scholarly journals EXPRESSION OF MATERNALLY AND EMBRYONICALLY DERIVED HYPOXANTHINE PHOSPHORIBOSYL TRANSFERASE (HPRT) ACTIVITY IN MOUSE EGGS AND EARLY EMBRYOS

Genetics ◽  
1983 ◽  
Vol 104 (4) ◽  
pp. 685-698
Author(s):  
Paul G Kratzer
Keyword(s):  
X Chromosome ◽  
Gene Dosage ◽  
Activity Level ◽  
Hypoxanthine Phosphoribosyl Transferase ◽  
Mouse Development ◽  
Cell Stage ◽  
Activity Increase ◽  
Phosphoribosyl Transferase ◽  
Early Embryos ◽  
Before And After

ABSTRACT X-chromosome activity in early mouse development has been studied by a gene dosage method that involves measuring the activity level of the X-linked enzyme hypoxanthine phosphoribosyl transferase (HPRT) in single eggs and embryos from XO females and from females heterozygous for In(X)1H, a paracentric inversion of the X chromosome. The HPRT activity in oocytes increased threefold over a 24-hr period beginning after ovulation. Afterward, the activity plateaued in unfertilized eggs but continued to increase for at least 66 hr in presumed OY embryos. Both before and after ovulation, the level of activity in unfertilized eggs from In(X)/X females was twice that from XO females, and the distributions of activity in eggs for both sets of females remained unimodal. Beginning with the two-cell stage, distributions of activity for embryos from In(X)/X females were trimodal, which is evidence for embryonic activity. It is proposed that activation of a maternal mRNA or proenzyme is responsible for the HPRT activity increase in oocytes and early embryos and is supplemented by dosage-dependent activity of the embryonic Hprt gene as early as the two-cell stage.

HPRT activity in embryos of a South American opossum Monodelphis domestica

1994 ◽  
Vol 6 (4) ◽  
pp. 529 ◽  
Author(s):  
PG Johnston ◽  
D Dean ◽  
JL VandeBerg ◽  
ES Robinson
Keyword(s):  
X Chromosome ◽  
Blastocyst Stage ◽  
Monodelphis Domestica ◽  
X Inactivation ◽  
Hypoxanthine Phosphoribosyl Transferase ◽  
South American ◽  
Cell Stage ◽  
Phosphoribosyl Transferase ◽  
Stage Of Development ◽  
American Opossum

Marsupial females show preferential paternal X-inactivation. However, the time at which X-inactivation occurs in early development has not yet been determined. A double microassay which measures the activities of X-linked hypoxanthine phosphoribosyl transferase (HPRT) and the autosomally-coded adenine phosphoribosyl transferase (APRT) from the same sample was performed on a collection of embryos from a South American opossum Monodelphis domestica. The embryos ranged in age from the 2-cell stage to the bilaminar blastocyst stage. The results indicate that their embryonic HPRT and APRT are not expressed until just before the unilaminar blastocyst stage in M. domestica. This is at a later stage of development than that in the mouse where embryonic HPRT and APRT expression first occurs at the 4-8-cell stage. It is concluded that HPRT is an uniformative enzyme for assessing X chromosome activity in cleaving embryos of M. domestica. The widespread distribution of HPRT:APRT ratios after the unilaminar blastocyst stage also makes it difficult to draw conclusions about the state of X chromosome activity in early marsupial development.

scholarly journals Regulation of X-linked gene expression during early mouse development by Rlim

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Feng Wang ◽  
JongDae Shin ◽  
Jeremy M Shea ◽  
Jun Yu ◽  
Ana Bošković ◽  
...  
Keyword(s):  
Gene Expression ◽  
X Chromosome ◽  
Gene Dosage ◽  
Mouse Genetics ◽  
Preimplantation Embryos ◽  
Mouse Development ◽  
Linked Gene ◽  
Temporal Regulation ◽  
Non Coding Rna ◽  
Early Mouse

