Left Ventricular Myocardial Noncompaction with Advanced Atrioventricular Conduction Disorder and Ventricular Arrhythmias in a Young Patient: Role of MIB1 Gene.

Left ventricular noncompaction (LVNC) is a structural abnormality of the left ventricle, usually described as an isolated condition, or sometimes associated with other structural cardiac diseases. LVNC is generally asymptomatic, although it may present conduction disorders, arrhythmias, and heart failure. Here, we present the case of a patient who came to our attention with a severe LVNC phenotype associated with advanced AV conduction disorder, and supraventricular and ventricular arrhythmias at young age, in which a novel MIB1, likely pathogenic, variation has been identified.

Ethnicity-related DMD Genotype Landscapes in European and Non-European Countries.

OBJECTIVE: Genetic diagnosis and mutation identification are now compulsory for Duchenne (DMD) and Becker muscular dystrophies (BMD), which are due to dystrophin (DMD) gene mutations, either for disease prevention or personalized therapies. To evaluate the ethnic-related genetic assortments of DMD mutations, which may impact on DMD genetic diagnosis pipelines, we studied 328 patients with DMD and BMD from non-European countries. METHODS: We performed a full DMD mutation detection in 328 patients from 10 Eastern European countries (Poland, Hungary, Lithuania, Romania, Serbia, Croatia, Bosnia, Bulgaria, Ukraine, and Russia) and 2 non-European countries (Cyprus and Algeria). We used both conventional methods (multiplex ligation-dependent probe amplification [MLPA] followed by gene-specific sequencing) and whole-exome sequencing (WES) as a pivotal study ran in 28 patients where DMD mutations were already identified by standard techniques. WES output was also interrogated for DMD gene modifiers. RESULTS: We identified DMD gene mutations in 222 male patients. We identified a remarkable allele heterogeneity among different populations with a mutation landscape often country specific. We also showed that WES is effective for picking up all DMD deletions and small mutations and its adoption could allow a detection rate close to 90% of all occurring mutations. Gene modifiers haplotypes were identified with some ethnic-specific configurations. CONCLUSIONS: Our data provide unreported mutation landscapes in different countries, suggesting that ethnicity may orient genetic diagnosis flowchart, which can be adjusted depending on the mutation type frequency, with impact in drug eligibility.

The Genetic Landscape of Dystrophin Mutations in Italy: A Nationwide Study.

Dystrophinopathies are inherited diseases caused by mutations in the dystrophin (DMD) gene for which testing is mandatory for genetic diagnosis, reproductive choices and eligibility for personalized trials. We genotyped the DMD gene in our Italian cohort of 1902 patients (BMD n = 740, 39%; DMD n =1162, 61%) within a nationwide study involving 11 diagnostic centers in a 10-year window (2008-2017). In DMD patients, we found deletions in 57%, duplications in 11% and small mutations in 32%. In BMD, we found deletions in 78%, duplications in 9% and small mutations in 13%. In BMD, there are a higher number of deletions, and small mutations are more frequent than duplications. Among small mutations that are generally frequent in both phenotypes, 44% of DMD and 36% of BMD are nonsense, thus, eligible for stop codon read-through therapy; 63% of all out-of-frame deletions are eligible for single exon skipping. Patients were also assigned to Italian regions and showed interesting regional differences in mutation distribution. The full genetic characterization in this large, nationwide cohort has allowed us to draw several correlations between DMD/BMD genotype landscapes and mutation frequency, mutation types, mutation locations along the gene, exon/intron architecture, and relevant protein domain, with effects on population genetic characteristics and new personalized therapies.

Mutation Load of Multiple Ion Channel Gene Mutations in Brugada Syndrome.

Brugada syndrome is a primary arrhythmic syndrome that accounts for 20% of all sudden cardiac death cases in individuals with a structurally normal heart. Pathogenic variants associated with Brugada syndrome have been identified in over 19 genes, with SCN5A as a pivotal gene accounting for nearly 30% of cases. In contrast to other arrhythmogenic channelopathies (such as long QT syndrome), digenic inheritance has never been reported in Brugada syndrome. Exploring 66 cardiac genes using a new custom next-generation sequencing panel, we identified a double heterozygosity for pathogenic mutations in SCN5A and TRPM4 in a Brugada syndrome patient. The parents were heterozygous for each variation. This novel finding highlights the role of mutation load in Brugada syndrome and strongly suggests the adoption of a gene panel to obtain an accurate genetic diagnosis, which is mandatory for risk stratification, prevention, and therapy.

Becker muscular dystrophy due to an intronic splicing mutation inducing a dual dystrophin transcript.

