The American College of Medical Genetics and Genomics (ACMG) recommends that clinical sequencing laboratories return secondary findings in 56 genes associated with medically actionable conditions. ...Our goal was to apply a systematic, stringent approach consistent with clinical standards to estimate the prevalence of pathogenic variants associated with such conditions using a diverse sequencing reference sample. Candidate variants in the 56 ACMG genes were selected from Phase 1 of the 1000 Genomes dataset, which contains sequencing information on 1,092 unrelated individuals from across the world. These variants were filtered using the Human Gene Mutation Database (HGMD) Professional version and defined parameters, appraised through literature review, and examined by a clinical laboratory specialist and expert physician. Over 70,000 genetic variants were extracted from the 56 genes, and filtering identified 237 variants annotated as disease causing by HGMD Professional. Literature review and expert evaluation determined that 7 of these variants were pathogenic or likely pathogenic. Furthermore, 5 additional truncating variants not listed as disease causing in HGMD Professional were identified as likely pathogenic. These 12 secondary findings are associated with diseases that could inform medical follow-up, including cancer predisposition syndromes, cardiac conditions, and familial hypercholesterolemia. The majority of the identified medically actionable findings were in individuals from the European (5/379) and Americas (4/181) ancestry groups, with fewer findings in Asian (2/286) and African (1/246) ancestry groups. Our results suggest that medically relevant secondary findings can be identified in approximately 1% (12/1092) of individuals in a diverse reference sample. As clinical sequencing laboratories continue to implement the ACMG recommendations, our results highlight that at least a small number of potentially important secondary findings can be selected for return. Our results also confirm that understudied populations will not reap proportionate benefits of genomic medicine, highlighting the need for continued research efforts on genetic diseases in these populations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
As a result of the pandemic, the traditional in‐person didactic lecture model was adapted to a virtual learning approach. Our Laboratory Genetics and Genomics fellowship program at Nationwide ...Children's hospital took advantage of this opportunity to organize a multi‐institutional Fellow's Conference to educate fellows from different programs on a wide range of medical genetics topics. We describe our approach of developing this lecture series utilizing subject‐matter experts across institutions. In addition, we discuss the value of such an approach in reducing the amount of time individual institutions spend creating and providing didactic content for their small number of learners. Our experience could serve as a model for other educators and program directors, including genetic counseling program directors, to develop multi‐institutional collaborations for didactic learning.
Objective
Epilepsy‐associated developmental lesions, including malformations of cortical development and low‐grade developmental tumors, represent a major cause of drug‐resistant seizures requiring ...surgical intervention in children. Brain‐restricted somatic mosaicism has been implicated in the genetic etiology of these lesions; however, many contributory genes remain unidentified.
Methods
We enrolled 50 children who were undergoing epilepsy surgery into a translational research study. Resected tissue was divided for clinical neuropathologic evaluation and genomic analysis. We performed exome and RNA sequencing to identify somatic variation and we confirmed our findings using high‐depth targeted DNA sequencing.
Results
We uncovered candidate disease‐causing somatic variation affecting 28 patients (56%), as well as candidate germline variants affecting 4 patients (8%). In agreement with previous studies, we identified somatic variation affecting solute carrier family 35 member A2 (SLC35A2) and mechanistic target of rapamycin kinase (MTOR) pathway genes in patients with focal cortical dysplasia. Somatic gains of chromosome 1q were detected in 30% (3 of 10) of patients with Type I focal cortical dysplasia (FCD)s. Somatic variation in mitogen‐activated protein kinase (MAPK) pathway genes (i.e., fibroblast growth factor receptor 1 FGFR1, FGFR2, B‐raf proto‐oncogene, serine/threonine kinase BRAF, and KRAS proto‐oncogene, GTPase KRAS) was associated with low‐grade epilepsy‐associated developmental tumors. RNA sequencing enabled the detection of somatic structural variation that would have otherwise been missed, and which accounted for more than one‐half of epilepsy‐associated tumor diagnoses. Sampling across multiple anatomic regions revealed that somatic variant allele fractions vary widely within epileptogenic tissue. Finally, we identified putative disease‐causing variants in genes not yet associated with focal cortical dysplasia.
