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PubMed2026

Two cases of mosaic germline SVA insertions in SMARCB1: implications for rhabdoid tumour predisposition diagnosis.

Rhabdoid tumour predisposition syndrome (RTPS) is a highly penetrant cancer predisposition syndrome caused by germline variants in SMARCB1 or less frequently in SMARCA4. Genetic testing for this syndrome involves sequence and deletion/duplication analysis of these two genes. Standard clinical testing is limited in detecting structural variants. Here we describe two patients who tested negative on standard clinical germline panel testing for RTPS but were each found to have a mosaic germline insertion of an SVA (SINE-VNTR-Alu) element in the SMARCB1 gene by more advanced comprehensive genomic analysis. These two cases demonstrate the importance of structural variants and broader genomic sequencing for individuals suspected of having an underlying germline cancer predisposition syndrome, such as RTPS.

Journal Article↗

PubMed2026

Bilateral Conversion Risk in Unilateral Retinoblastoma Using Age and Genetic Testing.

IMPORTANCE: Metachronous bilateral conversion in initially unilateral retinoblastoma is uncommon but clinically consequential, potentially requiring intensified treatment and carrying worse prognosis. Clarifying how age at diagnosis refines genetic-risk stratification could enable safer, more efficient surveillance protocols. OBJECTIVE: To estimate the incidence and timing of metachronous bilateral conversion in unilateral retinoblastoma and assess whether age at diagnosis and RB1 testing are associated with bilateral conversion risk. DESIGN, SETTING AND PARTICIPANTS: This was a retrospective cohort study at a tertiary center in Shanghai, China, including 1108 consecutive children with initially unilateral retinoblastoma diagnosed from July 2010 to October 2024 (after exclusions for short follow-up [n = 139], missing data [n = 53], or synchronous bilateral disease [n = 10]). The median (IQR) follow-up was 43.4 (24.2-67.6) months. EXPOSURES: Age at diagnosis and RB1 genetic status/subtypes assessed by next-generation sequencing and multiplex ligation-dependent probe amplification, including penetrance class (high vs low) and mosaic vs germline categorization. MAIN OUTCOMES AND MEASURES: Time to metachronous bilateral conversion; cumulative incidence functions with death as a competing risk; spatial distribution of fellow-eye tumors. RESULTS: Among 1108 patients (median [IQR] age at diagnosis, 22.2 [12.0-31.4] months; 591 [53.3%] male), 24 (2.2%) developed metachronous bilateral disease. At 24 months, cumulative incidence was 2.2% (95% CI, 1.3-3.1) overall. By genetic status, the 24-month cumulative incidence was 24.8% (95% CI, 13.8-35.9) in RB1 variant-positive vs 1.6% (95% CI, 0.0-3.1) in RB1 variant-negative patients. Among RB1 variant-positive patients, risk clustered among those diagnosed before 9 months, whereas no conversions were observed among those diagnosed at older than 9 months. Four RB1 variant-negative patients who were initially diagnosed at notably late ages (20.9, 42.7, 79.6, and 118 months) subsequently converted; these cases likely represent undetected low-level mosaicism, somatic variants below detection thresholds, or rare genomic events not captured by standard sequencing panels. Fellow-eye tumors did not involve macula and showed a nasal-predominant distribution. CONCLUSIONS AND RELEVANCE: The findings in this study suggest that age at diagnosis may refine genetic risk stratification for metachronous bilateral conversion. RB1 variant-positive patients diagnosed at 9 months or later represent a very low-risk subgroup that may warrant surveillance deescalation, while rare late conversions in RB1 variant-negative patients necessitate continued long-term monitoring.

Humans↗

PubMed2026

Molecular clusters and precision medicine in pheochromocytomas and paragangliomas.

