Diagnostic genome sequencing improves diagnostic yield: a prospective single-centre study in 1000 patients with inherited eye diseases.

PURPOSE: Genome sequencing (GS) is expected to reduce the diagnostic gap in rare disease genetics. We aimed to evaluate a scalable framework for genome-based analyses 'beyond the exome' in regular care of patients with inherited retinal degeneration (IRD) or inherited optic neuropathy (ION). METHODS: PCR-free short-read GS was performed on 1000 consecutive probands with IRD/ION in routine diagnostics. Complementary whole-blood RNA-sequencing (RNA-seq) was done in a subset of 74 patients. An open-source bioinformatics analysis pipeline was optimised for structural variant (SV) calling and combined RNA/DNA variation interpretation. RESULTS: A definite genetic diagnosis was established in 57.4% of cases. For another 16.7%, variants of uncertain significance were identified in known IRD/ION genes, while the underlying genetic cause remained unresolved in 25.9%. SVs or alterations in non-coding genomic regions made up for 12.7% of the observed variants. The RNA-seq studies supported the classification of two unclear variants. CONCLUSION: GS is feasible in clinical practice and reliably identifies causal variants in a substantial proportion of individuals. GS extends the diagnostic yield to rare non-coding variants and enables precise determination of SVs. The added diagnostic value of RNA-seq is limited by low expression levels of the major IRD disease genes in blood.

Recommendations for laboratory workflow that better support centralised amalgamation of genomic variant data: findings from CanVIG-UK national molecular laboratory survey.

BACKGROUND: National and international amalgamation of genomic data offers opportunity for research and audit, including analyses enabling improved classification of variants of uncertain significance. Review of individual-level data from National Health Service (NHS) testing of cancer susceptibility genes (2002-2023) submitted to the National Disease Registration Service revealed heterogeneity across participating laboratories regarding (1) the structure, quality and completeness of submitted data, and (2) the ease with which that data could be assembled locally for submission. METHODS: In May 2023, we undertook a closed online survey of 51 clinical scientists who provided consensus responses representing all 17 of 17 NHS molecular genetic laboratories in England and Wales which undertake NHS diagnostic analyses of cancer susceptibility genes. The survey included 18 questions relating to 'next-generation sequencing workflow' (11), 'variant classification' (3) and 'phenotypical context' (4). RESULTS: Widely differing processes were reported for transfer of variant data into their local LIMS (Laboratory Information Management System), for the formatting in which the variants are stored in the LIMS and which classes of variants are retained in the local LIMS. Differing local provisions and workflow for variant classifications were also reported, including the resources provided and the mechanisms by which classifications are stored. CONCLUSION: The survey responses illustrate heterogeneous laboratory workflow for preparation of genomic variant data from local LIMS for centralised submission. Workflow is often labour-intensive and inefficient, involving multiple manual steps which introduce opportunities for error. These survey findings and adoption of the concomitant recommendations may support improvement in laboratory dataflows, better facilitating submission of data for central amalgamation.

Validation of an automated, end-to-end metagenomic sequencing assay for agnostic detection of respiratory viruses.

BACKGROUND: Current molecular diagnostics are limited in the number and type of detectable pathogens. Metagenomic next generation sequencing (mNGS) is an emerging, and increasingly feasible, pathogen-agnostic diagnostic approach. Translational barriers prohibit the widespread adoption of this technology in clinical laboratories. We validate an end-to-end mNGS assay for detection of respiratory viruses. Our assay is optimized to reduce turnaround time, lower cost-per-sample, increase throughput, and deploy secure and actionable bioinformatic results. METHODS: We validated our assay using residual nasopharyngeal swab specimens from Vancouver General Hospital (n = 359), RT-PCR-positive, or negative for Influenza, SARS-CoV-2, and RSV. We quantified sample stability, assay precision, the effect of background nucleic acid levels, and analytical limits of detection. Diagnostic performance metrics were estimated. RESULTS: We report that our mNGS assay is highly precise, semi-quantitative, with analytical limits of detection ranging from 103-104 copies/mL. Our assay is highly specific (100%) and sensitive (61.9% Overall: 86.8%; RT-PCR Ct < 30). Multiplexing capabilities enable processing of up to 55-specimens simultaneously on an Oxford Nanopore GridION device, with results reported within 12-hours. CONCLUSIONS: This study outlines the diagnostic performance and feasibility of mNGS for respiratory viral diagnostics, infection control, and public health surveillance. We addressed translational barriers to widespread mNGS adoption.

