Giordano M, De Angelis M S, Mutani R, Richiardi P M
Department of Medical Sciences, Torino University, Novara, Italy.
J Med Genet. 1994 Feb;31(2):130-2. doi: 10.1136/jmg.31.2.130.
A new case of regression of the CTG copy number in the myotonic dystrophy allele was observed in a 7 year old boy. His affected father had an expanded allele of about 100 repeats in his lymphocyte DNA while the child showed a 60 repeat allele, of the same size as the present in the grandfather. Analysis of the father's sperm DNA allowed us to detect an expanded fragment of approximately the same size (62 repeats) as that present in the child's and grandfather's lymphocytes. This fragment was not detectable in the father's lymphocytes. Thus the regression is constitutive in the child, being already present in his father's germline. It is therefore likely that the regressed allele is present in all the tissues of the child, allowing a favourable prognosis.
在一名7岁男孩中观察到了肌强直性营养不良等位基因CTG拷贝数减少的新病例。他患病的父亲淋巴细胞DNA中有一个约100个重复序列的扩增等位基因，而孩子显示为60个重复序列的等位基因，与祖父的等位基因大小相同。对父亲精子DNA的分析使我们能够检测到与孩子和祖父淋巴细胞中存在的片段大小大致相同（62个重复序列）的扩增片段。该片段在父亲的淋巴细胞中无法检测到。因此，这种减少在孩子中是组成性的，在他父亲的生殖系中就已经存在。所以很可能减少的等位基因存在于孩子的所有组织中，从而有一个良好的预后。
