1
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Wagner S, Whiteley SL, Castelli M, Patel HR, Deveson IW, Blackburn J, Holleley CE, Marshall Graves JA, Georges A. Gene expression of male pathway genes sox9 and amh during early sex differentiation in a reptile departs from the classical amniote model. BMC Genomics 2023; 24:243. [PMID: 37147622 PMCID: PMC10163765 DOI: 10.1186/s12864-023-09334-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 04/25/2023] [Indexed: 05/07/2023] Open
Abstract
BACKGROUND Sex determination is the process whereby the bipotential embryonic gonads become committed to differentiate into testes or ovaries. In genetic sex determination (GSD), the sex determining trigger is encoded by a gene on the sex chromosomes, which activates a network of downstream genes; in mammals these include SOX9, AMH and DMRT1 in the male pathway, and FOXL2 in the female pathway. Although mammalian and avian GSD systems have been well studied, few data are available for reptilian GSD systems. RESULTS We conducted an unbiased transcriptome-wide analysis of gonad development throughout differentiation in central bearded dragon (Pogona vitticeps) embryos with GSD. We found that sex differentiation of transcriptomic profiles occurs at a very early stage, before the gonad consolidates as a body distinct from the gonad-kidney complex. The male pathway genes dmrt1 and amh and the female pathway gene foxl2 play a key role in early sex differentiation in P. vitticeps, but the central player of the mammalian male trajectory, sox9, is not differentially expressed in P. vitticeps at the bipotential stage. The most striking difference from GSD systems of other amniotes is the high expression of the male pathway genes amh and sox9 in female gonads during development. We propose that a default male trajectory progresses if not repressed by a W-linked dominant gene that tips the balance of gene expression towards the female trajectory. Further, weighted gene expression correlation network analysis revealed novel candidates for male and female sex differentiation. CONCLUSION Our data reveal that interpretation of putative mechanisms of GSD in reptiles cannot solely depend on lessons drawn from mammals.
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Affiliation(s)
- Susan Wagner
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
| | - Sarah L Whiteley
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
- Australian National Wildlife Collection CSIRO, National Research Collections Australia, Crace, ACT, Australia
| | - Meghan Castelli
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
- Australian National Wildlife Collection CSIRO, National Research Collections Australia, Crace, ACT, Australia
| | - Hardip R Patel
- Genome Sciences Department. John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Ira W Deveson
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- Faculty of Medicine, St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - James Blackburn
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- Faculty of Medicine, St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Clare E Holleley
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
- Australian National Wildlife Collection CSIRO, National Research Collections Australia, Crace, ACT, Australia
| | - Jennifer A Marshall Graves
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
- School of Life Sciences, La Trobe University, Bundoora, VIC, Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia.
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2
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Gessler TB, Wu Z, Valenzuela N. Transcriptomic thermal plasticity underlying gonadal development in a turtle with ZZ/ZW sex chromosomes despite canalized genotypic sex determination. Ecol Evol 2023; 13:e9854. [PMID: 36844670 PMCID: PMC9951354 DOI: 10.1002/ece3.9854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 02/07/2023] [Accepted: 02/08/2023] [Indexed: 02/28/2023] Open
Abstract
Understanding genome-wide responses to environmental conditions during embryogenesis is essential for discerning the evolution of developmental plasticity and canalization, two processes generating phenotypic variation targeted by natural selection. Here, we present the first comparative trajectory analysis of matched transcriptomic developmental time series from two reptiles incubated under identical conditions, a turtle with a ZZ/ZW system of genotypic sex determination (GSD), Apalone spinifera, and a turtle with temperature-dependent sex determination (TSD), Chrysemys picta. Results from our genome-wide, hypervariate gene expression analysis of sexed embryos across five developmental stages revealed that substantial transcriptional plasticity in the developing gonads can persist for >145 Myr, long after the canalization of sex determination via the evolution of sex chromosomes, while some gene-specific thermal sensitivity drifts or evolves anew. Such standing thermosensitivity represents an underappreciated evolutionary potential harbored by GSD species that may be co-opted during future adaptive shifts in developmental programing, such as a GSD to TSD reversal, if favored by ecological conditions. Additionally, we identified novel candidate regulators of vertebrate sexual development in GSD reptiles, including sex-determining candidate genes in a ZZ/ZW turtle.
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Affiliation(s)
- Thea B. Gessler
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowaUSA,Genetics and Genomics ProgramIowa State UniversityAmesIowaUSA
| | - Zhiqiang Wu
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowaUSA,Guangdong Laboratory for Lingnan Modern Agriculture, Agricultural Genomics Institute at ShenzhenChinese Academy of Agricultural SciencesShenzhenChina
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowaUSA
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3
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Temperature Incubation Influences Gonadal Gene Expression during Leopard Gecko Development. Animals (Basel) 2022; 12:ani12223186. [PMID: 36428413 PMCID: PMC9686823 DOI: 10.3390/ani12223186] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 11/10/2022] [Accepted: 11/16/2022] [Indexed: 11/19/2022] Open
Abstract
During development, sexual differentiation results in physiological, anatomical and metabolic differences that implicate not only the gonads but also other body structures. Sex in Leopard geckos is determined by egg incubation temperature. Based on the premise that the developmental decision of gender does not depend on a single gene, we performed an analysis on E. macularius to gain insights into the genes that may be involved in gonads' sexual differentiation during the thermosensitive period. All the genes were identified as differentially expressed at stage 30 during the labile phase of sex differentiation. In this way, the expression of genes known to be involved in gonadal sexual differentiation, such as WNT4, SOX9, DMRT1, Erα, Erβ, GnRH, P450 aromatase, PRLand PRL-R, was investigated. Other genes putatively involved in sex differentiation were sought by differential display. Our findings indicate that embryo exposure to a sex-determining temperature induces differential expression of several genes that are involved not only in gonadal differentiation, but also in several biological pathways (ALDOC, FREM1, BBIP1, CA5A, NADH5, L1 non-LTR retrotransposons, PKM). Our data perfectly fit within the new studies conducted in developmental biology, which indicate that in the developing embryo, in addition to gonadal differentiation, sex-specific tissue and metabolic polarization take place in all organisms.