Glioblastoma Tumor Microenvironment: An Important Modulator for Tumoral Progression and Therapy Resistance.

The race to find an effective treatment for glioblastoma (GBM) remains a critical topic, because of its high aggressivity and impact on survival and the quality of life. Currently, due to GBM's high heterogeneity, the conventional treatment success rate and response to therapy are relatively low, with a median survival rate of less than 20 months. A new point of view can be provided by the comprehension of the tumor microenvironment (TME) in pursuance of the development of new therapeutic strategies to aim for a longer survival rate with an improved quality of life and longer disease-free interval (DFI). The main components of the GBM TME are represented by the extracellular matrix (ECM), glioma cells and glioma stem cells (GSCs), immune cells (microglia, macrophages, neutrophils, lymphocytes), neuronal cells, all of them having dynamic interactions and being able to influence the tumoral growth, progression, and drug resistance thus being a potential therapeutic target. This paper will review the latest research on the GBM TME and the potential therapeutic targets to form an up-to-date strategy.

Multigeographic clinical assessment of a molecular diagnostic assay for detection of key codons to predict decreased susceptibility or resistance to cephalosporins in Neisseria gonorrhoeae.

Cephalosporin resistance in Neisseria gonorrhoeae has severely compromised the efficacy of World Health Organization (WHO)-recommended therapies. This study aimed to methodologically evaluate the optimized Six-CodonPlus assay, and additionally conducted a multicenter evaluation to assess its clinical application, especially for predicting antimicrobial resistance (AMR). For methodological evaluation, 397 sequence-known N. gonorrhoeae isolates were evaluated for specificity, 17 nongonococcal isolates were assessed for cross-reactivity, 159 uncultured urogenital swabs and urine samples were evaluated for sensitivity at the clinical level. For multicenter evaluation, 773 isolates with confirmed phenotypic data and 718 clinical urogenital swabs collected from four geographical cities were, respectively, utilized for the evaluation of AMR-prediction strategies and the clinical application of the assay. The assay accurately identified specific single-nucleotide polymorphisms in resistance-associated genes, the detection limits dropped to 10 copies/reaction for individual targets. The specificity reached 100% and no cross-reactivity occurred with double-target confirmation. The assay could be directly applied to clinical samples containing over 20 copies/reaction. Multicenter evaluation formulated two optimal strategies for decreased susceptibility prediction in specific scenarios, and one tactic for prediction of resistance and identification of FC428-like strains. High sensitivity of 86.84% (95% CI, 71.11-95.05) and specificity of 99.59% (95% CI, 98.71-99.89) for resistance prediction were demonstrated for ceftriaxone (CRO). Regarding N. gonorrhoeae identification among multicenter swabs, specificity reached 97.53% (95% CI, 95.49-98.69), and sensitivity reached 93.77% (95% CI, 90.04-96.22). The Six-CodonPlus assay exhibited excellent detection performance and formulated optimal AMR-related prediction strategy with regional adaptability, providing critical information for population screening and clinical treatment.

KRAS mutations detection methodology: from RFLP to CRISPR/Cas based methods.

In personalized cancer medicine, the identification of KRAS mutations is essential for making treatment decisions and improving patient outcomes. This work presents a comprehensive review of the current approaches for detection of KRAS mutations in different cancers. We highlight the value of fast and reliable KRAS mutations discovery and the effectiveness of molecular testing for selecting individuals who might benefit from targeted therapy. We provide an overview of various methods and tools available for detecting KRAS mutations, such as digital droplet PCR, next-generation sequencing (NGS), and polymerase chain reaction (PCR). We also address the difficulties and limitations in the identification of KRAS mutations, namely tumor heterogeneity and the emergence of resistance mechanisms. This article aims to guide clinicians in KRAS mutation identification.