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from chromaffin cells of the adrenal medulla and extra-adrenal paraganglia. Over the past two decades, the genomic characterization of PPGLs has profoundly transformed their diagnosis, classification, risk stratification, and therapeutic management. Up to 40% of PPGLs harbor germline pathogenic variants, the highest proportion among human neoplasms, and somatic driver events are identified in a substantial fraction of the remaining cases. Integrative multi-omic studies have established three main molecular clusters: a pseudohypoxic cluster driven by Krebs-cycle alterations (SDHx, FH, MDH2, DLST) and HIF-2α pathway alterations (VHL, EPAS1, EGLN1/2); a kinase-signaling cluster driven by activation of RAS/MAPK and PI3K/AKT pathways (RET, NF1, HRAS, TMEM127, MAX); and a Wnt-signaling cluster characterized primarily by MAML3 fusions. This review summarizes progress in PPGL genomics, highlighting geographic and sex-related particularities. Using EPAS1/HIF-2α and RET as paradigmatic examples, we illustrate how diverse germline, somatic, mosaic, and fusion events converge on common core signaling hubs that can be therapeutically exploited with FDA-approved selective inhibitors for relevant targets (e.g. belzutifan for HIF-2α; selpercatinib and pralsetinib for RET). We further review the genomic determinants of metastatic risk (SDHB, ATRX, TERT, and MAML3 fusions), the immune microenvironment of metastatic disease, and emerging radionuclide theranostics, liquid biopsy biomarkers, and integrative multi-omic approaches that are reshaping precision medicine for PPGLs.

Humans↗

PubMed2026

Integrating germline and tumor sequencing to improve hereditary cancer diagnosis and care.

A subset of cancers arises due to inherited germline pathogenic variants in specific genes, known as hereditary cancers. These genes typically include tumor suppressors, DNA repair and replication fidelity genes, and occasionally oncogenes. In most hereditary cancer syndromes, Knudson's two-hit hypothesis applies, where a second somatic event inactivates the remaining allele of a tumor suppressor or DNA repair gene, leading to tumorigenesis. Advancements in genome-wide sequencing have significantly enhanced our understanding of the mutational processes involved in hereditary cancers. In particular, the assessment of microsatellite instability (MSI), tumor mutational burden (TMB), and mutational signatures has emerged as a powerful tool for the identification of hereditary tumors. Tumors with high or ultra-high TMB often reflect underlying DNA repair deficiencies, while specific mutational signatures can pinpoint the defective pathway. These tumor mutational features are especially informative in syndromes involving mismatch repair (MMR), homologous recombination (HR), base excision repair (BER), nucleotide excision repair (NER), and polymerase proofreading. Moreover, tumor sequencing aids in the interpretation of germline variants, identifies somatic mosaicism, and helps differentiate hereditary from sporadic cancers. Additionally, tumor molecular features associated with DNA repair deficiencies offer insights into personalized therapies, such as the use of PARP inhibitors for BRCA1/2-deficient tumors and immune checkpoint inhibitors for MMR- and polymerase proofreading-deficient cancers. Tumor profiling also uncovers actionable mutations in oncogenes like RET and VHL, which can be targeted with specific therapies. This review explores the integration of tumor molecular features with germline genetic data to refine diagnosis, risk assessment, and therapeutic strategies in hereditary cancer.

Humans↗

PubMed2025

Detection and Characterization of RB1 Mosaicism in Patients With Retinoblastoma Receiving cfDNA Test.

