Non-random X-Inactivation in the Female Mule

Hamerton, J.L.; Giannelli, F.; Collins, Frank H.; Hallett, Janet; Fryer, Anthea; McGuire, Valerie; Short, R. V.

doi:10.1038/2221277a0

Cited by 30 publications

(10 citation statements)

References 9 publications

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“…The female mule pattern represented a combination of the two parental types. This observation of multiple bands resembles the previous findings of others with starch gel electrophoresis (20)(21)(22). In artificial mixtures of horse and donkey erythrocyte lysates, as well as in female mule erythrocytes, the minor (slower) donkey band was coincident with the major (faster) horse band.…”

Section: Biochemical Determinationssupporting

confidence: 90%

“…female mule (22, 23). By autoradiography, Hamerton et al (22) found that the donkey X-chromosome was late-replicating in approximately 90% of the cells of three female mules. In two of the animals, both skin fibroblasts and leukocytes were studied and considerable agreement was observed between the two tissues.…”

Section: Biochemical Determinationsmentioning

confidence: 99%

“…Nance (28) has shown that in a population of proven heterozygous human females, the expression of the two G6PD alleles (A and B) follows a Gaussian distribution, supporting the concept of random inactivation of the two X-chromosomes. Thus, the apparent "nonrandom inactivation" of the X-chromosomes in the mule (22) …”

Section: Biochemical Determinationsmentioning

confidence: 99%

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Cytological and Biochemical Correlation of Late X-Chromosome Replication and Gene Inactivation in the Mule

Cohen

Rattazzi

1971

Proc. Natl. Acad. Sci. U.S.A.

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The correlation between late X-chromosome replication and the quantitation of different Xlinked glucose-6-phosphate dehydrogenase electrophoretic forms was studied in a natural hybrid, the female mule. In all four animals examined, a significant deviation from the expected 1:1 ratio of random X-chromosome inactivation was observed, with the donkey X-chromosome the more frequently late-replicating one. The relative amounts of horse and donkey enzymes activities in lysates of mule skin fibroblasts and in peripheral blood were in agreement with this finding: the donkey enzyme was the minor component. Although random expression of the enzymes from the two parent species was not observed, sampling, selection, or adaptation may actually be responsible for the apparent "preferential inactivation". These studies support the hypothesis that late DNA replication indicates genetic inactivation.The theory of dosage compensation for X-linked loci in mammals (1) has been based on the apparent relationship between heterochromatin, late replication of one X-chromosome in females, and gene inactivation (2). Although the Lyon hypothesis has been generally accepted, supportive evidence has been derived from diverse experimental systems each yielding only a partial proof (3-11). Such investigations have been criticized recently on several grounds by Gruneberg (12 (0.05 jsg/ml) was added for the final 2 hr of incubation in both fibroblast and lymphocyte cultures. The cells were removed from the culture fluid and suspended in 1% sodium citrate for 15 min at 370C, then fixed with several changes of methanol-glacial acetic acid 3:1. Several drops of cell suspension were placed on a microscope slide that had been immersed in 70% methanol and passed through a flame. The preparation was examined with phase contrast optics after staining with 2% orcein in acetic acid.Autoradiography. Tritiated thymidine (6.7 Ci/mmol) was added to the cell cultures (final concentration 1 MCi/ml) for the last 6 hr of incubation, and colcemide was added for the final 4 hr. Slides, prepared as above, were dipped in Kodak Nuclear Track Emulsion (type NTB3),. stored at 40C for 10 days, and developed according to the method of Schmid (14). Photomicrographs were taken of cells that showed moderate grain counts with obvious localization of grains over a single chromosome. Silver grains were then reduced by using a 10% solution of potassium ferricyanide (30 min) followed by 24% sodium thiosulfate (several dips), and rinsed in distilled water. Those cells previously photographed were located and rephotographed without the overlying silver grains. In this way, a direct comparison could be made and the labeled chromosomes were definitively identified.Efforts were made to include only complete cells containing 63 chromosomes. For reasons discussed below, in the few cases in which this was not possible, only cells possessing both the donkey X-chromosome and the largest submetacentric element (see Fig. 1A; second line, first chromosome) were included. Biochemical ...