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4
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Abouheif E. My road to the ants: A model clade for eco-evo-devo. Curr Top Dev Biol 2022; 147:231-290. [PMID: 35337451 DOI: 10.1016/bs.ctdb.2022.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
This chapter is the story of how I pioneered ants as a system for studying eco-evo-devo, a field that integrates developmental biology with ecology and evolutionary biology. One aim of eco-evo-devo is to understand how the interactions between genes and their environments during development facilitates the origin and evolution of novel phenotypes. In a series of six parts, I review some of the key discoveries from my lab on how novel worker caste systems in ants--soldiers and supersoldiers--originated and evolved. I also discuss some of the ideas that emerged from these discoveries, including the role that polyphenisms, hidden developmental potentials, and rudimentary organs play in facilitating developmental and evolutionary change. As superorganisms, I argue that ants are uniquely positioned to reveal types of variation that are often difficult to observe in nature. In doing so, they have the potential to transform our view of biology and provide new perspectives in medicine, agriculture, and biodiversity conservation. With my story I hope to inspire the next generation of biologists to continue exploring the unknown regions of phenotypic space to solve some of our most pressing societal challenges.
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Affiliation(s)
- Ehab Abouheif
- Department of Biology, McGill University, Montreal, QC, Canada.
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5
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Bista B, Wu Z, Literman R, Valenzuela N. Thermosensitive sex chromosome dosage compensation in ZZ/ZW softshell turtles, Apalone spinifera. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200101. [PMID: 34304598 DOI: 10.1098/rstb.2020.0101] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Sex chromosome dosage compensation (SCDC) overcomes gene-dose imbalances that disturb transcriptional networks, as when ZW females or XY males are hemizygous for Z/X genes. Mounting data from non-model organisms reveal diverse SCDC mechanisms, yet their evolution remains obscure, because most informative lineages with variable sex chromosomes are unstudied. Here, we discovered SCDC in turtles and an unprecedented thermosensitive SCDC in eukaryotes. We contrasted RNA-seq expression of Z-genes, their autosomal orthologues, and control autosomal genes in Apalone spinifera (ZZ/ZW) and Chrysemys picta turtles with temperature-dependent sex determination (TSD) (proxy for ancestral expression). This approach disentangled chromosomal context effects on Z-linked and autosomal expression, from lineage effects owing to selection or drift. Embryonic Apalone SCDC is tissue- and age-dependent, regulated gene-by-gene, complete in females via Z-upregulation in both sexes (Type IV) but partial and environmentally plastic via Z-downregulation in males (accentuated at colder temperature), present in female hatchlings and a weakly suggestive in adult liver (Type I). Results indicate that embryonic SCDC evolved with/after sex chromosomes in Apalone's family Tryonichidae, while co-opting Z-gene upregulation present in the TSD ancestor. Notably, Apalone's SCDC resembles pygmy snake's, and differs from the full-SCDC of Anolis lizards who share homologous sex chromosomes (XY), advancing our understanding of how XX/XY and ZZ/ZW systems compensate gene-dose imbalance. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.
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Affiliation(s)
- Basanta Bista
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Zhiqiang Wu
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA.,Guangdong Laboratory for Lingnan Modern Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, People's Republic of China
| | - Robert Literman
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
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6
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Valenzuela N. Podocnemis expansa Turtles Hint to a Unifying Explanation for the Evolution of Temperature-Dependent Sex Determination in Long-Lived and Short-Lived Vertebrates. Sex Dev 2021; 15:23-37. [PMID: 34004596 DOI: 10.1159/000515208] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/07/2021] [Indexed: 11/19/2022] Open
Abstract
The adaptive significance of temperature-dependent sex determination (TSD) remains elusive for many long-lived reptiles. Various hypotheses proposed potential ecological drivers of TSD. The Charnov-Bull'77 model remains the most robust and explains the maintenance of TSD in short-lived vertebrates, where sex ratios correlate with seasonal temperatures within years that confer sex-specific fitness (colder springs produce females who grow larger and gain in fecundity, whereas warmer summers produce males who mature at smaller size). Yet, evidence of fitness differentials correlated with incubation temperature is scarce for long-lived taxa. Here, it is proposed that the Charnov-Bull'77 model applies similarly to long-lived taxa, but at a longer temporal scale, by revisiting ecological and genetic data from the long-lived turtle Podocnemis expansa. After ruling out multiple alternatives, it is hypothesized that warmer-drier years overproduce females and correlate with optimal resource availability in the flood plains, benefitting daughters more than sons, whereas resources are scarcer (due to reduced flowering/fruiting) during colder-rainier years that overproduce males, whose fitness is less impacted by slower growth rates. New technical advances and collaborative interdisciplinary efforts are delineated that should facilitate testing this hypothesis directly, illuminating the understanding of TSD evolution in P. expansa and other long-lived TSD reptiles.
