Identify the origin of de novo variants in TSC patients by ddPCR

Objective To investigate the genotype-phenotype correlation between TSC1 and TSC2 associated tuberous sclerosis complex(TSC). Methods Nineteen infants with TSC were enrolled in the study.Their clinical ma-nifestations and mutations of TSC gene were analyzed by chip capturing and next-generation sequencing. Results Among the total of 19 patients with TSC, 13 TSC2 mutations and 4 TSC1 mutations were detected.The ratio of TSC2/TSC1 mutation-positive cases was 3.4/1.Six mutations were novel.There were epilepsy in 10 cases carrying TSC2 mutations, including 4 cases(31%)with refractory to antiepileptic treatment, and 3 cases carrying TSC1 mutations, including 1 case(25%)with refractory to antiepileptic treatment.The incidence and severity(grade 2)of epilepsy, brain imaging were not different in TSC2 and TSC1 patients(P=0.480 7, 0.462 2). Compared with clinical manifestations, incidence of mental retardation(grade 1 or grade 2)was higher in TSC2 patients(85%, 11/13 cases)than TSC1 patients(50%, 2/4 cases). Also, the incidence of moderate and severe mental retardation(grade 2)was higher in TSC2 patients(54%, 7/13 cases) in comparison with TSC1 patients(25%, 1/4 cases). Compared with the phenotype of TSC2 and TSC1 patients, the frequencies of skin, renal and cardiac lesions were significantly higher in TSC2 patients than TSC1 patients. Conclusions TSC2 mutation may be the prominent molecular pathogenesis in Han population with TSC.TSC2 patients have much profound multisystemitc leisions than TSC1 patients, including mental retardation, epilepsy, facial angiofibromas and renal angiomyolipomas etc, which should be confirmed further in domestic multicenter and large samples. Key words: Tuberous sclerosis complex; Phenotype; Genes; Mutation

Detecting Low-Variant Allele Frequency Mosaic Pathogenic Variants of NF1, TSC2, and AKT3 Genes from Blood in Patients with Neurodevelopmental Disorders

3628 Background: Fusions and translocations account for 20% of cancer mortality globally. Maximizing their detection enhances the utility of precision medicine for various solid and hematologic cancers. Practice guidelines stress the importance of RNA sequencing. Novel assay techniques employing a comprehensive genomic profiling approach, including RNA sequencing, yield information beyond conventional DNA next generation sequencing (NGS) alone. Methods: Tumor samples (N = 1517) were assayed combining whole transcriptome (RNA) sequencing, whole exome (DNA) sequencing, and comparison of tumor sequence vs. paired normal DNA. Results were analyzed to determine the frequency of rare and common RNA fusion and variant detection. Findings were mapped to a knowledge-base of targeted treatment options. Results: Analysis detected 79 (5.2%) actionable fusions and 15 (1%) transcript variants across major solid and heme-based malignancies. Notably, we observed actionable transcript variants that are not detectable at the DNA level including: EGFRvIII, EGFRvIVa and EGFRvIVb in GBM; ARv7 in prostate, and METe14 in TNBC. Many fusion cases (42%, n = 33) had no other actionable molecular abnormalities. Novel fusions included: SLC12A/ROS1 in low-grade spindle cell neoplasm with myogenic differentiation, KANK1/NTRK2 in ganglioneuroblastoma, ETV6/NTRK3 in metastatic mammary analogue secretory carcinoma, FGFR1/SCT in germ cell tumor, ZNF33B/RET fusion in GBM, SH3BP4/ERBB4 and EML4/ALK in RCC, VTCN1/NRG1 in pancreatic cancer, and AGRN/NRG1 in cholangiocarcinoma. More common actionable fusion events included: EML4/ALK in NSCLC, KIAA1549/BRAF in pilocytic astrocytoma, FGFR2 and FGFR3 in cholangiocarcinoma and urothelial cancers and ESR1 in endocrine therapy-resistant breast cancers. The fusion events detected in heme-based malignancies included MLLT10 and MLLT4 in AML, BCR/ABL in leukemias, TCF3/PBX1 in B cell ALL, NPM1/ALK in ALCL, and novel fusion CIITA/CD274 in DLBCL. All RNA fusions and transcript variants found were matched to FDA-approved or investigational treatment options. Conclusions: Maximizing the rate of variant detection for targeted therapy relies on precise identification of common and rare fusion events. Without the addition of RNA sequencing, 15 transcript variants in our cohort would have been missed and 33 of the fusions may have gone undetected by conventional DNA NGS testing, resulting in zero targeted treatment options for this vulnerable population. Further use of comprehensive genomic profiling is vital to optimizing cancer care.

