scholarly journals Studies on Metatherian Sex Chromosomes III. The Use of Tritiated Uridine-induced Chromosome Aberrations to Distinguish Active and Inactive X Chromosomes

1977 ◽  
Vol 30 (2) ◽  
pp. 103 ◽  
Author(s):  
Jennifer A Donald ◽  
DW Cooper
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Aberrations ◽  
X Inactivation ◽  
Facultative Heterochromatin ◽  
Hybrid Female ◽  
X Chromosomes ◽  
Toxicity Effect ◽  
Red Kangaroo ◽  
Chromosome Regions

The paternal X inactivation system of kangaroos has been investigated in this study by using tritiated uridine-induced chromosome aberrations to distinguish the active from the inactive X. Previous work in eutherian mammals has demonstrated that constitutive heterochromatic chromosome regions are less susceptible to breakage by tritiated uri dine than euchromatic regions. The results of a comparison between the paternal X chromosome of a wallaroo x red kangaroo hybrid female and the two X chromosomes of a red kangaroo female suggested that the facultative heterochromatin of the X is also less susceptible to breakage by this treatment. However there were significantly more breaks of the paternal X in fibroblasts than in lymphocytes of the hybrid female, which agrees with biochemical findings suggesting activation of the paternal X in fibroblasts. Our results strengthen the suggestion of other workers that the reduced number of aberrations in heterochromatin occurs because such breaks occur principally when the DNA and labelled RNA are in apposition during transcription. Some evidence was found of an apparent toxicity effect of the tritiated uridine solution on the cells.

scholarly journals The differential staining pattern of the X chromosome in the embryonic and extraembryonic tissues of postimplantation homozygous tetraploid mouse embryos

1992 ◽  
Vol 59 (3) ◽  
pp. 205-214 ◽  
Author(s):  
S. Webb ◽  
T. J. de Vries ◽  
M. H. Kaufman
Keyword(s):  
X Chromosome ◽  
High Efficiency ◽  
Indirect Evidence ◽  
X Inactivation ◽  
Differential Staining ◽  
Hybrid Female ◽  
Cell Stage ◽  
X Chromosomes ◽  
F1 Hybrid ◽  
Inactivation Pattern

Summary(C57BL × CBA)F1 hybrid female mice were mated with hemizygous Rb(X.2)2Ad males to distinguish the paternal X chromosome. Homozygous tetraploids were produced by blastomere fusion at the 2-cell stage, and 161 of these were transferred to recipients and analysed on the 10th day of gestation. 59 implants contained resorptions and 76 contained either an embryo and/or extraembryonic membranes. 38 (20, XXXX and 18, XXYY) were analysed to investigate their X-inactivation pattern. Embryonic and yolk sac endodermally- and mesodermally-derived samples were analysed by G-banding and by Kanda analysis. In the XX and XY controls, the predicted pattern of X-inactivation was observed, though 12·2% of metaphases in the XX series displayed no X-inactivation. In the XY series the Y chromosome was seen in a high proportion of metaphases.In the XXXX tetraploids, 8 cell lineages were recognized with regard to their X-inactivation pattern, though most belonged to the following 3 categories: (XmXm)XpXp, Xm(XmXp)Xp and XmXm(XpXp). The other categories were only rarely encountered. In the embryonic and mesodermally-derived tissue the ratio of these groups was close to 1:2:1, whereas in the endodermally-derived tissue it was 1:4·11:4·88, due to preferential paternal X-inactivation. A significant but small proportion of all 3 tissues analysed displayed no evidence of X-inactivation. Indirect evidence suggests that this represents a genuine group because of the high efficiency of the Kanda staining. The presence of the Xm(XmXp)Xp category is consistent with the expectation that X-inactivation occurs randomly in 2 of the 4 X chromosomes present. The presence of small numbers of preparations with no evidence of X-inactivation and other unexpected categories suggests that these are probably selected against during development.