Significance
These results further elucidate the genetic basis of structural brain abnormalities leading to focal epilepsy in children and point to new candidate disease genes.
Cancers exhibit complex transcriptomes with aberrant splicing that induces isoform-level differential expression compared to non-diseased tissues. Transcriptomic profiling using short-read sequencing ...has utility in providing a cost-effective approach for evaluating isoform expression, although short-read assembly displays limitations in the accurate inference of full-length transcripts. Long-read RNA sequencing (Iso-Seq), using the Pacific Biosciences (PacBio) platform, can overcome such limitations by providing full-length isoform sequence resolution which requires no read assembly and represents native expressed transcripts. A constraint of the Iso-Seq protocol is due to fewer reads output per instrument run, which, as an example, can consequently affect the detection of lowly expressed transcripts. To address these deficiencies, we developed a concatenation workflow, PacBio Full-Length Isoform Concatemer Sequencing (PB_FLIC-Seq), designed to increase the number of unique, sequenced PacBio long-reads thereby improving overall detection of unique isoforms. In addition, we anticipate that the increase in read depth will help improve the detection of moderate to low-level expressed isoforms.
In sequencing a commercial reference (Spike-In RNA Variants; SIRV) with known isoform complexity we demonstrated a 3.4-fold increase in read output per run and improved SIRV recall when using the PB_FLIC-Seq method compared to the same samples processed with the Iso-Seq protocol. We applied this protocol to a translational cancer case, also demonstrating the utility of the PB_FLIC-Seq method for identifying differential full-length isoform expression in a pediatric diffuse midline glioma compared to its adjacent non-malignant tissue. Our data analysis revealed increased expression of extracellular matrix (ECM) genes within the tumor sample, including an isoform of the Secreted Protein Acidic and Cysteine Rich (SPARC) gene that was expressed 11,676-fold higher than in the adjacent non-malignant tissue. Finally, by using the PB_FLIC-Seq method, we detected several cancer-specific novel isoforms.
This work describes a concatenation-based methodology for increasing the number of sequenced full-length isoform reads on the PacBio platform, yielding improved discovery of expressed isoforms. We applied this workflow to profile the transcriptome of a pediatric diffuse midline glioma and adjacent non-malignant tissue. Our findings of cancer-specific novel isoform expression further highlight the importance of long-read sequencing for characterization of complex tumor transcriptomes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Biopsy specimens are subjected to an expanding portfolio of assays that regularly include mutation profiling via next-generation sequencing (NGS). Specimens derived via fine-needle aspiration, a ...common biopsy technique, are subjected to a variety of cytopreparatory methods compared with surgical biopsies that are almost uniformly processed as formalin-fixed, paraffin-embedded tissue. Therefore, the fine-needle aspiration–derived specimens most commonly accepted for molecular analysis are cell blocks (CBs), because they are processed most similarly to surgical biopsy tissue. However, CB preparations are fraught with challenges that risk unsuccessful sequencing and repeat biopsies, with the potential to further increase health care costs and delay clinical care. The diversity of cytopreparations and the resource-intensive clinical validation of NGS pose significant challenges to more consistent use of non-CB (NCB) cytology specimens. As part of clinical validation of a targeted NGS assay, DNA subjected to nine cytopreparatory methods was evaluated for sequencing performance and was shown to be uniformly acceptable for clinical NGS. Of the 379 clinical cases analyzed after validation, the majority (56%) were derived from NCB cytology specimens. This specimen class had the lowest DNA insufficiency rate (1.5%) and showed equivalent sequencing performance to surgical and CB formalin-fixed, paraffin-embedded tissue. NCB cytology specimens are valuable sources of tumor nucleic acid and are the preferred specimen type for clinical NGS at our institution.
