Histone H4 acetylation analyses in patients with polysomy X: implications for the mechanism of X inactivation.
In humans, it is thought that the X-inactivation phenomenon occurs no matter how many X chromosomes are present, and that only one of them remains active. Nevertheless, individuals who have an abnormal number of X chromosomes show a wide spectrum of abnormalities, which increase with the number of X chromosomes present in a given individual. It has been shown that the inactive X chromosome in female mammals is distinguished by a lack of histone H4 acetylation, and that this could be used as an accessible marker for distinguishing between Xi and Xa in spreads of metaphase chromosomes. We studied three X-polysomic patients for the presence of active chromatin by analysis of histone H4 acetylation on unfixed metaphase spreads. Using antisera to H4 acetylated at lysines 16, 8 and 5, respectively, we observed frequencies different from those expected from cells with only one underacetylated X chromosome. In particular, when antiserum to H4 acetylated at lysine 16 was used about 90% of the cells showed acetylation of all X chromosomes. This suggests a possible disturbance in the deacetylation process, probably due to the presence of multiple Xs.
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División de Genética, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México.
Ayala-Madrigal
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Medina
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D000107:Acetylation; D000782:Aneuploidy; D002478:Cells, Cultured; D002843:Chromatin / Q000737:chemistry; D004276:DNA, Satellite / Q000235:genetics; D005145:Face / Q000002:abnormalities; D005260:Female; D006657:Histones / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D007621:Karyotyping; D008214:Lymphocytes / Q000473:pathology; D012729:Sex Chromosome Aberrations / Q000235:genetics*; D014960:X Chromosome
D002843:Chromatin; D004276:DNA, Satellite; D006657:Histones