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Affiliation(s)
- Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
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7
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Vasudeva R, Deeming DC, Eady PE. Age‐specific sensitivity of sperm length and testes size to developmental temperature in the bruchid beetle. J Zool (1987) 2021. [DOI: 10.1111/jzo.12884] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- R. Vasudeva
- School of Biological Sciences Norwich Research Park University of East Anglia Norwich UK
| | - D. C. Deeming
- School of Life Sciences University of Lincoln Lincoln Lincolnshire UK
| | - P. E. Eady
- School of Life Sciences University of Lincoln Lincoln Lincolnshire UK
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8
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Molecular identification and expression analysis of foxl2 and sox9b in Oryzias celebensis. AQUACULTURE AND FISHERIES 2020. [DOI: 10.1016/j.aaf.2020.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Turtle Insights into the Evolution of the Reptilian Karyotype and the Genomic Architecture of Sex Determination. Genes (Basel) 2020; 11:genes11040416. [PMID: 32290488 PMCID: PMC7231036 DOI: 10.3390/genes11040416] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/06/2020] [Accepted: 04/08/2020] [Indexed: 01/01/2023] Open
Abstract
Sex chromosome evolution remains an evolutionary puzzle despite its importance in understanding sexual development and genome evolution. The seemingly random distribution of sex-determining systems in reptiles offers a unique opportunity to study sex chromosome evolution not afforded by mammals or birds. These reptilian systems derive from multiple transitions in sex determination, some independent, some convergent, that lead to the birth and death of sex chromosomes in various lineages. Here we focus on turtles, an emerging model group with growing genomic resources. We review karyotypic changes that accompanied the evolution of chromosomal systems of genotypic sex determination (GSD) in chelonians from systems under the control of environmental temperature (TSD). These transitions gave rise to 31 GSD species identified thus far (out of 101 turtles with known sex determination), 27 with a characterized sex chromosome system (13 of those karyotypically). These sex chromosomes are varied in terms of the ancestral autosome they co-opted and thus in their homology, as well as in their size (some are macro-, some are micro-chromosomes), heterogamety (some are XX/XY, some ZZ/ZW), dimorphism (some are virtually homomorphic, some heteromorphic with larger-X, larger W, or smaller-Y), age (the oldest system could be ~195 My old and the youngest < 25 My old). Combined, all data indicate that turtles follow some tenets of classic theoretical models of sex chromosome evolution while countering others. Finally, although the study of dosage compensation and molecular divergence of turtle sex chromosomes has lagged behind research on other aspects of their evolution, this gap is rapidly decreasing with the acceleration of ongoing research and growing genomic resources in this group.
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10
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Mizoguchi B, Valenzuela N. Alternative splicing and thermosensitive expression of Dmrt1 during urogenital development in the painted turtle, Chrysemys picta. PeerJ 2020; 8:e8639. [PMID: 32219017 PMCID: PMC7085901 DOI: 10.7717/peerj.8639] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 01/27/2020] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The doublesex and mab-3 related transcription factor 1 (Dmrt1) is a highly conserved gene across numerous vertebrates and invertebrates in sequence and function. Small aminoacid changes in Dmrt1 are associated with turnovers in sex determination in reptiles. Dmrt1 is upregulated in males during gonadal development in many species, including the painted turtle, Chrysemys picta, a reptile with temperature-dependent sex determination (TSD). Dmrt1 is reported to play different roles during sex determination and differentiation, yet whether these functions are controlled by distinct Dmrt1 spliceoforms remains unclear. While Dmrt1 isoforms have been characterized in various vertebrates, no study has investigated their existence in any turtle. METHODS We examine the painted turtle to identify novel Dmrt1 isoforms that may be present during urogenital development using PCR, profile their expression by RNA-seq across five embryonic stages at male- and female-producing temperatures, and validate their expression pattern via qPCR with transcript-specific fluorescent probes. RESULTS A novel Dmrt1 spliceoform was discovered for the first time in chelonians, lacking exons 2 and 3 (Dmrt1 ΔEx2Ex3). Dmrt1 canonical and ΔEx2Ex3 transcripts were differentialy expressed by temperature at stages 19 and 22 in developing gonads of painted turtles, after the onset of sex determination, and displayed a significant male-biased expression pattern. This transcriptional pattern differs from studies in other turtles and vertebrates that reported Dmrt1 differential expression before or at the onset of sex determination. This study provides the first insight into Dmrt1 transcriptional diversity in turtles and opens the door for future functional studies of the alternative Dmrt1 transcript uncovered here. CONCLUSIONS The discovery of an isoform in turtles indicate that alternative splicing may be a common feature of Dmrt1 across vertebrates, as isoforms are also found in crocodilians, birds, mammals and fish, and this variation remains unexplained. The relatively late-onset of Dmrt1 expression observed here contrasts with other turtles, indicating that Dmrt1 is not the topmost male sex -determining factor in C. picta. When placed in a phylogenetic context, this discrepancy underscores the divergent regulation of Dmrt1, and of sexual development more generally, across vertebrates.
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Affiliation(s)
- Beatriz Mizoguchi
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
| | - Nicole Valenzuela
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
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11
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Radhakrishnan S, Literman R, Neuwald JL, Valenzuela N. Thermal Response of Epigenetic Genes Informs Turtle Sex Determination with and without Sex Chromosomes. Sex Dev 2018; 12:308-319. [PMID: 30278451 DOI: 10.1159/000492188] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2018] [Indexed: 12/20/2022] Open
Abstract
Vertebrate sexual fate can be established by environmental cues (e.g., temperature-dependent sex determination, TSD) or by genetic content (genotypic sex determination, GSD). While methylation is implicated in TSD, the influence of broader epigenetic processes in sexual development remains obscure. Here, we investigated for the first time the embryonic gonadal expression of the genome-wide epigenetic machinery in turtles, including genes and noncoding RNAs (ncRNAs) involved in DNA/histone acetylation, methylation, ubiquitination, phosphorylation, and RNAi. This machinery was active and differentially thermosensitive in TSD versus GSD (ZZ/ZW) turtles. Methylation and histone acetylation genes responded the strongest. The results suggest these working hypotheses: (i) TSD might be mediated by epigenetically controlled hormonal pathways (via acetylation, methylation, and ncRNAs), or by (ii) hormonally controlled epigenetic processes, and (iii) key epigenetic events prior to the canonical thermosensitive period may explain differences between TSD and GSD. Novel epigenetic candidate regulators other than methylation were identified, including previously unknown ncRNAs that could potentially mediate gonadogenesis. These findings illuminate the molecular ecology of reptilian sex determination and permitted hypothesis building to help guide future functional studies on the epigenetic transduction of external cues in TSD versus GSD systems.
