Clinical, biochemical, cellular and molecular characterization of mitochondrial DNA depletion syndrome due to novel mutations in the MPV17 gene

Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are severe autosomal recessive disorders associated with decreased mtDNA copy number in clinically affected tissues. The hepatocerebral form (mtDNA depletion in liver and brain) has been associated with mutations in the POLG, PEO1 (Twinkle), DGUOK and MPV17 genes, the latter encoding a mitochondrial inner membrane protein of unknown function. The aims of this study were to clarify further the clinical, biochemical, cellular and molecular genetic features associated with MDS due to MPV17 gene mutations. We identified 12 pathogenic mutations in the MPV17 gene, of which 11 are novel, in 17 patients from 12 families. All patients manifested liver disease. Poor feeding, hypoglycaemia, raised serum lactate, hypotonia and faltering growth were common presenting features. mtDNA depletion in liver was demonstrated in all seven cases where liver tissue was available. Mosaic mtDNA depletion was found in primary fibroblasts by PicoGreen staining. These results confirm that MPV17 mutations are an important cause of hepatocerebral mtDNA depletion syndrome, and provide the first demonstration of mosaic mtDNA depletion in human MPV17 mutant fibroblast cultures. We found that a severe clinical phenotype was associated with profound tissue-specific mtDNA depletion in liver, and, in some cases, mosaic mtDNA depletion in fibroblasts

Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Background: Diagnosis of primary immunodeficiencies (PIDs) is complex and cumbersome yet important for the clinical management of the disease. Exome sequencing may provide a genetic diagnosis in a significant number of patients in a single genetic test. Methods: In May 2013, we implemented exome sequencing in routine diagnostics for patients suffering from PIDs. This study reports the clinical utility and diagnostic yield for a heterogeneous group of 254 consecutively referred PID patients from 249 families. For the majority of patients, the clinical diagnosis was based on clinical criteria including rare and/or unusual severe bacterial, viral, or fungal infections, sometimes accompanied by autoimmune manifestations. Functional immune defects were interpreted in the context of aberrant immune cell populations, aberrant antibody levels, or combinations of these factors. Results: For 62 patients (24%), exome sequencing identified pathogenic variants in well-established PID genes. An exome-wide analysis diagnosed 10 additional patients (4%), providing diagnoses for 72 patients (28%) from 68 families altogether. The genetic diagnosis directly indicated novel treatment options for 25 patients that received a diagnosis (34%). Conclusion: Exome sequencing as a first-tier test for PIDs granted a diagnosis for 28% of patients. Importantly, molecularly defined diagnoses indicated altered therapeutic options in 34% of cases. In addition, exome sequencing harbors advantages over gene panels as a truly generic test for all genetic diseases, including in silico extension of existing gene lists and re-analysis of existing data

Additional file 2: of Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Table S2. Shows all causative mutations identified in 72 patients from 68 families suffering from primary immunodeficiencies. (XLSX 17 kb

Additional file 4: of Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Table S4. (A) The number of patients with isolated or combined infections, and (B) the number of patients with isolated or combined immunophenotypes, and the percentage for which we have reported a genetic diagnosis. (XLSX 11 kb

Additional file 5: of Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Table S5. Quality information of the WES technology, with the mean target coverage, and the % of bases with >â 20Ă coverage. (XLSX 22 kb

Additional file 3: of Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Table S3. Variants of unknown significance (class 3) and variants in TRAF3 identified in 17 patients suffering from primary immunodeficiencies. (XLSX 11 kb

Additional file 1: of Exome sequencing in routine diagnostics: a generic test for 254 patients with primary immunodeficiencies

Table S1. Overview of all clinical characteristics of the patients included in our diagnostic PID cohort, including all immunophenotype characteristics. (XLSX 63 kb