A series of unfortunate events: familial case of DMD, two different mutational events and skewed X chromosome inactivation in a pregnant woman

LEONELA LUCE; CARCIONE, MICAELA;; MAZZANTI, CHIARA; , SZIJAN IRENE; SEBASTIÁN MENAZZI; LILIANA FRANCIPANE; JULIÁN NEVADO; PABLO LAPUNZINA; LILIANA ROSSETTI; PAMELA RADIC; MARTÍN ABELLEYRO; CARLOS DE BRASI; FLORENCIA GILIBERTO,

Copenhagen

Congreso; 24th INTERNATIONAL ANNUAL CONGRESS OF THE WORLD MUSCLE SOCIETY (WMS); 2019

World Muscle Sociaty

A series of unfortunate events: familial case of DMD, two different mutational events and skewed X chromosome inactivation in a pregnant womanLeonela Luce1,2, Micaela Carcione1,2, Chiara Mazzanti1,2, Irene Szijan1, Sebastián Menazzi3, Liliana Francipane3, Julián Nevado4,5, Pablo Lapunzina4,5, Liliana Rossetti6, Pamela Radic6, Martín Abelleyro6, Carlos De Brasi6 and Florencia Giliberto1,2. Afiliations:1Universidad de Buenos Aires; Departamento de Microbiología, Inmunología, Biotecnología y Genética; Cátedra de Genética; Laboratorio de Distrofinopatías. Buenos Aires, Argentina.2 CONICET - Universidad de Buenos Aires; Instituto de Inmunología, Genética y Metabolismo (INIGEM). Buenos Aires, Argentina. 3División de Genética, Hospital de Clínicas "José de San Martín", Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina. 4Hospital Universitario La Paz. Instituto de Genética Médica y Molecular (INGEMM).IdiPAZ, Madrid, Spain. 5Centro de Investigaciones Biomédicas en Red para Enfermedades Raras (CIBERER), Madrid, Spain. 6Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina. Duchenne muscular dystrophy (DMD) is a neuromuscular X-linked recessive disease caused by mutations in DMD gene. Here, we present a family with a DMD symptomatic pregnant woman and two affected boys. One of them had a previous multiplex PCR study showing a 45-54 exon deletion. Interestingly, during the prenatal diagnosis another mutation was discovered in the pregnant woman and her fetus, a 38-43 exon duplication. On the basis of this finding, we reanalyzed the initially studied boy, discovering both mutations in his gDNA. In order to unravel this riddle, we performed a complete molecular analysis in family members, applying the following techniques: MLPA, STRs segregation, Humara Assay, CGH Array, Sanger sequencing and WGS.As expected, the Humara assay revealed that the symptomatic female has skewed X-chromosome Inactivation (XCI), while an asymptomatic carrier showed a random XCI. Given the inheritance pattern of the rearrangements, only the affected child carried the del/dup, we could deduce that the deletion was the second mutational event. Furthermore, STRs segregation allowed the detection of a recombinant event in the affected boy, which could be related to the generation of the deletion. We were able to characterize the deletion breakpoints NC_000023.10:g.31664475_32111223del, suggesting the involvement of the non-homologous end joining mechanism. On the other hand, we limited the borders of the duplication up to NC_000023.10: g.(32245444_32247193)_(32380996_32385390)dup by CGH array. However, a thorough characterization of the duplication is currently being done.The profound analysis of complex structural variants, such as the presented one, would allow to detect predisposing mutagenic sequences and widen the understanding on the molecular events that takes place in DMD gene. Finally, this study highlights the importance of retesting patients with identified deletions by PCR, in order to reduce the probability of missing out other rearrangements which could affect the effectiveness of mutation-dependent therapies.