Parkinson's disease variant detection and disclosure: PD GENEration, a North American study.

Variants in seven genes (LRRK2, GBA1, PRKN, SNCA, PINK1, PARK7 and VPS35) have been formally adjudicated as causal contributors to Parkinson's disease; however, individuals with Parkinson's disease are often unaware of their genetic status since clinical testing is infrequently offered. As a result, genetic information is not incorporated into clinical care, and variant-targeted precision medicine trials struggle to enrol people with Parkinson's disease. Understanding the yield of genetic testing using an established gene panel in a large, geographically diverse North American population would help patients, clinicians, clinical researchers, laboratories and insurers better understand the importance of genetics in approaching Parkinson's disease. PD GENEration is an ongoing multi-centre, observational study (NCT04057794, NCT04994015) offering genetic testing with results disclosure and genetic counselling to those in the US (including Puerto Rico), Canada and the Dominican Republic, through local clinical sites or remotely through self-enrolment. DNA samples are analysed by next-generation sequencing including deletion/duplication analysis (Fulgent Genetics) with targeted testing of seven major Parkinson's disease-related genes. Variants classified as pathogenic/likely pathogenic/risk variants are disclosed to all tested participants by either neurologists or genetic counsellors. Demographic and clinical features are collected at baseline visits. Between September 2019 and June 2023, the study enrolled 10 510 participants across >85 centres, with 8301 having received results. Participants were: 59% male; 86% White, 2% Asian, 4% Black/African American, 9% Hispanic/Latino; mean age 67.4 ± 10.8 years. Reportable genetic variants were observed in 13% of all participants, including 18% of participants with one or more 'high risk factors' for a genetic aetiology: early onset (<50 years), high-risk ancestry (Ashkenazi Jewish/Basque/North African Berber), an affected first-degree relative; and, importantly, in 9.1% of people with none of these risk factors. Reportable variants in GBA1 were identified in 7.7% of all participants; 2.4% in LRRK2; 2.1% in PRKN; 0.1% in SNCA; and 0.2% in PINK1, PARK7 or VPS35 combined. Variants in more than one of the seven genes were identified in 0.4% of participants. Approximately 13% of study participants had a reportable genetic variant, with a 9% yield in people with no high-risk factors. This supports the promotion of universal access to genetic testing for Parkinson's disease, as well as therapeutic trials for GBA1 and LRRK2-related Parkinson's disease.

Development of a comprehensive cardiovascular disease genetic risk assessment test.

Background: Despite monogenic and polygenic contributions to cardiovascular disease (CVD), genetic testing is not widely adopted, and current tests are limited by the breadth of surveyed conditions and interpretation burden. Methods: We developed a comprehensive clinical genome CVD test with semi-automated interpretation. Monogenic conditions and risk alleles were selected based on the strength of disease association and evidence for increased disease risk, respectively. Non-CVD secondary findings genes, pharmacogenomic (PGx) variants and CVD polygenic risk scores (PRS) were assessed for inclusion. Test performance was modeled using 2,594 genomes from the 1000 Genomes Project, and further investigated in 20 previously tested individuals. Results: The CVD genome test is composed of a panel of 215 CVD gene-disease pairs, 35 non-CVD secondary findings genes, 4 risk alleles or genotypes, 10 PGx genes and a PRS for coronary artery disease. Modeling of test performance using samples from the 1000 Genomes Project revealed ~6% of individuals with a monogenic finding in a CVD-associated gene, 6% with a risk allele finding, ~1% with a non-CVD secondary finding, and 93% with CVD-associated PGx variants. Assessment of blinded clinical samples showed complete concordance with prior testing. An average of 4 variants were reviewed per case, with interpretation and reporting time ranging from 9-96 min. Conclusions: A genome sequencing based CVD genetic risk assessment can provide comprehensive genetic disease and genetic risk information to patients with CVD. The semi-automated and limited interpretation burden suggest that this testing approach could be scaled to support population-level initiatives.

Next-generation sequencing and analysis of consecutive patients referred for connective tissue disorders.