IMPORTANCE: Plasma cell-free DNA (cfDNA) testing is increasingly used for disease diagnosis and monitoring in retinoblastoma, with RB1 allele fraction in cfDNA actively corresponding to disease status and treatment response. However, while RB1 mosaicism has been reported in retinoblastoma, its clinical implications and potential impact on cfDNA testing remain unclear. OBJECTIVES: To identify RB1 mosaicism using paired plasma and buffy coat (containing lymphocytes, monocytes, granulocytes, and platelets) DNA testing, and to characterize the implications of RB1 mosaicism on cfDNA testing outcomes. DESIGN, SETTING, AND PARTICIPANTS: In this cross-sectional study, participants with retinoblastoma underwent testing with MSK-ACCESS (Memorial Sloan Kettering-Analysis of Circulating cfDNA to Examine Somatic Status), a clinical assay that combines plasma cfDNA and buffy coat genomic DNA sequencing, enabling the detection and differentiation of somatic, heterozygous, and mosaic variants, between July 2020 and April 2024 at the Memorial Sloan Kettering Cancer Center. Mosaic findings from MSK-ACCESS were correlated with those from a subgroup of patients who concurrently underwent testing using the MSK-IMPACT germline assay. Data analysis was performed from April to September 2024. EXPOSURE: RB1 mosaicism in retinoblastoma. MAIN OUTCOMES AND MEASURES: The RB1 variant allele fractions in cfDNA and buffy coat genomic DNA were used to detect RB1 mosaicism. RESULTS: A total of 136 consecutive patients with retinoblastoma (median age at diagnosis, 1.0 year [IQR, 0.4-1.7 years]; 74 [54.4%] female; 67 with bilateral disease and 69 with unilateral disease) who underwent testing with the MSK-ACCESS assay were included. RB1 mosaicism was identified in buffy coat DNA from 20 patients (14.7%), with consistent results detected in all 11 participants tested concurrently by the MSK-IMPACT (Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets) germline assay. Four participants with RB1 mosaicism previously tested negative for germline RB1 variants by external laboratories. Compared with heterozygous participants, participants with RB1 mosaicism had a lower risk of developing bilateral disease (91.7% vs 55.0%, respectively; difference, 36.7% [95% CI, 13.8%-59.6%]; P = .002). In cfDNA, the mosaicism variant was detected both before and after treatment, with variant allele fraction initially decreasing after treatment but then stabilizing at levels consistent with mosaicism, despite the absence of clinical disease. CONCLUSIONS AND RELEVANCE: The accurate detection and quantification of RB1 mosaicism are crucial. RB1 mosaicism should be considered when RB1 variants persist in cfDNA after treatment without evidence of disease; failure to do so may lead to false-positive results and overtreatment in patients with RB1 mosaicism. Identifying RB1 mosaicism may improve patient counseling, inform treatment decisions, and enhance surveillance efforts.

Humans↗

PubMed2026

Improving long-read somatic structural variant calling with pangenome and de novo personal genome assembly.

Accurate detection of mosaic and somatic structural variants (SVs) provides early diagnostic and therapeutic evidence for cancers. While long-read whole-genome sequencing leads to more accurate SV detection than short read sequencing, existing long-read SV callers only look at alignment against a single reference genome and are susceptible to systematic false discovery caused by germline differences between the individual genome and the reference genome. Here we develop a new SV filtering method that jointly considers the alignment against a pangenome and the de novo assembly of the germline genome. It dramatically reduces false positive mosaic and somatic SVs in cancer cell lines with little loss in sensitivity for existing long read SV callers. Our study highlights the essential need for pangenome or personal genome assembly to integrate SV calls for both SV discoveries and clinical diagnostics.

Journal Article↗

PubMed2026

Evaluation of germline transmission of electroporation-mediated double gene-edited cattle lines.

Gene editing in livestock using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) offers a promising approach for genetic improvement in cattle. This study evaluated germline transmission and mutation stability of double-knockout cattle generated by zygote electroporation. Previously reported myostatin/beta-lactoglobulin (MSTN/BLG) and newly generated α-1,3-galactosyltransferase (GGTA1/BLG) double-knockout cattle were produced using CRISPR/Cas9-mediated genome editing. Targeted deep sequencing demonstrated extensive somatic mosaicism across multiple tissues. Computer-assisted sperm analysis (CASA) demonstrated normal sperm motility in MSTN/BLG double-knockout males. Fertilization of wild-type oocytes produced heterozygous embryos, with mutation frequencies of 37.76 ± 10.74% at the MSTN locus and 54.80 ± 7.73% at the BLG locus, as assessed by T7 endonuclease I (T7E1) assay. MSTN/BLG double-knockout sperm were subsequently used for embryo production and for artificial insemination of GGTA1/BLG double-knockout females. Healthy offspring were successfully obtained (n = 3), alongside one stillborn calf. Targeted deep sequencing of all four progenies revealed highly variable allele frequencies that deviated substantially from the approximately 50% expected for heterozygous germline transmission. In contrast, whole-genome sequencing (WGS) results were consistent with Mendelian expectations, underscoring the limitations of PCR-based targeted sequencing for assessing germline transmission in mosaic founders. These results show that CRISPR/Cas9-edited embryos generated by electroporation can develop into healthy, sexually mature cattle capable of germline transmission. While variable transmission rates were observed owing to founder mosaicism, non-mosaic F1 offspring were successfully generated. However, direct, embryo-mediated gene-editing strategies remain technically and economically challenging for large-scale commercial calf production, and reports in cattle are limited. This study provides a reference for future applications of gene-edited embryos and their germline propagation.

