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1.
Am Nat ; 198(6): 678-693, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34762569

RESUMO

AbstractIn haplodiploids, (1) alleles spend twice as many generations in females as in males, (2) males are never heterozygous and therefore express recessive alleles, and (3) males sire daughters but not sons. Intralocus sexual conflict therefore operates differently in haplodiploids than in diploids and shares strong similarities with loci on X (or Z) chromosomes. The common co-occurrence of all three features makes it difficult to pinpoint their respective roles. However, they do not always co-occur in nature, and missing cases can be additionally studied with hypothetical life cycles. We model sexually antagonistic alleles in eight different sex determination systems and find that arguments 1 and 2 promote invasion and fixation of female-beneficial and male-beneficial alleles, respectively; argument 2 also improves prospects for polymorphism. Argument 3 harms the invasion prospects of sexually antagonistic alleles (irrespective of which sex benefits) but promotes fixation should invasion nevertheless occur. Disentangling the features helps to evaluate the validity of previous verbal arguments and yields better-informed predictions about intralocus sexual conflict under different sex determination systems, including hitherto undiscovered ones.


Assuntos
Caracteres Sexuais , Cromossomos Sexuais , Alelos , Diploide , Feminino , Humanos , Masculino , Seleção Genética
2.
BMC Genomics ; 22(1): 785, 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34727894

RESUMO

BACKGROUND: The genetic control of sex determination in teleost species is poorly understood. This is partly because of the diversity of mechanisms that determine sex in this large group of vertebrates, including constitutive genes linked to sex chromosomes, polygenic constitutive mechanisms, environmental factors, hermaphroditism, and unisexuality. Here we use a de novo genome assembly of New Zealand silver trevally (Pseudocaranx georgianus) together with sex-specific whole genome sequencing data to detect sexually divergent genomic regions, identify candidate genes and develop molecular makers. RESULTS: The de novo assembly of an unsexed trevally (Trevally_v1) resulted in a final assembly of 579.4 Mb in length, with a N50 of 25.2 Mb. Of the assembled scaffolds, 24 were of chromosome scale, ranging from 11 to 31 Mb in length. A total of 28,416 genes were annotated after 12.8 % of the assembly was masked with repetitive elements. Whole genome re-sequencing of 13 wild sexed trevally (seven males and six females) identified two sexually divergent regions located on two scaffolds, including a 6 kb region at the proximal end of chromosome 21. Blast analyses revealed similarity between one region and the aromatase genes cyp19 (a1a/b) (E-value < 1.00E-25, identity > 78.8 %). Males contained higher numbers of heterozygous variants in both regions, while females showed regions of very low read-depth, indicative of male-specificity of this genomic region. Molecular markers were developed and subsequently tested on 96 histologically-sexed fish (42 males and 54 females). Three markers amplified in absolute correspondence with sex (positive in males, negative in females). CONCLUSIONS: The higher number of heterozygous variants in males combined with the absence of these regions in females support a XY sex-determination model, indicating that the trevally_v1 genome assembly was developed from a male specimen. This sex system contrasts with the ZW sex-determination model documented in closely related carangid species. Our results indicate a sex-determining function of a cyp19a1a-like gene, suggesting the molecular pathway of sex determination is somewhat conserved in this family. The genomic resources developed here will facilitate future comparative work, and enable improved insights into the varied sex determination pathways in teleosts. The sex marker developed in this study will be a valuable resource for aquaculture selective breeding programmes, and for determining sex ratios in wild populations.