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12
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Expression profiles of amh and foxl2 in Schizothorax kozlovi, and their response to temperature during the early developmental stage. J Genet 2018. [DOI: 10.1007/s12041-018-0889-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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13
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Radhakrishnan S, Literman R, Mizoguchi B, Valenzuela N. MeDIP-seq and nCpG analyses illuminate sexually dimorphic methylation of gonadal development genes with high historic methylation in turtle hatchlings with temperature-dependent sex determination. Epigenetics Chromatin 2017; 10:28. [PMID: 28533820 PMCID: PMC5438563 DOI: 10.1186/s13072-017-0136-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 05/12/2017] [Indexed: 12/15/2022] Open
Abstract
Background DNA methylation alters gene expression but not DNA sequence and mediates some cases of phenotypic plasticity. Temperature-dependent sex determination (TSD) epitomizes phenotypic plasticity where environmental temperature drives embryonic sexual fate, as occurs commonly in turtles. Importantly, the temperature-specific transcription of two genes underlying gonadal differentiation is known to be induced by differential methylation in TSD fish, turtle and alligator. Yet, how extensive is the link between DNA methylation and TSD remains unclear. Here we test for broad differences in genome-wide DNA methylation between male and female hatchling gonads of the TSD painted turtle Chrysemys picta using methyl DNA immunoprecipitation sequencing, to identify differentially methylated candidates for future study. We also examine the genome-wide nCpG distribution (which affects DNA methylation) in painted turtles and test for historic methylation in genes regulating vertebrate gonadogenesis. Results Turtle global methylation was consistent with other vertebrates (57% of the genome, 78% of all CpG dinucleotides). Numerous genes predicted to regulate turtle gonadogenesis exhibited sex-specific methylation and were proximal to methylated repeats. nCpG distribution predicted actual turtle DNA methylation and was bimodal in gene promoters (as other vertebrates) and introns (unlike other vertebrates). Differentially methylated genes, including regulators of sexual development, had lower nCpG content indicative of higher historic methylation. Conclusions Ours is the first evidence suggesting that sexually dimorphic DNA methylation is pervasive in turtle gonads (perhaps mediated by repeat methylation) and that it targets numerous regulators of gonadal development, consistent with the hypothesis that it may regulate thermosensitive transcription in TSD vertebrates. However, further research during embryogenesis will help test this hypothesis and the alternative that instead, most differential methylation observed in hatchlings is the by-product of sexual differentiation and not its cause. Electronic supplementary material The online version of this article (doi:10.1186/s13072-017-0136-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Srihari Radhakrishnan
- Bioinformatics and Computational Biology Program, Iowa State University, Ames, IA 50011 USA.,Department of Ecology, Evolution and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011 USA
| | - Robert Literman
- Ecology and Evolutionary Biology Program, Iowa State University, Ames, IA 50011 USA.,Department of Ecology, Evolution and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011 USA
| | - Beatriz Mizoguchi
- Interdepartmental Genetics and Genomics Program, Iowa State University, Ames, IA 50011 USA.,Department of Ecology, Evolution and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011 USA
| | - Nicole Valenzuela
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011 USA
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14
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Radhakrishnan S, Literman R, Neuwald J, Severin A, Valenzuela N. Transcriptomic responses to environmental temperature by turtles with temperature-dependent and genotypic sex determination assessed by RNAseq inform the genetic architecture of embryonic gonadal development. PLoS One 2017; 12:e0172044. [PMID: 28296881 PMCID: PMC5352168 DOI: 10.1371/journal.pone.0172044] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 01/30/2017] [Indexed: 12/24/2022] Open
Abstract
Vertebrate sexual fate is decided primarily by the individual's genotype (GSD), by the environmental temperature during development (TSD), or both. Turtles exhibit TSD and GSD, making them ideal to study the evolution of sex determination. Here we analyze temperature-specific gonadal transcriptomes (RNA-sequencing validated by qPCR) of painted turtles (Chrysemys picta TSD) before and during the thermosensitive period, and at equivalent stages in soft-shell turtles (Apalone spinifera-GSD), to test whether TSD's and GSD's transcriptional circuitry is identical but deployed differently between mechanisms. Our data show that most elements of the mammalian urogenital network are active during turtle gonadogenesis, but their transcription is generally more thermoresponsive in TSD than GSD, and concordant with their sex-specific function in mammals [e.g., upregulation of Amh, Ar, Esr1, Fog2, Gata4, Igf1r, Insr, and Lhx9 at male-producing temperature, and of β-catenin, Foxl2, Aromatase (Cyp19a1), Fst, Nf-kb, Crabp2 at female-producing temperature in Chrysemys]. Notably, antagonistic elements in gonadogenesis (e.g., β-catenin and Insr) were thermosensitive only in TSD early-embryos. Cirbp showed warm-temperature upregulation in both turtles disputing its purported key TSD role. Genes that may convert thermal inputs into sex-specific development (e.g., signaling and hormonal pathways, RNA-binding and heat-shock) were differentially regulated. Jak-Stat, Nf-κB, retinoic-acid, Wnt, and Mapk-signaling (not Akt and Ras-signaling) potentially mediate TSD thermosensitivity. Numerous species-specific ncRNAs (including Xist) were differentially-expressed, mostly upregulated at colder temperatures, as were unannotated loci that constitute novel TSD candidates. Cirbp showed warm-temperature upregulation in both turtles. Consistent transcription between turtles and alligator revealed putatively-critical reptilian TSD elements for male (Sf1, Amh, Amhr2) and female (Crabp2 and Hspb1) gonadogenesis. In conclusion, while preliminary, our data helps illuminate the regulation and evolution of vertebrate sex determination, and contribute genomic resources to guide further research into this fundamental biological process.
