Genomic Organization of Repetitive DNAs and Differentiation of an XX/XY Sex Chromosome System in the Amazonian Puffer Fish, Colomesus asellus (Tetraodontiformes)

2017 ◽  
Vol 153 (2) ◽  
pp. 96-104 ◽  
Author(s):  
Patrik F. Viana ◽  
Tariq Ezaz ◽  
Leandro Marajó ◽  
Milena Ferreira ◽  
Jansen Zuanon ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
First Record ◽  
Nucleolus Organizer ◽  
X Chromosomes ◽  
Nucleolus Organizer Regions ◽  
Rdna Sites ◽  
Puffer Fish ◽  
Specific Amplification ◽  
Sex Chromosome System

The genus Colomesus is the sole representative of the family Tetraodontidae in the Amazon region. Here, Colomesus asellus was analyzed using conventional and molecular cytogenetic protocols. Its diploid chromosome number is 2n = 46 with 12 meta-, 10 submeta-, 16 subtelo-, and 8 acrocentric chromosomes and a fundamental number of FN = 84. An XX/XY sex chromosome system was identified. Mapping of 18S rDNA correlated with the nucleolus organizer regions (Ag-NORs) in the short arms of the 2 X chromosomes in females and in the Y chromosome in males. C-banding revealed heterochromatin in the centromeric regions of all chromosomes, except for pair 3. Prominent sex chromosome-specific heterochromatin amplification was observed, covering the short arms of the Y chromosome almost entirely. FISH with telomeric and tropomyosin (tpm1) sequences, respectively, revealed terminal signals in all chromosomes. The analysis of extended DNA fibers confirmed the colocalization and the interspersed pattern of the telomeric and tpm1 sequences. Thus, this study highlights the remarkable evolutionary dynamism presented by the Amazonian puffer fish regarding the differentiation of a heteromorphic XY sex chromosome system and a particular sex-specific amplification of rDNA sites. This is the first record of such an association in the Tetraodontidae family.

The polytene chromosomes of Simulium furculatum (Shewell) (Diptera: Simuliidae)

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 522-530
Author(s):  
Fiona F. Hunter
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Polytene Chromosomes ◽  
Species Group ◽  
Western Canada ◽  
Black Flies ◽  
X Chromosomes ◽  
Group A ◽  
Sex Chromosome System

To test whether Simulium furculatum (Shewell) belongs to the Simulium vernum (Macquart) species-group, a comparison was made of the polytene chromosomes of S. furculatum and the S. vernum "Knebworth" standard. Only two chromosome arms (of six) could be completely analysed. It is argued that S. furculatum does not belong to the S. vernum species-group. A complex sex-chromosome system (X1, X2, Y1) is found in both eastern and western Canada. Phylogenetically, the single Y chromosome is intermediate between the two X chromosomes. Intraspecific inversion polymorphisms, which serve to differentiate eastern from western populations, are also identified. Only one sibling is indicated.Key words: black flies, Simulium furculatum, Simulium vernum, cytotaxonomy, polytene chromosomes, sex chromosomes.

scholarly journals Karyotype description and evidence of multiple sex chromosome system X1X1X2X2/X1X2Y in Potamotrygon aff. motoro and P. falkneri (Chondrichthyes: Potamotrygonidae) in the upper Paraná River basin, Brazil

2011 ◽  
Vol 9 (1) ◽  
pp. 201-208 ◽  
Author(s):  
Vanessa Paes da Cruz ◽  
Cristiane Kioko Shimabukuro-Dias ◽  
Claudio Oliveira ◽  
Fausto Foresti
Keyword(s):  
Sex Chromosome ◽  
Chromosomal Rearrangements ◽  
Chromosomal Evolution ◽  
Nucleolus Organizer ◽  
Banding Technique ◽  
Nucleolus Organizer Regions ◽  
Sex Chromosome System ◽  
Upper Paraná River ◽  
Upper Paraná River Basin ◽  
Almost All

Cytogenetic analysis of Potamotrygon aff. motoro and P. falkneri indicated the occurrence of an X1X1X2X2/X1X2 Y multiple sex chromosome system in both species, with 2n = 66 chromosomes for females and 2n = 65 chromosomes for males. The nucleolus organizer regions (NORs) identified using Ag-NOR technique showed that both species have multiple Ag-NORs (5 to 7 chromosomes stained). C-banding technique indicated the presence of heterochromatic blocks in the centromeric regions of almost all chromosomes in both species. Through this study there was evidence of heterogeneity in the karyotypes, which suggests that chromosomal rearrangements such as inversions and/or translocations occurred during the chromosomal evolution in two species of this genus.

scholarly journals Cytogenetic characterization of Hypostomus soniae Hollanda-Carvalho & Weber, 2004 from the Teles Pires River, southern Amazon basin: evidence of an early stage of an XX/XY sex chromosome system