Assuntos
Peixes , Genoma , Animais , Feminino , Peixes/genética , Genômica , Masculino , Nova Zelândia , Cromossomos Sexuais/genética
3.
BMC Genomics ; 22(1): 710, 2021 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-34600471

RESUMO

BACKGROUND: Sex chromosomes are in some species largely undifferentiated (homomorphic) with restricted sex determination regions. Homomorphic but different sex chromosomes are found in the closely related genera Populus and Salix indicating flexible sex determination systems, ideal for studies of processes involved in sex chromosome evolution. We have performed genome-wide association studies of sex and analysed sex chromosomes in a population of 265 wild collected Salix viminalis accessions and studied the sex determining locus. RESULTS: A total of 19,592 markers were used in association analyses using both Fisher's exact tests and a single-marker mixed linear model, which resulted in 48 and 41 sex-associated (SA) markers respectively. Across all 48 SA markers, females were much more often heterozygous than males, which is expected if females were the heterogametic sex. The majority of the SA markers were, based on positions in the S. purpurea genome, located on chromosome 15, previously demonstrated to be the sex chromosome. Interestingly, when mapping the genotyping-by-sequencing sequence tag harbouring the two SA markers with the highest significance to the S. viminalis genomic scaffolds, five regions of very high similarity were found: three on a scaffold that represents a part of chromosome 15, one on a scaffold that represents a part of chromosome 9 and one on a scaffold not anchored to the genome. Based on segregation differences of the alleles at the two marker positions and on differences in PCR amplification between females and males we conclude that females had multiple copies of this DNA fragment (chromosome 9 and 15), whereas males only had one (chromosome 9). We therefore postulate that the female specific sequences have been copied from chromosome 9 and inserted on chromosome 15, subsequently developing into a hemizygous W chromosome linked region. CONCLUSIONS: Our results support that sex determination in S. viminalis is controlled by one locus on chromosome 15. The segregation patterns observed at the SA markers furthermore confirm that S. viminalis females are the heterogametic sex. We also identified a translocation from chromosome 9 to the W chromosome.


Assuntos
Cromossomos de Plantas/genética , Variações do Número de Cópias de DNA , Salix , Marcadores Genéticos , Estudo de Associação Genômica Ampla , Salix/genética , Cromossomos Sexuais/genética
4.
Braz J Biol ; 83: e248814, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34550286

RESUMO

The karyotype and constitutive heterochromatin pattern of the white stork Ciconia ciconia samples obtained from Manzala lake, Dimiaat, Egypt was described. Somatic cells of Ciconia ciconia samples have diploid number 2n= 68 chromosomes. Out of 68 chromosomes, 11 pairs including sex chromosomes were macrochromosomes and the remaining pairs were microchromosomes. Of the 11 macrochromosome pairs, no.1, 2, 4 and 5 were submetacentric and pairs no. 6, 7 and 8 were described as metacentric. In addition, the autosome pair no.3 was subtelocentric, while autosome pair no.9 was acrocentric. Also, the sex chromosome Z represents the fourth one in size and it was classified as submetacentric while, W chromosome appeared as medium size and was acrocentric. Furthermore, C-banding pattern (constitutive heterochromatin) revealed variation in their sizes and occurrence between macrochromosomes. Pairs no. 7 and 8 of autosomes exhibited unusual distribution of heterochromatin, where they appeared as entirely heterochromatic. This may be related to the origin of sex chromosomes Z and W. However, there is no sufficient evidence illustrate the appearance of entirely heterochromatic autosomes. Therefore, there is no available cytogenetic literature that describes the C-banding and karyotype of Ciconia Ciconia, so the results herein are important and may assist in cytogenetic study and evolutionary pattern of Ciconiiformes.


Assuntos
Heterocromatina , Cromossomos Sexuais , Animais , Aves , Heterocromatina/genética , Cariótipo , Cariotipagem , Cromossomos Sexuais/genética
5.
An Acad Bras Cienc ; 93(4): e20201650, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34586322

RESUMO

Taxonomic and cytogenetic aspects of Proceratophrys have not been thoroughly clarified in the literature; thus, the objective of the present study was to provide unprecedent karyotype data regarding P. schirchi, P. laticeps and P. melanopogon. Additionally, the karyotype of P. boiei (2n = 22) and its ZZ / ZW sex chromosome system was analyzed for different populations of southeastern and southern Brazil. All Proceratophrys species have a diploid number of 2n = 22 chromosomes. In P. schirchi, a strong C-band was found in the long arm in one of the homologues of the pair 8 in female metaphasic cells, denoting that this chromosome pair could represent the heteromorphic sex chromosome in a ZZ / ZW sex system. Despite the conserved number of chromosomes, there are considerable chromosomal differences in P. melanopogon and P. boiei (southern Brazil), strongly differentiating them cytogenetically from other species of the genus. Moreover, with the confirmation of chromosomal heteromorphism related to sexual differentiation in P. boiei and the possible description of this system in P. schirchi, the Proceratophrys genus can be regarded as an interesting group for evolutionary studies and sex chromosome differentiation in anurans.