We describe a 29-year-old patient who complained of left thigh muscle weakness since he was 23 and of moderate proximal weakness of both lower limbs with difficulty in climbing stairs and running since he was 27. Mild weakness of iliopsoas and quadriceps muscles and muscle atrophy of both the distal forearm and thigh were observed upon clinical examination. He harboured a novel c.1150-3C>G substitution in the DMD gene, affecting the intron 10 acceptor splice site and causing exon 11 skipping and an out-of-frame transcript. However, protein of normal molecular weight but in reduced amounts was observed on Western Blot analysis. Reverse transcription analysis on muscle RNA showed production, via alternative splicing, of a transcript missing exon 11 as well as a low abundant full-length transcript which is enough to avoid the severe Duchenne phenotype. Our study showed that a reduced amount of full length dystrophin leads to a mild form of Becker muscular dystrophy. These results confirm earlier findings that low amounts of dystrophin can be associated with a milder phenotype, which is promising for therapies aiming at dystrophin restoration.

Paternal germline mosaicism in collagen VI related myopathies.

BACKGROUND: Collagen VI-related disorders are a group of muscular diseases characterized by muscle wasting and weakness, joint contractures, distal laxity, serious respiratory dysfunction and cutaneous alterations, due to mutations in the COL6A1, COL6A2 and COL6A3 genes, encoding for collagen VI, a critical component of the extracellular matrix. The severe Ullrich congenital muscular dystrophy (UCMD) can be due to autosomal recessive mutations in one of the three genes with a related 25% recurrence risk. In the majority of UCMD cases nevertheless, the underlying mutation is thought to arise de novo and the recurrence risk is considered as low. METHODS AND RESULTS: Here we report a family with recurrence of UCMD in two half-sibs. In both, the molecular analysis revealed heterozygosity for the c.896G > A missense mutation in COL6A1 exon 10 (Gly299Glu) and for the COL6A1 c.1823-8G > A variation within COL6A1 intron 29. The intronic variation was inherited from the father and RNA analysis in skin fibroblasts allowed to exclude its role in affecting COL6A1 transcript processing. The Gly299Glu mutation occurred apparently de novo in the two sibs. CONCLUSION: The described mutational segregation strongly suggests the occurrence of paternal germline mosaicism. This is the first report of UCMD recurrence due to a germline mosaic COL6 gene mutation. Mosaicism deserves to be considered as possible inheritance pattern in genetic counseling and recurrence risk estimation in collagen VI-related diseases.

Characterization of a rare case of Ullrich congenital muscular dystrophy due to truncating mutations within the COL6A1 gene C-terminal domain: a case report.

BACKGROUND: Mutations within the C-terminal region of the COL6A1 gene are only detected in Ullrich/Bethlem patients on extremely rare occasions. CASE PRESENTATION: Herein we report two Brazilian brothers with a classic Ullrich phenotype and compound heterozygous for two truncating mutations in COL6A1 gene, expected to result in the loss of the α1(VI) chain C2 subdomain. Despite the reduction in COL6A1 RNA level due to nonsense RNA decay, three truncated alpha1 (VI) chains were produced as protein variants encoded by different out-of-frame transcripts. Collagen VI matrix was severely decreased and intracellular protein retention evident. CONCLUSION: The altered deposition of the fibronectin network highlighted abnormal interactions of the mutated collagen VI, lacking the α1(VI) C2 domain, within the extracellular matrix, focusing further studies on the possible role played by collagen VI in fibronectin deposition and organization.

Exon skipping-mediated dystrophin reading frame restoration for small mutations.

Exon skipping using antisense oligonucleotides (AONs) has successfully been used to reframe the mRNA in various Duchenne muscular dystrophy patients carrying deletions in the DMD gene. In this study we tested the feasibility of the exon skipping approach for patients with small mutations in in-frame exons. We first identified 54 disease-causing point mutations. We selected five patients with nonsense or frameshifting mutations in exons 10, 16, 26, 33, and 34. Wild-type and mutation specific 2'OMePS AONs were tested in cell-free splicing assays and in cultured cells derived from the selected patients. The obtained results confirm cell-free splicing assay as an alternative system to test exon skipping propensity when patients' cells are unavailable. In myogenic cells, similar levels of exon skipping were observed for wild-type and mutation specific AONs for exons 16, 26, and 33, whereas for exon 10 and exon 34 the efficacy of the AONs was significantly different. Interestingly, in some cases skipping efficiencies for mutated exons were quite dissimilar when compared with previous reports on the respective wild-type exons. This behavior may be related to the effect of the mutations on exon skipping propensity, and highlights the complexity of identifying optimal AONs for skipping exons with small mutations.

