Cachia P G, Culligan D J, Thomas E D, Whittaker J, Jacobs A, Padua R A
Department of Haematology, University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom.
Genomics. 1992 Sep;14(1):70-4. doi: 10.1016/s0888-7543(05)80285-x.
Differences in the methylation status of certain cytosine residues between active and inactive X chromosomes can be used to determine X-inactivation in females heterozygous for X-linked restriction fragment length polymorphisms. We have studied methylation patterns in 105 females heterozygous at the DXS255 locus by Southern blotting of PstI and MspI or HpaII double digests and hybridization with the probe M27B. Unequivocal patterns of unilateral or bilateral X-inactivation were obtained in 15/64 and 49/64 cases, respectively. In the remaining 41 cases the results were unclear due to the absence of HpaII digestion of one or both PstI fragments. In 7 samples an unequivocal digestion pattern was demonstrated on repeat analysis, suggesting that the initial ambiguous pattern was due to incomplete HpaII digestion. In certain individuals, methylation at the 5' CCGG DXS255 locus may be affected by factors other than X-inactivation, making analysis of clonality with the M27B probe impossible. These individuals should be clearly identified in studies of clonality.
活性和非活性X染色体上某些胞嘧啶残基甲基化状态的差异，可用于确定X连锁限制性片段长度多态性杂合女性中的X染色体失活情况。我们通过对PstI和MspI或HpaII双酶切产物进行Southern印迹，并与探针M27B杂交，研究了105名在DXS255位点杂合的女性的甲基化模式。在64例中的15例和64例中的49例中，分别获得了明确的单侧或双侧X染色体失活模式。在其余41例中，由于一个或两个PstI片段没有被HpaII酶切，结果不明确。在7个样本中，重复分析显示出明确的酶切模式，表明最初的模糊模式是由于HpaII酶切不完全所致。在某些个体中，5' CCGG DXS255位点的甲基化可能受X染色体失活以外的因素影响，使得用M27B探针分析克隆性变得不可能。在克隆性研究中应明确识别出这些个体。
