MOLECULAR DIAGNOSIS OF DYSTROPHINOTHIES AND GENE CHARACTERIZATION

LUCE, LEONELA; MAZZANTI, CHIARA; CARCIONE, MICAELA; GILIBERTO, FLORENCIA

Congreso; XIV Curso de la Escuela Latinoamericana de Genética Humana y Médica. Caxias do Sul, Brasil; 2018

Dystrophinopathies are X-linked diseases caused by mutations in DMD gene, associated with the development of Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD) and X-linked Dilated Cardiomyopathy (XLDC). DMD is the most frequent and severe dystrophy, affects 1:3500 born males. De-novo mutations and germline mosaicism are responsible for 1/3 of cases, while 2/3 are familial. Molecular alterations in DMD gene are gross deletions/duplications in 80% of cases and small mutations in 20%. Hitherto there is no effective treatment for these pathologies, which highlights the importance of performing genetic assessment to the affected families so as to detect mutation carriers and prevent diseased newborns. However, two mutation-specific therapies for DMD were recently approved: Exon Skipping of exon 51 and Premature Stop Codon Read-through. Therefore, accurate detection and characterization of the causing mutation is essential to allow genetic counseling, patient follow-up and determine the suitable therapy. In order to achieve an accurate molecular diagnosis in patients and at-risk family members, we performed an algorithm based on: MLPA, simplex PCR, Sanger sequencing, Whole Exome Sequencing (WES) and STRs segregation analysis. In the last 6 years we could determine the DMD/BMD diagnosis in the 73,5% of patient. 22 resulted candidates for Read-through and 12 for the exon skipping treatments. The reading frame rule was corroborated in the 78.9% of patients. The molecular alterations we found accounted for: 54% deletions, 11% duplications, 29% small mutations (14% nonsense), 1% del/dup and 5% were not detected. We have classified and uploaded to public databases the 148 small variants we have found in the DMD gen, as benign, VUS or pathogenic. We also, could establish an association between the most frequent deletion intron breakpoints and the abundance of dinucleotide microsatellites loci. Interestingly, could demonstrated that dystrophin expression is altered in non-myogenic tumors, corroborating DMD gene new physiopathological implication with tumor development. In conclusion, the work we have been performing since 1992 and the analysis of more than 1500 samples allow the characterization of the DMD/BMD argentine population and contribute to the understanding of the genetic/molecular basis of these pathologies.