A reliable transcriptomic risk-score applicable to formalin-fixed paraffin-embedded biopsies improves outcome prediction in localized prostate cancer.

BACKGROUND: Clinical manifestation of prostate cancer (PCa) is highly variable. Aggressive tumors require radical treatment while clinically non-significant ones may be suitable for active surveillance. We previously developed the prognostic ProstaTrend RNA signature based on transcriptome-wide microarray and RNA-sequencing (RNA-Seq) analyses, primarily of prostatectomy specimens. An RNA-Seq study of formalin-fixed paraffin-embedded (FFPE) tumor biopsies has now allowed us to use this test as a basis for the development of a novel test that is applicable to FFPE biopsies as a tool for early routine PCa diagnostics. METHODS: All patients of the FFPE biopsy cohort were treated by radical prostatectomy and median follow-up for biochemical recurrence (BCR) was 9 years. Based on the transcriptome data of 176 FFPE biopsies, we filtered ProstaTrend for genes susceptible to FFPE-associated degradation via regression analysis. ProstaTrend was additionally restricted to genes with concordant prognostic effects in the RNA-Seq TCGA prostate adenocarcinoma (PRAD) cohort to ensure robust and broad applicability. The prognostic relevance of the refined Transcriptomic Risk Score (TRS) was analyzed by Kaplan-Meier curves and Cox-regression models in our FFPE-biopsy cohort and 9 other public datasets from PCa patients with BCR as primary endpoint. In addition, we developed a prostate single-cell atlas of 41 PCa patients from 5 publicly available studies to analyze gene expression of ProstaTrend genes in different cell compartments. RESULTS: Validation of the TRS using the original ProstaTrend signature in the cohort of FFPE biopsies revealed a relevant impact of FFPE-associated degradation on gene expression and consequently no significant association with prognosis (Cox-regression, p-value > 0.05) in FFPE tissue. However, the TRS based on the new version of the ProstaTrend-ffpe signature, which included 204 genes (of originally 1396 genes), was significantly associated with BCR in the FFPE biopsy cohort (Cox-regression p-value < 0.001) and retained prognostic relevance when adjusted for Gleason Grade Groups. We confirmed a significant association with BCR in 9 independent cohorts including 1109 patients. Comparison of the prognostic performance of the TRS with 17 other prognostically relevant PCa panels revealed that ProstaTrend-ffpe was among the best-ranked panels. We generated a PCa cell atlas to associate ProstaTrend genes with cell lineages or cell types. Tumor-specific luminal cells have a significantly higher TRS than normal luminal cells in all analyzed datasets. In addition, TRS of epithelial and luminal cells was correlated with increased Gleason score in 3 studies. CONCLUSIONS: We developed a prognostic gene-expression signature for PCa that can be applied to FFPE biopsies and may be suitable to support clinical decision-making.

A novel test and treat program for hepatitis C virus infection utilizing HCV core antigen testing, among police and general population, Islamabad, Pakistan, 2022.

Hepatitis C virus core antigen (HCVcAg) testing can simplify and decrease costs of HCV infection confirmation compared to molecular testing (nucleic acid testing). We piloted HCVcAg testing for the confirmation of active infection. The study was conducted during June through December 2022 among the police and the general population of Islamabad, Pakistan age 18 years and older. Initial screening for HCV antibody was conducted using a rapid diagnostic test (RDT) for all consenting participants. Those who tested positive had venous blood samples tested for HCVcAg, platelets and aspartate aminotransferase (AST). Persons with HCVcAg values ≥3 fmol/L were defined as viremic, and they were offered treatment with direct acting antiviral (DAA) medications, sofosbuvir and daclatasvir. Aspartate aminotransferase to platelet ratio index (APRI) was calculated for each HCV infected person, and those with an APRI score <1.5 received treatment for 12 weeks, while those with APRI ≥ to 1.5 received 24 weeks of treatment. A total of 15,628 persons were screened for anti-HCV using RDT and 643 (4.1%) tested positive. HCVcAg values of ≥3 fmol/L was found in 399/643 (62.1%), and all were offered and accepted treatment. Of those treated, 273/399 (68.4%) returned for a follow-up SVR and HCVcAg was not detected in 261/273, a 95.6% cure rate. The pilot study demonstrated the effectiveness of reaching and treating an urban population using RDT for screening and HCVcAg for confirmation of infection and test of cure.