A novel custom high density-comparative genomic hybridization array detects common rearrangements as well as deep intronic mutations in dystrophinopathies.

BACKGROUND: The commonest pathogenic DMD changes are intragenic deletions/duplications which make up to 78% of all cases and point mutations (roughly 20%) detectable through direct sequencing. The remaining mutations (about 2%) are thought to be pure intronic rearrangements/mutations or 5'-3' UTR changes. In order to screen the huge DMD gene for all types of copy number variation mutations we designed a novel custom high density comparative genomic hybridisation array which contains the full genomic region of the DMD gene and spans from 100 kb upstream to 100 kb downstream of the 2.2 Mb DMD gene. RESULTS: We studied 12 DMD/BMD patients who either had no detectable mutations or carried previously identified quantitative pathogenic changes in the DMD gene. We validated the array on patients with previously known mutations as well as unaffected controls, we identified three novel pure intronic rearrangements and we defined all the mutation breakpoints both in the introns and in the 3' UTR region. We also detected a novel polymorphic intron 2 deletion/duplication variation. Despite the high resolution of this approach, RNA studies were required to confirm the functional significance of the intronic mutations identified by CGH. In addition, RNA analysis identified three intronic pathogenic variations affecting splicing which had not been detected by the CGH analysis. CONCLUSION: This novel technology represents an effective high throughput tool to identify both common and rarer DMD rearrangements. RNA studies are required in order to validate the significance of the CGH array findings. The combination of these tools will fully cover the identification of causative DMD rearrangements in both coding and non-coding regions, particularly in patients in whom standard although extensive techniques are unable to detect a mutation.

Reactivation of infectious simian virus 40 from normal human tissues.

In this study, 82 DNA samples of simian virus 40 (SV40)-positive human tumors and normal tissues were transfected into SV40-permissive monkey cells. SV40 wild-type strain 776 was reactivated from two DNA samples, derived from peripheral blood mononuclear cells (PBMCs) of a blood donor and from a vulvar tissue. SV40 reactivation was confirmed by obtaining rescue of SV40 from the DNA of the vulvar tissue in a second transfection experiment. This investigation indicates that infectious SV40 is present in normal human tissues and suggests that (i) PBMCs are probably vectors of SV40 to different tissues of the host and (ii) blood and sexual transmission may be routes of SV40 infection in humans, leading to (iii) virus spread in the human population.

Tumor-host interaction mediates the regression of BK virus-induced vascular tumors in mice: involvement of transforming growth factor-beta1.

Several sexually transmitted viruses have been associated with the development of Kaposi's sarcoma (KS), a highly vascularized multi-focal neoplasm, characterized by the presence of spindle-shaped and endothelial cells, fibroblasts and macrophages. As BK virus (BKV) sequences were found in 100% of primary KS and 75% of KS cell lines, we established an experimental model to test whether BKV may be involved in the pathogenesis of KS. For this purpose, we transformed primary and spontaneously immortalized murine endothelial cells with BKV or with a plasmid containing BKV early region, which encodes BKV T antigen. Murine endothelial cells lost endothelial markers after transformation by BKV and, when inoculated s.c. in nude mice, induced tumors which regressed 7-30 days after onset, whereas spontaneously immortalized murine endothelial MHE cells induced progressing tumors, which brought the animals to death. Histologic examination showed an initial formation of vessels around the tumors, followed by the appearance of a dense population of fibroblasts and mononuclear cells in the peritumoral tissue. Subsequently, tumors appeared to be infiltrated by mononuclear cells and surrounded by a thick fibrous wall with scattered fibroblasts and without vessels. Areas of necrosis developed in the tumor mass and finally the neoplastic tissue completely degenerated. The medium conditioned by BKV-transformed cells induced proliferation and migration of human fibroblasts and NIH3T3 cells. These effects were inhibited by an anti-transforming growth factor-beta1 (TGF-beta1) antibody. Northern blot analysis revealed that BKV-transformed cells express a greater amount of TGF-beta1 RNA than normal murine endothelial cells. Besides, TGF-beta1 was not expressed in progressing tumors induced by spontaneously immortalized endothelial MHE cells, whereas it was highly expressed during the regression of tumors induced by BKV-transformed MHE and primary endothelial cells. Over-expression of TGF-beta1 may be responsible for the mononuclear cell infiltration, inhibition of angiogenesis and formation of the fibrotic wall around tumors, inducing tumor regression through tumor cell necrosis and nutritional starvation. These results prompt us to test whether production of TGF-beta1 is associated with spontaneous KS regression in human patients. In this case, KS regression could be induced or accelerated by any means that enhances TGF-beta1 production at the tumor site.