Application of triplet-primer PCR technology for the genetic testing and prenatal diagnosis of patients with Myotonic dystrophy type 1

Abstract

To explore the application of triplet-primer PCR (TP-PCR) for the genetic testing and prenatal diagnosis in patients with Myotonic dystrophy type 1 (DM1). A total of 60 individuals from 48 pedigrees undergoing genetic testing at the Genetic and Prenatal Diagnosis Center of the First Affiliated Hospital of Zhengzhou University from May 2018 to October 2022 were selected as the study subjects. TP-PCR combined with capillary electrophoresis was applied to determine the number of CTG repeats of the DMPK gene, and prenatal testing was provided to four DM1 pedigrees. This study was approved by the First Affiliated Hospital of Zhengzhou University (Ethics No. KS-2018-KY-36). A total of 52 DM1 patients were detected, mostly with muscle weakness, muscular atrophy and myotonia as the initial symptoms, along with typical myotonic potentials. Some patients also had abnormalities of other systems. The number of abnormal CTG repeats of the DMPK gene was > 50, whilst the number of CTG repeats on the normal allele had ranged from 5 to 18. The number of the most common normal CAG repeats was 6 (30.77%, 16/52). Among the four DM1 pedigrees undergoing prenatal diagnosis, one fetus was healthy, whilst three fetuses were found to have abnormal CTG repeats (> 50 times) and diagnosed with DM1. TP-PCR can diagnose DM1 patients with speed and accuracy. However, this method cannot accurately determine the number of CTG repeats when it exceeds 50.