Glioblastoma is the most common primary malignancy of the adult central nervous system. Gliomagenesis involves a complex range of alterations, including sequence changes, copy number variations ...(CNVs), and epigenetic modifications, that have clinical implications for disease classification and prognosis. Thus, multiple testing modalities are required to support a complete diagnostic workup. The goal of this study was to streamline the multipart workflow by predicting both sequence changes and CNVs (specifically EGFR amplifications) from a single next-generation sequencing (NGS) test. Eighty-six primary and secondary glioblastomas were submitted for clinical NGS to report sequence variants from a concise panel of cancer-relevant genes. Most specimens underwent concomitant testing by methylation-specific polymerase chain reaction, immunohistochemistry, and fluorescence in situ hybridization. Using data generated during the course of clinical testing, we found that NGS-based variant predictions were concordant with immunohistochemistry and fluorescence in situ hybridization for IDH mutation and EGFR amplification status, respectively. We also noted that EGFR amplifications correlated with polysomy of chromosome 7, 19, and 20, and loss of PTEN and CDKN2A. EGFR-unamplified cases had lower rates of chromosome 7 polysomy, and PTEN and CDKN2A loss, but more CNVs overall. TP53, NF1, ATRX, and PDGFRA mutations were nearly exclusive to specimens without EGFR amplification. EGFR amplification was not associated with longer progression-free survival in this cohort, but amplifications were enriched in a group with slightly longer overall survival despite radiographic evidence of disease progression. Further study is needed to explore the mechanisms responsible for noted patterns of co-occurring variants and to correlate them with specific clinical outcomes.
•A single, somatic NGS test accurately detected both sequence changes and CNVs.•EGFR-amplified and -unamplified cases had distinct molecular profiles.•EGFR amplification correlated with gain of chr 7, 19, and 20.•EGFR-unamplified cases had overall more CNVs and point mutations.•EGFR-amplified cases had longer survival despite radiological evidence of progression.
Approximately 10% of pediatric malignancies are secondary to germline alterations in cancer-predisposing genes. Checkpoint kinase 2 (
) germline loss-of-function variants have been reported in ...pediatric cancer patients, but clinical phenotypes and outcomes are poorly described. We present our single-institution experience of pediatric oncology patients with
germline alterations, including clinical presentations and outcomes.
Pediatric oncology patients with
germline alterations were identified among those assessed by clinical or translational research at the Institute for Genomic Medicine at Nationwide Children's Hospital. A chart review of disease course was conducted on identified patients.
We identified 6 patients with germline
variants from a cohort of 300 individuals, including 1 patient with concurrent presentation of Burkitt lymphoma and neuroblastoma, 3 patients with brain tumors, 1 patient with Ewing sarcoma, and 1 patient with myelodysplastic syndrome. Three patients had a family history of malignancies. Four patients were in remission; one was undergoing treatment; one patient had developed treatment-related meningiomas. We review prior data regarding
variants in this population, challenges associated with variant interpretation, and genetic counseling for individuals with
variants.
germline loss-of-function alterations occur in patients with a variety of pediatric tumors. Larger multicenter studies will improve our understanding of the incidence, phenotype, and molecular biology of
germline variants in pediatric cancers.
Papillary hemangioma (PH) is a small, primarily dermal lesion occurring predominantly in the head and neck in both children and adults. Its signature characteristics are dilated thin-walled channels ...containing papillary clusters of mainly capillary-sized vessels and endothelial cytoplasmic eosinophilic inclusions. Given certain histopathologic similarities to congenital hemangioma which harbor mutations in GNAQ and GNA11 , we investigated whether similar mutations are present in PH. Seven PH specimens were studied. All presented in the first 4 years of life, with one being noted at birth. With the exception of one lesion, all were in the head and neck. Lesions were bluish and ranged in size from 0.5 to 2.8 cm. Four samples had GNA11 p.Q209L and 3 had GNAQ p.Q209L missense mutations. Mutations in GNA11 and GNAQ are associated with other types of somatic vascular lesions including capillary malformation, congenital hemangioma, anastomosing hemangioma, thrombotic anastomosing hemangioma, and hepatic small cell neoplasm. Shared mutations in GNA11 and GNAQ may account for some overlapping clinical and pathologic features in these entities, perhaps explicable by the timing of the mutation or influence of the germline phenotype.
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