Mammalian X-linked gene expression is highly regulated as female cells contain two and male one X chromosome (X). To adjust the X gene dosage between genders, female mouse preimplantation embryos undergo an imprinted form of X chromosome inactivation (iXCI) that requires both Rlim (also known as Rnf12) and the long non-coding RNA Xist. Moreover, it is thought that gene expression from the single active X is upregulated to correct for bi-allelic autosomal (A) gene expression. We have combined mouse genetics with RNA-seq on single mouse embryos to investigate functions of Rlim on the temporal regulation of iXCI and Xist. Our results reveal crucial roles of Rlim for the maintenance of high Xist RNA levels, Xist clouds and X-silencing in female embryos at blastocyst stages, while initial Xist expression appears Rlim-independent. We find further that X/A upregulation is initiated in early male and female preimplantation embryos.

scholarly journals Blastomeres arising from the first cleavage division have distinguishable fates in normal mouse development

Development ◽  
2001 ◽  
Vol 128 (19) ◽  
pp. 3739-3748 ◽  
Author(s):  
Karolina Piotrowska ◽  
Florence Wianny ◽  
Roger A. Pedersen ◽  
Magdalena Zernicka-Goetz
Keyword(s):  
Inner Cell Mass ◽  
Angular Displacement ◽  
Cell Mass ◽  
Boundary Region ◽  
Lineage Tracing ◽  
Mouse Development ◽  
Cleavage Division ◽  
Cell Stage ◽  
Early Embryos ◽  
Cell Mouse Embryo

Two independent studies have recently suggested similar models in which the embryonic and abembryonic parts of the mouse blastocyst become separated already by the first cleavage division. However, no lineage tracing studies carried out so far on early embryos provide the support for such a hypothesis. Thus, to re-examine the fate of blastomeres of the two-cell mouse embryo, we have undertaken lineage tracing studies using a non-perturbing method. We show that two-cell stage blastomeres have a strong tendency to develop into cells that comprise either the embryonic or the abembryonic parts of the blastocyst. Moreover, the two-cell stage blastomere that is first to divide will preferentially contribute its progeny to the embryonic part. Nevertheless, we find that the blastocyst embryonic-abembryonic axis is not perfectly orthogonal to the first cleavage plane, but often shows some angular displacement from it. Consequently, there is a boundary zone adjacent to the interior margin of the blastocoel that is populated by cells derived from both earlier and later dividing blastomeres. The majority of cells that inhabit this boundary region are, however, derived from the later dividing two-cell stage blastomere that contributes predominantly to the abembryonic part of the blastocyst. Thus, at the two-cell stage it is already possible to predict which cell will contribute a greater proportion of its progeny to the abembryonic part of the blastocyst (region including the blastocyst cavity) and which to the embryonic part (region containing the inner cell mass) that will give rise to the embryo proper.

scholarly journals Two-Step Imprinted X Inactivation: Repeat versus Genic Silencing in the Mouse

2010 ◽  
Vol 30 (13) ◽  
pp. 3187-3205 ◽  
Author(s):  
Satoshi H. Namekawa ◽  
Bernhard Payer ◽  
Khanh D. Huynh ◽  
Rudolf Jaenisch ◽  
Jeannie T. Lee
Keyword(s):  
X Chromosome ◽  
De Novo ◽  
Germ Line ◽  
Blastocyst Stage ◽  
Repetitive Elements ◽  
Mouse Development ◽  
Cell Stage ◽  
Xist Rna ◽  
Preimplantation Mouse ◽  
Early Mouse

ABSTRACT Mammals compensate for unequal X-linked gene dosages between the sexes by inactivating one X chromosome in the female. In marsupials and in the early mouse embryo, X chromosome inactivation (XCI) is imprinted to occur selectively on the paternal X chromosome (XP). The mechanisms and events underlying XP imprinting remain unclear. Here, we find that the imprinted XP can be functionally divided into two domains, one comprising traditional coding genes (genic) and the other comprising intergenic repetitive elements. XP repetitive element silencing occurs by the two-cell stage, does not require Xist, and occurs several divisions prior to genic silencing. In contrast, genic silencing initiates at the morula-to-blastocyst stage and absolutely requires Xist. Genes translocate into the presilenced repeat region as they are inactivated, whereas active genes remain outside. Thus, during the gamete-embryo transition, imprinted XCI occurs in two steps, with repeat silencing preceding genic inactivation. Nucleolar association may underlie the epigenetic asymmetry of XP and XM. We hypothesize that transgenerational information (the imprint) is carried by repeats from the paternal germ line or that, alternatively, repetitive elements are silenced at the two-cell stage in a parent-of-origin-specific manner. Our model incorporates aspects of the so-called classical, de novo, and preinactivation hypotheses and suggests that Xist RNA functions relatively late during preimplantation mouse development.