Best practice guidelines on genetic diagnostics of facioscapulohumeral muscular dystrophy: Update of the 2012 guidelines.

The gold standard for facioscapulohumeral muscular dystrophy (FSHD) genetic diagnostic procedures was published in 2012. With the increasing complexity of the genetics of FSHD1 and 2, the increase of genetic testing centers, and the start of clinical trials for FSHD, it is crucial to provide an update on our knowledge of the genetic features of the FSHD loci and renew the international consensus on the molecular testing recommendations. To this end, members of the FSHD European Trial Network summarized the evidence presented during the 2022 ENMC meeting on Genetic diagnosis, clinical outcome measures, and biomarkers. The working group additionally invited genetic and clinical experts from the USA, India, Japan, Australia, South-Africa, and Brazil to provide a global perspective. Six virtual meetings were organized to reach consensus on the minimal requirements for genetic confirmation of FSHD1 and FSHD2. Here, we present the clinical and genetic features of FSHD, specific features of FSHD1 and FSHD2, pros and cons of established and new technologies (Southern blot in combination with either linear or pulsed-field gel electrophoresis, molecular combing, optical genome mapping, FSHD2 methylation analysis and FSHD2 genotyping), the possibilities and challenges of prenatal testing, including pre-implantation genetic testing, and the minimal requirements and recommendations for genetic confirmation of FSHD1 and FSHD2. This consensus is expected to contribute to current clinical management and trial-readiness for FSHD.

Comprehensive assessment of vaginal infections using a single swab.

BACKGROUND: The decision to use a particular test to diagnose patients presenting with symptoms of vaginitis and/or STI is based primarily on the prevailing standards of care in the clinic at which the patient evaluation takes place. As a result, laboratory testing of vaginal samples for these patients often involves either an STI or a vaginitis test, but rarely both options simultaneously, which complicates the diagnosis and management of concurrent infections. METHODS: Using de-identified remnant vaginal specimens from symptomatic patients previously tested for STI (Chlamydia trachomatis (CT), Neisseria gonorrhoeae (GC) and Trichomonas vaginalis (TV)) with the Becton Dickinson (BD) CTGCTV2 assay for BD MAX System, positivity for bacterial vaginosis (BV) and Candida spp (associated with vulvovaginal candidiasis (VVC)) were evaluated using the molecular-based BD MAX Vaginal Panel. FINDINGS: The rate of STI/BV co-infection was 79.4% (227/286) in this symptomatic population, while that of STI/VVC was 27.0% (77/285). Women diagnosed with any one of the three STIs tested had an OR 2.86 (95% CI, 1.99, 4.11; p<0.0001) for a concurrent BV infection and OR 0.96 (95% CI, 0.67, 1.37; p=0.8085) for infection with Candida species. CONCLUSION: Our results suggest that women being tested for STI have a high prevalence of co-infection with BV and a lower, although appreciable, prevalence of co-infection with VVC. The detection of co-occurring vaginal infections can be facilitated by molecular testing using a single sample.

Impact of molecular ciprofloxacin resistance testing in management of gonorrhoea in a large urban clinic.

