Length of (CTG)n triplet repeats in myotonic dystrophy protein kinase gene (DMPK) was estimated in tumors, normal tissues of the same organs, muscles, and leukocytes from three myotonic dystrophy (DM) patients and a non-DM patient. Using cDNA 25 as a probe, a Southern blot analysis of EcoRI- and Bgl
Frequency of intergenerational contractions of the CTG repeats in myotonic dystrophy
✍ Scribed by A. López de Munain; A.M. Cobo; A. Sáenz; A. Blanco; J.J. Poza; L. Martorell; J.F. Martí-Massó; M. Baiget
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 337 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0741-0395
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✦ Synopsis
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.
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## Abstract Myotonic dystrophy type 1 is caused by the expansion of a CTG repeat in the 3′ UTR of the __DMPK__ gene. A length exceeding 50 CTG triplets is pathogenic. Intermediate alleles with 35–49 triplets are not disease‐causing but show instability in intergenerational transmissions. We report
Myotonic dystrophy (DM) is associated with an increased number of CTG repeats in the 3 untranslated region of the myotonin gene. Because DM has been observed less frequently in Ashkenazic Jews and non-Jews than in North African and Yemenite Jews in Israel, a study of the CTG repeat polymorphism was