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Section: Biochemical Determinationssupporting

confidence: 90%

Section: Biochemical Determinationsmentioning

confidence: 99%

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Cytological and Biochemical Correlation of Late X-Chromosome Replication and Gene Inactivation in the Mule

Cohen

Rattazzi

1971

Proc. Natl. Acad. Sci. U.S.A.

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“…In 1964, Mukherjee and Sinha (1964) found cytological evidence for random X inactivation in leukocytes of a single female mule, supporting the Lyon hypothesis. In 1969, Hamerton et al (1969Hamerton et al ( , 1971 reported nonrandom X inactivation in female mules, suggesting that the X inactivation might be aberrant in mules. However, subsequent studies revealed that this could be due to selection during cell culture and/or the sampling effect of random X inactivation (Mukherjee and Mukherjee 1970;Mukherjee and Milet 1972;Serov et al 1978).…”

Section: [Supplemental Materials Is Available For This Article]mentioning

confidence: 99%

Random X inactivation in the mule and horse placenta

et al. 2012

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In eutherian mammals, dosage compensation of X-linked genes is achieved by X chromosome inactivation. X inactivation is random in embryonic and adult tissues, but imprinted X inactivation (paternal X silencing) has been identified in the extra-embryonic membranes of the mouse, rat, and cow. Few other species have been studied for this trait, and the data from studies of the human placenta have been discordant or inconclusive. Here, we quantify X inactivation using RNA sequencing of placental tissue from reciprocal hybrids of horse and donkey (mule and hinny). In placental tissue from the equid hybrids and the horse parent, the allelic expression pattern was consistent with random X inactivation, and imprinted X inactivation can clearly be excluded. We characterized horse and donkey XIST gene and demonstrated that XIST allelic expression in female hybrid placental and fetal tissues is negatively correlated with the other X-linked genes chromosome-wide, which is consistent with the XIST-mediated mechanism of X inactivation discovered previously in mice. As the most structurally and morphologically diverse organ in mammals, the placenta also appears to show diverse mechanisms for dosage compensation that may result in differences in conceptus development across species.

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“…However, an analogy could perhaps be drawn between the suppression of nucleolar function in species hybrids and the inactivation of one, or part of one, of the X chromosomes in mammals (Lyon, 1961(Lyon, , 1962. Although normally random inactivation of the paternal or maternal X occurs in man and mouse, Hamerton et al (1969) showed that in the female mule (horse x donkey), the paternal X preferentially shows late labelling and is presumably also preferentially inactivated, since the product of the paternally derived glucose-6-phosphate dehydrogenase allele, which is X-linked, is only weakly represented. This makes the parallel between behaviour of sex and of nucleolar chromosomes even closer: consistent inactivation of the same (or part of the same) X chromosome in a female hybrid mammal and of the same parental nucleolar organiser in some plant hybrids; the presence of a differential segment in sex chromosomes and of a condensed satellite thread in plant hybrids; and dosage compensation in certain X-linked genes (data summarised by Thompson, 1965) and sometimes in production of nucleolar material (McClintock, 1934;Beerman, 1960;Longwell and Svihla, 1960;Brown and Gurdon, 1964).…”

Section: Discussionmentioning

confidence: 99%

Nucleolar suppression, its inheritance and association with taxonomy and sex in the genus Ribes

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1971

Heredity

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Non-random X-Inactivation in the Female Mule

Cited by 30 publications

References 9 publications

Cytological and Biochemical Correlation of Late X-Chromosome Replication and Gene Inactivation in the Mule

Cytological and Biochemical Correlation of Late X-Chromosome Replication and Gene Inactivation in the Mule

Random X inactivation in the mule and horse placenta

Nucleolar suppression, its inheritance and association with taxonomy and sex in the genus Ribes

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