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 Human Genes Escaping X-inactivation Revealed by Single Cell Expression Data

2018 ◽  
Author(s):  
Kerem Wainer Katsir ◽  
Michal Linial
Keyword(s):  
Single Cell ◽  
X Chromosome ◽  
Noncoding Rna ◽  
Phenotypic Variability ◽  
Cell Types ◽  
X Inactivation ◽  
Specific Expression ◽  
X Chromosomes ◽  
Human Genes ◽  
Cumulative Knowledge

AbstractBackgroundIn mammals, sex chromosomes pose an inherent imbalance of gene expression between sexes. In each female somatic cell, random inactivation of one of the X-chromosomes restores this balance. While most genes from the inactivated X-chromosome are silenced, 15-25% are known to escape X-inactivation (termed escapees). The expression levels of these genes are attributed to sex-dependent phenotypic variability.ResultsWe used single-cell RNA-Seq to detect escapees in somatic cells. As only one X-chromosome is inactivated in each cell, the origin of expression from the active or inactive chromosome can be determined from the variation of sequenced RNAs. We analyzed primary, healthy fibroblasts (n=104), and clonal lymphoblasts with sequenced parental genomes (n=25) by measuring the degree of allelic-specific expression (ASE) from heterozygous sites. We identified 24 and 49 candidate escapees, at varying degree of confidence, from the fibroblast and lymphoblast transcriptomes, respectively. We critically test the validity of escapee annotations by comparing our findings with a large collection of independent studies. We find that most genes (66%) from the unified set were previously reported as escapees. Furthermore, out of the overlooked escapees, 11 are long noncoding RNA (lncRNAs).ConclusionsX-chromosome inactivation and escaping from it are robust, permanent phenomena that are best studies at a single-cell resolution. The cumulative information from individual cells increases the potential of identifying escapees. Moreover, despite the use of a limited number of cells, clonal cells (i.e., same X-chromosomes are coordinately inhibited) with genomic phasing are valuable for detecting escapees at high confidence. Generalizing the method to uncharacterized genomic loci resulted in lncRNAs escapees which account for 20% of the listed candidates. By confirming genes as escapees and propose others as candidates from two different cell types, we contribute to the cumulative knowledge and reliability of human escapees.

Regulation of imprinted X-chromosome inactivation in mice by Tsix

Development ◽  
2001 ◽  
Vol 128 (8) ◽  
pp. 1275-1286 ◽  
Author(s):  
T. Sado ◽  
Z. Wang ◽  
H. Sasaki ◽  
E. Li
Keyword(s):  
X Chromosome ◽  
X Chromosome Inactivation ◽  
X Inactivation ◽  
Chromosome Inactivation ◽  
Maternal Allele ◽  
Xist Expression ◽  
Developmental Defects ◽  
X Chromosomes ◽  
Embryonic Tissues ◽  
Early Embryonic Lethality

In mammals, X-chromosome inactivation is imprinted in the extra-embryonic lineages with paternal X chromosome being preferentially inactivated. In this study, we investigate the role of Tsix, the antisense transcript from the Xist locus, in regulation of Xist expression and X-inactivation. We show that Tsix is transcribed from two putative promoters and its transcripts are processed. Expression of Tsix is first detected in blastocysts and is imprinted with only the maternal allele transcribed. The imprinted expression of Tsix persists in the extra-embryonic tissues after implantation, but is erased in embryonic tissues. To investigate the function of Tsix in X-inactivation, we disrupted Tsix by insertion of an IRES(β)geo cassette in the second exon, which blocked transcripts from both promoters. While disruption of the paternal Tsix allele has no adverse effects on embryonic development, inheritance of a disrupted maternal allele results in ectopic Xist expression and early embryonic lethality, owing to inactivation of both X chromosomes in females and single X chromosome in males. Further, early developmental defects of female embryos with maternal transmission of Tsix mutation can be rescued by paternal inheritance of the Xist deletion. These results provide genetic evidence that Tsix plays a crucial role in maintaining Xist silencing in cis and in regulation of imprinted X-inactivation in the extra-embryonic tissues.

