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At least 19 recordsLinked to original sources
PubMed1977

X inactivation pattern in an unbalanced X-autosome translocation with gonadal dysgenesis.

An unbalanced X-autosome translocation was observed in a patient with primary amenorrhea, Turner phenotype and bilateral streak gonads. The karyotype of the proposita was 45,X,-X,+der(6),t(X;6). Autoradiography and BUDR pretreatment revealed differential inactivation of the X chromosomes. Sex chromatin pattern was in good agreement with the types of the X inactivation. Our finding brings out some further questions regarding inactivation of the human X chromosome and the human X chromosome and the related phenotypical changes.

Adult↗
PubMed1978

Preferential X inactivation in human placenta membranes: is the paternal X inactive in early embryonic development of female mammals?

In placenta membranes of newborn girls carrying electrophoretically distinguishable G6PD alleles, the maternally derived isozyme is expressed preferentially. This phenomenon cannot be explained by allelic differences in enzyme activity or by somatic selection directed against cells with particular G6PD phenotypes. Instead, it may be that in this tissue X inactivation is nonrandom. Preferential expression of the maternal X chromosome, as has been shown in marsupials and in extraembryonic membranes of rodents and now in man, may reflect the state of activity of the X chromosomes in the early stages of female embryonic development.

Female↗
PubMed1977

Influence of gene duplication and X-inactivation on mouse mitochondrial malic enzyme activity and electrophoretic patterns.

We have investigated, with and without the influence of X-inactivation, the relationship between autosomal gene-dosage and gene-product in a mammalian system, the mouse. The gene was mitochondrial malic enzyme (Mod-2), shown to lie on Chromosome 7 between the albino (c) and shaker-1 (sh-1) loci, and the enzyme was its product, mitochondrial malic enzyme (MOD-2). Gene duplication, with and without the influence of X-inactivation, was achieved using a translocation that involves the insertion of a portion of Chr 7, including Mod-2, into the X, T(X;7)1Ct. A 1:1 relationship for Mod-2 dosage and MOD-2 activity was found in heart mitochondria. Evidence of X-inactivation of Mod-2 was noted in heart and kidney preparations from females carrying a Mod-2 duplication (one copy of Mod-2 in the X and two copies of Mod-2 on Chr 7). We conclude that the expression of an autosomal locus attached to X-chromatin depends upon whether the translocation is in a balanced or unbalanced state.

Alleles↗
PubMed1979

Expression of PGK-A in the Australian brush-tailed possum, Trichosurus vulpecula (Kerr), consistent with paternal X inactivation.

An extensive survey of erythrocytes of marsupials other than kangaroos for electrophoretic variation if X-linked enzymes revealed two rare PGK-A phenotypes in the phalangerid Trichosurus vupecula and one in Trichosurus caninus. Four putatively heterozygous females expressed only the variant allelic isozyme in some tissues but expressed a trace of the normal isozyme in others. A putatively hemizygous male expressed only the variant isozyme in all tissues. The phenotypic patterns were consistent with those observed in kangaroos known to exhibit partial or complete parternal X inactivation in cells of females. Tow of the T. vulpecula were a mother and her female pouch young, further suggesting that paternal X inactivation occurs in T. vulpecula. This peculiar mechanism of dosage compensation may not be restricted to kangaroos.

Animals↗
PubMed1978

X-inactivation pattern in three cases of X/autosome translocation.

We describe an X/15 translocation which was balanced in a phenotypically normal mother [46,X,t(X;15)(p22;q15)] and unbalanced in her phenotypically abnormal daughter [46,X,der(X),t(X;15)(p22;q15)mat]. A third case involves a balanced X/21 translocation in a girl with a multiple congenital anomaly-retardation syndrome [46,X,t(X;21)(p11;p11?)]. 5-BrdU acridine orange banding on lymphocytes revealed late replication of the normal X chromosome in the mother and of the normal or abnormal X chromosome in the two other cases. Our findings are only partially consistent with previous observations. All X-inactivation patterns can be explained by random inactivation and subsequent selection against specific cell lines. Furthermore, the findings in our patient with X/21 translocation support the hypothesis of the existence of one inactivation center on Xq.

Abnormalities, Multiple↗
PubMed1979

Position of the human X inactivation center on Xq.

In three women with a 46,XXq- chromosome constitution, the length of the deletion was expressed as the ratio of the remaining part of Xq to Xp c' over a + b. In one of them (KH) this ratio was 0.33, in another (GE) 0.59, and in the third (AP) the ratio fell between these values. The break in KH is more or less on the border of the Q-dark proximal region. A comparison with relevant X-autosomal translocations indicates that the X inactivation center lies near, but not at the border of, the Q-dark and the adjoining bright region (c and d).

Adult↗
PubMed1979

X;15 translocation in a retarded girl: X inactivation pattern and attempt to localise the hexosaminidase A and other loci.

Cytogenetic studies on a retarded girl showed a complex S;15 translocation, karyotype 45,X,-15,+t(X15). The translocation X chromosome was non-randomly partially inactivated, the inactivation being mainly confined to the X segment and in some cells only to the X long arm. Gene marker studies failed to show anomalous segregation of the hexosaminidase A gene or any other gene markers tested.

Abnormalities, Multiple↗
PubMed1976

Studies on metatherian sex chromosomes II. The improbability of a stable balanced polymorphism at an X-linked locus with the paternal X inactivation system of kangaroos.