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Affiliation(s)
- Srihari Radhakrishnan
- Bioinformatics and Computational Biology Program, Iowa State University, Ames, IA, United States of America
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
| | - Robert Literman
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
- Ecology and Evolutionary Biology Program, Iowa State University, Ames, IA, United States of America
| | - Jennifer Neuwald
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
| | - Andrew Severin
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
- Genome Informatics Facility, Iowa State University, Ames, IA, United States of America
| | - Nicole Valenzuela
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, United States of America
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15
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Mizoguchi BA, Valenzuela N. Ecotoxicological Perspectives of Sex Determination. Sex Dev 2016; 10:45-57. [DOI: 10.1159/000444770] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2015] [Indexed: 11/19/2022] Open
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16
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Badenhorst D, Hillier LW, Literman R, Montiel EE, Radhakrishnan S, Shen Y, Minx P, Janes DE, Warren WC, Edwards SV, Valenzuela N. Physical Mapping and Refinement of the Painted Turtle Genome (Chrysemys picta) Inform Amniote Genome Evolution and Challenge Turtle-Bird Chromosomal Conservation. Genome Biol Evol 2015; 7:2038-50. [PMID: 26108489 PMCID: PMC4524486 DOI: 10.1093/gbe/evv119] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2015] [Indexed: 01/04/2023] Open
Abstract
Comparative genomics continues illuminating amniote genome evolution, but for many lineages our understanding remains incomplete. Here, we refine the assembly (CPI 3.0.3 NCBI AHGY00000000.2) and develop a cytogenetic map of the painted turtle (Chrysemys picta-CPI) genome, the first in turtles and in vertebrates with temperature-dependent sex determination. A comparison of turtle genomes with those of chicken, selected nonavian reptiles, and human revealed shared and novel genomic features, such as numerous chromosomal rearrangements. The largest conserved syntenic blocks between birds and turtles exist in four macrochromosomes, whereas rearrangements were evident in these and other chromosomes, disproving that turtles and birds retain fully conserved macrochromosomes for greater than 300 Myr. C-banding revealed large heterochromatic blocks in the centromeric region of only few chromosomes. The nucleolar-organizing region (NOR) mapped to a single CPI microchromosome, whereas in some turtles and lizards the NOR maps to nonhomologous sex-chromosomes, thus revealing independent translocations of the NOR in various reptilian lineages. There was no evidence for recent chromosomal fusions as interstitial telomeric-DNA was absent. Some repeat elements (CR1-like, Gypsy) were enriched in the centromeres of five chromosomes, whereas others were widespread in the CPI genome. Bacterial artificial chromosome (BAC) clones were hybridized to 18 of the 25 CPI chromosomes and anchored to a G-banded ideogram. Several CPI sex-determining genes mapped to five chromosomes, and homology was detected between yet other CPI autosomes and the globally nonhomologous sex chromosomes of chicken, other turtles, and squamates, underscoring the independent evolution of vertebrate sex-determining mechanisms.
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Affiliation(s)
- Daleen Badenhorst
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
| | | | - Robert Literman
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
| | | | | | - Yingjia Shen
- The Genome Institute at Washington University, St Louis
| | - Patrick Minx
- The Genome Institute at Washington University, St Louis
| | - Daniel E Janes
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University Department of Organismic and Evolutionary Biology, Harvard University
| | | | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University
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17
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Incubation temperature affects the immune function of hatchling soft-shelled turtles, Pelodiscus sinensis. Sci Rep 2015; 5:10594. [PMID: 26028216 PMCID: PMC4450580 DOI: 10.1038/srep10594] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 04/20/2015] [Indexed: 12/24/2022] Open
Abstract
Identifying how developmental temperature affects the immune system is critical for understanding how ectothermic animals defend against pathogens and their fitness in the changing world. However, reptiles have received little attention regarding this issue. We incubated eggs at three ecologically relevant temperatures to determine how incubation temperature affects the immune function of hatchling soft-shelled turtles, Pelodiscus sinensis. When exposed to bacterial infections, hatchlings from 24 °C had lower cumulative mortalities (55%, therefore, higher immunocompetence) than those from 28 °C (85%) or 32 °C (100%). Consistent with higher immunocompetence, hatchlings from low incubation temperature had higher IgM, IgD, and CD3γ expressions than their counterparts from the other two higher incubation temperatures. Conversely, the activity of immunity-related enzymes did not match the among-temperature difference in immune function. Specifically, enzyme activity was higher at intermediate temperatures (alkaline phosphatase) or was not affected by incubation temperature (acid phosphatase, lysozyme). Our study is the first to provide unequivocal evidence (at the molecular and organismal level) about the significant effect of incubation temperature on offspring immunity in reptiles. Our results also indicate that the reduced immunity induced by high developmental temperatures might increase the vulnerability of reptiles to the outbreak of diseases under global warming scenarios.
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18
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Prontera P, Donti E. Hypothesis: gonadal temperature influences sex-specific imprinting. Front Genet 2014; 5:294. [PMID: 25202325 PMCID: PMC4142806 DOI: 10.3389/fgene.2014.00294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 08/07/2014] [Indexed: 11/29/2022] Open
Abstract
Various explanations have been advanced for the evolution of genomic imprinting, the most popular of these being the parental conflict hypothesis. However, while this theory may explain why there has been selection for imprinting certain genes, it does not explain how the maternal and paternal genomes can be distinguished from each other. Here, we hypothesize that the temperature at which male and female gonads are physiologically exposed could be, at least for some loci, the primary factor leading to the different imprinting between the sexes.