OBJECTIVES: Antibiotic resistance in gonorrhoea is of significant public health concern with the emergence of resistance to last-line therapies such as ceftriaxone. Despite around half of Neisseria gonorrhoeae isolates tested in the UK being susceptible to ciprofloxacin, very little ciprofloxacin is used in clinical practice. Testing for the S91F mutation associated with ciprofloxacin resistance is now available in CE-marked assays and may reduce the requirement for ceftriaxone, but many patients are treated empirically, or as sexual contacts, which may limit any benefit. We describe the real-world impact of such testing on antimicrobial use and clinical outcomes in people found to have gonorrhoea in a large urban UK sexual health clinic. METHODS: Molecular ciprofloxacin resistance testing (ResistancePlus GC assay (SpeeDx)) was undertaken as an additional test after initial diagnosis (m2000 Realtime CT/NG assay (Abbott Molecular)) in those not already known to have had antimicrobial treatment. Data from a 6-month period (from March to September 2022) were analysed to determine treatment choice and treatment outcome. RESULTS: A total of 998 clinical samples tested positive for N. gonorrhoeae in 682 episodes of infection. Of the 560 (56%) samples eligible for resistance testing, 269 (48.0%) were reported as wild-type, 180 (32.1%) were predicted to be resistant, 63 (11.3%) had an indeterminate resistance profile, and in 48 (8.6%) samples, N. gonorrhoeae was not detected. Ciprofloxacin was prescribed in 172 (75%) of 228 episodes in which the wild-type strain was detected. Four (2%) of those treated with ciprofloxacin had a positive test-of-cure sample by NAAT, with no reinfection risk. All four had ciprofloxacin-susceptible infection by phenotypic antimicrobial susceptibility testing. CONCLUSIONS: In routine practice in a large UK clinic, molecular ciprofloxacin resistance testing led to a significant shift in antibiotic use, reducing use of ceftriaxone. Testing can be targeted to reduce unnecessary additional testing. Longer term impact on antimicrobial resistance requires ongoing surveillance.

Molecular detection of ceftriaxone resistance in Neisseria gonorrhoeae clinical specimens: a tool for public health control.

OBJECTIVES: This study aimed to validate and implement a rapid screening assay for molecular detection of the penA-60 allele that is associated with ceftriaxone resistance in Neisseria gonorrhoeae for use on both isolate lysates and clinical specimen DNA extracts. METHODS: A N. gonorrhoeae penA real-time (RT)-PCR was adapted to include a species-specific pap confirmation target and a commercially available internal control to monitor for PCR inhibition.The modified assay was validated using N. gonorrhoeae-positive (n=24) and N. gonorrhoeae-negative (n=42) clinical specimens and isolate lysates. The panel included seven samples with resistance conferred by penA alleles targeted by the assay and four samples with different penA alleles. The feasibility of using the penA RT-PCR for molecular surveillance was assessed using clinical specimens from 54 individuals attending a London sexual health clinic who also had a N. gonorrhoeae isolate included in the 2020 Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP). RESULTS: The assay correctly identified N. gonorrhoeae specimens (n=7) with penA-60/64 alleles targeted by the assay. No penA false negatives/positives were detected, giving the penA target of the assay a sensitivity, specificity, positive and negative predicted values (PPV, NPV) of 100% (95% CIs; sensitivity; 56.1-100%, specificity; 93.6-100%, PPV; 56.1-100%, NPV; 93.6-100%).No cross-reactivity with other Neisseria species or other urogenital pathogens was detected. The N. gonorrhoeae target (pap) was detected in 73 out of 78 of the N. gonorrhoeae-positive specimens, resulting in 92.6% sensitivity (95% CI 83.0% to 97.3%), 100% specificity (95% CI 75.9% to 100%) and PPV, and a NPV of 89.4% (95% CI 52.5% to 90.9%). No penA-59/60/64 alleles were detected within the clinical specimens from the GRASP 2020 feasibility molecular surveillance study (n=54 individuals). CONCLUSION: The implementation of this PCR assay for patient management, public health and surveillance purposes enables the rapid detection of gonococcal ceftriaxone resistance conferred by the most widely circulating penA alleles.

Evaluation of the fully automated, sample-to-result Seegene STARlet-AIOS platform for detection of SARS-CoV-2, influenza virus A, influenza virus B, and RSV.

