Purpose of Review
RNA analysis is beginning to be integrated into clinical laboratory genomics, and a review of its current uses and limitations is warranted. Here, we summarize the scope and utility ...of RNA analysis in the context of clinical genetic testing, including considerations for genetic counseling.
Recent Findings
RNA analysis is a powerful approach for interpreting some variants of uncertain significance, for analyzing splicing alterations, for providing additional functional evidence for sequence and structural variants, and for discovering novel variants. However, a review of RNA sequencing methods has noted variability in both laboratory processes and findings. Genetic counseling related to RNA analysis has to take into account nonstandardized laboratory processes, sample-type limitations, and differences in variant-interpretation outcomes.
Summary
RNA analysis is an important complement to DNA testing, although limitations still exist. Maximizing the utility of RNA analysis will require appropriate patient referrals and standardization of laboratory processes as the practice continues to expand the ability to identify and resolve molecular diagnoses.
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1584
Background: Multi-gene testing for cancer predisposition is increasingly utilized in clinical care. Although the diagnostic yield and management implications of such testing in ...breast, ovarian and colorectal cancer are relatively well understood, data for other cancer types are still emerging. In this study we retrospectively examined 39,147 patients referred for hereditary cancer syndrome testing for pathogenic germline variants in 80 cancer risk genes, focusing on those patients with renal, sarcoma, paraganglioma, melanoma, and pancreatic cancers. Methods: Test results and personal/family history were extracted from a sequential series of de-identified clinical test reports. Data for genes not clinically ordered were analyzed under an IRB approved research protocol. Common low penetrance risk alleles were excluded. Results: Overall, 14.3% (5,589) of patients carried germline pathogenic mutations in 80 cancer risk genes. Of the 949 patients with renal cancer 20% (190) were positive, and 44% of these findings were “unexpected”, meaning they appeared in genes that are not commonly requisitioned in renal cancer patients. Of the 423 sarcoma patients, 16% (68) had positive findings, 45% of which were “unexpected”. For both cancer types, greater than 90% of these “unexpected” findings were in genes with published management recommendations. Similar results were observed in melanoma, paraganglioma and pancreatic cancer patients. A second or third pathogenic variant, many of which were also “unexpected”, were found in 3.6% of positive cases. Conclusions: In this series of patients we estimate almost 12% of pathogenic variants across cancer indications are “unexpected”. These data suggest many actionable pathogenic variants are being missed due to adherence to overly restrictive, narrowly constructed tumor-specific panels. Clinicians should expand the scope of their test panels in order to capture variants with the potential to impact patients and their family members by informing implementation of established management guidelines.
Importance
Variants of uncertain significance (VUSs) are rampant in clinical genetic testing, frustrating clinicians, patients, and laboratories because the uncertainty hinders diagnoses and clinical ...management. A comprehensive assessment of VUSs across many disease genes is needed to guide efforts to reduce uncertainty.
Objective
To describe the sources, gene distribution, and population-level attributes of VUSs and to evaluate the impact of the different types of evidence used to reclassify them.
Design, Setting, and Participants
This cohort study used germline DNA variant data from individuals referred by clinicians for diagnostic genetic testing for hereditary disorders. Participants included individuals for whom gene panel testing was conducted between September 9, 2014, and September 7, 2022. Data were analyzed from September 1, 2022, to April 1, 2023.
Main Outcomes and Measures
The outcomes of interest were VUS rates (stratified by age; clinician-reported race, ethnicity, and ancestry groups; types of gene panels; and variant attributes), percentage of VUSs reclassified as benign or likely benign vs pathogenic or likely pathogenic, and enrichment of evidence types used for reclassifying VUSs.
Results
The study cohort included 1 689 845 individuals ranging in age from 0 to 89 years at time of testing (median age, 50 years), with 1 203 210 (71.2%) female individuals. There were 39 150 Ashkenazi Jewish individuals (2.3%), 64 730 Asian individuals (3.8%), 126 739 Black individuals (7.5%), 5539 French Canadian individuals (0.3%), 169 714 Hispanic individuals (10.0%), 5058 Native American individuals (0.3%), 2696 Pacific Islander individuals (0.2%), 4842 Sephardic Jewish individuals (0.3%), and 974 383 White individuals (57.7%). Among all individuals tested, 692 227 (41.0%) had at least 1 VUS and 535 385 (31.7%) had only VUS results. The number of VUSs per individual increased as more genes were tested, and most VUSs were missense changes (86.6%). More VUSs were observed per sequenced gene in individuals who were not from a European White population, in middle-aged and older adults, and in individuals who underwent testing for disorders with incomplete penetrance. Of 37 699 unique VUSs that were reclassified, 30 239 (80.2%) were ultimately categorized as benign or likely benign. A mean (SD) of 30.7 (20.0) months elapsed for VUSs to be reclassified to benign or likely benign, and a mean (SD) of 22.4 (18.9) months elapsed for VUSs to be reclassified to pathogenic or likely pathogenic. Clinical evidence contributed most to reclassification.