125 INCOMPLETE COMPENSATORY UP-REGULATION OF X-LINKED GENES IN BOVINE GERMLINE, EARLY EMBRYOS, AND SOMATIC TISSUES

2017 ◽  
Vol 29 (1) ◽  
pp. 171 ◽  
Author(s):  
J. Duan ◽  
N. K. Jue ◽  
Z. Jiang ◽  
R. O'Neill ◽  
E. Wolf ◽  
...  
Keyword(s):  
X Chromosome ◽  
Germ Cells ◽  
Dosage Compensation ◽  
Chromosome Inactivation ◽  
Data Sets ◽  
Rna Seq ◽  
Cell Stage ◽  
Embryonic Tissues ◽  
Early Embryos ◽  
Somatic Tissues

The maintenance of a proper gene dosage is essential in cellular networks. To resolve the dosage imbalance between eutherian females (XX) and male (XY), X chromosome inactivation (XCI) occurs in females, while X-chromosome dosage compensation up-regulates the active X to balance its expression with that of autosome pairs [Ohno’s hypothesis; Ohno 1967 Sex Chromosomes and Sex-linked Genes (Springer-Verlag), p. 99]. These phenomena have been well studied in humans and mice, despite many controversies over the existence of such up-regulation. Using RNA sequencing data, we determined X chromosome dosage compensation in the bovine by analysing the global expression profiles of germ cells, embryos, and somatic tissues. Eight bovine RNA-seq data sets were obtained in from the Gene Expression Omnibus, covering bovine immature/mature oocytes (GSE59186 and GSE52415), pre-implantation conceptuses (GSE59186, GSE52415, and GSE56513), extra-embryonic tissues (PRJNA229443), and male/female somatic tissues (GSE74076, GSE63509, PRJEB6377, and GSE65125). The RNAseq data were trimmed and non-uniquely (paralogs included) mapped to the bovine reference genome assembly UMD3.1.1 using Hisat2 (version 2.0.5) aligner. The mRNA level of each gene, estimated by transformed transcripts per kilobase million was quantified by IsoEM (version 1.1.5). These RNA-seq data sets represented 4 chromosome scenarios in cells: XXXX:AAAA (diploid immature oocyte with DNA duplication), XX:AA (haploid mature oocyte with DNA duplication), XX:AA and X:AA (gradual changed X status in bovine pre-implantation conceptuses), and X:AA (extra-embryonic tissues and somatic cells in female with one active X or XY male) were analysed for dosage compensation. A total of 959 X-linked genes and 20,316 autosome genes were used to calculate the relative X to autosomal gene (A) expression (RXE): log2 (X expression) − log2 (A expression). The following dosage determinations were made: RXE values ≥ 0: complete dosage compensation (or X: A ratio ≥ 1); RXE values < 0: in-complete dosage compensation; RXE value = −1: no dosage compensation (or X: A ratio = 0.5). Our analyses showed a decreased RXE after fertilization, from −0.33 in matured oocytes to −0.50 at the 2-cell stage, indicating that the sperm that undergo meiotic sex chromosome inactivation (MSCI) bring in inactive X chromosomes to the matured oocytes. Subsequently, the activation of the bovine embryonic genome at the 4- to 8-cell stage increased RXE from −0.54 to −0.05. This was followed by a sharp RXE decline from −0.02 at the 16-cell stage, 0.1 at the 32-cell stage to −0.29 at the compact morula stage, which is known as paternal X inactivation stage in the bovine. Finally, RXE was stabilised from blastocysts −0.19 through the Day 19 conceptuses −0.25 to somatic tissue average −0.21 with a pattern of incomplete X compensation. These findings support X expression up-regulation as proposed by Ohno. No significant RXE differences were observed between bovine female and male somatic tissues, further supporting Ohno’s hypothesis, which predicts a balance in the expression of X-linked genes to that of autosomes. This study confirms Ohno’s hypothesis of X dosage compensation in bovine germ cells, early embryos, and somatic tissues.

