DNA analysis of a pedigree with myotonic dystrophy in Songjiang county, Shanghai.
OBJECTIVE
To make the molecular analysis of a pedigree with myotonic dystrophy (DM) in Songjiang county, Shanghai, and to observe the connection between CTG repeat number and clinical features.


METHODS
In twenty-three individuals of a pedigree with DM, CTG trinucleotide repeat numbers located in the 3' untranslated region of a protein kinase gene (MTPK) on chromosome 19q13.2-3 were analyzed by using Long Expand TM Template PCR system.


RESULTS
Four of eight clinical patients had expanded DM allele, the other four had no expanded CTG copies. Seven of eight suspicious DM cases had expanded CTG repeat numbers and were therefore genetically diagnosed as DM, and an asymptomatic individual was diagnosed as a doubted DM patient by DNA analysis. High risk of DM in six of seven individuals was ruled out, and a clinical doubted DM individual was ascertained a normal person by molecular analysis. A positive correlation was found beween early onset and expanded CTG repeat number in six parents (or grandparents)/child pairs, but in the pair II 2 /IV 7 CTG repeat numbers were reduced from 3100 in the grandmother to 175 in her grandson and there was no anticipation phenomenon.


CONCLUSIONS
The measurement of CTG repeat number can help to ascertain the diagnosis of DM in clinical and preclinical patients, but some clinically- diagnosed DM patients might have normal CTG repeat numbers. Anticipation phenomena were common in the pedigree.
Xie
H
H
Department of Neurology, Changhai Hospital, the Second Military Medical University, Shanghai, 200433 P.R.China. hjxie@smmu.edu.cn
Zheng
H
H
Zheng
S
S
Deng
B
B
Xu
J
J
Cui
Y
Y
Wang
Y
Y
Xu
Z
Z
Ren
D
D
D000293:Adolescent; D000328:Adult; D002648:Child; D004247:DNA / Q000032:analysis*; D005260:Female; D018628:Gene Dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D018911:Trinucleotide Repeats
D004247:DNA