Aphids and Ants, Mutualistic Species, Share a Mariner Element with an Unusual Location on Aphid Chromosomes

Aphids (Hemiptera, Aphididae) are small phytophagous insects. The aim of this study was to determine if the mariner elements found in the ant genomes are also present in Aphis fabae and Aphis hederae genomes and the possible existence of horizontal transfer events. Aphids maintain a relationship of mutualism with the ants. The close contact between these insects could favour horizontal transfer events of transposable elements. Myrmar mariner element isolated from Myrmica ruginodis and Tapinoma ibericum ants have also been found in the two Aphis species: A. fabae and A. hederae (Afabmar-Mr and Ahedmar-Mr elements). Besides, Afabmar-Mr could be an active transposon. Myrmar-like elements are also present in other insect species as well as in one Crustacean species. The phylogenetic study carried out with all Myrmar-like elements suggests the existence of horizontal transfer. Most aphids have 2n = 8 with a XX-X0 sex determination system. Their complicated life cycle is mostly parthenogenetic with sexual individuals only in autumn. The production of X0 males, originated by XX females which produce only spermatozoa with one X chromosome, must necessarily occur through specialized cytogenetic and molecular mechanisms which are not entirely known. In both aphid species, the mariner elements are located on all chromosomes, including the X chromosomes. However, on the two X chromosomes, no positive signals are detected in their small DAPI-negative telomere regions. The rDNA sites are located, as in the majority of Aphids species, on one of the telomere regions of each X chromosome. The hybridization patterns obtained by double FISH demonstrate that Afabmar-Mr and Ahedmar-Mr elements do not hybridize at the rDNA sites of their host species. Possible causes for the absence of these transposons in the rDNA genes are discussed, probably related with the X chromosome biology.

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Primary sex determination in the nematode C. elegans

Development ◽

10.1242/dev.101.supplement.5 ◽

1987 ◽

Vol 101 (Supplement) ◽

pp. 5-16 ◽

Cited By ~ 3

Author(s):

Jonathan Hodgkin

Keyword(s):

Sex Determination ◽

X Chromosome ◽

Germ Line ◽

X Chromosomes ◽

C Elegans ◽

Female Sex ◽

Determination System ◽

One Step ◽

Sex Determination System ◽

Specific Control

Most nematodes have XO male/XX female sex determination. C. elegans is anomalous, having XX hermaphrodites rather than females. The hermaphrodite condition appears to result from the modification of a basic male/female sex-determination system, which permits both spermatogenesis and oogenesis to occur within a female soma. This modification is achieved by a germ-line-specific control acting at one step in a cascade of autosomal regulatory genes, which respond to X-chromosome dosage and direct male, female, or hermaphrodite development. Mutations of one of these genes can be used to construct artificial strains with ZZ male/WZ female sex determination. Primary sex determination normally depends on the ratio of X chromosomes to autosomes, as in Drosophila, and there appear to be multiple sites on the X chromosome that contribute to this ratio. Also, as in Drosophila, X-chromosome expression is compensated to equalize gene activity in XX and XO animals. Interactions between dosage compensation and sex determination are described and discussed.

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STATISTICAL MECHANICS MODELS FOR X-CHROMOSOME INACTIVATION

Advances in Complex Systems ◽

10.1142/s0219525910002566 ◽

2010 ◽

Vol 13 (03) ◽

pp. 367-376

Author(s):

ANTONIO SCIALDONE ◽

MARIO NICODEMI

Keyword(s):

Statistical Mechanics ◽

X Chromosome ◽

Molecular Mechanisms ◽

X Chromosome Inactivation ◽

Chromosome Inactivation ◽

Regulatory Mechanisms ◽

Random Choice ◽

X Chromosomes ◽

Cellular Processes ◽

Regulatory Processes

We present statistical mechanics models to understand the physical and molecular mechanisms of X-Chromosome Inactivation (XCI), the process whereby a female mammal cell inactivates one of its two X-chromosomes. During XCI, X-chromosomes undergo a series of complex regulatory processes. At the beginning of XCI, the X's recognize and pair, then only one X which is randomly chosen is inactivated. Afterwards, the two X's move to different positions in the cell nucleus according to their different status (active/silenced). Our models illustrate about the still mysterious physical bases underlying all these regulatory steps, i.e., X-chromosome pairing, random choice of inactive X, and "shuttling" of the X's to their post-XCI locations. Our models are based on general and robust thermodynamic roots, and their validity can go beyond XCI, to explain analogous regulatory mechanisms in a variety of cellular processes.

