The existence of highly differentiated X and Y chromosomes in mammals raises the issue of X-linked gene dosage compensation between XX females and XY males to avoid what would be similar to a monosomy X in males(Veiti...The existence of highly differentiated X and Y chromosomes in mammals raises the issue of X-linked gene dosage compensation between XX females and XY males to avoid what would be similar to a monosomy X in males(Veitia et al.,2015).Inactivation of one copy of the X chromosomes in females provides a dosage-compensation mechanism equalizing the expression of X-linked genes in males and females(Ohno et al.,1959;Lyon,1961).展开更多
X chromosome inactivation is a mechanism that modulates the expression of X-linked genes in eutherian females(XX).Ohno proposed that to achieve a proper balance between X-linked and autosomal genes,those on the active...X chromosome inactivation is a mechanism that modulates the expression of X-linked genes in eutherian females(XX).Ohno proposed that to achieve a proper balance between X-linked and autosomal genes,those on the active X should also undergo a 2-fold upregula-tion.Although some support for Ohno's hypothesis has been provided through the years,recent genomic studies testing this hypoth-esis have brought contradictory results and fueled debate.Thus far,there are as many results in favor as against Ohno's hypothesis,depending on the nature of the datasets and the various assumptions and thresholds involved in the analyses.However,they have con-firmed the importance of dosage balance between X-linked and autosomal genes involved in stoichiometric relationships.These facts as well as questions and hypotheses are discussed below.展开更多
There are known cases where a cell sub-population bearing a selective advantage tends to or eventually replaces another cell subpopulation within an organism. This process is supposed to underlie the purging of the mo...There are known cases where a cell sub-population bearing a selective advantage tends to or eventually replaces another cell subpopulation within an organism. This process is supposed to underlie the purging of the most frequent mitochon-drial DNA pathogenic variant from leuko-cytes and other tissues. It is also likely to explain the normal increase of sex chromo-some aneuploidy in human leukocytes with age or under pathological conditions and the expansion of a cell subpopulation after the spontaneous in vivo reversion to normal of an inherited pathogenic variant.展开更多
文摘The existence of highly differentiated X and Y chromosomes in mammals raises the issue of X-linked gene dosage compensation between XX females and XY males to avoid what would be similar to a monosomy X in males(Veitia et al.,2015).Inactivation of one copy of the X chromosomes in females provides a dosage-compensation mechanism equalizing the expression of X-linked genes in males and females(Ohno et al.,1959;Lyon,1961).
基金This work was supported by the Centre Nationalde la R echerche Scientifique(CN RS,France),Paris Diderot-Paris7 University,and the Agence Nationale de la Recherche(ANR,lceberg Project).
文摘X chromosome inactivation is a mechanism that modulates the expression of X-linked genes in eutherian females(XX).Ohno proposed that to achieve a proper balance between X-linked and autosomal genes,those on the active X should also undergo a 2-fold upregula-tion.Although some support for Ohno's hypothesis has been provided through the years,recent genomic studies testing this hypoth-esis have brought contradictory results and fueled debate.Thus far,there are as many results in favor as against Ohno's hypothesis,depending on the nature of the datasets and the various assumptions and thresholds involved in the analyses.However,they have con-firmed the importance of dosage balance between X-linked and autosomal genes involved in stoichiometric relationships.These facts as well as questions and hypotheses are discussed below.
文摘There are known cases where a cell sub-population bearing a selective advantage tends to or eventually replaces another cell subpopulation within an organism. This process is supposed to underlie the purging of the most frequent mitochon-drial DNA pathogenic variant from leuko-cytes and other tissues. It is also likely to explain the normal increase of sex chromo-some aneuploidy in human leukocytes with age or under pathological conditions and the expansion of a cell subpopulation after the spontaneous in vivo reversion to normal of an inherited pathogenic variant.