Animals↗

PubMed2026

Mutation timing, accumulation, and selection in the male germline shape inheritance risk for developmental disorders.

De novo mutations (DNMs) in the paternal germline are a major cause of developmental disorders, but how mutation timing, paternal age, and spermatogonial selection jointly shape transmissible risk within individual fathers is unclear. We combined trio whole-genome sequencing from 167 families with deep targeted NanoSeq profiling of sperm from 127 fathers of children with confirmed pathogenic DNMs. Transmitted DNM burden and paternal sperm mutation burden, spectra, and selection landscape were indistinguishable from population reference cohorts. Six fathers carried pathogenic early mosaic variants detectable in sperm at variant allele fractions (VAFs) of 0.7%-14.8%, creating individual recurrence-risk outliers. However, early mosaics accounted for ∼8% of the cohort-aggregated pathogenic burden exome-wide, compared with ∼18% from known positively selected drivers and ∼74% from other rare variants accumulating with paternal age. Thus, paternal de novo disease risk is shaped primarily by universal age-associated mutation and selection, while early mosaicism creates uncommon but clinically important high-risk individuals.

DNMs↗

PubMed2025

Novel Insights into the Clinical Features, Genetic Spectrum and Clonal Evolution of Patients Carrying NLRP3 Mosaicism.

NLRP3 mosaicism is a well-established mechanism causing the monogenic autoinflammatory disease named cryopyrin-associated periodic syndromes (CAPS). The number of reported patients with NLRP3 mosaicism is small, and the knowledge about the long-term disease behavior is limited. Herein we assembled the largest cohort of individuals with NLRP3 mosaicism reported to date to obtain additional evidence that strengthens the understanding of this disease. The novel genetic data were obtained by using Sanger and next-generation sequencing methods, whereas in vitro analyses determined the functional consequences of detected variants. A total of seventeen individuals with NLRP3 mosaicism were enrolled, with 16/17 experiencing different CAPS phenotypes. An overrepresentation of late-onset forms was detected (37.5%). Overall, clinical manifestations, analytical results, and outcomes of treatments were markedly similar to those detected in patients with germline variants. A large mutational diversity was identified, with 16 different variants among 17 individuals. Two main patterns of mosaicism (extended vs. myeloid-restricted) were detected, with the last one overrepresented in the late-onset group. The evaluation of mosaicism over time identified three different patterns, being the group with stable mosaicism the largest one. Collected evidence supports the marked similarities among patients carrying somatic or germline NLRP3 variants. The overrepresentation of NLRP3 mosaicism in late-onset forms should be considered in patients with inflammatory manifestations starting in adulthood. Analysis of mosaicism at the biological level confirms the two known patterns of corporal distribution and reveals that mosaicism remains stable over time in most patients, but it may also vary during the course of the disease.

Humans↗

PubMed2026

Clinical Variant Interpretation with the Integrative Genomics Viewer (IGV) for Molecular Pathologists.

The integrative genomics viewer (IGV) is a pivotal tool in clinical genomics, enabling the visualization and interpretation of complex sequencing data. Bringing clinical knowledge to bear with visual evaluation of sequencing results is the primary means by which molecular pathologists and other professionals assess and finalize cases. A variety of software tools can assist, but their relationship to the underlying data must be understood and applied systematically. This study includes essential background on next-generation sequencing (NGS) data file types (e.g., FASTQ, BAM, VCF) with a discussion of their format and purpose. We then describe features of IGV that derive nuances from these files. We utilize a series of curated practical cases based on clinical vignettes through which the reader will interact with clinical NGS sequencing data using the IGV software to review various types of clinically relevant variants relative to the human reference genome. These clinical vignettes have been curated to describe examples of some of the complexities of interpretation of genomic data, and how utilizing IGV as part of a routine workflow can provide additional interpretive information for variants beyond routine bioinformatic software algorithm variant calls. The visual inspection of genomic variants utilizing the tools within IGV can unmask subtle contextual cues (i.e., variant allele frequency, strand bias, tissue-specific context) that can influence the interpretation of genomic variants. Although this study focuses on using IGV for the detection and interpretation of somatic variants, the provided applications can be extrapolated for use in the germline setting, including analysis of complex variants and detection of mosaicism.

Humans↗

PubMed2025

History and clinical epidemiology of NF2-related schwannomatosis.