Assuntos
Anuros , Diploide , Animais , Anuros/genética , Citogenética , Feminino , Cariotipagem , Cromossomos Sexuais/genética
6.
Cells ; 10(9)2021 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-34571879

RESUMO

Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.


Assuntos
Cromatina Sexual/metabolismo , Cromossomos Sexuais/genética , Animais , Hibridização Genômica Comparativa , Feminino , Hibridização in Situ Fluorescente , Cariótipo , Masculino , Mariposas/genética , Especificidade da Espécie
7.
Cells ; 10(9)2021 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-34571960

RESUMO

Meiosis involves a series of specific chromosome events, namely homologous synapsis, recombination, and segregation. Disruption of either recombination or synapsis in mammals results in the interruption of meiosis progression during the first meiotic prophase. This is usually accompanied by a defective transcriptional inactivation of the X and Y chromosomes, which triggers a meiosis breakdown in many mutant models. However, epigenetic changes and transcriptional regulation are also expected to affect autosomes. In this work, we studied the dynamics of epigenetic markers related to chromatin silencing, transcriptional regulation, and meiotic sex chromosome inactivation throughout meiosis in knockout mice for genes encoding for recombination proteins SPO11, DMC1, HOP2 and MLH1, and the synaptonemal complex proteins SYCP1 and SYCP3. These models are defective in recombination and/or synapsis and promote apoptosis at different stages of progression. Our results indicate that impairment of recombination and synapsis alter the dynamics and localization pattern of epigenetic marks, as well as the transcriptional regulation of both autosomes and sex chromosomes throughout prophase-I progression. We also observed that the morphological progression of spermatocytes throughout meiosis and the dynamics of epigenetic marks are processes that can be desynchronized upon synapsis or recombination alteration. Moreover, we detected an overlap of early and late epigenetic signatures in most mutants, indicating that the normal epigenetic transitions are disrupted. This can alter the transcriptional shift that occurs in spermatocytes in mid prophase-I and suggest that the epigenetic regulation of sex chromosomes, but also of autosomes, is an important factor in the impairment of meiosis progression in mammals.


Assuntos
Pareamento Cromossômico/genética , Epigênese Genética/genética , Mamíferos/genética , Meiose/genética , Proteínas Recombinantes/genética , Recombinação Genética/genética , Animais , Apoptose/genética , Marcadores Genéticos/genética , Masculino , Camundongos , Cromossomos Sexuais/genética , Espermatócitos/fisiologia , Transcrição Genética/genética
8.
Int J Mol Sci ; 22(16)2021 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-34445352

RESUMO

The Masculinizer (Masc) gene has been known to control sex development and dosage compensation in lepidopterans. However, it remains unclear whether its ortholog exists and plays the same roles in distantly related lepidopterans such as Helicoverpa armigera. To address this question, we cloned Masc from H. armigera (HaMasc), which contains all essential functional domains of BmMasc, albeit with less than 30% amino acid sequence identity with BmMasc. Genomic PCR and qPCR analyses showed that HaMasc is a Z chromosome-linked gene since its genomic content in males (ZZ) was two times greater than that in females (ZW). RT-PCR and RT-qPCR analyses revealed that HaMasc expression was sex- and stage-biased, with significantly more transcripts in males and eggs than in females and other stages. Transfection of a mixture of three siRNAs of HaMasc into a male embryonic cell line of H. armigera led to the appearance of female-specific mRNA splicing isoforms of H. armigeradoublesex (Hadsx), a downstream target gene of HaMasc in the H. armigera sex determination pathway. The knockdown of HaMasc, starting from the third instar larvae resulted in a shift of Hadsx splicing from male to female isoforms, smaller male pupa and testes, fewer but larger/longer spermatocytes and sperm bundles, delayed pupation and internal fusion of the testes and follicles. These data demonstrate that HaMasc functions as a masculinizing gene in the H. armigera sex-determination cascade.