Female kangaroos and perhaps other female marsupials have a unique form of dosage compensation for X-linked genes in their soma. In these animals the paternal X is inactive. Heterozygote females therefore have the phenotype of one or the other of the homozygotes, with the allele which is expressed coming from their mother. The unexpressed paternally derived allele may, however, be transmitted to the next generation in the usual Mendelian manner and there be expressed. Such a combination of haploid phenotypic expression and diploid genotypic behaviour on the part of X-linked genes in kangaroos makes their population genetics unique. This paper examines the possibilities for balancing selection in the kangaroo X chromosome system and shows that balanced polymorphisms are unlikely to occur. If 1 - a, 1, 1 - b and 1 are the selection coefficients of the alpha1 females, alpha2 females, alpha1 males and alpha2 males respectively (where alpha1 is the phenotype when A1 is expressed and alpha2 the phenotype when A2 is expressed), then the equilibrium is reached when the gene frequency of A1 in females = 0-5(a-1 + b-1), which takes values between 0 and 1 for only a few of the biologically likely values of a and b.

Animals↗
PubMed1976

Stability of X chromosome differentiation in mouse embryos. Reversal may not be responsible for the extreme X-inactivation mosaicism in extraembryonic membranes.

By means of a double labeling method with H3-thymidine and 5-bromodeoxyuridine, it was found that the X chromosome showed no sign of change from an allocyclic to an isocyclic state, or vice vers in 6.5- and 7.5-day mouse embryos. Thus, reversal of allocycly may not account for the predominance of cells with the paternally derived X chromosome inactive in the yolk sac and the chorion of the mouse embryo.

Animals↗
PubMed1977

Studies on metatherian sex chromosomes. IV. X linkage of PGK-A with paternal X inactivation confirmed in erythrocytes of grey kangaroos by pedigree analysis.

Pedigree and population data are presented for erythrocyte phosphoglycerate kinase A (PGK-A) allozymes in the two species of grey kangaroo. The pedigree data confirm the hypothesis that PGK-A is X linked, the paternally derived X chromosomes being inactive in nucleated erythroblast precursors of the enucleate erythrocytes in females. The existence of different allozyme variants in eastern and western grey kangaroos further supports their division into separate species.

Animals↗
PubMed1979

In search of non-random X inactivation: studies of fetal membranes heterozygous for glucose-6-phosphate dehydrogenase.

Extraembryonic membranes and fetal tissues were obtained from 55 specimens of 5--11 weeks conceptual age. The glucose-6-phosphate dehydrogenase (G6PD) electrophoretic phenotype was determined and correlated with that of maternal blood. Fifteen specimens were heterozygous for G6PD A, and for nine of these the maternal allele could be determined. In none of these specimens did the isozyme pattern of the membraneous chorion or chorionic villi differ significantly from that of fetal tissue. We have obtained no evidence of non-random inactivation in extraembryonic membranes of human fetal specimens at this stage of development.

Extrachromosomal Inheritance↗
PubMed1978

[Quantitative description of the process of cellular radiation inactivation. X. Closing remarks. Ways for further development of the concepts].

The series of communications to check the applicability of one of the most likely models of the loss of reproductive integrity of irradiated eukaryotic cells has been completed by this paper. Many radiobiologists accept the cytogenetic model but no one has analyzed mathematically its applicability. We have succeeded in explaining some significant experimental data and therefore our model is something more than a simple working hypothesis. In this paper the model is considered to prove its significance as the first approach to a more detailed study of the phenomenon.

Cell Survival↗
PubMed1979

Non-inactivation of an x-chromosome locus in man.

Cloned fibroblasts from women heterozygous for X-linked ichthyosis (steroid sulfatase deficiency) were examined to see whether or not this locus is subject to X-inactivation. Of 103 clones examined, all had normal levels of steroid sulfatase activity. Two of the women studied were also heterozygous for glucose-6-phosphate dehydrogenase deficiency. This allowed the demonstration that both X chromosomes were represented as the active X in various clones and that selection did not account for these findings. Thus, the steroid sulfatase locus, like the Xga locus to which it is linked, appears to escape X-inactivation in man.

Dehydroepiandrosterone↗
PubMed2024

Quantification of escape from X chromosome inactivation with single-cell omics data reveals heterogeneity across cell types and tissues.

Several X-linked genes escape from X chromosome inactivation (XCI), while differences in escape across cell types and tissues are still poorly characterized. Here, we developed scLinaX for directly quantifying relative gene expression from the inactivated X chromosome with droplet-based single-cell RNA sequencing (scRNA-seq) data. The scLinaX and differentially expressed gene analyses with large-scale blood scRNA-seq datasets consistently identified the stronger escape in lymphocytes than in myeloid cells. An extension of scLinaX to a 10x multiome dataset (scLinaX-multi) suggested a stronger escape in lymphocytes than in myeloid cells at the chromatin-accessibility level. The scLinaX analysis of human multiple-organ scRNA-seq datasets also identified the relatively strong degree of escape from XCI in lymphoid tissues and lymphocytes. Finally, effect size comparisons of genome-wide association studies between sexes suggested the underlying impact of escape on the genotype-phenotype association. Overall, scLinaX and the quantified escape catalog identified the heterogeneity of escape across cell types and tissues.

X Chromosome Inactivation↗