genetics   MeSH
• Karyotype * MeSH
• Metaphase genetics   MeSH
• Evolution, Molecular * MeSH
• Sex Chromosomes genetics   MeSH
• DNA, Ribosomal genetics   MeSH
• Telomere genetics   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Ribosomal MeSH

Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a probe, whole chromosome painting (WCP), and comparative genome hybridization. All Caimaninae species have a diploid chromosome number (2n) 42 and karyotypes dominated by acrocentric chromosomes, in contrast to both species of Alligatorinae, which have 2n = 32 and karyotypes that are predominantly metacentric, suggesting fusion/fission rearrangements. Our WCP results supported this scenario by revealing the homeology of the largest metacentric pair present in both Alligator spp. with two smaller pairs of acrocentrics in Caimaninae species. The clusters of 18S rDNA were found on one chromosome pair in all species, except for Paleosuchus spp., which possessed three chromosome pairs bearing these sites. Similarly, comparative genomic hybridization demonstrated an advanced stage of sequence divergence among the caiman genomes, with Paleosuchus standing out as the most divergent. Thus, although Alligatoridae exhibited rather low species diversity and some level of karyotype stasis, their genomic content indicates that they are not as conserved as previously thought. These new data deepen the discussion of cytotaxonomy in this family.

• Keywords
• Alligatoridae, chromosome, cytogenomics, molecular cytogenetics,
• MeSH
• Alligators and Crocodiles classification   genetics   MeSH
• Chromosomes genetics   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Karyotype * MeSH
• Evolution, Molecular * MeSH
• Comparative Genomic Hybridization MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Turtles, a speciose group consisting of more than 300 species, demonstrate karyotypes with diploid chromosome numbers ranging from 2n = 26 to 2n = 68. However, cytogenetic analyses have been conducted only to 1/3rd of the turtle species, often limited to conventional staining methods. In order to expand our knowledge of the karyotype evolution in turtles, we examined the topology of the (TTAGGG)n telomeric repeats and the rDNA loci by fluorescence in situ hybridization (FISH) on the karyotypes of two emydids: the Sicilian pond turtle, Emys trinacris, and the yellow-bellied slider, Trachemys scripta scripta (family Emydidae). Furthermore, AT-rich and GC-rich chromosome regions were detected by DAPI and CMA3 stains, respectively. The cytogenetic analysis revealed that telomeric sequences are restricted to the terminal ends of all chromosomes and the rDNA loci are localized in one pair of microchromosomes in both species. The karyotype of the Sicilian endemic E. trinacris with diploid number 2n = 50, consisting of 13 pairs of macrochromosomes and 12 pairs of microchromosomes, is presented here for first time. Our comparative examination revealed similar cytogenetic features in Emys trinacris and the closely related E. orbicularis, as well as to other previously studied emydid species, demonstrating a low rate of karyotype evolution, as chromosomal rearrangements are rather infrequent in this group of turtles.

• Keywords
• Emys trinacris, FISH, Trachemys scripta scripta, karyotype, rDNA, telomeric sequences,
• MeSH
• Cytogenetics methods   MeSH
• In Situ Hybridization, Fluorescence methods   MeSH
• Karyotype * MeSH
• Evolution, Molecular * MeSH
• DNA, Ribosomal genetics   MeSH
• Telomere genetics   MeSH
• Turtles genetics   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Ribosomal MeSH

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.

• Keywords
• FISH, ITRs, ITSs, evolution, in situ hybridization, interstitial telomeric repeats, interstitial telomeric sequences, karyotype, telomeres, turtles,
• MeSH
• Centromere genetics   MeSH
• Snakes genetics   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Lizards genetics   MeSH
• Karyotype MeSH
• Sex Chromosomes genetics   MeSH
• Repetitive Sequences, Nucleic Acid genetics   MeSH
• Telomere genetics   MeSH
• Turtles genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Lacertid lizards are a widely radiated group of squamate reptiles with long-term stable ZZ/ZW sex chromosomes. Despite their family-wide homology of Z-specific gene content, previous cytogenetic studies revealed significant variability in the size, morphology, and heterochromatin distribution of their W chromosome. However, there is little evidence about the accumulation and distribution of repetitive content on lacertid chromosomes, especially on their W chromosome. In order to expand our knowledge of the evolution of sex chromosome repetitive content, we examined the topology of telomeric and microsatellite motifs that tend to often accumulate on the sex chromosomes of reptiles in the karyotypes of 15 species of lacertids by fluorescence in situ hybridization (FISH). The topology of the above-mentioned motifs was compared to the pattern of heterochromatin distribution, as revealed by C-banding. Our results show that the topologies of the examined motifs on the W chromosome do not seem to follow a strong phylogenetic signal, indicating independent and species-specific accumulations. In addition, the degeneration of the W chromosome can also affect the Z chromosome and potentially also other parts of the genome. Our study provides solid evidence that the repetitive content of the degenerated sex chromosomes is one of the most evolutionary dynamic parts of the genome.

• Keywords
• C-banding, FISH, GATA, evolution, heterochromatin, karyotype, microsatellites, sex chromosomes, telomeres,
• MeSH
• Chromosomes genetics   MeSH
• Species Specificity MeSH
• Phylogeny MeSH
• Heterochromatin genetics   ultrastructure   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Lizards genetics   MeSH
• Karyotype MeSH
• Microsatellite Repeats genetics   MeSH
• Evolution, Molecular * MeSH
• Nucleotide Motifs MeSH
• Sex Chromosomes genetics   MeSH
• Chromosome Banding MeSH
• Repetitive Sequences, Nucleic Acid MeSH
• Telomere genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• Heterochromatin MeSH