Rapid advances in DNA sequencing technologies have made it increasingly cost-effective to obtain accurate and timely large-scale genomic sequence data on individuals (short read massively parallel or next generation [next-gen]). A next-gen molecular diagnostic approach that has seen rapid deployment in the clinic over the last year is exome sequencing. Whole exome sequencing covers all protein-coding genes in the genome (≈1.1% of genome), and an exome test for a single patient generates ≈6 gigabases (109 bp) of DNA sequence data. A key challenge facing routine use of next-gen data in patient diagnosis and management is data interpretation. What sequence variant findings are relevant to diagnosis (pathogenic mutations)? What sequence variant findings are relevant to clinical care but not necessarily to patient diagnosis (clinically actionable incidental data)? What sequence information should be stored, and where can it be stored? This review provides a tutorial on current approaches to answering these questions. A recent landmark study showed that application of next-gen sequencing to a large cohort of idiopathic dilated cardiomyopathy patients found ≈27% of patients to show mutations of the titin gene, the most complex gene in the genome (363 exons). We use titin in cardiomyopathy as an exemplar for explaining next-gen sequencing approaches and data interpretation. Decreasing sequencing costs and broad dissemination of next-generation (next-gen) equipment and expertise are increasing availability of massively parallel sequencing of patient DNA samples (short read massively parallel or next-gen sequencing).1,2 Most rapidly expanding is exome sequencing, where all protein-coding sequences (exons) are selected from total genomic DNA and selectively sequenced.3 Alternative approaches to next-gen sequencing include targeted sequencing (TS) and whole genome (complete genome) sequencing. Currently, marketed targeted Sanger sequencing panels using traditional individual exon-by-exon sequencing remain expensive and time consuming, and massively parallel next-gen approaches are beginning to supplant …

Increased expression of tuberin in human uterine leiomyoma

BackgroundAlthough mosaic variation has been known to cause disease for decades, high-throughput sequencing technologies with the analytical sensitivity to consistently detect variants at reduced allelic fractions have only recently emerged as routine clinical diagnostic tests. To date, few systematic analyses of mosaic variants detected by diagnostic exome sequencing for diverse clinical indications have been performed.MethodsTo investigate the frequency, type, allelic fraction, and phenotypic consequences of clinically relevant somatic mosaic single nucleotide variants (SNVs) and characteristics of the corresponding genes, we retrospectively queried reported mosaic variants from a cohort of ~ 12,000 samples submitted for clinical exome sequencing (ES) at Baylor Genetics.ResultsWe found 120 mosaic variants involving 107 genes, including 80 mosaic SNVs in proband samples and 40 in parental/grandparental samples. Average mosaic alternate allele fraction (AAF) detected in autosomes and in X-linked disease genes in females was 18.2% compared with 34.8% in X-linked disease genes in males. Of these mosaic variants, 74 variants (61.7%) were classified as pathogenic or likely pathogenic and 46 (38.3%) as variants of uncertain significance. Mosaic variants occurred in disease genes associated with autosomal dominant (AD) or AD/autosomal recessive (AR) (67/120, 55.8%), X-linked (33/120, 27.5%), AD/somatic (10/120, 8.3%), and AR (8/120, 6.7%) inheritance. Of note, 1.7% (2/120) of variants were found in genes in which only somatic events have been described. Nine genes had recurrent mosaic events in unrelated individuals which accounted for 18.3% (22/120) of all detected mosaic variants in this study. The proband group was enriched for mosaicism affecting Ras signaling pathway genes.ConclusionsIn sum, an estimated 1.5% of all molecular diagnoses made in this cohort could be attributed to a mosaic variant detected in the proband, while parental mosaicism was identified in 0.3% of families analyzed. As ES design favors breadth over depth of coverage, this estimate of the prevalence of mosaic variants likely represents an underestimate of the total number of clinically relevant mosaic variants in our cohort.