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Affiliation(s)
- Paolo Prontera
- Medical Genetics Unit, Department of Surgical and Biomedical Sciences, University of Perugia Perugia, Italy
| | - Emilio Donti
- Medical Genetics Unit, Department of Surgical and Biomedical Sciences, University of Perugia Perugia, Italy
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19
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Literman R, Badenhorst D, Valenzuela N. qPCR-based molecular sexing by copy number variation in rRNA genes and its utility for sex identification in soft-shell turtles. Methods Ecol Evol 2014. [DOI: 10.1111/2041-210x.12228] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robert Literman
- Department of Ecology, Evolution and Organismal Biology; Iowa State University; 251 Bessey Hall Ames IA 50011 USA
| | - Daleen Badenhorst
- Department of Ecology, Evolution and Organismal Biology; Iowa State University; 251 Bessey Hall Ames IA 50011 USA
| | - Nicole Valenzuela
- Department of Ecology, Evolution and Organismal Biology; Iowa State University; 251 Bessey Hall Ames IA 50011 USA
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20
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Shen ZG, Wang HP. Molecular players involved in temperature-dependent sex determination and sex differentiation in Teleost fish. Genet Sel Evol 2014; 46:26. [PMID: 24735220 PMCID: PMC4108122 DOI: 10.1186/1297-9686-46-26] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Accepted: 03/24/2014] [Indexed: 12/11/2022] Open
Abstract
The molecular mechanisms that underlie sex determination and differentiation are conserved and diversified. In fish species, temperature-dependent sex determination and differentiation seem to be ubiquitous and molecular players involved in these mechanisms may be conserved. Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In this paper, we review recent advances on the molecular players that participate in the sex determination and differentiation in fish species, by putting emphasis on temperature-dependent sex determination and differentiation, which include temperature-dependent sex determination and genetic sex determination plus temperature effects. Application of temperature-dependent sex differentiation in farmed fish and the consequences of temperature-induced sex reversal are discussed.
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Affiliation(s)
| | - Han-Ping Wang
- Aquaculture Genetics and Breeding Laboratory, The Ohio State University South Centers, Piketon, Ohio 45661, USA.
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21
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Janes DE, Elsey RM, Langan EM, Valenzuela N, Edwards SV. Sex-biased expression of sex-differentiating genes FOXL2 and FGF9 in American alligators, alligator Mississippiensis. Sex Dev 2013; 7:253-60. [PMID: 23689672 DOI: 10.1159/000350787] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2013] [Indexed: 01/12/2023] Open
Abstract
Across amniotes, sex-determining mechanisms exhibit great variation, yet the genes that govern sexual differentiation are largely conserved. Studies of evolution of sex-determining and sex-differentiating genes require an exhaustive characterization of functions of those genes such as FOXL2 and FGF9. FOXL2 is associated with ovarian development, and FGF9 is known to play a role in testicular organogenesis in mammals and other amniotes. As a step toward characterization of the evolutionary history of sexual development, we measured expression of FOXL2 and FGF9 across 3 developmental stages and 8 juvenile tissue types in male and female American alligators, Alligator mississippiensis. We report surprisingly high expression of FOXL2 before the stage of embryonic development when sex is determined in response to temperature, and sustained and variable expression of FGF9 in juvenile male, but not female tissue types. Novel characterization of gene expression in reptiles with temperature-dependent sex determination such as American alligators may inform the evolution of sex-determining and sex-differentiating gene networks, as they suggest alternative functions from which the genes may have been exapted. Future functional profiling of sex-differentiating genes should similarly follow other genes and other species to enable a broad comparison across sex-determining mechanisms.
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Affiliation(s)
- D E Janes
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Mass., USA.
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22
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Valenzuela N, Neuwald JL, Literman R. Transcriptional evolution underlying vertebrate sexual development. Dev Dyn 2012; 242:307-19. [DOI: 10.1002/dvdy.23897] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2012] [Indexed: 12/30/2022] Open
Affiliation(s)
- Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology; Iowa State University; Ames; Iowa
| | - Jennifer L. Neuwald
- Department of Ecology, Evolution, and Organismal Biology; Iowa State University; Ames; Iowa
| | - Robert Literman
- Department of Ecology, Evolution, and Organismal Biology; Iowa State University; Ames; Iowa
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23
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Uller T, Helanterä H. From the origin of sex-determining factors to the evolution of sex-determining systems. QUARTERLY REVIEW OF BIOLOGY 2011; 86:163-80. [PMID: 21954700 DOI: 10.1086/661118] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sex determination is typically classified as either genotypic or environmental. However, this dichotomy obscures the developmental origin and evolutionary modification of determinants of sex, and therefore hinders an understanding of the processes that generates diversity in sex-determining systems. Recent research on reptiles and fish emphasizes that sex determination is a multifactorial regulatory process that is best understood as a threshold dichotomy rather than as the result of genetically inherited triggers of development. Here we critically assess the relationship between the developmental origin of sex-determining factors and evolutionary transitions in sex-determining systems. Our perspective emphasizes the importance of both genetic and nongenetic causes in evolution of sex determination and may help to generate predictions with respect to the evolutionary patterns of sex-determining systems and the underlying diversity of developmental and genetic regulatory networks.
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Affiliation(s)
- Tobias Uller
- Edward Grey Institute, Department of Zoology, University of Oxford Oxford OX1 3PS United Kingdom.
