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

Thépot, Dominique

doi:10.3390/genes12111822

Cited by 16 publications

(8 citation statements)

References 285 publications

(514 reference statements)

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“…Reptiles are a well-known model organism in the study of sex chromosome diversification and include species with temperature dependent sex determination (TSD) and genetic sex determination (GSD) with either male or female heterogamety (see e.g., [ 39 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]).…”

Section: Discussionmentioning

confidence: 99%

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: 99%

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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“…Among amniotes, sex‐determining genes are known only in viviparous mammals ( sry ) and birds ( dmrt1 ), and candidates have been proposed in a few more lineages (reviewed in Thépot, 2021). The X‐specific region of D. deharvengi includes at least 10 genes with well‐documented roles in gonad development and differentiation ( akap8l , axin2 , dhh , foxd3 , gata2 , gdf9 , hoxc8 , lhx9 , nsd1 , rnf2 , and sox9 ).…”

Section: Discussionmentioning

confidence: 99%

XX/XY sex chromosomes in a blind lizard (Dibamidae): Towards understanding the evolution of sex determination in squamates

Rovatsos

Galoyan

Spangenberg

et al. 2022

J of Evolutionary Biology

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The reconstruction of the evolutionary history of sex determination in squamate reptiles (lizards and snakes) is complicated by missing data in many lineages, erroneous reports, and often questionable inferences on state homology. Therefore, despite the large effort, the reconstruction of the ancestral sex determination in squamate reptiles is still controversial. With the hope to shed light on this problem, we aspired to identify the sex chromosome gene content in Dibamus deharvengi, the representative of the family Dibamidae, the putative sister clade to all other squamates. Our analyses revealed XX/XY sex‐determination system in D. deharvengi: the X chromosome contains genes with homologues scattered across chicken chromosomes 8, 12, 13, 18, 30, and 33, and the Y chromosome seems to largely degenerate. To the best of our knowledge, this combination has never been reported to form sex chromosomes in any amniote lineage. It suggests that the sex chromosomes can represent an apomorphy of a clade including D. deharvengi. Our findings cover an important gap in the knowledge of sex determination in reptiles and further support multiple independent origins of sex chromosomes in this group.

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“…Because of their biology and phylogenic position, turtles hold clues to unlock numerous biological mysteries, including current biomedical questions. Indeed, turtles are an emerging model for ecology, evolution, and human health (Valenzuela, 2009), currently studied to understand physiology, life histories, chromosome evolution, as ecotoxicology sentinels, and to decipher biological pathways for sexual development and reproduction (Bista & Valenzuela, 2020; Chaousis et al, 2021; Congdon et al, 2022; Lee et al, 2020; Mizoguchi et al, 2022; Montiel et al, 2016; Sabath et al, 2016; Thépot, 2021). But while reptile genomics is thriving, reptilian transgenics remains challenging despite pioneering in vivo gene editing in anole lizards (Rasys et al, 2019) and recent work in mourning geckos (Lozito et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the First Turtle Organoids: A Model for Investigating Unique Adaptations with Biomedical Potential

Zdyrski

Gabriel

Gessler

et al. 2023

Preprint

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Painted turtles are remarkable for their well-developed freeze tolerance and associated resilience to hypoxia/anoxia, oxidative stress, and ability to supercool. They are, therefore, are an ideal model for biomedical research on hypoxia-induced injuries (such as strokes), tissue cooling during extensive surgeries, and organ cryopreservation. Yet, the seasonal reproduction and slow maturation of turtles hinder basic and applied biomedical research. To overcome these limitations, we have developed for the first time, adult stem cell-derived turtle hepatic organoids, which provide 3D self-assembled structures that closely mimic their original tissue and allow for in vitro testing and experimentation without constantly harvesting donor tissue and screening offspring. Our pioneering work with turtles represents the first for this vertebrate Order and complements the only other organoid lines from non-avian reptiles, which were produced from snake venom glands. Here we report the isolation and characterization of hepatic organoids derived from painted, snapping, and spiny softshell turtles spanning ~175 million years of evolution, with a subset being preserved in a biobank. Morphological and transcriptomics revealed organoid cells resembling cholangiocytes, which was then compared to the tissue of origin. Deriving organoids from multiple turtle species and life stages demonstrates that our organoid culturing techniques are broadly applicable to chelonians, permitting the development of functional genomic tools currently missing in most herpetological research. When combined with genetic editing, this platform will further support studies of genome-to-phenome mapping, gene function, genome architecture, and adaptive responses to climate change, among others. We discuss the unique abilities of painted turtles, including their overwintering potential, an adaptation with important implications for ecological, evolutionary, and biomedical research.

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

Cited by 16 publications

References 285 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)

XX/XY sex chromosomes in a blind lizard (Dibamidae): Towards understanding the evolution of sex determination in squamates

Characterization of the First Turtle Organoids: A Model for Investigating Unique Adaptations with Biomedical Potential

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