Early, accurate, and bulk detection of respiratory pathogens is essential for patient management and infection control. STARlet-All-in-One System (AIOS) (Seegene) is a new, fully automated, sample-to-result, molecular diagnostic platform. This study describes the first evaluation of STARlet-AIOS, by testing the Allplex™ SARS-CoV-2 (AS) and Allplex™ SARS-CoV-2/FluA/FluB/RSV combination (AC) assays in comparison to the SARS-CoV-2 assays used at our institute. Over a 3-week period, all naso-/oropharyngeal specimens tested for SARS-CoV-2 using either GeneXpert, Panther, or in-house developed test (LDT) were tested on the AIOS using the AS or AC assays. In addition, retrospective cohorts of specimens containing SARS-CoV-2, influenza virus A, influenza virus B, and RSV were tested. Discrepant results were re-tested with another assay used in this study. Hands-on time (HOT) and turn-around time (TAT) of the different systems were monitored and compared. A total of 738 specimens were tested on the AIOS using the AS assay. In addition, 210 specimens were tested using the AC assay. Overall agreement for SARS-CoV-2 detection was established as 98.5% and 95.2% for the AS and AC assay, respectively. Retrospective testing revealed high agreements for all targets, except for influenza virus A (agreement of 87.5%). HOT of the system was comparable to the HOT of GeneXpert and Panther and TAT comparable to Panther and LDT. The AIOS proved to be a robust sample-to-result system with low HOT and moderate TAT. This study showed reliable detection of SARS-CoV-2, influenza virus B, and RSV, whereas detection of influenza virus A using the AC assay appeared to be suboptimal.

Nanopore sequencing for smear-negative pulmonary tuberculosis-a multicentre prospective study in China.

PURPOSE: In this prospective study, the diagnosis accuracy of nanopore sequencing-based Mycobacterium tuberculosis (MTB) detection was determined through examining bronchoalveolar lavage fluid (BALF) samples from pulmonary tuberculosis (PTB) -suspected patients. Compared the diagnostic performance of nanopore sequencing, mycobacterial growth indicator tube (MGIT) culture and Xpert MTB/rifampin resistance (MTB/RIF) assays. METHODS: Specimens collected from suspected PTB cases across China from September 2021 to April 2022 were tested then assay diagnostic accuracy rates were compared. RESULTS: Among the 111 suspected PTB cases that were ultimately diagnosed as PTB, the diagnostic rate of nanopore sequencing was statistically significant different from other assays (P < 0.05). Fleiss' kappa values of 0.219 and 0.303 indicated fair consistency levels between MTB detection results obtained using nanopore sequencing versus other assays, respectively. Respective PTB diagnostic sensitivity rates of MGIT culture, Xpert MTB/RIF and nanopore sequencing of 36.11%, 40.28% and 83.33% indicated superior sensitivity of nanopore sequencing. Analysis of area under the curve (AUC), Youden's index and accuracy values and the negative predictive value (NPV) indicated superior MTB detection performance for nanopore sequencing (with Xpert MTB/RIF ranking second), while the PTB diagnostic accuracy rate of nanopore sequencing exceeded corresponding rates of the other methods. CONCLUSIONS: In comparison with MGIT culture and Xpert MTB/RIF assays, BALF's nanopore sequencing provided superior MTB detection sensitivity and thus is suitable for testing of sputum-scarce suspected PTB cases. However, negative results obtained using these assays should be confirmed based on additional evidence before ruling out a PTB diagnosis.

Validation and depth evaluation of low-pass genome sequencing in prenatal diagnosis using 387 amniotic fluid samples.

BACKGROUND: Low-pass genome sequencing (LP GS) is an alternative to chromosomal microarray analysis (CMA). However, validations of LP GS as a prenatal diagnostic test for amniotic fluid are rare. Moreover, sequencing depth of LP GS in prenatal diagnosis has not been evaluated. OBJECTIVE: The diagnostic performance of LP GS was compared with CMA using 375 amniotic fluid samples. Then, sequencing depth was evaluated by downsampling. RESULTS: CMA and LP GS had the same diagnostic yield (8.3%, 31/375). LP GS showed all copy number variations (CNVs) detected by CMA and six additional variant of uncertain significance CNVs (>100 kb) in samples with negative CMA results; CNV size influenced LP GS detection sensitivity. CNV detection was greatly influenced by sequencing depth when the CNV size was small or the CNV was located in the azoospermia factor c (AZFc) region of the Y chromosome. Large CNVs were less affected by sequencing depth and more stably detected. There were 155 CNVs detected by LP GS with at least a 50% reciprocal overlap with CNVs detected by CMA. With 25 M uniquely aligned high-quality reads (UAHRs), the detection sensitivity for the 155 CNVs was 99.14%. LP GS using samples with 25 M UAHRs showed the same performance as LP GS using total UAHRs. Considering the detection sensitivity, cost and interpretation workload, 25 M UAHRs are optimal for detecting most aneuploidies and microdeletions/microduplications. CONCLUSION: LP GS is a promising, robust alternative to CMA in clinical settings. A total of 25 M UAHRs are sufficient for detecting aneuploidies and most microdeletions/microduplications.