Assuntos
Proteínas de Insetos/fisiologia , Mariposas/genética , Processos de Determinação Sexual/genética , Sequência de Aminoácidos , Animais , Clonagem Molecular , Compensação de Dosagem (Genética) , Feminino , Proteínas de Insetos/genética , Larva , Masculino , Mariposas/classificação , Filogenia , Isoformas de RNA , Análise de Sequência de DNA , Cromossomos Sexuais
9.
Int J Mol Sci ; 22(16)2021 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-34445371

RESUMO

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.


Assuntos
Análise Citogenética/métodos , Lagartos/classificação , Cromossomos Sexuais/genética , Animais , Hibridização Genômica Comparativa , DNA Ribossômico/genética , Diploide , Evolução Molecular , Feminino , Hibridização in Situ Fluorescente , Cariotipagem , Lagartos/genética , Masculino , Processos de Determinação Sexual
10.
Gynecol Obstet Invest ; 86(4): 379-387, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34384080

RESUMO

OBJECTIVE: This study was designed to investigate the efficiency of noninvasive prenatal testing (NIPT) for screening fetal sex chromosome aneuploidies (SCAs) through sequencing of cell-free DNA in maternal plasma. METHODS: This is a retrospective study on the positive NIPT results for SCAs collected from our hospital between January 2012 and December 2018. Samples with positive NIPT results for SCAs were then confirmed by prenatal or postnatal karyotyping analysis. RESULTS: After cytogenetic analysis, abnormal karyotypes were confirmed in 104 cases and the overall positive predictive value (PPV) of NIPT for SCAs was 43.40% (102/235). The most frequently detected karyotypes included 47,XXY (n = 42), 47,XXX (n = 20), 47,XYY (n = 16), and 45,X (n = 2). Meanwhile, 10 cases were confirmed with mosaic karyotype 45,X/46,XX and 14 cases with numerical or structural chromosome abnormalities, including a double trisomy 48,XXX,+18. Cytogenetic results from the other 131 cases showed normal XX or XY, which were discordant with NIPT results. Upon analysis of parental karyotypes, 29 (12.34%) showed false positivity in NIPT results that were caused by maternal sex chromosome abnormalities. CONCLUSION: NIPT is an effective screening tool for SCA with a PPV of 43.40%. Maternal karyotype abnormalities occurred in 12.34% of the cases with abnormal NIPT. Diagnostic testing of the fetus and the mother are recommended.


Assuntos
Teste Pré-Natal não Invasivo , Aneuploidia , Feminino , Humanos , Gravidez , Diagnóstico Pré-Natal , Estudos Retrospectivos , Aberrações dos Cromossomos Sexuais , Cromossomos Sexuais/genética
11.
Am J Bot ; 108(8): 1374-1387, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34406658

RESUMO

PREMISE: The evolution of sex chromosomes is driven by sexual dimorphism, yet it can be challenging to document sexually dimorphic traits in dioecious plant species. At the genetic level, sexual dimorphism can be identified through sequence variation between females and males associated with sexually antagonistic traits and different fitness optima. This study aims to examine sexual dimorphism for 26 traits in three populations of Salix purpurea (a diversity panel and F1 and F2 populations) and determine the effect of the traits on biomass yield, a key trait in Salix bioenergy crops across multiple years, locations, and under manipulated growth conditions. METHODS: Sexual dimorphism was evaluated for morphological, phenological, physiological, and wood composition traits in a diversity panel of unrelated S. purpurea accessions and in full-sib F1 and F2 families produced through controlled cross pollinations and grown in replicated field trials. RESULTS: We observed sexual dimorphism in the timing of development for several traits that were highly predictive of biomass yield across three populations of S. purpurea. Across all populations and years surveyed, males had significantly shallower branching angle. Male plants highly predictive of biomass yield across three populations of S. purpurea also accumulated more nitrogen under fertilizer amendment as measured by SPAD in the diversity panel and had greater susceptibility to the rust fungus Melampsora americana in the F2 family. Allometric modelling of biomass yield showed an effect of sex and of location on the interaction between yield and stem height. CONCLUSIONS: These results provide evidence of sexual dimorphism for certain traits in S. purpurea that may be involved in sex chromosome evolution.


