Requirements for X-linked zygotic gene activity during cellularization of early Drosophila embryos

Development ◽  
1988 ◽  
Vol 104 (3) ◽  
pp. 483-493 ◽  
Author(s):  
E. Wieschaus ◽  
D. Sweeton
Keyword(s):  
X Chromosome ◽  
Single Cells ◽  
Cortical Actin ◽  
X Chromosomes ◽  
Abnormal Distribution ◽  
Single Region ◽  
Zygotic Gene ◽  
Blastoderm Stage ◽  
Chromosome Material ◽  
Drosophila Embryos

To examine the requirements for X-chromosomal transcription during precellular stages of Drosophila embryogenesis, attached X-chromosomes and XY translocations were used to generate embryos deficient for large cytologically defined regions of that chromosome. Embryos that lack all X-chromosome material (‘nullo-X embryos’) develop normally to the cycle-14 syncytial blastoderm stage, but fail to partition their nuclei to single cells during cellularization. The cellularization defects can first be detected in the abnormal distribution of cortical actin and nuclei during early cycle 14. The same defects are produced by deletions of only a single region on the X-chromosome, between 6F and 7A. Nullo-X embryos carrying a duplication of this region cellularize and develop normally to the onset of gastrulation.

scholarly journals MALE-STERILIZING INTERACTIONS BETWEEN DUPLICATIONS AND DEFICIENCIES FOR PROXIMAL X-CHROMOSOME MATERIAL IN DROSOPHILA MELANOGASTER

Genetics ◽  
1981 ◽  
Vol 99 (1) ◽  
pp. 49-64
Author(s):  
Rezaur Rahman ◽  
Dan L Lindsley
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Male Fertility ◽  
Primary Spermatocyte ◽  
Single Factor ◽  
X Chromosomes ◽  
Recessive Lethal ◽  
Lethal Mutations ◽  
Y Chromosomes ◽  
Chromosome Material

ABSTRACT The genetic limits of sixty-four deficiencies in the vicinity of the euchromatic-heterochromatic junction of the X chromosome were mapped with respect to a number of proximal recessive lethal mutations. They were also tested for male fertility in combination with three Y chromosomes carrying different amounts of proximal X-chromosome-derived material (BSYy+, y+Ymal126 and y  +  Ymal  +). All deficiencies that did not include the locus of bb and a few that did were male-fertile in all male-viable Df(1)/Dp(1;Y) combinations. Nineteen bb deficiencies fell into six different classes by virtue of their male-fertility phenotypes when combined with the duplicated Y chromosomes. The six categories of deficiencies are consistent with a formalism that invokes three factors or regions at the base of the X, one distal and two proximal to bb, which bind a substance critical for precocious inactivation of the X chromosome in the primary spermatocyte. Free duplications carrying these regions or factors compete for the substance in such a way that, in the presence of such duplications, proximally deficient X chromosomes are unable to command sufficient substance for proper control of X-chromosome gene activity preparatory to spermatogenesis. We conclude that there is no single factor at the base of the X that is required for the fertility of males whose genotype is otherwise normal.

scholarly journals Patchy, incomplete, and heterogeneous X-inactivation in the human placenta

2019 ◽  
Author(s):  
Tanya N. Phung ◽  
Kimberly C. Olney ◽  
Harvey J. Kliman ◽  
Melissa A. Wilson
Keyword(s):  
X Chromosome ◽  
Human Placenta ◽  
Strong Evidence ◽  
Prenatal Testing ◽  
Female Offspring ◽  
X Inactivation ◽  
Single Individual ◽  
X Chromosomes ◽  
Healthy Pregnancy ◽  
Single Region

AbstractThe placenta is formed after the first few weeks of pregnancy and is the genotype of the fetus. It acts as an immune modulator in the uterine environment to sustain a successful pregnancy. One of the X chromosomes in XX females is silenced by a process called X-inactivation. Prior research suggests that incorrect dosage on the X chromosome could lead to poor development of the placenta and ultimately result in complications in pregnancy. Previous studies of X- inactivation in the placenta were either in non-human placentas, or were limited to only a few SNPs and genes in human placentas. Thus, it is not clear whether within human placenta, X- inactivation is completely homogeneous, patchy, or mosaic. Further, X-inactivation is not complete in humans; as many as one-third of the genes on the X chromosome escape X- inactivation, but variability in genes that escape X-inactivation in the placenta has not been investigated. We sequenced RNA from 60 placenta samples from 30 full-term, uncomplicated pregnancies with female offspring. We can confidently rule out X-inactivation being completely mosaic in the human placenta. Rather, we find strong evidence that X-inactivation in the human placenta is patchy, with large potential clonal expansions of either silenced maternal or paternal X-chromosomes, with provocative suggestions of bias towards silencing the paternal X. We also find variation in the degree of silencing, where a high portion of variants (between 26.8-75.3% in any sample) are silenced incompletely. Finally, we find evidence for variability in genes that escape X-inactivation within and among placenta samples.SignificanceThe placenta is formed early during development, is essential for healthy pregnancy, and is largely composed of DNA from the offspring, and thus can be XX or XY. One of the X chromosomes in XX females is silenced by a process called X-inactivation. We studied patterns of X-inactivation in two regions of the placenta across 30 placentas, and find strong evidence for large patches of either maternally or paternally silenced X-chromosomes in the human placenta. We also found that the genes that escape X-inactivation vary both across individuals, and within the placenta of a single individual, suggesting mechanisms for variability in placenta function, and implications for prenatal testing that samples only a single region of the placenta.