scholarly journals A Syntenic Region Conserved from Fish to Mammalian X Chromosome

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Guijun Guan ◽  
Meisheng Yi ◽  
Tohru Kobayashi ◽  
Yunhan Hong ◽  
Yoshitaka Nagahama
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Random Amplified Polymorphic Dna ◽  
Comparative Genomic ◽  
X Chromosomes ◽  
Ancestral Origin ◽  
Dna Contents ◽  
Determining Factors ◽  
Unpaired Region ◽  
Syntenic Segment

Sex chromosomes bearing the sex-determining gene initiate development along the male or female pathway, no matter which sex is determined by XY male or ZW female heterogamety. Sex chromosomes originate from ancient autosomes but evolved rapidly after the acquisition of sex-determining factors which are highly divergent between species. In the heterogametic male system (XY system), the X chromosome is relatively evolutionary silent and maintains most of its ancestral genes, in contrast to its Y counterpart that has evolved rapidly and degenerated. Sex in a teleost fish, the Nile tilapia (Oreochromis niloticus), is determined genetically via an XY system, in which an unpaired region is present in the largest chromosome pair. We defined the differences in DNA contents present in this chromosome with a two-color comparative genomic hybridization (CGH) and the random amplified polymorphic DNA (RAPD) approach in XY males. We further identified a syntenic segment within this region that is well conserved in several teleosts. Through comparative genome analysis, this syntenic segment was also shown to be present in mammalian X chromosomes, suggesting a common ancestral origin of vertebrate sex chromosomes.

scholarly journals Studies on Metatherian Sex Chromosomes. IX. Sex Chromosomes of the Greater Glider (Marsupialia : Petauridae)

1979 ◽  
Vol 32 (3) ◽  
pp. 375 ◽  
Author(s):  
JD Murray ◽  
GM McKay ◽  
GB Sharman
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
National Park ◽  
Secondary Constriction ◽  
X Chromosomes ◽  
Cultured Fibroblasts ◽  
Multiple Sex Chromosomes ◽  
Eastern Australia ◽  
Xy Bivalent ◽  
Secondary Constrictions

The greater glider, currently but incorrectly known as Schoinobates vo/ans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY m,ales as in all other populations, and one with XY1Y2 males. Y or Yb but not Y 2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary sperrnatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes. [Other keywords: C-banding, eytotaxonomy, multiple sex chromosomes, XY bivalent.]

Molecular Characterization of Tiny Ring X Chromosomes from Females with Functional X Chromosome Disomy and Lack of cis X Inactivation

Genomics ◽  
1995 ◽  
Vol 27 (1) ◽  
pp. 182-188 ◽  
Author(s):  
Mihir M. Jani ◽  
Beth S. Torchia ◽  
G.Shashidhar Pai ◽  
Barbara R. Migeon
Keyword(s):  
Molecular Characterization ◽  
X Chromosome ◽  
X Inactivation ◽  
X Chromosomes

Euchromatic domains in plant chromosomes as revealed by H4 histone acetylation and early DNA replication

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 343-350 ◽  
Author(s):  
Boris Vyskot ◽  
Jiri Siroky ◽  
Renata Hladilova ◽  
Nikolai D Belyaev ◽  
Bryan M Turner
Keyword(s):  
Dna Replication ◽  
Sex Chromosomes ◽  
Silene Latifolia ◽  
Histone H4 ◽  
X Chromosomes ◽  
Plant Chromosomes ◽  
Histone H4 Acetylation ◽  
Immunofluorescence Labeling ◽  
Silene Species ◽  
Chromosome Regions