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24
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Abstract
Species living in seasonal environments often adaptively time their reproduction in response to photoperiod cues. We characterized the expression of genes in the flowering-time regulatory network across wild populations of the common sunflower, Helianthus annuus, that we found to be adaptively differentiated for photoperiod response. The observed clinal variation was associated with changes at multiple hierarchical levels in multiple pathways. Paralogue-specific changes in FT homologue expression and tissue-specific changes in SOC1 homologue expression were associated with loss and reversal of plasticity, respectively, suggesting that redundancy and modularity are gene network characteristics easily exploited by natural selection to produce evolutionary innovation. Distinct genetic mechanisms contribute to convergent evolution of photoperiod responses within sunflower, suggesting regulatory network architecture does not impose strong constraints on the evolution of phenotypic plasticity.
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25
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26
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Charlesworth D, Mank JE. The birds and the bees and the flowers and the trees: lessons from genetic mapping of sex determination in plants and animals. Genetics 2010; 186:9-31. [PMID: 20855574 PMCID: PMC2940314 DOI: 10.1534/genetics.110.117697] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The ability to identify genetic markers in nonmodel systems has allowed geneticists to construct linkage maps for a diversity of species, and the sex-determining locus is often among the first to be mapped. Sex determination is an important area of study in developmental and evolutionary biology, as well as ecology. Its importance for organisms might suggest that sex determination is highly conserved. However, genetic studies have shown that sex determination mechanisms, and the genes involved, are surprisingly labile. We review studies using genetic mapping and phylogenetic inferences, which can help reveal evolutionary pattern within this lability and potentially identify the changes that have occurred among different sex determination systems. We define some of the terminology, particularly where confusion arises in writing about such a diverse range of organisms, and highlight some major differences between plants and animals, and some important similarities. We stress the importance of studying taxa suitable for testing hypotheses, and the need for phylogenetic studies directed to taxa where the patterns of changes can be most reliably inferred, if the ultimate goal of testing hypotheses regarding the selective forces that have led to changes in such an essential trait is to become feasible.
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Affiliation(s)
- Deborah Charlesworth
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, United Kingdom.
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27
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Duffy TA, Picha ME, Won ET, Borski RJ, McElroy AE, Conover DO. Ontogenesis of gonadal aromatase gene expression in atlantic silverside (Menidia menidia) Populations with genetic and temperature-dependent sex determination. ACTA ACUST UNITED AC 2010; 313:421-31. [DOI: 10.1002/jez.612] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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28
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Janes DE, Organ CL, Edwards SV. Variability in sex-determining mechanisms influences genome complexity in reptilia. Cytogenet Genome Res 2010; 127:242-8. [PMID: 20203474 DOI: 10.1159/000293283] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In this review, we describe the history of amniote sex determination as a classic example of Darwinian evolution. We suggest that evolutionary changes in sex determination provide a foundation for understanding important aspects of chromosome and genome organization that otherwise appear haphazard in their origins and contents. Species with genotypic sex determination often possess heteromorphic sex chromosomes, whereas species with environmental sex determination lack them. Through a series of mutations followed by selection at key genes, sex-determining mechanisms have turned over many times throughout the amniote lineage. As a consequence, amniote genomes have undergone gains or losses of sex chromosomes. We review the genomic and ecological contexts in which either temperature-dependent or genotypic sex determination has evolved. Once genotypic sex determination emerges in a lineage, viviparity and heteromorphic sex chromosomes become more likely to evolve. For example, in extinct marine reptiles, genotypic sex determination apparently led to viviparity, which in turn facilitated their pelagic radiation. Sex chromosomes comprise genome regions that differ from autosomes in recombination rate, mutation rate, levels of polymorphism, and the presence of sex-determining and sexually antagonistic genes. In short, many aspects of amniote genome complexity, life history, and adaptive radiation appear contingent on evolutionary changes in sex-determining mechanisms.
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Affiliation(s)
- D E Janes
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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29
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Rhen T, Schroeder A. Molecular mechanisms of sex determination in reptiles. Sex Dev 2010; 4:16-28. [PMID: 20145384 PMCID: PMC2918650 DOI: 10.1159/000282495] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 08/15/2009] [Indexed: 01/17/2023] Open
Abstract
Charles Darwin first provided a lucid explanation of how gender differences evolve nearly 140 years ago. Yet, a disconnect remains between his theory of sexual selection and the mechanisms that underlie the development of males and females. In particular, comparisons between representatives of different phyla (i.e., flies and mice) reveal distinct genetic mechanisms for sexual differentiation. Such differences are hard to comprehend unless we study organisms that bridge the phylogenetic gap. Analysis of variation within monophyletic groups (i.e., amniotes) is just as important if we hope to elucidate the evolution of mechanisms underlying sexual differentiation. Here we review the molecular, cellular, morphological, and physiological changes associated with sex determination in reptiles. Most research on the molecular biology of sex determination in reptiles describes expression patterns for orthologs of mammalian sex-determining genes. Many of these genes have evolutionarily conserved expression profiles (i.e., DMRT1 and SOX9 are expressed at a higher level in developing testes vs. developing ovaries in all species), which suggests functional conservation. However, expression profiling alone does not test gene function and will not identify novel sex-determining genes or gene interactions. For that reason, we provide a prospectus on various techniques that promise to reveal new sex-determining genes and regulatory interactions among these genes. We offer specific examples of novel candidate genes and a new signaling pathway in support of these techniques.
