Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from a Systematic Distribution of Available Data?

Mezzasalma, Marcello; Guarino, Fabio Maria; Odierna, Gaëtano

doi:10.3390/genes12091341

Cited by 21 publications

(18 citation statements)

References 159 publications

(280 reference statements)

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“…In Uroplatus , the traslocation of NORs probably occurred among different chromosomes, from those of the smallest pairs (16th and 10th pair in U. finiavana and U. ebenaui ) to middle-sized (6th pair in U. fimbriatus and U. henkeli ) and large chromosomes (2nd pair in U. phantasticus , U. alluaudi , U. guentheri , and U. pietschmanni ) ([ 24 ] this study) ( Figure 4 ). The condition displayed by U. fiera (NORs on the 2nd pair and an extra, unpaired locus, on one of the chromosomes of the 16th pair), is quite rare in reptiles, but similar configurations have been documented in Lacertidae, Opluridae, Leiocephalidae and Helodermatidae (see e.g., [ 37 , 38 , 39 , 40 , 42 , 43 , 44 , 45 ]).…”

Section: Discussionmentioning

confidence: 83%

“…Taking into account different karyological features which are considered plesiomorphic in squamates (high total number of chromosomes, number of dot-shaped microchromosomes and loci on NORs on the smallest pairs (see e.g., [ 37 , 38 , 39 , 40 , 41 ]), the karyotype of U. ebenaui (2n = 38, with NORs on one of the smallest pair) should be considered as a primitive state in Uroplatus . From karyotypes with a similar structure, the chromosomal diversification in the genus probably proceeded toward a progressive reduction in the total chromosome number (2n = 36 in U. phantasticus , U. alluaudi , U. finiavana , U. fimbriatus , U. henkeli and U. pietschmanni and 2n = 34 in U .…”

Section: Discussionmentioning

confidence: 99%

“…We highlight that this group of geckos provides an example of an early stage of the transition between “symmetrical” (mostly composed by acrocentric chromosomes and without a clear distinction between macro- and microchromosomes) and “asymmetrical” karyotypes (with a high number of biarmed chromosomes and a clear distinction between macro- and microchromosomes) [ 45 ], which is hypothesized to represent a major evolutionary trend of the karyological diversification of squamates [ 39 , 49 ].…”

Section: Discussionmentioning

confidence: 99%

“…Bigger dimensions of the heteromorphic chromosome (Y/W) usually indicate its relatively recent diversification by means of heterochromatin addition and amplification, which is usually followed by the degeneration of the Y/W chromosome, down to the size of a microchromosome [ 39 , 51 , 52 , 53 ]. The lack of other heteromorphic sex chromosomes in the other Uroplatus species studied so far, also seems to support the relatively recent origin of the heteromorphic pair in U. ebenaui.…”

Section: Discussionmentioning

confidence: 99%

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First Insights on the Karyotype Diversification of the Endemic Malagasy Leaf-Toed Geckos (Squamata: Gekkonidae: Uroplatus)