Heritable connective tissue disorders (HCTDs) consist of a wide array of genetic disorders such as Ehlers-Danlos syndrome, Marfan syndrome, and osteogenesis imperfecta. The diagnosis relies on clinical presentation and family history to guide genetic testing with next-generation sequencing (NGS) for identification of gene variants in HCTDs. NGS was performed on a cohort of 100 consecutive, unrelated patients referred for a connective tissue disorder at Fulgent Genetics, an accredited commercial laboratory. One hundred seventeen gene variants were found in 76 patients with 10 recognized pathogenic or likely pathogenic variants seen in nine patients. The remaining variants were grouped as unknown clinical significance with 36 meeting three out of four pathogenicity criteria, or potentially pathogenic, as defined in our study in 33 patients. They were judged as potentially pathogenic for clinical care and management with disease surveillance based on the specific gene and phenotypic presentation. Gene variants in collagen-related proteins were the most frequent with ZNF469 and ADAMTSL2 variants most often identified. Joint hypermobility was the most frequent clinical finding. Variants were found in 76% of patients who had distinct clinical features of a HCTD. The data were stratified to provide insight into frequency and types of variants, their classification, and clinical manifestations.

Genetic Etiologies for Chronic Kidney Disease Revealed through Next-Generation Renal Gene Panel.

INTRODUCTION: Chronic kidney disease (CKD) is a major public health issue in the USA. Identification of monogenic causes of CKD, which are present in ∼10% of adult cases, can impact prognosis and patient management. Broad gene panels can provide unbiased testing approaches, which are advantageous in phenotypically heterogeneous diseases. However, the use and yield of broad genetic panels by nephrologists in clinical practice is not yet well characterized. METHODS: Renal genetic testing, ordered exclusively for clinical purposes, predominantly by general and transplant nephrologists within the USA, was performed on 1,007 consecutive unique patient samples. Testing was performed using a commercially available next-generation sequencing-based 382 gene kidney disease panel. Pathogenic (P) and likely pathogenic (LP) variants were reported. Positive findings included a monoallelic P/LP variant in an autosomal dominant or X-linked gene and biallelic P/LP variants in autosomal recessive genes. RESULTS: Positive genetic findings were identified in 21.1% (212/1,007) of cases. A total of 220 positive results were identified across 48 genes. Positive results occurred most frequently in the PKD1 (34.1%), COL4A5 (10.9%), PKD2 (10.0%), COL4A4 (6.4%), COL4A3 (5.9%), and TTR (4.1%) genes. Variants identified in the remaining 42 genes comprised 28.6% of the total positive findings, including single positive results in 26 genes. Positive results in >1 gene were identified in 7.5% (16/212) of cases. CONCLUSIONS: Use of broad panel genetic testing by clinical nephrologists had a high success rate, similar to results obtained by academic centers specializing in genetics.

Assessing Variant Causality and Severity Using Retinal Pigment Epithelial Cells Derived from Stargardt Disease Patients.

Purpose: Modern molecular genetics has revolutionized gene discovery, genetic diagnoses, and precision medicine yet many patients remain unable to benefit from these advances as disease-causing variants remain elusive for up to half of Mendelian genetic disorders. Patient-derived induced pluripotent stem (iPS) cells and transcriptomics were used to identify the fate of unsolved ABCA4 alleles in patients with Stargardt disease. Methods: Multiple independent iPS lines were generated from skin biopsies of three patients with Stargardt disease harboring a single identified pathogenic ABCA4 variant. Derived retinal pigment epithelial cells (dRPE) from a normal control and patient cells were subjected to RNA-Seq on the Novaseq6000 platform, analyzed using DESeq2 with calculation of allele specific imbalance from the pathogenic or a known linked variant. Protein analysis was performed using the automated Simple Western system. Results: Nine dRPE samples were generated, with transcriptome analysis on eight. Allele-specific expression indicated normal transcripts expressed from splice variants albeit at low levels, and missense transcripts expressed at near-normal levels. Corresponding protein was not easily detected. Patient phenotype correlation indicated missense variants expressed at high levels have more deleterious outcomes. Transcriptome analysis suggests mitochondrial membrane biodynamics and the unfolded protein response pathway may be relevant in Stargardt disease. Conclusions: Patient-specific iPS-derived RPE cells set the stage to assess non-expressing variants in difficult-to-detect genomic regions using easily biopsied tissue. Translational Relevance: This "Disease in a Dish" approach is likely to enhance the ability of patients to participate in and benefit from clinical trials while providing insights into perturbations in RPE biology.

A Streamlined Approach to Prader-Willi and Angelman Syndrome Molecular Diagnostics.