Conclusions and Relevance
This cohort study of approximately 1.6 million individuals highlighted the need for better methods for interpreting missense variants, increased availability of clinical and experimental evidence for variant classification, and more diverse representation of race, ethnicity, and ancestry groups in genomic databases. Data from this study could provide a sound basis for understanding the sources and resolution of VUSs and navigating appropriate next steps in patient care.
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disorder that may lead to sudden death and can affect humans and other primates. In 2012, the alpha male bonobo of the Milwaukee County Zoo ...died suddenly and histologic evaluation found features of ARVC. This study sought to discover a possible genetic cause for ARVC in this individual. We sequenced our subject's DNA to search for deleterious variants in genes involved in cardiovascular disorders. Variants found were annotated according to the human genome, following currently available classification used for human diseases. Sequencing from the DNA of an unrelated unaffected bonobo was also used for prediction of pathogenicity. Twenty-four variants of uncertain clinical significance (VUSs) but no pathogenic variants were found in the proband studied. Further familial, functional, and bonobo population studies are needed to determine if any of the VUSs or a combination of the VUSs found may be associated with the clinical findings. Future genotype-phenotype establishment will be beneficial for the appropriate care of the captive zoo bonobo population world-wide as well as conservation of the bobono species in its native habitat.
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1577
Background: Somatic mutation analysis by next-generation sequencing (NGS) is an expanding clinical assessment offered to cancer patients. Studies report that 4–12% of patients have ...a positive tumor mutation profiling (TMP) result in a known cancer predisposition gene also identified in their germline, which has potential implications for the patient’s acute treatment, ongoing surveillance, and the screening of family members. We report a series of patients with TMP coupled with germline genetic testing and include yield of pathogenic germline mutations, discordance between germline and TMP findings, and potential clinical impact. Methods: Our study used de-identified data from 182 consecutive patients who underwent TMP followed by germline testing with an NGS-based hereditary cancer gene panel. Results: 50/182 cases (27%) had one or more likely pathogenic or pathogenic (LP/P) germline variants, which is higher than previous reports. Among these 50, 28 (56%) met guidelines for germline testing by personal or family history criteria, 10 (20%) met recently established NCCN criteria for germline testing of patients with BRCA1/2 tumor variants, and 12 (24%) had TMP results that suggested a germline mutation but did not meet any guidelines for germline testing. We identified 52 LP/P germline variants in BRCA2 (17), BRCA1 (7), PALB2 (6), MUTYH (5), CHEK2 (2), and 15 other genes, all with established guidelines that would impact the clinical management of patients and their family members. In 9/50 cases, germline testing revealed variants that were absent in TMP results and provided new information with clinical implications for patients and their families, including variants in BRCA1 and CHEK2. Conclusions: In TMP patients, 50 of 182 had a medically actionable germline mutation with established management guidelines. Among these 50, 12 (24%) met neither current personal or family criteria nor the latest NCCN guidelines for germline testing in patients with TMP. Also striking were nine patients whose germline LP/P mutations were absent in TMP results. These data suggest that indications for germline testing of cancer patients must be expanded to avoid missing important germline findings in patients undergoing TMP.
The gene mutated in Bloom's syndrome, BLM, is important in the repair of damaged replication forks, and it has both pro- and anti-recombinogenic roles in homologous recombination (HR). At damaged ...forks, BLM interacts with RAD51 recombinase, the essential enzyme in HR that catalyzes homology-dependent strand invasion. We have previously shown that defects in BLM modification by the small ubiquitin-related modifier (SUMO) cause increased γ-H2AX foci. Because the increased γ-H2AX could result from defective repair of spontaneous DNA damage, we hypothesized that SUMO modification regulates BLM's function in HR repair at damaged forks. To test this hypothesis, we treated cells that stably expressed a normal BLM (BLM+) or a SUMO-mutant BLM (SM-BLM) with hydroxyurea (HU) and examined the effects of stalled replication forks on RAD51 and its DNA repair functions. HU treatment generated excess γ-H2AX in SM-BLM compared to BLM+ cells, consistent with a defect in replication-fork repair. SM-BLM cells accumulated increased numbers of DNA breaks and were hypersensitive to DNA damage. Importantly, HU treatment failed to induce sister-chromatid exchanges in SM-BLM cells compared to BLM+ cells, indicating a specific defect in HR repair and suggesting that RAD51 function could be compromised. Consistent with this hypothesis, RAD51 localization to HU-induced repair foci was impaired in SM-BLM cells. These data suggested that RAD51 might interact noncovalently with SUMO. We found that in vitro RAD51 interacts noncovalently with SUMO and that it interacts more efficiently with SUMO-modified BLM compared to unmodified BLM. These data suggest that SUMOylation controls the switch between BLM's pro- and anti-recombinogenic roles in HR. In the absence of BLM SUMOylation, BLM perturbs RAD51 localization at damaged replication forks and inhibits fork repair by HR. Conversely, BLM SUMOylation relieves its inhibitory effects on HR, and it promotes RAD51 function.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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