NF2-related schwanomatosis (NF2-SWN) (previously Neurofibromatosis 2) as characterised by bilateral vestibular schwannomas (VS) was first described in 1822. However, due to the erroneous conflation of individuals with bilateral eighth nerve tumours with von Recklinghausen disease (currently Neurofibromatosis 1, NF1) in 1917 the literature was confusing for much of the 20th century. Even when the conditions were separated officially in 1987 (with separate localisation of the genes), NF2-SWN remained classified as a neurofibromatosis despite the tumours pathognomonic for NF1, neurofibromas, not being a feature of NF2-schwannomatosis. It is only in 2022 that NF2-SWN was correctly delineated as a schwannomatosis. The epidemiology of NF2-SWN has only been possible to delineate after the separation of NF2-SWN from the much more frequent nerve sheath predisposing tumour condition NF1. Two research groups have published on the birth prevalence and population prevalence of NF2-SWN in the UK and Finland. The most highly ascertained assessment of NF2-SWN cases from the Manchester region of England (population 4.8 million) gave a diagnostic prevalence of 1 in 50,500 and calculated birth prevalences of 1 in 27,956 respectively. However, an updated prevalence across England in 2024 (population 55 million) gave a prevalence of at least 1 in 58,000. NF2-SWN usually presents with bilateral vestibular schwannoma, but can present with meningioma or spinal tumour or ophthalmic features before a VS diagnosis or with a unilateral VS and other tumours and rarely with a unilateral VS alone. Molecular testing is now extremely helpful in confirming the diagnosis of mosaic (present in up to 50% of de novo cases) versus germline NF2 and distinguishing from other tumour predisposition conditions especially in childhood or cases with less common presentation. This chapter summarises the clinical epidemiology of NF2-SWN differentiating the condition from the overlapping non NF2-SWN.

Humans↗

PubMed2026

Mechanism of age-related accumulation of mtDNA mutations in human blood.

Accumulation of mutant mitochondrial DNA (mtDNA) heteroplasmy is among the strongest signatures of ageing1. Here we investigated the underlying mechanism by calling mtDNA sequence, mtDNA abundance and mtDNA heteroplasmic variants in human blood using whole-genome sequences from approximately 750,000 individuals. We observed that mtDNA single-nucleotide variants (mtSNVs) accumulate sharply at age 60 years, occur at low levels of heteroplasmy, exhibit little evidence of positive selection and are likely to be predominantly neutral. The mutational spectrum of mtSNVs does not reflect oxidative lesions, as is commonly invoked, but is more consistent with mtDNA replication errors. To understand why mtSNVs become detectable with age, we performed a genome-wide association study for heteroplasmic mtSNV burden, identifying germline variants near TERT, TCL1A and SMC4, all of which have been linked to clonal haematopoiesis (CH)2. Rare-variant analysis also showed that high mtSNV burden is associated with mutations in numerous CH driver genes. These genetic associations persisted even after exclusion of individuals with known CH driver mutations. Our results support a model in which 'cryptic' mtDNA mutations initially arise randomly as replication errors but are undetectable in bulk. They then become apparent only through age-related expansion of cellular clones in blood. We propose that the high copy number and mutation rate of mtDNA make it a sensitive blood-based marker of somatic mosaicism due to CH. Our work mechanistically unifies three prominent signatures of ageing: common germline variants in TERT, CH and observed accrual of mtDNA mutations.

Humans↗

PubMed2026

Costello Syndrome Associated With Somatic Mosaicism of Rare p.Gly13Asp HRAS Variant: Expanding the Phenotypic Spectrum.