Mezzasalma

Brunelli

Odierna

et al. 2022

Animals

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We provide here the first karyotype description of eight Uroplatus species and a characterization of their chromosomal diversity. We performed a molecular taxonomic assessment of several Uroplatus samples using the mitochondrial 12S marker and a comparative cytogenetic analysis with standard karyotyping, silver staining (Ag-NOR) and sequential C-banding + Giemsa, +Chromomycin A3 (CMA3), +4′,6-diamidino-2-phenylindole (DAPI). We found chromosomal variability in terms of chromosome number (2n = 34–38), heterochromatin composition and number and localization of loci or Nucleolar Organizer Regions (NORs) (alternatively on the 2nd, 6th, 10th or 16th pair). Chromosome morphology is almost constant, with karyotypes composed of acrocentric chromosomes, gradually decreasing in length. C-banding evidenced a general low content of heterochromatin, mostly localized on pericentromeric and telomeric regions. Centromeric bands varied among the species studied, resulting in CMA3 positive and DAPI negative or positive to both fluorochromes. We also provide evidence of a first putative heteromorphic sex chromosome system in the genus. In fact, in U. alluaudi the 10th pair was highly heteromorphic, with a metacentric, largely heterochromatic W chromosome, which was much bigger than the Z. We propose an evolutionary scenario of chromosome reduction from 2n = 38 to 2n = 34, by means of translocations of microchromosomes on larger chromosomes (often involving the NOR-bearing microchromosomes). Adding our data to those available from the literature, we show that similar processes characterized the evolutionary radiation of a larger gecko clade. Finally, we hypothesize that sex chromosome diversification occurred independently in different genera.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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First Insights on the Karyotype Diversification of the Endemic Malagasy Leaf-Toed Geckos (Squamata: Gekkonidae: Uroplatus)

Mezzasalma

Brunelli

Odierna

et al. 2022

Animals

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“…A more detailed description of lizard karyotype features, sex determination and sex chromosome systems can be found in the present Special Issue "Sex chromosome evolution and Meiosis" [295].…”

Section: Pleurodontamentioning

confidence: 99%

Sex Chromosomes and Master Sex-Determining Genes in Turtles and Other Reptiles

Thépot

2021

Genes

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Among tetrapods, the well differentiated heteromorphic sex chromosomes of birds and mammals have been highly investigated and their master sex-determining (MSD) gene, Dmrt1 and SRY, respectively, have been identified. The homomorphic sex chromosomes of reptiles have been the least studied, but the gap with birds and mammals has begun to fill. This review describes our current knowledge of reptilian sex chromosomes at the cytogenetic and molecular level. Most of it arose recently from various studies comparing male to female gene content. This includes restriction site-associated DNA sequencing (RAD-Seq) experiments in several male and female samples, RNA sequencing and identification of Z- or X-linked genes by male/female comparative transcriptome coverage, and male/female transcriptomic or transcriptome/genome substraction approaches allowing the identification of Y- or W-linked transcripts. A few putative master sex-determining (MSD) genes have been proposed, but none has been demonstrated yet. Lastly, future directions in the field of reptilian sex chromosomes and their MSD gene studies are considered.

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Pivotal temperature is not for everyone: Evidence for temperature‐dependent sex determination in three gecko species

Straková,

Kubička,

Červenka

et al. 2024

J Exp Zool Pt A

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The prevalence of environmental sex determination (ESD) in squamate reptiles is often overestimated in the literature. This is surprising because we have reliable data demonstrating ESD in only a few species. The documentation of ESD in three species of geckos presented here has significantly increased our knowledge, given that satisfactory evidence for ESD existed in only eight other gecko species. For the first time, we document the occurrence of ESD in the family Sphaerodactylidae. Our finding of unexpected variability in the shapes of reaction norms among geckos highlights that traditional descriptions using parameters such as pivotal temperature, that is, temperature producing a 50:50 sex ratio, are unsatisfactory. For example, the gecko Pachydactylus tigrinus lacks any pivotal temperature and its sex ratios are strongly female‐biased across the entire range of viable temperatures. We argue for the effective capture of the relationship between temperature and sex ratio using specific nonlinear models rather than using classical simplistic descriptions and classifications of reaction norms.

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Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from a Systematic Distribution of Available Data?

Cited by 21 publications

References 159 publications

First Insights on the Karyotype Diversification of the Endemic Malagasy Leaf-Toed Geckos (Squamata: Gekkonidae: Uroplatus)

First Insights on the Karyotype Diversification of the Endemic Malagasy Leaf-Toed Geckos (Squamata: Gekkonidae: Uroplatus)

Sex Chromosomes and Master Sex-Determining Genes in Turtles and Other Reptiles

Pivotal temperature is not for everyone: Evidence for temperature‐dependent sex determination in three gecko species

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