Establishing or ruling out a molecular diagnosis of Prader-Willi or Angelman syndrome (PWS/AS) presents unique challenges due to the variety of different genetic alterations that can lead to these conditions. Point mutations, copy number changes, uniparental isodisomy (i-UPD) 15 of two subclasses (segmental or total isodisomy), uniparental heterodisomy (h-UPD), and defects in the chromosome 15 imprinting center can all cause PWS/AS. Here, we outline a combined approach using whole-exome sequencing (WES) and DNA methylation data with methylation-sensitive multiplex ligation-dependent probe amplification (MLPA) to establish both the disease diagnosis and the mechanism of disease with high sensitivity using current standard of care technology and improved efficiency compared to serial methods. The authors encourage the use of this approach in the clinical setting to confirm and establish the diagnosis and genetic defect which may account for the secondary genetic conditions that may be seen in those with isodisomy 15, impacting surveillance and counseling with more accurate recurrence risks. Other similarly affected individuals due to other gene disorders or cytogenetic anomalies such as Rett syndrome or microdeletions would also be identified with this streamlined approach.

Congenital myasthenic syndrome caused by a frameshift insertion mutation in GFPT1.

OBJECTIVE: Description of a new variant of the glutamine-fructose-6-phosphate transaminase 1 (GFPT1) gene causing congenital myasthenic syndrome (CMS) in 3 children from 2 unrelated families. METHODS: Muscle biopsies, EMG, and whole-exome sequencing were performed. RESULTS: All 3 patients presented with congenital hypotonia, muscle weakness, respiratory insufficiency, head lag, areflexia, and gastrointestinal dysfunction. Genetic analysis identified a homozygous frameshift insertion in the GFPT1 gene (NM_001244710.1: c.686dupC; p.Arg230Ter) that was shared by all 3 patients. In one of the patients, inheritance of the variant was through uniparental disomy (UPD) with maternal origin. Repetitive nerve stimulation and single-fiber EMG was consistent with the clinical diagnosis of CMS with a postjunctional defect. Ultrastructural evaluation of the muscle biopsy from one of the patients showed extremely attenuated postsynaptic folds at neuromuscular junctions and extensive autophagic vacuolar pathology. CONCLUSIONS: These results expand on the spectrum of known loss-of-function GFPT1 mutations in CMS12 and in one family demonstrate a novel mode of inheritance due to UPD.

Prenatal presentation and diagnosis of Baraitser-Winter syndrome using exome sequencing.

Baraitser-Winter cerebrofrontofacial syndrome (BWCFF) is a rare autosomal dominant developmental disorder associated with missense mutations in the genes ACTB or ACTG1. The classic presentation of BWCFF is discerned by the combination of unique craniofacial characteristics including ocular coloboma, intellectual disability, and hypertelorism. Congenital contractures and organ malformations are often present, including structural defects in the brain, heart, renal, and musculoskeletal system. However, there is limited documentation regarding its prenatal presentation that may encourage healthcare providers to be aware of this disorder when presented throughout pregnancy. Herein we describe a case of a pregnancy with large cystic hygroma and omphalocele. Whole exome sequencing (WES) was performed and a de novo, heterozygous, likely pathogenic mutation in ACTB was detected, c.1004G>A (p.Arg335His), conferring a diagnosis of BWCFF.

The Value of Parental Testing by Next-Generation Sequencing Includes the Detection of Germline Mosaicism.

When a potential disease-causing variant is detected in a proband, parental testing is used to determine the mode of inheritance. This study demonstrates that next-generation sequencing (NGS) is uniquely well suited for parental testing, in particular because of its ability to detect clinically relevant germline mosaicism. Parental variant testing by NGS was performed in a clinical laboratory for 1 year. The detection of mosaicism by NGS was compared with its detection by Sanger sequencing. Eight cases of previously unrevealed mosaicism were detected by NGS across eight different genes. Mosaic variants were differentiated from sequencing noise using custom bioinformatics analyses in combination with familial inheritance data and complementary Sanger sequencing. Sanger sequencing detected mosaic variants with allele fractions ≥8% by NGS, but could not detect mosaic variants below that level. Detection of germline mosaicism by NGS is invaluable to parents, providing a more accurate recurrence risk that can alter decisions on family planning and pregnancy management. Because NGS can also confirm parentage and increase scalability, it simultaneously streamlines and strengthens the variant curation process. These features make NGS the ideal method for parental testing, superior even to Sanger sequencing for most genomic loci.

Disruption of CTNND2, encoding delta-catenin, causes a penetrant attention deficit disorder and myopia.

Attention deficit hyperactivity disorder (ADHD) is a common and highly heritable neurodevelopmental disorder with poorly understood pathophysiology and genetic mechanisms. A balanced chromosomal translocation interrupts CTNND2 in several members of a family with profound attentional deficit and myopia, and disruption of the gene was found in a separate unrelated individual with ADHD and myopia. CTNND2 encodes a brain-specific member of the adherens junction complex essential for postsynaptic and dendritic development, a site of potential pathophysiology in attentional disorders. Therefore, we propose that the severe and highly penetrant nature of the ADHD phenotype in affected individuals identifies CTNND2 as a potential gateway to ADHD pathophysiology similar to the DISC1 translocation in psychosis or AUTS2 in autism.

