Dosage compensation in mammals is achieved by the transcriptional inactivation of one X chromosome in female cells. From the time X chromosome inactivation was initially described, it was clear that several mechanisms must be precisely integrated to achieve correct regulation of this complex process. X-inactivation appears to be triggered upon differentiation, suggesting its regulation by devel...

INTRODUCTION Patients with invasive ovarian cancer were recently shown to have a higher frequency of skewed X chromosome inactivation in peripheral blood cells compared to patients with borderline cancer and controls. In this study, we analysed the X inactivation pattern in peripheral blood from 216 breast cancer patients. METHODS X inactivation analysis was performed using HpaII predigestion...

We thank Dr Ozcelik for his careful reading of our review and his thoughtful letter. Dr Ozcelik raises the issue of nonequivalence of monosomy X frequency and X-chromosome inactivation pattern (XCIP). The first refers to the proportion of cells with a single X chromosome, wherein transcription occurs from the lone X chromosome. The second refers to the ratio of inactivated maternal to paternal ...

A 20-month-old female presented with a palpable abdominal mass. Imaging revealed bilateral renal masses and pulmonary nodules. The genetic evaluation identified de novo 540kb X-chromosome deletion involving GPC3, PHF6, HPRT1, highly skewed X-inactivation (100:0). This clinical picture was suggestive of Wilms’ tumor in the setting Simpson-Golabi-Behmel Syndrome.

X chromosome inactivation results in the cis-limited inactivation of most, but not all, genes on one of the two X chromosomes in mammalian females. The molecular basis for inactivation is unknown. In order to examine the transcriptional activity of human X-linked genes, a series of mouse-human somatic cell hybrids under positive selection for the active or inactive human X chromosome has been c...

We thank Dr Ozcelik for his careful reading of our review and his thoughtful letter. Dr Ozcelik raises the issue of nonequivalence of monosomy X frequency and X-chromosome inactivation pattern (XCIP). The first refers to the proportion of cells with a single X chromosome, wherein transcription occurs from the lone X chromosome. The second refers to the ratio of inactivated maternal to paternal ...

Random inactivation of one of the two female X chromosomes establishes dosage compensation between XY males and XX females in placental mammals. X inactivation is controlled by the X inactivation center (Xic). Recent advances in genome sequencing show that the Xic has evolved from an ancestral vertebrate gene cluster in placental mammals and has undergone separate rearrangements in marsupials. ...

Previous evidence had shown that, when a mammalian X-chromosome is broken by a translocation, only one of the two X-chromosome segments shows cytological signs of X-inactivation in the form of late replication or Kanda staining. In the two mouse X-autosome translocations T(X;4)37H and T(X;11)38H the X-chromosome break is in the A1-A2 bands; in both, the shorter translocation product fails to ex...

SUMMARY Genomic imprinting and X chromosome inactivation (XCI) require epigenetic mechanisms to direct allele-specific expression. Despite their critical roles in embryonic development, how universal regulators coordinate these specific tasks from single locus chromosome-scale remains understudied. Here, we systematically disrupted multiple essential pathways within polymorphic F1 zygo...