The use of fetal exome sequencing in prenatal diagnosis: a points to consider document of the American College of Medical Genetics and Genomics (ACMG)

Genetic variants in relevant genes coexisting with MRI lesions in children with drug-resistant epilepsy (DRE) can negatively influence epilepsy surgery outcomes. Still, presurgical evaluation does not include genetic diagnostics routinely. Here, we report our presurgical evaluation algorithm that includes routine genetic testing. We analyzed retrospectively the data of 68 children with DRE operated at a mean age of 7.8 years (IQR: 8.1 years) at our center. In 49 children, genetic test results were available. We identified 21 gene variants (ACMG III: n = 7, ACMG IV: n = 2, ACMG V: n = 12) in 19 patients (45.2%) in the genes TSC1, TSC2, MECP2, DEPDC5, HUWE1, GRIN1, ASH1I, TRIO, KIF5C, CDON, ANKD11, TGFBR2, ATN1, COL4A1, JAK2, KCNQ2, ATP1A2, and GLI3 by whole-exome sequencing as well as deletions and duplications by array CGH in six patients. While the results did not change the surgery indication, they supported counseling with respect to postoperative chance of seizure freedom and weaning of antiseizure medication (ASM). The presence of genetic findings leads to the postoperative retention of at least one ASM. In our cohort, the International League against Epilepsy (ILAE) seizure outcome did not differ between patients with and without abnormal genetic findings. However, in the 7/68 patients with an unsatisfactory ILAE seizure outcome IV or V 12 months postsurgery, 2 had an abnormal or suspicious genetic finding as a putative explanation for persisting seizures postsurgery, and 3 had received palliative surgery including one TSC patient. This study highlights the importance of genetic testing in children with DRE to address putative underlying germline variants as genetic epilepsy causes or predisposing factors that guide patient and/or parent counseling on a case-by-case with respect to their individual chance of postoperative seizure freedom and ASM weaning. PLAIN LANGUAGE SUMMARY: Genetic variants in children with drug-resistant epilepsy (DRE) can negatively influence epilepsy surgery outcomes. However, presurgical evaluation does not include genetic diagnostics routinely. This retrospective study analyzed the genetic testing results of the 68 pediatric patients who received epilepsy surgery in our center. We identified 21 gene variants by whole-exome sequencing as well as deletions and duplications by array CGH in 6 patients. These results highlight the importance of genetic testing in children with DRE to guide patient and/or parent counseling on a case-by-case with respect to their individual chance of postoperative seizure freedom and ASM weaning.

We performed a comprehensive molecular genetic examination of 76 patients with tuberous sclerosis. For establish molecular diagnosis of the disease, we applied a new medical technology that includes targeted high-throughput parallel DNA sequencing (NGS), multiplex ligation-dependent probe amplification (MLPA), and Sanger sequencing. Search for point mutations and small indels in the TSC1 and TSC2 genes was carried out with next generation sequencing on the Ion S5 instrument. In order to filter out sequencing artifacts, to establish pathogenicity of the detected single nucleotide substitutions, and to identify familial cases, Sanger sequencing was performed. To search for extended deletions, the MLPA method was used. In 46% cases mutations have been detected, 70% in the TSC2 gene, and 30% in the TSC1 gene. Overwhelming majority of mutations were detected by NGS (91.9%), and 8.1% were detected by MLPA.

The mouse homologue of the human tuberous sclerosis 2 (TSC2) gene maps to chromosome 17, but does not fall within the t w18 or t th20 deletions

Tuberous sclerosis complex is an inherited tumour suppressor syndrome, caused by a mutation in either the TSC1 or TSC2 gene. The disease is characterised by a broad phenotypic spectrum that...

Objective To investigate clinical features and detect mutations in a case of tuberous sclerosis complex (TSC) caused by a somatic mosaic mutation in the TSC2 gene. Methods Peripheral blood samples were obtained from a patient with suspected TSC, his parents, and 200 unrelated healthy controls. Genomic DNA was extracted from these blood samples, polymerase chain reaction (PCR) and next-generation sequencing were performed to amplify all the exons and their flanking sequences of the TSC1 and TSC2 genes followed by DNA sequencing, so as to identify mutations in the TSC1 and TSC2 genes. DNA was also extracted from lesional skin tissues of the patient, and PCR was conducted to amplify the target fragment of the TSC2 gene followed by DNA sequencing. Results The patient clinically presented with facial angiofibroma, depigmented patches on the waist, periungual fibroma and angioleio-myolipoma of the kidney, which were consistent with the diagnosis of TSC. A mutation c.5130_5131insT (p.V1711Cfs*18) was identified in the TSC2 gene in the patient. A higher frequency of the mutation was found in the DNA of the tumor tissue than in that of the peripheral blood. No such a mutation was found in his parents′ DNA, unrelated healthy controls or any public database. Conclusion The somatic mosaic mutation c.5130_5131insT in the TSC2 gene is responsible for the phenotype of TSC in the patient. Key words: Tuberous sclerosis complex; Mosaicism; TSC2 gene

