A MULTI-TECHNIQUE MOLECULAR ANALYSIS OF A DMD FAMILY WITH TWO
INDEPENDENT MUTATIONAL EVENTS AND A MANIFESTING PREGNANT WOMAN.
BIOINFORMATIC ANALYSIS OF MOLECULAR SCARS AT BREAKPOINT JUNCTIONS AND
HYPOTHESIZATION OF THE UNDERLYING MOLECULAR MECHANISMS.
Our work depicts a familial Duchenne muscular dystrophy case with a
complex structural variant (cxSV) and a manifesting pregnant woman. Were
our aims to provide molecular diagnosis and hypothesize mechanisms
underlying the origin of the cxSV. We implemented a multi-technique
approach including MLPA, STRs-segregation, AR-assay, SNP-array, WGS and
a bioinformatic algorithm for identification of double strand breaks
(DSB) stimulator motifs. We established the carrier status of the
prenatal sample and explained its mother´s symptomatology by skewed
X-chromosome inactivation. Furthermore, an ancestral familial ex38-43
duplication plus a de novo ex45-54 deletion was revealed in the proband,
who carried the cxSV in a recombinant maternal X-chromosome.
Characterization of cxSV´s breakpoints junction and its surrounding
sequences allowed us to identify DSB stimulator motifs. The
replication-dependent “Fork Stalling and Template Switching” mechanism
was predicted to be the most likely scenario for the duplication´s
origin. Whilst, the de novo deletion could arise from a germline event
of inter-chromosome non-allelic recombination involving the
“Non-Homologous End Joining” mechanism. The multi-technique strategy
enabled precise diagnosis, accurate genetic assessment and widen the
understanding of the molecular mechanisms involved in SVs’ generation.
Finally, the further comprehension of the occurrence of DMD variants,
favors the development of new gene therapy strategies.