Chromatin modifications during oogenesis in the mouse: removal of somatic subtypes of histone H1 from oocyte chromatin occurs post-natally through a post-transcriptional mechanism

1997 ◽  
Vol 110 (4) ◽  
pp. 477-487 ◽  
Author(s):  
H.J. Clarke ◽  
M. Bustin ◽  
C. Oblin
Keyword(s):  
Cell Types ◽  
Histone H1 ◽  
Early Embryo ◽  
Rt Pcr ◽  
Cell Stage ◽  
Embryonic Genome ◽  
Early Embryos ◽  
Before And After ◽  
Subtype H1

We examined the distribution of the somatic subtypes of histone H1 and the variant subtype, H1(0), and their encoding mRNAs during oogenesis and early embryogenesis in the mouse. As detected using immunocytochemistry, somatic H1 was present in the nuclei of oocytes of 18-day embryos. Following birth, however, somatic H1 became less abundant in both growing and non-growing oocytes, beginning as early as 4 days of age in the growing oocytes, and was scarcely detectable by 19 days. Together with previous results, this defines a period of time when somatic H1 is depleted in oocytes, namely, from shortly after birth when the oocytes are at prophase I until the 4-cell stage following fertilization. At the stages when somatic H1 was undetectable, oocyte nuclei could be stained using an antibody raised against histone H1(0), which suggests that this may be a major linker histone in these cells. In contrast to the post-natal loss of somatic H1 protein, mRNAs encoding four (H1a, H1b, H1d, H1e) of the five somatic subtypes were present, as detected using RT-PCR in growing oocytes of 9-day pups, and all five subtypes including H1c were present in fully grown oocytes of adults. All five subtypes were also present in embryos, both before and after activation of the embryonic genome. mRNA encoding H1(0) was also detected in oocytes and early embryos. Whole-mount in situ hybridization using cloned H1c and H1e cDNAs revealed that the mRNAs were present in the cytoplasm of oocytes and 1-cell embryos, in contrast to the sea urchin early embryo where they are sequestered in the cell nucleus. We suggest that, as in many somatic cell types, the chromatin of mouse oocytes becomes depleted of somatic H1 and relatively enriched in histone H1(0) postnatally, and that somatic H1 is reassembled onto chromatin in cleavage-stage embryos. The post-natal loss of somatic H1 appears to be regulated post-transcriptionally by a mechanism not involving nuclear localization.

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 Retinoic acid signaling is critical during the totipotency window in early mammalian development

2021 ◽  
Author(s):  
Ane Iturbide ◽  
Mayra L. Ruiz Tejeda Segura ◽  
Camille Noll ◽  
Kenji Schorpp ◽  
Ina Rothenaigner ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Regulatory Networks ◽  
Es Cells ◽  
Embryonic Stem ◽  
Mammalian Development ◽  
Cell Stage ◽  
Cell Potential ◽  
Cellular Models ◽  
Early Embryos ◽  
Genome Activation

AbstractTotipotent cells hold enormous potential for regenerative medicine. Thus, the development of cellular models recapitulating totipotent-like features is of paramount importance. Cells resembling the totipotent cells of early embryos arise spontaneously in mouse embryonic stem (ES) cell cultures. Such ‘2-cell-like-cells’ (2CLCs) recapitulate 2-cell-stage features and display expanded cell potential. Here, we used 2CLCs to perform a small-molecule screen to identify new pathways regulating the 2-cell-stage program. We identified retinoids as robust inducers of 2CLCs and the retinoic acid (RA)-signaling pathway as a key component of the regulatory circuitry of totipotent cells in embryos. Using single-cell RNA-seq, we reveal the transcriptional dynamics of 2CLC reprogramming and show that ES cells undergo distinct cellular trajectories in response to RA. Importantly, endogenous RA activity in early embryos is essential for zygotic genome activation and developmental progression. Overall, our data shed light on the gene regulatory networks controlling cellular plasticity and the totipotency program.

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