BACKGROUND: Costello syndrome (CS) is a rare RASopathy, mostly caused by de novo heterozygous pathogenic variants in the HRAS gene. Over 80% of cases involve the germline p.Gly12Ser variant, resulting in a fairly uniform phenotype of neuro-cardio-facio-cutaneous involvement with an increased risk of malignancy. Consequences of other rare HRAS variants are less well understood due to the limited number of reported cases. METHODS: An adult, young woman was referred due to sparse, slow-growing scalp hair, Blaschko-linear hyperpigmentation, acanthosis nigricans, palmoplantar hyperkeratosis, and joint hyperlaxity. Molecular, imaging, and detailed laboratory studies were performed. RESULTS: Although initial clinical exome- and whole-exome sequencing (WES) were inconclusive, indicating possible mosaicism, subsequent WES from hair-derived DNA samples revealed somatic mosaicism for the rare HRAS p.Gly13Asp variant. Brain MRIs showed a cerebral cavernoma, while cardiological evaluation, urinalysis, abdominal, and pelvic ultrasound were unremarkable. Nevertheless, she remains under close follow-up. CONCLUSION: Among the ten reported individuals carrying the p.Gly13Asp variant, our patient is only the second with confirmed mosaicism and the fifth mosaic CS case described to date. This case expands the phenotypic spectrum of CS and highlights the need for multi-tissue analysis in attenuated or atypical presentations to ensure a correct diagnosis, oncological risk assessment, and informed genetic and reproductive counseling.

Humans↗

PubMed2026

Somatic mosaicism in the brain: linking development, ageing and neurodegeneration.

Somatic mosaicism is increasingly recognized as a pervasive feature of the human brain and a potential contributor to neurological disease across the lifespan. Unlike germline variants, somatic variants arise post-zygotically and are unevenly distributed across regions, cell types and even individual neurons, enabling focal biological effects that can scale to network-level dysfunction. In this Review, we synthesize current evidence that developmental timing, clonal architecture and cell-type-specific selective pressures shape how somatic variants influence brain structure and function. Early embryonic variants can produce broad regional clones and severe phenotypes, whereas later events are usually more restricted; with ageing, ongoing DNA damage and imperfect repair generate private variants that might cumulatively reduce cellular resilience. We also summarize advances in detection approaches, including bulk, error-corrected and single-cell sequencing, and discuss their strengths and current limitations for clinical translation. Emerging data link brain somatic variants to neurodevelopmental and neurodegenerative phenotypes, supporting a unified framework in which mosaic genetics bridges focal lesions and distributed neurological syndromes. Integrating genomic, cellular and physiological analyses in longitudinal human studies will be essential to define causality, identify biomarkers and guide future targeted interventions.

Journal Article↗

PubMed2025

Heritable virus-induced germline editing in tomato.

Here, we report the successful implementation of heritable virus-induced genome editing (VIGE) in tomato (Solanum lycopersicum). We generated three transgenic tomato lines expressing Streptococcus pyogenes Cas9 (SpCas9) under the control of Cauliflower mosaic virus 35S (35S), S. lycopersicum ribosomal protein S5A (SlRPS5A), or S. lycopersicum YAO promoters (SlYAO). These three lines were tested for somatic and heritable editing using the tobacco rattle virus (TRV)-based system carrying guide RNAs (gRNAs) fused with mobile RNA sequences. TRV with gRNA targeted to Phytoene desaturase (SlPDS) and Downy mildew resistance 6 (SlDMR6) genes fused to mobile RNA sequences showed significant somatic editing efficiency in all three tomato lines expressing SpCas9. However, the progenies from the SlYAO promoter-driven SpCas9 tomato infected with TRV with gRNA targeted to SlDMR6 fused to the mobile RNA sequence resulted in monoallelic mutations with a frequency of 3%. Optimization of environmental conditions, such as reduced light intensity, significantly increased heritable editing frequencies, from 0% to 86% at the SlPDS and from 3% to 100% at the SlDMR6, including biallelic mutations. These findings underscore the use of appropriate promoters to express Cas nucleases and optimized environmental conditions to enhance heritable genome editing efficiency in tomato using VIGE. Furthermore, our method enables the generation of mutants without additional tissue culture or transformation once a SpCas9-expressing tomato line is established.

Solanum lycopersicum↗

PubMed2025

A personalized multi-platform assessment of somatic mosaicism in the human frontal cortex.

Somatic mutations in individual cells create genomic mosaicism, influencing genetic disorders and cancers. While clonal mutations in cancers are well-studied, rarer somatic variants in normal tissues remain poorly characterized. This study systematically evaluates detection methods using a personalized donor-specific assembly (DSA) from a neurotypical individual's dorsolateral prefrontal cortex assessed with Oxford Nanopore, NovaSeq, linked-read sequencing, Cas9-targeted long-read sequencing (TEnCATS), and single-neuron MALBAC amplification. The haplotype-resolved DSA improved cross-platform analysis, dramatically increasing phasing rates. Germline SNVs, structural variations (SVs), and transposable elements (TEs) were recalled with 99.4%-99.7% accuracy in bulk tissue, and phased haplotype analysis reduced false positives by 15.4%-75.1% for putative somatic candidates. Long-read single-neuron sequencing detected nine somatic SV candidates, demonstrating enhanced sensitivity for rare variants, while TEnCATS identified eight low-frequency somatic TE candidates. These findings highlight advanced methodologies for precise somatic variant detection, critical for understanding mosaicism's role in health and disease.