Biallelic frameshift variants in PHLDB1 cause mild-type osteogenesis imperfecta with regressive spondylometaphyseal changes.

BACKGROUND: Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders characterised by susceptibility to fractures, primarily due to defects in type 1 collagen. The aim of this study is to present a novel OI phenotype and its causative candidate gene. METHODS: Whole-exome sequencing and clinical evaluation were performed in five patients from two unrelated families. PHLDB1 mRNA expression in blood and fibroblasts was investigated by real-time PCR, and western blot analysis was further performed on skin fibroblasts. RESULTS: The common findings among the five affected children were recurrent fractures and/or osteopaenia, platyspondyly, short and bowed long bones, and widened metaphyses. Metaphyseal and vertebral changes regressed after early childhood, and no fractures occurred under bisphosphonate treatment. We identified biallelic NM_001144758.3:c.2392dup and NM_001144758.3:c.2690_2693del pathogenic variants in PHLDB1 in the affected patients, respectively, in the families; parents were heterozygous for these variants. PHLDB1 encodes pleckstrin homology-like domain family B member-1 (PHLDB1) protein, which has a role in insulin-dependent Akt phosphorylation. Compared with controls, a decrease in the expression levels of PHLDB1 in the blood and skin fibroblast samples was detected. Western blot analysis of cultured fibroblasts further confirmed the loss of PHLDB1. CONCLUSION: Two biallelic frameshift variants in the candidate gene PHLDB1 were identified in independent families with a novel, mild-type, autosomal recessive OI. The demonstration of decreased PHLDB1 mRNA expression levels in blood and fibroblast samples supports the hypothesis that PHLDB1 pathogenic variants are causative for the observed phenotype.

Strategic validation of variants of uncertain significance in ECHS1 genetic testing.

BACKGROUND: Enoyl-CoA hydratase short-chain 1 (ECHS1) is an enzyme involved in the metabolism of branched chain amino acids and fatty acids. Mutations in the ECHS1 gene lead to mitochondrial short-chain enoyl-CoA hydratase 1 deficiency, resulting in the accumulation of intermediates of valine. This is one of the most common causative genes in mitochondrial diseases. While genetic analysis studies have diagnosed numerous cases with ECHS1 variants, the increasing number of variants of uncertain significance (VUS) in genetic diagnosis is a major problem. METHODS: Here, we constructed an assay system to verify VUS function for ECHS1 gene. A high-throughput assay using ECHS1 knockout cells was performed to index these phenotypes by expressing cDNAs containing VUS. In parallel with the VUS validation system, a genetic analysis of samples from patients with mitochondrial disease was performed. The effect on gene expression in cases was verified by RNA-seq and proteome analysis. RESULTS: The functional validation of VUS identified novel variants causing loss of ECHS1 function. The VUS validation system also revealed the effect of the VUS in the compound heterozygous state and provided a new methodology for variant interpretation. Moreover, we performed multiomics analysis and identified a synonymous substitution p.P163= that results in splicing abnormality. The multiomics analysis complemented the diagnosis of some cases that could not be diagnosed by the VUS validation system. CONCLUSIONS: In summary, this study uncovered new ECHS1 cases based on VUS validation and omics analysis; these analyses are applicable to the functional evaluation of other genes associated with mitochondrial disease.

Fast and reliable detection of repeat expansions in spinocerebellar ataxia using exomes.