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Mechanisms of Choice in X-Chromosome Inactivation

10.20944/preprints202201.0183.v1 ◽

2022 ◽

Author(s):

Giulia Furlan ◽

Rafael Galupa

Keyword(s):

X Chromosome ◽

Molecular Mechanisms ◽

X Chromosome Inactivation ◽

X Inactivation ◽

Current Understanding ◽

Chromosome Inactivation ◽

X Chromosomes

Early in development, placental and marsupial mammals harbouring at least two X chromosomes per nuclei are faced with a choice that affects the rest of their lives: which of those X chromosomes to transcriptionally inactivate. This choice underlies phenotypical diversity in the composition of tissues and organs and in their response to environment, and can determine whether an individual will be healthy or affected by an X-linked disease. Here, we review our current understanding of the process of choice during X-chromosome inactivation and its implications, focusing on the strategies evolved by different mammalian lineages and on the known and unknown molecular mechanisms and players involved. We also call for a revised manner in which to think about choice during random X-inactivation.

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Dosage Compensation Systems

Introduction to Epigenetics - Learning Materials in Biosciences ◽

10.1007/978-3-030-68670-3_4 ◽

2021 ◽

pp. 67-89

Author(s):

Renato Paro ◽

Ueli Grossniklaus ◽

Raffaella Santoro ◽

Anton Wutz

Keyword(s):

Gene Expression ◽

X Chromosome ◽

Dosage Compensation ◽

Molecular Mechanisms ◽

Sex Chromosome ◽

Fruit Fly ◽

X Chromosomes ◽

Compensation Systems ◽

A Cell ◽

Males And Females

AbstractThis chapter provides an introduction to chromosome-wide dosage compensation systems. We will examine the evolution of dosage compensation, which is thought to be driven by the appearance of differentiated sex chromosomes. In a subset of species with X chromosomal sex determination or XY sex chromosome systems, expression of X-linked genes is regulated by chromosome-wide modifications that equalize gene expression differences between males and females. The molecular mechanisms of X chromosome-wide dosage compensation have been studied in flies, worms, and mammals. Each of these species uses a distinct dosage compensation strategy with a different molecular mechanism. In the wormCaenorhabditis elegans, gene expression on the two X chromosomes of hermaphrodites is reduced to a level that approximates a single X chromosome in males. The fruit flyDrosophila melanogasterachieves dosage compensation by increased transcription of the single X chromosome in males to a level that is similar to the two X chromosomes in females. Lastly, in mammals, one of the two X chromosomes in female cells is transcriptionally inactive and a single X chromosome is transcribed in both sexes. Studies of dosage compensation systems provide insights into how epigenetic regulation controls gene expression and chromatin organization differentially within a cell.

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Bisection of the X chromosome disrupts the initiation of chromosome silencing during meiosis in Caenorhabditis elegans

Nature Communications ◽

10.1038/s41467-021-24815-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yisrael Rappaport ◽

Hanna Achache ◽

Roni Falk ◽

Omer Murik ◽

Oren Ram ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Rna Polymerase Ii ◽

X Chromosome ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Transcription Analysis ◽

X Chromosomes ◽

Unique Character ◽

Active Transcription ◽

Heterogametic Sex

AbstractDuring meiosis, gene expression is silenced in aberrantly unsynapsed chromatin and in heterogametic sex chromosomes. Initiation of sex chromosome silencing is disrupted in meiocytes with sex chromosome-autosome translocations. To determine whether this is due to aberrant synapsis or loss of continuity of sex chromosomes, we engineered Caenorhabditis elegans nematodes with non-translocated, bisected X chromosomes. In early meiocytes of mutant males and hermaphrodites, X segments are enriched with euchromatin assembly markers and active RNA polymerase II staining, indicating active transcription. Analysis of RNA-seq data showed that genes from the X chromosome are upregulated in gonads of mutant worms. Contrary to previous models, which predicted that any unsynapsed chromatin is silenced during meiosis, our data indicate that unsynapsed X segments are transcribed. Therefore, our results suggest that sex chromosome chromatin has a unique character that facilitates its meiotic expression when its continuity is lost, regardless of whether or not it is synapsed.

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DNA methylation and behavioral dysfunction in males with 47,XXY and 49,XXXXY: a pilot study

Clinical Epigenetics ◽

10.1186/s13148-021-01123-4 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Richard S. Lee ◽

Sophia Q. Song ◽

Henri M. Garrison-Desany ◽

Jenny L. Carey ◽

Patricia Lasutschinkow ◽

...