Requirements for autosomal gene activity during precellular stages of Drosophila melanogaster

Development ◽  
1988 ◽  
Vol 104 (3) ◽  
pp. 495-509 ◽  
Author(s):  
P.T. Merrill ◽  
D. Sweeton ◽  
E. Wieschaus
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Single Cells ◽  
Gene Activity ◽  
Autosomal Gene ◽  
The Third ◽  
Specific Effects ◽  
Morphological Defects ◽  
Zygotic Gene

To identify early requirements for zygotic gene activity in Drosophila, we used compound autosomes and autosome-Y translocations to generate embryos deficient for cytologically defined portions of the genome. No obvious gross morphological defects were observed in any deficiency class until the beginning of cycle 14. Only seven autosomal regions were identified with discrete effects visible prior to the onset of gastrulation. These regions include genes with locus-specific effects on the clearing of the cortical cytoplasm during early cycle 14, (22AB), the initiation of the slow and fast phases of cellularization (26BF and 40AC, respectively), the apical-basal distribution of nuclei during cycle 14 (71C-75C) and the closing off of furrow canals during cellularization (100AC). The distal tip of the third chromosome also contains two loci (99DF and 100AC) whose deletion causes multiple nuclei to be cellularized into single cells, a phenotype similar to that produced in embryos totally lacking the X-chromosome.

scholarly journals Production of X0 clones in XX females of Drosophila

1991 ◽  
Vol 57 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Daniel Bachiller ◽  
Lucas Sánchez
Keyword(s):  
X Chromosome ◽  
Larval Stage ◽  
Rare Event ◽  
The State ◽  
X Chromosomes ◽  
Larval Stages ◽  
Sex Lethal ◽  
Blastoderm Stage ◽  
State Of Activity

SummaryThe experiments reported here are aimed at determining whether mutations deleting the function of the Sex-lethal (Sxl) gene are able to suppress the lethality of X0 clones, induced in females after the time when the state of activity of Sxl is irreversibly fixed by the ratio of the number of X chromosomes to sets of autosomes (X: A). This analysis was carried out by comparing the frequency of induced male clones (X0 constitution) in SxlfLS/ + and Sxl+/Sxl+ females, following irradiation at blastoderm and larval stages. The genotype used in these experiments, however, could also give rise to 2X; 2A cells homozygous for SxlfLS, and such cells would also differentiate male structures. To minimize this possibility, we have constructed a genotype made up of a ring and a rod X chromosome. In such ring-rod females the production of 2X; 2A clones homozygous for SxlfLS is a rather rare event, if possible at all. X0 male clones were produced in both types of females following irradiation at blastoderm stage, while X0 male clones were only observed in SxlfLS/ + females when irradiation took place at larval stage. In this latter case, the only X0 male clones were those that contained the SxlfLS mutation. These results support the idea of Sánchez & Nöthiger (1983) that the X: A signal irreversibly sets the state of activity of Sxl at blastoderm stage, and in addition show that X0 clones generated after that time are viable if they contain a Sxl− mutation. These results are compatible with the idea of Sxl being the only gene that responds to the X:A signal.

Laser scanning confocal microscopic analysis of cytoskeletal and nuclear reorganization in live Drosophila embryos

1993 ◽  
Vol 51 ◽  
pp. 174-175
Author(s):  
William Theurkauf
Keyword(s):  
Laser Scanning ◽  
Microscopic Analysis ◽  
Large Cell ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Cortical Actin ◽  
Nuclear Reorganization ◽  
Cytoskeletal Elements ◽  
Microtubule Structure ◽  
Drosophila Embryos

Cell division in eucaryotes depends on coordinated changes in nuclear and cytoskeletal components. In Drosophila melanogaster embryos, the first 13 nuclear divisions occur without cytokinesis. During the final four divisions, nuclei divide in a uniform monolayer at the surface of the embryo. These surface divisions are accompanied by dramatic changes in cortical actin and microtubule structure (Karr and Alberts, 1986), and inhibitor studies indicate that these changes are essential to orderly mitosis (Zalokar and Erk, 1976). Because the early embryo is syncytial, fluorescent probes introduced by microinjection are incorporated in structures associated with all of the nuclei in the blastoderm. In addition, the nuclei divide synchronously every 10 to 20 min. These characteristics make the syncytial blastoderm embryo an excellent system for the analysis of mitotic reorganization of both nuclear and cytoskeletal elements. However, the Drosophila embryo is a large cell, and resolution of cytoskeletal filaments and nuclear structure is hampered by out-of focus signal.

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

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.

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

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.

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

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.

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

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.

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

Genetics ◽  
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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