Leal C A, Ayala-Madrigal M L, Figuera L E, Medina C
División de Genética, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México.
Hum Genet. 1998 Jul;103(1):29-33. doi: 10.1007/s004390050778.
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.
在人类中，人们认为无论存在多少条X染色体，X染色体失活现象都会发生，并且其中只有一条保持活跃。然而，拥有异常数量X染色体的个体表现出广泛的异常情况，且这些异常会随着特定个体中X染色体数量的增加而增多。研究表明，雌性哺乳动物中失活的X染色体的特征是缺乏组蛋白H4乙酰化，并且这可以用作在中期染色体铺片中区分Xi和Xa的可及标记。我们通过分析未固定的中期铺片中组蛋白H4乙酰化情况，研究了三名X多体患者中活性染色质的存在情况。分别使用针对赖氨酸16、8和5处乙酰化的H4的抗血清，我们观察到的频率与仅具有一条低乙酰化X染色体的细胞所预期的频率不同。特别是，当使用针对赖氨酸16处乙酰化的H4的抗血清时，约90%的细胞显示所有X染色体都发生了乙酰化。这表明去乙酰化过程可能受到干扰，可能是由于存在多条X染色体所致。