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Affiliation(s)
- T. Rhen
- Department of Biology, University of North Dakota, Grand Forks, N. Dak., USA
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30
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Blázquez M, Navarro-Martín L, Piferrer F. Expression profiles of sex differentiation-related genes during ontogenesis in the European sea bass acclimated to two different temperatures. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2009; 312:686-700. [PMID: 19338052 DOI: 10.1002/jez.b.21286] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The European sea bass is a teleost fish that lacks sex chromosomes and for which temperature influences sex ratios. However, correlation between temperature, developmental stage at a given age and sex-specific gene expression is hampered by the lack of sex markers. To study this correlation, fish were exposed to feminizing (15 degrees C) or masculinizing temperature (21 degrees C) from 0-120 days post fertilization, throughout the thermosensitive period (TSP). Aromatase (cyp19a1a), 11beta-hydroxylase (cyp11b), androgen receptor (arb) and estrogen receptors (era, erb1 and erb2) were assessed by qPCR prior and during sex differentiation. Canonical discriminant analysis (CDA), with length--as proxy for developmental stage--and cyp19a1a expression as predictors, was validated and used to reliably assign gonadal sex to fish sampled within and outside the TSP. Differences in cyp19a1a and cyp11b expression could be detected 1-month before the first signs of histological sex differentiation. Cyp19a1a and cyp11b were significantly higher in future females and males, respectively, and revealed as robust molecular markers to predict future ovarian and testicular differentiation. In contrast, no association between phenotypic sex and arb, era, erb1 and erb2 expression was found, suggesting that these genes do not contribute to the differentiation of a particular sex. The CDA-based approach implemented here could be used to sex undifferentiated animals in species where genetic sex cannot be known owing to the lack of simple sex determining systems, as it is the case of many fish and reptiles with or without temperature-dependent sex determination, and provide a useful tool to relate gene expression and phenotypic sex.
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Affiliation(s)
- Mercedes Blázquez
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Barcelona, Spain
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31
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Valenzuela N. The painted turtle, Chrysemys picta: a model system for vertebrate evolution, ecology, and human health. Cold Spring Harb Protoc 2009; 2009:pdb.emo124. [PMID: 20147199 DOI: 10.1101/pdb.emo124] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Painted turtles (Chrysemys picta) are representatives of a vertebrate clade whose biology and phylogenetic position hold a key to our understanding of fundamental aspects of vertebrate evolution. These features make them an ideal emerging model system. Extensive ecological and physiological research provide the context in which to place new research advances in evolutionary genetics, genomics, evolutionary developmental biology, and ecological developmental biology which are enabled by current resources, such as a bacterial artificial chromosome (BAC) library of C. picta, and the imminent development of additional ones such as genome sequences and cDNA and expressed sequence tag (EST) libraries. This integrative approach will allow the research community to continue making advances to provide functional and evolutionary explanations for the lability of biological traits found not only among reptiles but vertebrates in general. Moreover, because humans and reptiles share a common ancestor, and given the ease of using nonplacental vertebrates in experimental biology compared with mammalian embryos, painted turtles are also an emerging model system for biomedical research. For example, painted turtles have been studied to understand many biological responses to overwintering and anoxia, as potential sentinels for environmental xenobiotics, and as a model to decipher the ecology and evolution of sexual development and reproduction. Thus, painted turtles are an excellent reptilian model system for studies with human health, environmental, ecological, and evolutionary significance.
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Affiliation(s)
- Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA.
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32
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Analyzing the coordinated gene network underlying temperature-dependent sex determination in reptiles. Semin Cell Dev Biol 2008; 20:293-303. [PMID: 19022389 DOI: 10.1016/j.semcdb.2008.10.010] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 10/24/2008] [Indexed: 02/07/2023]
Abstract
Although gonadogenesis has been extensively studied in vertebrates with genetic sex determination, investigations at the molecular level in nontraditional model organisms with temperature-dependent sex determination are relatively new areas of research. Results show that while the key players of the molecular network underlying gonad development appear to be retained, their functions range from conserved to novel roles. In this review, we summarize experiments investigating candidate molecular players underlying temperature-dependent sex determination. We discuss some of the problems encountered unraveling this network, pose potential solutions, and suggest rewarding future directions of research.
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Dong GH, Ma YN, Ding HL, Jin J, Cao Y, Zhao YD, He QC. Effects of housing characteristics and home environmental factors on respiratory symptoms of 10,784 elementary school children from northeast china. ACTA ACUST UNITED AC 2008; 76:82-91. [PMID: 18337632 DOI: 10.1159/000121370] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 12/27/2007] [Indexed: 11/19/2022]
Abstract
BACKGROUND Only few studies have assessed the relative impact of housing characteristics and home environmental factors on asthma and asthma-related symptoms in Chinese children, and to our knowledge, few studies have elaborated respiratory symptoms and allergies in this context. OBJECTIVE It was the aim of this study to assess the effects of housing characteristics, pet keeping, home decorations and other indoor environmental factors on respiratory health of Chinese children. METHODS We studied 10,784 children (6-13 years old) from 12 districts in Liaoning province, Northeast China. Information on respiratory health, housing characteristics and environmental pollution was obtained by a standard questionnaire from the American Thoracic Society. RESULTS Prevalence of asthma-related symptoms was higher for those living along the main stem of traffic, and for those with a house nearby a pollution source. Lower prevalence rates of respiratory morbidity were associated with households with a bigger area of residence and more rooms. Pet keeping was associated with doctor-diagnosed asthma (OR = 1.52; 95% CI 1.25-1.84). Home decorations also increased the risk of doctor-diagnosed asthma (OR = 1.72; 95% CI 1.45-2.04) and current asthma (OR = 1.43; 95% CI 1.06-1.93). Environmental tobacco smoke, pests and visible mold on walls were associated with the occurrence of asthma symptoms. CONCLUSION Home environmental factors are particularly important for the development of respiratory morbidity among children.
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Affiliation(s)
- Guang-Hui Dong
- Department of Biostatistics and Epidemiology, School of Public Health, China Medical University, Shenyang, PR China
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