Assuntos
Basidiomycota , Salix , Basidiomycota/genética , Salix/genética , Caracteres Sexuais , Cromossomos Sexuais
12.
Am J Nurs ; 121(9): 11, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34438410

RESUMO

Health care providers remain ill prepared to recognize these conditions and support patients and their families.


Assuntos
Cuidadores/psicologia , Aconselhamento Genético/psicologia , Relações Profissional-Família , Aberrações dos Cromossomos Sexuais , Conscientização , Criança , Humanos , Cromossomos Sexuais
13.
FASEB J ; 35(9): e21876, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34449112

RESUMO

Compared with the well-described XY sex determination system in mammals, the avian ZW sex determination system is poorly understood. Knockdown and overexpression studies identified doublesex and mab-3-related transcription factor 1 (DMRT1) as the testis-determining gene in chicken. However, the detailed effects of DMRT1 gene disruption from embryonic to adult development are not clear. Herein, we have generated DMRT1-disrupted chickens using the clustered regularly interspaced short palindromic repeats-associated protein 9 system, followed by an analysis of physiological, hormonal, and molecular changes in the genome-modified chickens. In the early stages of male chicken development, disruption of DMRT1 induced gonad feminization with extensive physiological and molecular changes; however, functional feminine reproductivity could not be implemented with disturbed hormone synthesis. Subsequent RNA-sequencing analysis of the DMRT1-disrupted chicken gonads revealed gene networks, including several novel genes linearly and non-linearly associated with DMRT1, which are involved in gonad feminization. By comparing the gonads of wild type with the genome-modified chickens, a set of genes were identified that is involved in the ZW sex determination system independent of DMRT1. Our results extend beyond the Z-dosage hypothesis to provide further information about the avian ZW sex determination system and epigenetic effects of gonad feminization.


Assuntos
Galinhas/genética , Feminização/genética , Gônadas/fisiologia , Fatores de Transcrição/genética , Animais , Feminino , Regulação da Expressão Gênica no Desenvolvimento/genética , Redes Reguladoras de Genes/genética , Masculino , Ovário/fisiologia , Cromossomos Sexuais , Testículo/fisiologia
14.
Nat Ecol Evol ; 5(10): 1394-1402, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34413504

RESUMO

Sexual dimorphism is ubiquitous in nature but its evolution is puzzling given that the mostly shared genome constrains independent evolution in the sexes. Sex differences should result from asymmetries between the sexes in selection or genetic variation but studies investigating both simultaneously are lacking. Here, we combine a quantitative genetic analysis of body size variation, partitioned into autosomal and sex chromosome contributions and ten generations of experimental evolution to dissect the evolution of sexual body size dimorphism in seed beetles (Callosobruchus maculatus) subjected to sexually antagonistic or sex-limited selection. Female additive genetic variance (VA) was primarily linked to autosomes, exhibiting a strong intersexual genetic correlation with males ([Formula: see text] = 0.926), while X- and Y-linked genes further contributed to the male VA and X-linked genes contributed to female dominance variance. Consistent with these estimates, sexual body size dimorphism did not evolve in response to female-limited selection but evolved by 30-50% under male-limited and sexually antagonistic selection. Remarkably, Y-linked variance alone could change dimorphism by 30%, despite the C. maculatus Y chromosome being small and heterochromatic. Our results demonstrate how the potential for sexual dimorphism to evolve depends on both its underlying genetic basis and the nature of sex-specific selection.