Somatic mosaic variants contribute to focal epilepsy, but genetic analysis has been limited to patients with drug-resistant epilepsy (DRE) who undergo surgical resection, as the variants are mainly brain-limited. Stereoelectroencephalography (sEEG) has become part of the evaluation for many patients with focal DRE, and sEEG electrodes provide a potential source of small amounts of brain-derived DNA. We aimed to identify, validate, and assess the distribution of potentially clinically relevant mosaic variants in DNA extracted from trace brain tissue on individual sEEG electrodes. We enrolled a prospective cohort of eleven pediatric patients with DRE who had sEEG electrodes implanted for invasive monitoring, one of whom was previously reported. We extracted unamplified DNA from the trace brain tissue on each sEEG electrode and also performed whole-genome amplification for each sample. We extracted DNA from resected brain tissue and blood/saliva samples where available. We performed deep panel and exome sequencing on a subset of samples from each case and analysis for potentially clinically relevant candidate germline and mosaic variants. We validated candidate mosaic variants using amplicon sequencing and assessed the variant allele fraction (VAF) in amplified and unamplified electrode-derived DNA and across electrodes. We extracted DNA from >150 individual electrodes from 11 individuals and obtained higher concentrations of whole-genome amplified vs unamplified DNA. Immunohistochemistry confirmed the presence of neurons in the brain tissue on electrodes. Deep sequencing and analysis demonstrated similar depth of coverage between amplified and unamplified samples but significantly more called mosaic variants in amplified samples. In addition to the mosaic PIK3CA variant detected in a previously reported case from our group, we identified and validated four potentially clinically relevant mosaic variants in electrode-derived DNA in three patients who underwent laser ablation and did not have resected brain tissue samples available. The variants were detected in both amplified and unamplified electrode-derived DNA, with higher VAFs observed in DNA from electrodes in closest proximity to the electrical seizure focus in some cases. This study demonstrates that mosaic variants can be identified and validated from DNA extracted from trace brain tissue on individual sEEG electrodes in patients with drug-resistant focal epilepsy and in both amplified and unamplified electrode-derived DNA samples. Our findings support a relationship between the extent of regional genetic abnormality and electrophysiology, and suggest that with further optimization, this minimally invasive diagnostic approach holds promise for advancing precision medicine for patients with DRE as part of the surgical evaluation.

Background Tuberous Sclerosis Complex is an autosomal dominant multi-system disorder with an incidence of about 1 in 6000 live births. Defects in either TSC1 (* 605284) or TSC2 (* 191092) genes encoding the components of the Tuberous Sclerosis Complex are responsible for the disease. Therefore, consideration of TSC1/TSC2 pathogenic variations is recommended in the updated diagnostic criteria of Tuberous Sclerosis Complex.Aims To present the TSC1/TSC2 screening results of a mixed patient population as well as possible new variants in 23 cases from 20 different families who were referred to our Genetic Diseases Diagnosis Center with the signs and symptoms of Tuberous Sclerosis Complex.Study designRetrospective, cross-sectional study.Methods Germline TSC1/TSC2 variants were screened in DNA samples extracted from peripheral blood samples of 23 patients from 20 unrelated families using targeted high-throughput sequencing and multiplex ligation-dependent probe amplification methods. The variants identified were classified according to ACMG 2015 guidelines.Results In total, 5 different pathogenic/likely pathogenic changes have been defined. All these pathogenic/likely pathogenic variants were located in the TSC2 gene. Three of the pathogenic/likely pathogenic variants were novel. Two patients who are twin sisters were found to have TSC2/PKD1 contiguous deletion syndrome. One of the 3 novel variants was a mosaic in-frame deletion. We did not identify any pathogenic variants of the TSC1 gene.Conclusion The novelty of most of the variants found, including a mosaic likely pathogenic variant, and the presence of a large genomic rearrangement, supports the importance of a comprehensive approach in analyzing TSC1/TSC2 genes. Genetic diagnosis should be performed with caution, considering the possibility of mosaic variants with low allelic fractions.

Alternative Splicing of the Tuberous Sclerosis 2 ( TSC2) Gene in Human and Mouse Tissues