Fundamentals of RNA Analysis on Biobanked Specimens.

Compared to DNA, analysis of RNA is one step closer on the central dogma of biology to assessing cellular function. This makes it an extremely valuable target for research and clinical testing in nearly all areas of molecular biology. Most RNA molecules are ephemeral by nature. They exist as temporary intermediates, ostensibly enabling data transfer between the genome and the organism. Their ribose backbone renders them sensitive to simple degradation over time and they are the target molecule for numerous and abundant ribonucleases which have evolved to chop them to pieces with extreme efficiency. At the biochemical level, this means that they degrade rapidly in most physiological and laboratory conditions and are thus challenging to study. When considering specimen banking, it is critical to keep this reality in mind, as some commonly used banking modalities will not adequately preserve the relevant RNA molecules in a measureable state.In this chapter, we explore the broad range of RNA testing methodologies in current use, with particular focus on how specimen preparation impacts analysis. Following an overview in the introduction, Subheading 2 covers the major specimen types amenable to RNA analysis in the context of biobanking. Subheading 3 discusses the applications of various RNA analysis modalities to research and clinical testing.

Geleophysic dysplasia: 48 year clinical update with emphasis on cardiac care.

Geleophysic dysplasia is a rare skeletal dysplasia often complicated by progressive cardiac disease. Information about long-term outcomes is limited. A clinical update of the oldest surviving patient described with geleophysic dysplasia type 1 is provided. Special note is made in relation to the cardiac disease and interventions. Genetic testing of ADAMTSL2 revealed a previously reported missense mutation as well as a novel nonsense mutation, which can be added to the list of causative mutations in geleophysic dysplasia.

Coupling clinical exome sequencing with functional characterization studies to diagnose a patient with familial Mediterranean fever and MED13L haploinsufficiency syndromes.

Clinicians should consider that clinical exome sequencing provides the unique potential to disentangle complex phenotypes into multiple genetic etiologies. Further, functional studies on variants of uncertain significance are necessary to arrive at an accurate diagnosis for the patient.

De novo loss-of-function variants in STAG2 are associated with developmental delay, microcephaly, and congenital anomalies.

The cohesin complex is an evolutionarily conserved multi-subunit protein complex which regulates sister chromatid cohesion during mitosis and meiosis. Additionally, the cohesin complex regulates DNA replication, DNA repair, and transcription. The core of the complex consists of four subunits: SMC1A, SMC3, RAD21, and STAG1/2. Loss-of-function mutations in many of these proteins have been implicated in human developmental disorders collectively termed "cohesinopathies." Through clinical exome sequencing (CES) of an 8-year-old girl with a clinical history of global developmental delay, microcephaly, microtia with hearing loss, language delay, ADHD, and dysmorphic features, we describe a heterozygous de novo variant (c.205C>T; p.(Arg69*)) in the integral cohesin structural protein, STAG2. This variant is associated with decreased STAG2 protein expression. The analyses of metaphase spreads did not exhibit premature sister chromatid separation; however, delayed sister chromatid cohesion was observed. To further support the pathogenicity of STAG2 variants, we identified two additional female cases from the DECIPHER research database with mutations in STAG2 and phenotypes similar to our patient. Interestingly, the clinical features of these three cases are remarkably similar to those observed in other well-established cohesinopathies. Herein, we suggest that STAG2 is a dosage-sensitive gene and that heterozygous loss-of-function variants lead to a cohesinopathy.

Novel association of familial testicular germ cell tumor and autosomal dominant polycystic kidney disease with PKD1 mutation.

Adolescent brothers were diagnosed with testicular germ cell tumors within the same month. Both were found to have multiple renal cysts on pretreatment imaging done for staging. The proband, his brother, and their mother, were all found to have a novel splice variant in intron 8 of the PKD1 gene by clinical exome sequencing. This is the second family reported with both familial testicular germ cell tumor (FTGCT) and autosomal dominant polycystic kidney disease (ADPKD), and the first described association of FTGCT with a splice variant in PKD1. We suggest that this novel variant in PKD1 may convey increased risk for FTGCT in addition to causing ADPKD.

Current practices and guidelines for clinical next-generation sequencing oncology testing.