2019 ◽  
Vol 13 (4) ◽  
pp. 411-422 ◽  
Author(s):  
Luciene Castuera de Oliveira ◽  
Marcos Otávio Ribeiro ◽  
Gerlane de Medeiros Costa ◽  
Cláudio Henrique Zawadzki ◽  
Ana Camila Prizon-Nakajima ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Sex Chromosome ◽  
Early Stage ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Structural Difference ◽  
Chromosomal Polymorphism ◽  
Nucleolus Organizer ◽  
Rdna Sites ◽  
Sex Chromosome System

In the present study, we analyzed individuals of Hypostomus soniae (Loricariidae) collected from the Teles Pires River, southern Amazon basin, Brazil. Hypostomus soniae has a diploid chromosome number of 2n = 64 and a karyotype composed of 12 metacentric (m), 22 submetacentric (sm), 14 subtelocentric (st), and 16 acrocentric (a) chromosomes, with a structural difference between the chromosomes of the two sexes: the presence of a block of heterochromatin in sm pair No. 26, which appears to represent a putative initial stage of the differentiation of an XX/XY sex chromosome system. This chromosome, which had a heterochromatin block, and was designated proto-Y (pY), varied in the length of the long arm (q) in comparison with its homolog, resulting from the addition of constitutive heterochromatin. It is further distinguished by the presence of major ribosomal cistrons in a subterminal position of the long arm (q). The Nucleolus Organizer Region (NOR) had different phenotypes among the H. soniae individuals in terms of the number of Ag-NORs and 18S rDNA sites. The origin, distribution and maintenance of the chromosomal polymorphism found in H. soniae reinforced the hypothesis of the existence of a proto-Y chromosome, demonstrating the rise of an XX/XY sex chromosome system.

Synaptonemal complex analysis in spermatocytes of tilapia, Oreochromis niloticus (Pisces, Cichlidae)

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1124-1128 ◽  
Author(s):  
Fausto Foresti ◽  
Claudio Oliveira ◽  
Pedro Manoel Galetti Junior ◽  
Lurdes Foresti de Almeida-Toledo
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Oreochromis Niloticus ◽  
Complex Analysis ◽  
Sex Chromosome ◽  
Light And Electron Microscopy ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Synaptonemal Complex Analysis ◽  
Sex Chromosome System

Some adaptations of the synaptonemal complex (SC) whole-mounting technique first used in plants permitted its application to meiotic studies in tilapia, Oreochromis niloticus. Direct observation of the chromosome pairing process and bivalent structure during the meiotic prophase of this fish species by light and electron microscopy permitted the analysis of SCs in autosomes and the possible identification of sex chromosomes. The analysis of SCs in spermatocytes of O. niloticus revealed that all 22 bivalent chromosomes completely paired, except for the occurrence of a size heteromorphism in the terminal region of the largest bivalent associated with the presence of an incompletely paired segment during the synapsis process, which may be the cytological visualization of an XX/XY sex chromosome system in this species.Key words: fish cytogenetics, synaptonemal complex, fish meiosis, sex chromosomes, nucleolus organizer regions.

From brain determination to testis determination: evolution of the mammalian sex-determining gene

2001 ◽  
Vol 13 (8) ◽  
pp. 665 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Critical Role ◽  
Dominant Gene ◽  
Comparative Gene Mapping ◽  
Good Account ◽  
Mole Vole ◽  
Sex Chromosome System ◽  
Testis Determination ◽  
Autosome Pair

In mammals, sex is determined by an XY male:XX female sex chromosome system in which a male-dominant gene on the Y chromosome (SRY) determines testis formation. Sex chromosomes evolved from an ordinary autosome pair as the Y chromosome was progressively degraded. The Y chromosome has lost nearly all of its 1500 original genes, and those that survived did so because they evolved a critical role in male determination or differentiation. SRY is typical of Y-borne genes. Comparative gene mapping and sequencing shows that SRY arose quite recently as a degraded version of the SOX3 gene on the X chromosome. SOX3 is expressed predominantly in brain, and so is more likely to be a brain-determining than a testis-determining gene. The male-dominant action of SRY may be an illusion, as its structure suggests that it works by interfering with the action of a related gene, which in turn inhibits testis development. This hypothesis can give a good account of how a brain-determining gene acquired a role in testis determination via differential dosage of SOX3. SRY has no central role in sex determination and it can be replaced as a trigger and lost, as have many other Y-borne genes in recent evolutionary history. The absence of SRY in two species of the mole vole (Ellobius) suggests that its useful life is already running out.

scholarly journals A second X chromosome contributes to resilience in a mouse model of Alzheimer’s disease

2020 ◽  
Vol 12 (558) ◽  
pp. eaaz5677 ◽  
Author(s):  
Emily J. Davis ◽  
Lauren Broestl ◽  
Samira Abdulai-Saiku ◽  
Kurtresha Worden ◽  
Luke W. Bonham ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Testicular Development ◽  
X Chromosomes ◽  
Model Of Alzheimer’S Disease ◽  
Preclinical Ad ◽  
Brain Expression