Assuntos
Besouros , Caracteres Sexuais , Animais , Tamanho Corporal , Besouros/genética , Feminino , Genes Ligados ao Cromossomo Y , Masculino , Cromossomos Sexuais
15.
PLoS Genet ; 17(8): e1009420, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34339412

RESUMO

Sex determination in the silkworm, Bombyx mori, is based on Feminizer (Fem), a W-linked Fem piRNA that triggers female development in WZ individuals, and the Z-linked Masculinizer (Masc), which initiates male development and dosage compensation in ZZ individuals. While Fem piRNA is missing in a close relative of B. mori, Masc determines sex in several representatives of distant lepidopteran lineages. We studied the molecular mechanisms of sex determination in the Mediterranean flour moth, Ephestia kuehniella (Pyralidae). We identified an E. kuehniella Masc ortholog, EkMasc, and its paralog resulting from a recent duplication, EkMascB. Both genes are located on the Z chromosome and encode a similar Masc protein that contains two conserved domains but has lost the conserved double zinc finger domain. We developed PCR-based genetic sexing and demonstrated a peak in the expression of EkMasc and EkMascB genes only in early male embryos. Simultaneous knock-down experiments of both EkMasc and EkMascB using RNAi during early embryogenesis led to a shift from male- to female-specific splicing of the E. kuehniella doublesex gene (Ekdsx), their downstream effector, in ZZ embryos and resulted in a strong female-biased sex-ratio. Our results thus confirmed the conserved role of EkMasc and/or EkMascB in masculinization. We suggest that the C-terminal proline-rich domain, we have identified in all functionally confirmed Masc proteins, in conjunction with the masculinizing domain, is important for transcriptional regulation of sex determination in Lepidoptera. The function of the Masc double zinc finger domain is still unknown, but appears to have been lost in E. kuehniella.


Assuntos
Duplicação Gênica , Proteínas de Insetos/genética , Mariposas/embriologia , Cromossomos Sexuais/genética , Processamento Alternativo , Animais , Compensação de Dosagem (Genética) , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Insetos/química , Masculino , Mariposas/genética , Especificidade de Órgãos , Domínios Proteicos , Processos de Determinação Sexual
16.
Philos Trans R Soc Lond B Biol Sci ; 376(1832): 20200091, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34247498

RESUMO

To date, more than 20 different vertebrate master sex-determining genes have been identified on different sex chromosomes of mammals, birds, frogs and fish. Interestingly, six of these genes are transcription factors (Dmrt1- or Sox3- related) and 13 others belong to the TGF-ß signalling pathway (Amh, Amhr2, Bmpr1b, Gsdf and Gdf6). This pattern suggests that only a limited group of factors/signalling pathways are prone to become top regulators again and again. Although being clearly a subordinate member of the sex-regulatory network in mammals, the TGF-ß signalling pathway made it to the top recurrently and independently. Facing this rolling wave of TGF-ß signalling pathways, this review will decipher how the TGF-ß signalling pathways cope with the canonical sex gene regulatory network and challenge the current evolutionary concepts accounting for the diversity of sex-determining mechanisms. 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 I)'.


Assuntos
Evolução Molecular , Cromossomos Sexuais/genética , Processos de Determinação Sexual , Transdução de Sinais , Fator de Crescimento Transformador beta/genética , Vertebrados/genética , Animais , Redes Reguladoras de Genes , Filogenia , Fator de Crescimento Transformador beta/metabolismo
17.
Philos Trans R Soc Lond B Biol Sci ; 376(1832): 20200109, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34247500

RESUMO

With or without sex chromosomes, sex determination is a synthesis of many molecular events that drives a community of cells towards a coordinated tissue fate. In this review, we will consider how a sex determination pathway can be engaged and stabilized without an inherited genetic determinant. In many reptilian species, no sex chromosomes have been identified, yet a conserved network of gene expression is initiated. Recent studies propose that epigenetic regulation mediates the effects of temperature on these genes through dynamic post-transcriptional, post-translational and metabolic pathways. It is likely that there is no singular regulator of sex determination, but rather an accumulation of molecular events that shift the scales towards one fate over another until a threshold is reached sufficient to maintain and stabilize one pathway and repress the alternative pathway. Investigations into the mechanism underlying sex determination without sex chromosomes should focus on cellular processes that are frequently activated by multiple stimuli or can synthesize multiple inputs and drive a coordinated response. 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 I)'.