Multi-platform Sequencing↗

PubMed2024

The Genetic Determinants and Genomic Consequences of Non-Leukemogenic Somatic Point Mutations.

Clonal hematopoiesis (CH) is defined by the expansion of a lineage of genetically identical cells in blood. Genetic lesions that confer a fitness advantage, such as point mutations or mosaic chromosomal alterations (mCAs) in genes associated with hematologic malignancy, are frequent mediators of CH. However, recent analyses of both single cell-derived colonies of hematopoietic cells and population sequencing cohorts have revealed CH frequently occurs in the absence of known driver genetic lesions. To characterize CH without known driver genetic lesions, we used 51,399 deeply sequenced whole genomes from the NHLBI TOPMed sequencing initiative to perform simultaneous germline and somatic mutation analyses among individuals without leukemogenic point mutations (LPM), which we term CH-LPMneg. We quantified CH by estimating the total mutation burden. Because estimating somatic mutation burden without a paired-tissue sample is challenging, we developed a novel statistical method, the Genomic and Epigenomic informed Mutation (GEM) rate, that uses external genomic and epigenomic data sources to distinguish artifactual signals from true somatic mutations. We performed a genome-wide association study of GEM to discover the germline determinants of CH-LPMneg. After fine-mapping and variant-to-gene analyses, we identified seven genes associated with CH-LPMneg (TCL1A, TERT, SMC4, NRIP1, PRDM16, MSRA, SCARB1), and one locus associated with a sex-associated mutation pathway (SRGAP2C). We performed a secondary analysis excluding individuals with mCAs, finding that the genetic architecture was largely unaffected by their inclusion. Functional analyses of SMC4 and NRIP1 implicated altered HSC self-renewal and proliferation as the primary mediator of mutation burden in blood. We then performed comprehensive multi-tissue transcriptomic analyses, finding that the expression levels of 404 genes are associated with GEM. Finally, we performed phenotypic association meta-analyses across four cohorts, finding that GEM is associated with increased white blood cell count and increased risk for incident peripheral artery disease, but is not significantly associated with incident stroke or coronary disease events. Overall, we develop GEM for quantifying mutation burden from WGS without a paired-tissue sample and use GEM to discover the genetic, genomic, and phenotypic correlates of CH-LPMneg.

Journal Article↗

PubMed2026

Deep tissue sequencing improves genetic diagnostic yield in focal cortical dysplasia.

Focal cortical dysplasias (FCDs) are malformations of cortical development associated with drug-resistant focal epilepsy. We analyzed surgical tissue from 25 consecutive cases recruited from adult and pediatric epilepsy surgery programs. We performed high-depth sequencing of lesional tissue, validated somatic variants using droplet digital PCR or amplicon sequencing, and investigated genotype-phenotype correlations. A pathogenic or likely pathogenic variant was detected in 64% (n = 16/25) of cases. Of these, five cases with FCDIIa or FCDIIb had germline variants in NPRL3 (n = 3) or DEPDC5 (n = 2). Somatic variants were identified in 44% (n = 11/25) of cases. The genetic yield for FCDIIb was 77% of cases having a pathogenic mTOR pathway variant detected (n = 10/13), and for FCDIIa 66% (n = 6/9). High depth sequencing approaches allowed detection of somatic variants with very low (down to 0.4%) variant allele fractions (VAFs). No pathogenic variants were detected in 3 cases with FCDI. 62% (n = 15/24) of the cases with ≥12 months follow up experienced a favourable seizure outcome (Engel 1-2) following surgery. Of note, n = 9 patients required repeat surgery to resect residual dysplasia. Determining a genetic diagnosis reveals aetiology and paves the way to precision therapies that may benefit those with FCD who do not respond to current treatments.

Humans↗