A major sex difference in Alzheimer’s disease (AD) is that men with the disease die earlier than do women. In aging and preclinical AD, men also show more cognitive deficits. Here, we show that the X chromosome affects AD-related vulnerability in mice expressing the human amyloid precursor protein (hAPP), a model of AD. XY-hAPP mice genetically modified to develop testicles or ovaries showed worse mortality and deficits than did XX-hAPP mice with either gonad, indicating a sex chromosome effect. To dissect whether the absence of a second X chromosome or the presence of a Y chromosome conferred a disadvantage on male mice, we varied sex chromosome dosage. With or without a Y chromosome, hAPP mice with one X chromosome showed worse mortality and deficits than did those with two X chromosomes. Thus, adding a second X chromosome conferred resilience to XY males and XO females. In addition, the Y chromosome, its sex-determining region Y gene (Sry), or testicular development modified mortality in hAPP mice with one X chromosome such that XY males with testicles survived longer than did XY or XO females with ovaries. Furthermore, a second X chromosome conferred resilience potentially through the candidate gene Kdm6a, which does not undergo X-linked inactivation. In humans, genetic variation in KDM6A was linked to higher brain expression and associated with less cognitive decline in aging and preclinical AD, suggesting its relevance to human brain health. Our study suggests a potential role for sex chromosomes in modulating disease vulnerability related to AD.

scholarly journals Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers

2019 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E. Wright ◽  
Benjamin A. Sandkam ◽  
Jake Morris ◽  
Natasha I. Bloch ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Sequencing Data ◽  
Chromosome Differentiation ◽  
Shared Ancestry ◽  
Sex Chromosome System ◽  
Suppressed Recombination

ABSTRACTOnce recombination is halted between the X and Y chromosome, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about variation in sex chromosome differentiation within clades. Here, we combined whole genome and transcriptome sequencing data to characterise the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged 30 mya. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata are largely homomorphic, with recombination persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely non-recombining and strikingly heteromorphic. ln addition to being highly divergent, the sex chromosome system in P. picta includes a neo-sex chromosome, the result of a fusion between the ancestral sex chromosome and part of chromosome 7. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of complete dosage compensation in this species, the first such documented case in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.

scholarly journals Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression

2020 ◽  
Vol 12 (6) ◽  
pp. 965-977 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E Wright ◽  
Judith E Mank
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Rna Seq ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
Chromosome Integrity ◽  
Heterogametic Sex

Abstract The loss of recombination triggers divergence between the sex chromosomes and promotes degeneration of the sex-limited chromosome. Several livebearers within the genus Poecilia share a male-heterogametic sex chromosome system that is roughly 20 Myr old, with extreme variation in the degree of Y chromosome divergence. In Poecilia picta, the Y is highly degenerate and associated with complete X chromosome dosage compensation. In contrast, although recombination is restricted across almost the entire length of the sex chromosomes in Poecilia reticulata and Poecilia wingei, divergence between the X chromosome and the Y chromosome is very low. This clade therefore offers a unique opportunity to study the forces that accelerate or hinder sex chromosome divergence. We used RNA-seq data from multiple families of both P. reticulata and P. wingei, the species with low levels of sex chromosome divergence, to differentiate X and Y coding sequences based on sex-limited SNP inheritance. Phylogenetic tree analyses reveal that occasional recombination has persisted between the sex chromosomes for much of their length, as X- and Y-linked sequences cluster by species instead of by gametolog. This incomplete recombination suppression maintains the extensive homomorphy observed in these systems. In addition, we see differences between the previously identified strata in the phylogenetic clustering of X–Y orthologs, with those that cluster by chromosome located in the older stratum, the region previously associated with the sex-determining locus. However, recombination arrest appears to have expanded throughout the sex chromosomes more gradually instead of through a stepwise process associated with inversions.

Ultrastructural analysis of the X1X2X3O sex chromosome system during the spermatogenesis of Tegenaria domestica (Arachnida)

1982 ◽  
Vol 58 (1) ◽  
pp. 411-422
Author(s):  
R. Benavente ◽  
R. Wettstein ◽  
M. Papa
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Ultrastructural Study ◽  
Chromosome Structure ◽  
Sex Chromosome ◽  
X Chromosomes ◽  
Sex Chromosome System ◽  
Available Information ◽  
Dense Chromatin

An ultrastructural study was performed on the sex chromosomes (male X1X2X3O) during the spermatogenesis of Tegenaria domestica (Arachnida, Agelenidae). This study was carried out using random and serially cut sections. During pachytene and diplotene the three X chromosomes are longitudinally paired. Each of these consists of a central core of condensed chromatin, surrounded by a field of dense chromatin projections through which the chromosomes are in contact with one another. These projections may be responsible for the recognition and pairing of the sex chromosomes and in some way participate in their non-disjunction during anaphase I. A study of the structure and behaviour of the sex chromosomes during spermatogenesis is also presented. The available information on non-synaptonemal complex-mediated chromosome pairing and a systematization of sex chromosome structure in spiders are discussed.

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