Using specific polyclonal antisera raised against acetylated isoforms of histone H4, we have analyzed their distribution in the dioecious plant Silene latifolia (syn.Melandrium album) possessing heteromorphic sex chromosomes. Our previous studies on this species have shown that one of the two X chromosomes in homogametic female cells is heavily methylated and late replicating, as a possible consequence of dosage compensation. Here we report that there are no detectable differences in intensity and distribution of H4 acetylation between these two X chromosomes. In S. latifolia only distal-subtelomeric chromosome regions, on both the sex chromosomes and autosomes, display strong signals of H4 acetylation at N-terminal lysines 5, 8, and 12. These acetylated domains correspond to the very early replicating distal chromosome regions as revealed by 5-bromodeoxyuridine pulses followed by the indirect immunofluorescence microscopy. The distribution of H4 acetylated at lysine 16 was uniform along the chromosomes. The unique distal-subtelomeric H4 acetylation signals were also observed in three other Silene species (S. vulgaris, S. pendula, andS. chalcedonica), but not in two non-related plant species tested (Allium cepa and Nicotiana tabacum). The presented data as well as our recent studies on the structure of S. latifolia chromosome ends indicate that Silene species possess the specific distal-subtelomeric location of euchromatin, gene-rich regions on chromosomes.Key words: histone H4 acetylation, DNA replication, euchromatin, immunofluorescence labeling, Silene spp.

scholarly journals Dosage compensation in sciarids is achieved by hypertranscription of the single X chromosome in males.

Genetics ◽  
1994 ◽  
Vol 138 (3) ◽  
pp. 787-790
Author(s):  
P R da Cunha ◽  
B Granadino ◽  
A L Perondini ◽  
L Sánchez
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
X Chromosomes ◽  
Different Doses

Abstract Dosage compensation refers to the process whereby females and males with different doses of sex chromosomes have similar amounts of products from sex chromosome-linked genes. We analyzed the process of dosage compensation in Sciara ocellaris, Diptera of the suborder Nematocera. By autoradiography and measurements of X-linked rRNA in females (XX) and males (XO), we found that the rate of transcription of the single X chromosome in males is similar to that of the two X chromosomes in females. This, together with the bloated appearance of the X chromosome in males, support the idea that in sciarids dosage compensation is accomplished by hypertranscription of the X chromosome in males.

scholarly journals Identification of sex chromosomes using genomic and cytogenetic methods in a range-expanding spider, Argiope bruennichi (Araneae: Araneidae)

2021 ◽  
Author(s):  
Monica M Sheffer ◽  
Mathilde M Cordellier ◽  
Martin Forman ◽  
Malte Grewoldt ◽  
Katharina Hoffmann ◽  
...  
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Chromosome Complement ◽  
Gc Content ◽  
Sexually Dimorphic ◽  
Behavioral Experiments ◽  
X Chromosomes ◽  
Male Karyotype ◽  
And Behavior

Differences between sexes in growth, ecology and behavior strongly shape species biology. In some animal groups, such as spiders, it is difficult or impossible to identify the sex of juveniles. This information would be useful for field surveys, behavioral experiments, and ecological studies on e.g. sex ratios and dispersal. In species with sex chromosomes, sex can be determined based on the specific sex chromosome complement. Additionally, information on the sequence of sex chromosomes provides the basis for studying sex chromosome evolution. We combined cytogenetic and genomic data to identify the sex chromosomes in the sexually dimorphic spider Argiope bruennichi, and designed RT-qPCR sex markers. We found that genome size and GC content of this spider falls into the range reported for the majority of araneids. The male karyotype is formed by 24 acrocentric chromosomes with an X1X20 sex chromosome system, with little similarity between X chromosomes, suggesting origin of these chromosomes by X chromosome fission or early duplication of an X chromosome and subsequent independent differentiation of the copies. Our data suggest similarly sized X chromosomes in A. bruennichi. They are smaller chromosomes of the complement. Our findings open the door to new directions in spider evolutionary and ecological research.

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