Novel Intronic Mutations Introduce Pseudoexons in DMD That Cause Muscular Dystrophy in Patients

Abstract

Background: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are two subtypes of muscular dystrophy diseases caused by pathogenic mutations in the DMD gene. Until now, more than 4,600 disease-causing mutations in DMD have been reported. However, only 33 mutations were deep intronic, cases with this type of mutations were limited.Methods: In this study, we used a combination of complementary DNA (cDNA) and target DNA sequencing analysis in addition to conventional whole-exome sequencing (WES).Results: Three novel hemizygous mutations IVS11 + 17811C > G (c.1331 + 17811C > G), IVS21 + 3252A > G (c.2803 + 3252A > G) and IVS40 + 362A > G (c.5739 + 362A > G) were identified in DMD patients, while a reported hemizygous mutation IVS62-285A > G (c.9225-285A > G) was found in the BMD patient. These DMD mutations lead to pseudoexon insertions, causing the generation of truncated and dysfunctional dystrophin.Conclusion: This study defines three novel and one reported intronic mutations, which can result in DMD/BMD. We also emphasize the need to combine WES and cDNA-based methods to detect the variant in the very large DMD gene in which the mutational spectrum is complex.

Innovative Computerized Dystrophin Quantification Method Based on Spectral Confocal Microscopy

“…In this context, standardised results are fundamental since the regulatory agencies would welcome an objective methodology to assess dystrophin upregulation by therapies. In addition, some mutations such as deep intronic variants cannot be detected by routine genetic tests due to the huge genomic size of DMD gene and in these cases, muscle biopsies are needed for diagnosis by identifying a decrease or absence of dystrophin [ 19 , 20 , 21 ]. There is also a need to improve the quantification for BMD patients with minimal loss of dystrophin, as well as in female carriers, in whom the diagnosis can be very challenging due to minimal muscle histological variability and mosaic expression of dystrophin [ 22 ].…”