Histone H4 acetylation analyses in patients with polysomy X: implications for the mechanism of X inactivation |
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Authors: | C A Leal M L Ayala-Madrigal L E Figuera C Medina |
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Institution: | (1) División de Genética, Centro de Investigación Biomédica de Occidente, IMSS, Sierra Mojada 800, Col. Independencia, c.p. 44340, Apartado Postal 1-3838 Guadalajara, Jalisco, México,;(2) División de Investigación Quirúrgica, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México,;(3) División de Medicina Molecular, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México, |
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Abstract: | 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.
Received: 25 April 1997 / Accepted: 15 March 1998 |
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