López de Munain A, Cobo A M, Sáenz A, Blanco A, Poza J J, Martorell L, Martí-Massó J F, Baiget M
Department of Neurology, Hospital Ntra.Sra de Aránzazu, San Sebastián, Basque Country, Spain.
Genet Epidemiol. 1996;13(5):483-7. doi: 10.1002/(SICI)1098-2272(1996)13:5<483::AID-GEPI4>3.0.CO;2-3.
Myotonic dystrophy (MD), an autosomal dominant multisystemic disorder with a high phenotypic variability, is the most common muscular dystrophy in adult life. The mutation underlying DM has been characterized as an expanded CTG trinucleotide repeat sequence in the 3 untranslated region of a protein kinase gene on chromosome 19q13.2-13.3. We have analyzed the presence of CTG intergenerational variations on transmission in parent-child pairs affected with DM. The series includes 90% of all living affected descendants (symptomatic or asymptomatic) from a given myotonic dystrophy (DM) patient. A contraction of the CTG repeat size was observed in ten parent-child pairs (14.1%) and remained unchanged in five (7%) pairs. The number of CTG repeats decreased in 2/30 maternal transmissions (6.7%) and in 8/41 paternal transmissions (19.5%). We found 14 asymptomatic individuals carrying the CTG expansion among the offspring. In six of them, a contraction of the CTG repeat was observed, and in all six cases, the DM allele was paternally transmitted. Since nearly all the asymptomatic family members of DM patients were analyzed in this series, the observed percentage of contractions can be considered more realistic, even though the number of parent-child pairs is small.
强直性肌营养不良（MD）是一种常染色体显性多系统疾病，具有高度的表型变异性，是成人期最常见的肌营养不良症。DM的潜在突变已被确定为位于19号染色体q13.2 - 13.3上蛋白激酶基因3'非翻译区的CTG三核苷酸重复序列扩增。我们分析了受DM影响的亲子对中CTG在代际传递中的变化情况。该系列包括来自一名特定强直性肌营养不良（DM）患者的所有在世受影响后代（有症状或无症状）的90%。在十对亲子对（14.1%）中观察到CTG重复序列长度缩短，五对（7%）保持不变。在30次母系传递中有2次（6.7%）、41次父系传递中有8次（19.5%）CTG重复序列数量减少。我们在后代中发现14名携带CTG扩增的无症状个体。其中6人观察到CTG重复序列缩短，且在所有6例中，DM等位基因都是父系传递的。由于本系列分析了几乎所有DM患者的无症状家庭成员，尽管亲子对数量较少，但观察到的缩短百分比可被认为更接近实际情况。