Usually, molecular diagnosis of spinocerebellar ataxia is based on a step-by-step approach with targeted sizing of four repeat expansions accounting for most dominant cases, then targeted sequencing of other genes. Nowadays, genome sequencing allows detection of most pathogenic variants in a single step. The ExpansionHunter tool can detect expansions in short-read genome sequencing data. Recent studies have shown that ExpansionHunter can also be used to identify repeat expansions in exome sequencing data. We tested ExpansionHunter on spinocerebellar ataxia exomes in a research context as a second-line analysis, after exclusion of main CAG repeat expansions in half of the probands. First, we confirmed the detection of expansions in seven known expansion carriers and then, after targeted analysis of ATXN1, 2, 3 and 7, CACNA1A, TBP, ATN1, NOP56, AR and HTT in 498 exomes, we found 22 additional pathogenic expansions. Comparison with capillary migration sizing in 247 individuals and confirmation of all expanded alleles detected by ExpansionHunter demonstrated that for these loci, sensitivity and specificity reached 100%. ExpansionHunter detected but underestimated the repeat size for larger expansions, and the normal alleles distribution at each locus should be taken into account to detect expansions. Exome combined with ExpansionHunter is reliable to detect repeat expansions in selected loci as first-line analysis in spinocerebellar ataxia.

Conclusion of diagnostic odysseys due to inversions disrupting GLI3 and FBN1.

Many genetic testing methodologies are biased towards picking up structural variants (SVs) that alter copy number. Copy-neutral rearrangements such as inversions are therefore likely to suffer from underascertainment. In this study, manual review prompted by a virtual multidisciplinary team meeting and subsequent bioinformatic prioritisation of data from the 100K Genomes Project was performed across 43 genes linked to well-characterised skeletal disorders. Ten individuals from three independent families were found to harbour diagnostic inversions. In two families, inverted segments of 1.2/14.8 Mb unequivocally disrupted GLI3 and segregated with skeletal features consistent with Greig cephalopolysyndactyly syndrome. For one family, phenotypic blending was due to the opposing breakpoint lying ~45 kb from HOXA13 In the third family, long suspected to have Marfan syndrome, a 2.0 Mb inversion disrupting FBN1 was identified. These findings resolved lengthy diagnostic odysseys of 9-20 years and highlight the importance of direct interaction between clinicians and data-analysts. These exemplars of a rare mutational class inform future SV prioritisation strategies within the NHS Genomic Medicine Service and similar genome sequencing initiatives. In over 30 years since these two disease-gene associations were identified, large inversions have yet to be described and so our results extend the mutational spectra linked to these conditions.

Comprehensive laboratory diagnosis of Fanconi anaemia: comparison of cellular and molecular analysis.

BACKGROUND: Fanconi anaemia (FA) is a rare inherited bone marrow failure disease caused by germline pathogenic variants in any of the 22 genes involved in the FA-DNA interstrand crosslink (ICL) repair pathway. Accurate laboratory investigations are required for FA diagnosis for the clinical management of the patients. We performed chromosome breakage analysis (CBA), FANCD2 ubiquitination (FANCD2-Ub) analysis and exome sequencing of 142 Indian patients with FA and evaluated the efficiencies of these methods in FA diagnosis. METHODS: We performed CBA and FANCD2-Ub analysis in the blood cells and fibroblasts of patients with FA. Exome sequencing with improved bioinformatics to detect the single number variants and CNV was carried out for all the patients. Functional validation of the variants with unknown significance was done by lentiviral complementation assay. RESULTS: Our study showed that FANCD2-Ub analysis and CBA on peripheral blood cells could diagnose 97% and 91.5% of FA cases, respectively. Exome sequencing identified the FA genotypes consisting of 45 novel variants in 95.7% of the patients with FA. FANCA (60.2%), FANCL (19.8%) and FANCG (11.7%) were the most frequently mutated genes in the Indian population. A FANCL founder mutation c.1092G>A; p.K364=was identified at a very high frequency (~19%) in our patients. CONCLUSION: We performed a comprehensive analysis of the cellular and molecular tests for the accurate diagnosis of FA. A new algorithm for rapid and cost-effective molecular diagnosis for~90% of FA cases has been established.