Dataset Information

The X to Autosome Expression Ratio in Haploid and Diploid Human Embryonic Stem Cells.

ABSTRACT: Ohno proposed that the expression levels of X-linked genes have been doubled to compensate the degeneration of Y-linked homologs during the evolution of mammalian sex chromosomes, but RNA sequencing in human somatic tissues showed no such upregulation for the vast majority of X-linked genes. Here we report that the X to autosome expression ratio equals ?1 in haploid human parthenogenetic embryonic stem (pES) cells and ?0.5 in diploidized pES cells, both with one active X chromosome. Although we confirmed the upregulation of ?5% of X-linked genes encoding members of large protein complexes in diploids, these genes are also upregulated in haploids, breaking the otherwise balanced dosage. These findings argue against Ohno's hypothesis for both haploid and diploid cells and demonstrate that, at least in humans, precise gene regulation for dosage balance, even for members of large protein complexes, is much less critical than is commonly thought.

SUBMITTER: Chen X

PROVIDER: S-EPMC5100046 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Publications

The X to Autosome Expression Ratio in Haploid and Diploid Human Embryonic Stem Cells.

Chen Xiaoshu X Zhang Jianzhi J

Molecular biology and evolution 20160904 12

Ohno proposed that the expression levels of X-linked genes have been doubled to compensate the degeneration of Y-linked homologs during the evolution of mammalian sex chromosomes, but RNA sequencing in human somatic tissues showed no such upregulation for the vast majority of X-linked genes. Here we report that the X to autosome expression ratio equals ∼1 in haploid human parthenogenetic embryonic stem (pES) cells and ∼0.5 in diploidized pES cells, both with one active X chromosome. Although we ...[more]

PMID: 27593371

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Project description:BACKGROUND:Algal isomorphic biphasic life cycles alternate between free-living diploid (tetrasporophytes) and haploid (dioicious gametophytes) phases and the hypotheses explaining their maintenance are still debated. Classic models state that conditional differentiation between phases is required for the evolutionary stability of biphasic life cycles while other authors proposed that the uneven ploidy abundances observed in the field are explained by their cytological differences in spore production. RESULTS:We monitored the state and fate of individuals of the red seaweed Gracilaria chilensis periodically for 3 years in five intertidal pools from two sites with distinct conditions. We tested for differentiation in fecundity and spore survival among the gametophyte males and females (haploids) and the tetrasporophytes (diploids). We tested for the influence of fecundity and spore survival on the observed uneven ploidy abundances in recruits. The probability of a frond becoming fecund was size-dependent, highest for the haploid males and lowest for the haploid females, with the diploids displaying intermediate probabilities. Fecund diploids released more tetraspores than carpospores released by the haploid females. Spore survival depended on ploidy and on the local density of co-habiting adult fronds. An advantage of diploid over haploid germlings was observed at very low and very high adult fronds densities. CONCLUSIONS:Neither spore production nor spore survival determined the highly variable ploidy ratio within G. chilensis recruits. This result invalidates the hypothesis of natural cytological differences in spore production as the only driver of uneven field ploidy abundances in this species. Diploid spores (carpospores) survived better than haploid spores (tetraspores), especially in locations and time periods that were associated with the occurrence of strong biotic and abiotic stressors. We hypothesise that carpospore survival is higher due to support by their haploid female progenitors passing-on nutrients and chemical compounds improving survival under stressful conditions.

Dataset Information

The X to Autosome Expression Ratio in Haploid and Diploid Human Embryonic Stem Cells.

Publications

The X to Autosome Expression Ratio in Haploid and Diploid Human Embryonic Stem Cells.

Similar Datasets

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