Keyword(s):

Pilot Study ◽

X Chromosome ◽

Child Behavior Checklist ◽

Epigenetic Modification ◽

Cpg Methylation ◽

Monoamine Oxidase A ◽

Low Fertility ◽

X Chromosomes ◽

Behavioral Dysfunction ◽

Study Results

Abstract Background Equal dosage of X-linked genes between males and females is maintained by the X-inactivation of the second X chromosome in females through epigenetic mechanisms. Boys with aneuploidy of the X chromosome exhibit a host of symptoms such as low fertility, musculoskeletal anomalies, and cognitive and behavioral deficits that are presumed to be caused by the abnormal dosage of these genes. The objective of this pilot study is to assess the relationship between CpG methylation, an epigenetic modification, at several genes on the X chromosome and behavioral dysfunction in boys with supernumerary X chromosomes. Results Two parental questionnaires, the Behavior Rating Inventory of Executive Function (BRIEF) and Child Behavior Checklist (CBCL), were analyzed, and they showed expected differences in both internal and external behaviors between neurotypical (46,XY) boys and boys with 49,XXXXY. There were several CpGs in AR and MAOA of boys with 49,XXXXY whose methylation levels were skewed from levels predicted from having one active (Xa) and three inactive (Xi) X chromosomes. Further, methylation levels of multiple CpGs in MAOA showed nominally significant association with externalizing behavior on the CBCL, and the methylation level of one CpG in AR showed nominally significant association with the BRIEF Regulation Index. Conclusions Boys with 49,XXXXY displayed higher levels of CpG methylation at regulatory intronic regions in X-linked genes encoding the androgen receptor (AR) and monoamine oxidase A (MAOA), compared to that in boys with 47,XXY and neurotypical boys. Our pilot study results suggest a link between CpG methylation levels and behavior in boys with 49,XXXXY.

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Ultrastructural and molecular analysis of the origin and differentiation of cells mediating brittle star skeletal regeneration

BMC Biology ◽

10.1186/s12915-020-00937-7 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Laura Piovani ◽

Anna Czarkwiani ◽

Cinzia Ferrario ◽

Michela Sugni ◽

Paola Oliveri

Keyword(s):

Molecular Mechanisms ◽

Close Contact ◽

Skeletal Development ◽

Morphological Differentiation ◽

Brittle Star ◽

Marker Genes ◽

Body Parts ◽

Coelomic Cavity ◽

Expression Of Genes ◽

Skeletal Regeneration

Abstract Background Regeneration is the ability to re-grow body parts or tissues after trauma, and it is widespread across metazoans. Cells involved in regeneration can arise from a pool of undifferentiated proliferative cells or be recruited from pre-existing differentiated tissues. Both mechanisms have been described in different phyla; however, the cellular and molecular mechanisms employed by different animals to restore lost tissues as well as the source of cells involved in regeneration remain largely unknown. Echinoderms are a clade of deuterostome invertebrates that show striking larval and adult regenerative abilities in all extant classes. Here, we use the brittle star Amphiura filiformis to investigate the origin and differentiation of cells involved in skeletal regeneration using a combination of microscopy techniques and molecular markers. Results Our ultrastructural analyses at different regenerative stages identify a population of morphologically undifferentiated cells which appear in close contact with the proliferating epithelium of the regenerating aboral coelomic cavity. These cells express skeletogenic marker genes, such as the transcription factor alx1 and the differentiation genes c-lectin and msp130L, and display a gradient of morphological differentiation from the aboral coelomic cavity towards the epidermis. Cells closer to the epidermis, which are in contact with developing spicules, have the morphology of mature skeletal cells (sclerocytes), and express several skeletogenic transcription factors and differentiation genes. Moreover, as regeneration progresses, sclerocytes show a different combinatorial expression of genes in various skeletal elements. Conclusions We hypothesize that sclerocyte precursors originate from the epithelium of the proliferating aboral coelomic cavity. As these cells migrate towards the epidermis, they differentiate and start secreting spicules. Moreover, our study shows that molecular and cellular processes involved in skeletal regeneration resemble those used during skeletal development, hinting at a possible conservation of developmental programmes during adult regeneration. Finally, we highlight that many genes involved in echinoderm skeletogenesis also play a role in vertebrate skeleton formation, suggesting a possible common origin of the deuterostome endoskeleton pathway.