Assuntos
Epigênese Genética , Evolução Molecular , Cromossomos Sexuais , Processos de Determinação Sexual , Vertebrados/genética , Animais
18.
Philos Trans R Soc Lond B Biol Sci ; 376(1832): 20200426, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34247497

RESUMO

Triggers and biological processes controlling male or female gonadal differentiation vary in vertebrates, with sex determination (SD) governed by environmental factors or simple to complex genetic mechanisms that evolved repeatedly and independently in various groups. Here, we review sex evolution across major clades of vertebrates with information on SD, sexual development and reproductive modes. We offer an up-to-date review of divergence times, species diversity, genomic resources, genome size, occurrence and nature of polyploids, SD systems, sex chromosomes, SD genes, dosage compensation and sex-biased gene expression. Advances in sequencing technologies now enable us to study the evolution of SD at broader evolutionary scales, and we now hope to pursue a sexomics integrative research initiative across vertebrates. The vertebrate sexome comprises interdisciplinary and integrated information on sexual differentiation, development and reproduction at all biological levels, from genomes, transcriptomes and proteomes, to the organs involved in sexual and sex-specific processes, including gonads, secondary sex organs and those with transcriptional sex-bias. The sexome also includes ontogenetic and behavioural aspects of sexual differentiation, including malfunction and impairment of SD, sexual differentiation and fertility. Starting from data generated by high-throughput approaches, we encourage others to contribute expertise to building understanding of the sexomes of many key vertebrate species. 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 I)'.


Assuntos
Evolução Biológica , Tamanho do Genoma , Cromossomos Sexuais/genética , Processos de Determinação Sexual , Diferenciação Sexual/genética , Vertebrados/genética , Animais , Evolução Molecular , Feminino , Masculino , Ovário/crescimento & desenvolvimento , Testículo/crescimento & desenvolvimento
19.
Philos Trans R Soc Lond B Biol Sci ; 376(1832): 20200093, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34247501

RESUMO

Genetic degeneration is an extraordinary feature of sex chromosomes, with the loss of functions of Y-linked genes in species with XY systems, and W-linked genes in ZW systems, eventually affecting almost all genes. Although degeneration is familiar to most biologists, important aspects are not yet well understood, including how quickly a Y or W chromosome can become completely degenerated. I review the current understanding of the time-course of degeneration. Degeneration starts after crossing over between the sex chromosome pair stops, and theoretical models predict an initially fast degeneration rate and a later much slower one. It has become possible to estimate the two quantities that the models suggest are the most important in determining degeneration rates-the size of the sex-linked region, and the time when recombination became suppressed (which can be estimated using Y-X or W-Z sequence divergence). However, quantifying degeneration is still difficult. I review evidence on gene losses (based on coverage analysis) or loss of function (by classifying coding sequences into functional alleles and pseudogenes). I also review evidence about whether small genome regions degenerate, or only large ones, whether selective constraints on the genes in a sex-linked region also strongly affect degeneration rates, and about how long it takes before all (or almost all) genes are lost. 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 I)'.


Assuntos
Cromossomos Sexuais/genética , Vertebrados/genética , Animais
20.
Philos Trans R Soc Lond B Biol Sci ; 376(1832): 20200094, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34247502

RESUMO

Sex-antagonistic (SA) genes are widely considered to be crucial players in the evolution of sex chromosomes, being instrumental in the arrest of recombination and degeneration of Y chromosomes, as well as important drivers of sex-chromosome turnovers. To test such claims, one needs to focus on systems at the early stages of differentiation, ideally with a high turnover rate. Here, I review recent work on two families of amphibians, Ranidae (true frogs) and Hylidae (tree frogs), to show that results gathered so far from these groups provide no support for a significant role of SA genes in the evolutionary dynamics of their sex chromosomes. The findings support instead a central role for neutral processes and deleterious mutations. 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 I)'.


Assuntos
Anuros/genética , Evolução Molecular , Cromossomos Sexuais/genética , Animais , Fenótipo , Ranidae/genética
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