Next-generation sequencing (NGS) has been rapidly integrated into molecular pathology, dramatically increasing the breadth genomic of information available to oncologists and their patients. This review will explore the ways in which this new technology is currently applied to bolster care for patients with solid tumors and hematological malignancies, focusing on practices and guidelines for assessing the technical validity and clinical utility of DNA variants identified during clinical NGS oncology testing.

De Novo Occurrence of a Variant in ARL3 and Apparent Autosomal Dominant Transmission of Retinitis Pigmentosa.

BACKGROUND: Retinitis pigmentosa is a phenotype with diverse genetic causes. Due to this genetic heterogeneity, genome-wide identification and analysis of protein-altering DNA variants by exome sequencing is a powerful tool for novel variant and disease gene discovery. In this study, exome sequencing analysis was used to search for potentially causal DNA variants in a two-generation pedigree with apparent dominant retinitis pigmentosa. METHODS: Variant identification and analysis of three affected members (mother and two affected offspring) was performed via exome sequencing. Parental samples of the index case were used to establish inheritance. Follow-up testing of 94 additional retinitis pigmentosa pedigrees was performed via retrospective analysis or Sanger sequencing. RESULTS AND CONCLUSIONS: A total of 136 high quality coding variants in 123 genes were identified which are consistent with autosomal dominant disease. Of these, one of the strongest genetic and functional candidates is a c.269A>G (p.Tyr90Cys) variant in ARL3. Follow-up testing established that this variant occurred de novo in the index case. No additional putative causal variants in ARL3 were identified in the follow-up cohort, suggesting that if ARL3 variants can cause adRP it is an extremely rare phenomenon.

An infant with MLH3 variants, FOXG1-duplication and multiple, benign cranial and spinal tumors: A clinical exome sequencing study.

A 4-month-old male infant presented with severe developmental delay, cerebellar, brainstem, and cutaneous hemangiomas, bilateral tumors (vestibular, hypoglossal, cervical, and lumbar spinal), and few café-au-lait macules. Cerebellar and lumbar tumor biopsies revealed venous telangiectasia and intraneural perineuroma, respectively. Sequencing NF1, NF2, and RASA1 (blood), and NF2 and SMARCB1 (lumbar biopsy) was negative for pathogenic mutations. Clinical exome sequencing (CES), requested for tumor syndrome diagnosis, revealed two heterozygous missense variants, c.359T>C;p.Phe120Ser and c.3344G>A;p.Arg1115Gln, in MLH3 (NM_001040108.1), a DNA mismatch repair (MMR) gene, Polyphen-predicted as probably damaging, and benign, respectively. Sanger sequencing confirmed both variants in the proband, and their absence in the mother; biological father unavailable. Both biopsied tissues were negative for microsatellite instability, and expressed MLH1, MSH2, PMS2, MSH6, and MLH3 immunohistochemically. Chromosomal microarray showed a 133 kb segment copy number duplication of 14q12 region encompassing FOXG1, possibly explaining the developmental delay, but not the tumors. The presence of MLH3 variants with multiple benign neural and vascular tumors was intriguing for their possible role in the pathogenesis of these neoplasms, which were suspicious for, but not diagnostic of, constitutional MMR deficiency. However, functional assays of non-neoplastic patient-derived cells showed intact base-base MMR function. Also, no previous FOXG1-aberrant patient was reported with tumors. We now report a 3-year-old FOXG1-duplicated patient with a yet undescribed tumor syndrome with clinical features of neurofibromatosis types I and II, where several validation studies could not ascertain the significance of CES findings; further studies may elucidate precise mechanisms and diagnosis for clinical management, including tumor surveillance.

Clinical exome sequencing in neurogenetic and neuropsychiatric disorders.

Exome sequencing has recently been elevated to the standard of care for genetic diagnostic testing, particularly for genetically diverse and clinically heterogeneous disorders. This review provides a clinically oriented discussion of the next-generation sequencing technology that makes exome sequencing possible and how such technology is applied to the diagnosis of Mendelian disease, including clinically significant de novo variation, interpretation of variants of uncertain clinical significance, the future potential for genetic assessments of disease risk, and the substantial benefits in diagnostic efficiency. Important caveats are also discussed, including the implications of incidental or secondary findings detected during exome sequencing and the relationship of exome sequencing to other methods of clinical genomic testing, such as chromosomal microarray and genome sequencing. Overall, the widespread adoption and use of exome sequencing in routine clinical practice is expected to improve diagnosis rates and reduce test costs, while leading to improvements in patient outcomes and a renewed emphasis on disease management.