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Absence of X-chromosome dosage compensation in the primordial germ cells of Drosophila embryos

Scientific Reports ◽

10.1038/s41598-021-84402-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ryoma Ota ◽

Makoto Hayashi ◽

Shumpei Morita ◽

Hiroki Miura ◽

Satoru Kobayashi

Keyword(s):

X Chromosome ◽

Germ Cells ◽

Dosage Compensation ◽

Sex Chromosome ◽

Primordial Germ Cells ◽

Histone H4 ◽

X Chromosomes ◽

Essential Components ◽

Msl Complex ◽

Male Specific

AbstractDosage compensation is a mechanism that equalizes sex chromosome gene expression between the sexes. In Drosophila, individuals with two X chromosomes (XX) become female, whereas males have one X chromosome (XY). In males, dosage compensation of the X chromosome in the soma is achieved by five proteins and two non-coding RNAs, which assemble into the male-specific lethal (MSL) complex to upregulate X-linked genes twofold. By contrast, it remains unclear whether dosage compensation occurs in the germline. To address this issue, we performed transcriptome analysis of male and female primordial germ cells (PGCs). We found that the expression levels of X-linked genes were approximately twofold higher in female PGCs than in male PGCs. Acetylation of lysine residue 16 on histone H4 (H4K16ac), which is catalyzed by the MSL complex, was undetectable in these cells. In male PGCs, hyperactivation of X-linked genes and H4K16ac were induced by overexpression of the essential components of the MSL complex, which were expressed at very low levels in PGCs. Together, these findings indicate that failure of MSL complex formation results in the absence of X-chromosome dosage compensation in male PGCs.

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Escape from X Chromosome Inactivation and the Female Predominance in Autoimmune Diseases

International Journal of Molecular Sciences ◽

10.3390/ijms22031114 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1114

Author(s):

Ali Youness ◽

Charles-Henry Miquel ◽

Jean-Charles Guéry

Keyword(s):

Autoimmune Diseases ◽

X Chromosome ◽

Gene Dosage ◽

X Chromosome Inactivation ◽

Chromosome Inactivation ◽

X Chromosomes ◽

Female Sex Hormones ◽

Inactive X Chromosome ◽

Immune Related Genes ◽

Female Specific

Women represent 80% of people affected by autoimmune diseases. Although, many studies have demonstrated a role for sex hormone receptor signaling, particularly estrogens, in the direct regulation of innate and adaptive components of the immune system, recent data suggest that female sex hormones are not the only cause of the female predisposition to autoimmunity. Besides sex steroid hormones, growing evidence points towards the role of X-linked genetic factors. In female mammals, one of the two X chromosomes is randomly inactivated during embryonic development, resulting in a cellular mosaicism, where about one-half of the cells in a given tissue express either the maternal X chromosome or the paternal one. X chromosome inactivation (XCI) is however not complete and 15 to 23% of genes from the inactive X chromosome (Xi) escape XCI, thereby contributing to the emergence of a female-specific heterogeneous population of cells with bi-allelic expression of some X-linked genes. Although the direct contribution of this genetic mechanism in the female susceptibility to autoimmunity still remains to be established, the cellular mosaicism resulting from XCI escape is likely to create a unique functional plasticity within female immune cells. Here, we review recent findings identifying key immune related genes that escape XCI and the relationship between gene dosage imbalance and functional responsiveness in female cells.

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SITE-SPECIFIC INSTABILITY IN DROSOPHILA MELANOGASTER: EVIDENCE FOR TRANSPOSITION OF DESTABILIZING ELEMENT

Genetics ◽

10.1093/genetics/101.3-4.461 ◽

1982 ◽

Vol 101 (3-4) ◽

pp. 461-476

Author(s):

Todd R Laverty ◽

J K Lim

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Lethal Mutation ◽

Chromosome Rearrangements ◽

Chromosome Break ◽

Secondary Mutation ◽

X Chromosomes ◽

Site Specific ◽

Normal Sequence ◽

Lethal Mutations

ABSTRACT In this study, we show that at least one lethal mutation at the 3F-4A region of the X chromosome can generate an array of chromosome rearrangements, all with one chromosome break in the 3F-4A region. The mutation at 3F-4A (secondary mutation) was detected in an X chromosome carrying a reverse mutation of an unstable lethal mutation, which was mapped in the 6F1-2 doublet (primary mutation). The primary lethal mutation at 6F1-2 had occurred in an unstable chromosome (Uc) described previously (Lim 1979). Prior to reversion, the 6F1-2 mutation had generated an array of chromosome rearrangements, all having one break in the 6F1-2 doublet (Lim 1979, 1980). In the X chromosomes carrying the 3F-4A secondary lethal mutation the 6F1-2 doublet was normal and stable, as was the 3F-4A region in the X chromosome carrying the primary lethal mutation. The disappearance of the instability having a set of genetic properties at one region (6F1-2) accompanied by its appearance elsewhere in the chromosome (3F-4A) implies that a transposition of the destabilizing element took place. The mutant at 3F-4A and other secondary mutants exhibited all but one (reinversion of an inversion to the normal sequence) of the eight properties of the primary lethal mutations. These observations support the view that a transposable destabilizing element is responsible for the hypermutability observed in the unstable chromosome and its derivaties.

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