American College Of Medical Genetics Research Articles

Exploring the clinical utility of exome sequencing/Mono, Duo, Trio in prenatal testing: a retrospective study in a tertiary care centre in South India.

With the availability of Next Generation Sequencing (NGS) diagnosis of genetic disorders has improved significantly. Its use is also applicable to ascertain diagnosis and management in a perinatal setting. The study aims to detect the genetic aetiology of various congenital structural and functional defects using NGS technology in the reproductive cohort at a tertiary centre. The secondary objective is to address challenges in the interpretation of variants. This was a retrospective study of couples who underwent exome sequencing (Mono-testing proband only or Duo-testing parents only or Trio-testing proband and parents) for suspected single gene disorders between years 2020-2022 at a tertiary care perinatal center in the South India. American College of Medical Genetics (ACMG) guidelines were followed to classify the pathogenicity of the variants identified by exome sequencing. The overall diagnostic yield as defined by pathogenic/likely pathogenic variants obtained was (23/43) 53.4 %. The individual subsets have the following diagnostic yield viz., Mono 5/6 (83 %); Carrier 16/32 (50 %); Trio 2/5 (40 %). Diagnostic yield was significantly higher in consanguineous couples. However, miscarriage history, and organ system involvement did not have a significant effect on the diagnostic yield. Prenatal diagnosis was offered for seven patients based on the exome result. One fetus was confirmed with a compound heterozygous pathogenic variant. Diagnostic yield of exome sequencing in our cohort was 53 %. The detection of pathogenic variants was maximum in those cases undergoing Mono exome sequencing. In places where there is a high prevalence of consanguinity and endogamy, NGS may be offered as first line test in the context of prenatal diagnosis.

Subset of retinoblastoma tumours is associated with BRCA1/2 mutations

BackgroundWe investigated the potential association between pathogenic BRCA1/2 variants and retinoblastoma pathogenicity.MethodsIn this single-centre, retrospective case series, we performed hereditary cancer panel tests using blood samples for patients with retinoblastoma...

Abnormal function of EPHA2/p.R957P mutant in congenital cataract.

To identify genetic defects in a Chinese family with congenital posterior polar cataracts and assess the pathogenicity. A four-generation Chinese family affected with autosomal dominant congenital cataract was recruited. Nineteen individuals took part in this study including 5 affected and 14 unaffected individuals. Sanger sequencing targeted hot-spot regions of 27 congenital cataract-causing genes for variant discovery. The pathogenicity of the variant was evaluated by the guidelines of American College of Medical Genetics and InterVar software. Confocal microscopy was applied to detect the subcellular localization of fluorescence-labeled ephrin type-A receptor 2 (EPHA2). Co-immunoprecipitation assay was implemented to estimate the interaction between EphA2 and other lens membrane proteins. The mRNA and protein expression were analyzed by reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting assay, respectively. The cell migration was analyzed by wound healing assay. Zebrafish model was generated by ectopic expression of human EPHA2/p.R957P mutant to demonstrate whether the mutant could cause lens opacity in vivo. A novel missense and pathogenic variant c.2870G>C was identified in the sterile alpha motif (SAM) domain of EPHA2. Functional studies demonstrated the variant's impact: reduced EPHA2 protein expression, altered subcellular localization, and disrupted interactions with other lens membrane proteins. This mutant notably enhanced human lens epithelial cell migration, and induced a central cloudy region and roughness in zebrafish lenses with ectopic expression of human EPHA2/p.R957P mutant under differential interference contrast (DIC) optics. Novel pathogenic c.2870G>C variant of EPHA2 in a Chinese congenital cataract family contributes to disease pathogenesis.

Clinical characteristics and genetic analysis of a patient with Acephalic spermatozoa syndrome due to variant of PMFBP1 gene

To analyze the clinical characteristics and genetic basis of a male patient with primary infertility caused by Acephalic spermatozoa syndrome. A patient who had presented at the Henan Provincial People's Hospital on October 1, 2022 was selected as the study subject. Clinical data and results of laboratory exams and sperm electron microscopy were collected. The patient was subjected to whole exome sequencing (WES), and candidate variants were verified by Sanger sequencing and pathogenicity analysis. WES revealed that the patient has harbored compound heterozygous variants of the PMFBP1 gene, namely c.853del (p.Ala285Leufs*24) and c.1276A>T (p.Lys426X), which were both unreported previously. Sanger sequencing suggested that the c.853del (p.Ala285Leufs*24) variant has derived from his deceased mother, whilst the c.1276A>T (p.Lys426X) variant has derived from his father. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were classified as pathogenic (PVS1+PM2_Supporting+PP4). The compound heterozygous variants of the PMFBP1 gene probably underlay the Acephalic spermatozoa syndrome in this patient. The discovery of the novel variants has also enriched the mutational spectrum of Acephalic spermatozoa syndrome.

Identification of a novel variant in a patient with Calsequestrin 1 related myopathy

To explore the genetic basis of a myopathic patient with pathological characteristics including tubular aggregates and vacuoles. Next generation sequencing was carried out for the patient, and candidate variant was verified by Sanger sequencing. Genetic testing revealed that the patient has harbored a heterozygous c.730G>C (p.D244H) variant of Calsequestrin 1 (CASQ1) gene. The same variant was not found in his unaffected parents. Based on guidelines from the American College of Medical Genetics and Genomics, the variant was rated as pathogenic (PS1+PM2+PP3). The novel c.730G>C (p.D244H) variant of the CASQ1 gene probably underlay the myopathy in this patient. Above finding has enriched the mutational spectrum of the CASQ1 gene.

Genetic analysis of a child with Generalized arterial calcification of infancy due to variant of ABCC6 gene

To explore the clinical manifestations and genetic basis for a rare case of Generalized arterial calcification of infancy (GACI). A 44-day-old female infant who was treated at Baoding Hospital of Beijing Children's Hospital Affiliated to Capital Medical University on August 26, 2022 was selected as the study subject. Clinical data of the child was collected, and Trio-whole exome sequencing (Trio-WES), whole genome copy number variation sequencing (CNV-seq) and minigene splicing assay were carried out to analyze the pathogenicity of the variants. The child had presented with fever and high inflammatory indicators, for which treatment with various antibiotics was ineffective. Ultrasound had revealed extensive arterial calcification and arterial wall thickening. The child was suspected for GACI with arteritis related to the primary disease. Her fever was relieved by treatment with glucocorticoid and biological agents. Trio-WES revealed that she has harbored compound heterozygous variants of the ABCC6 gene, namely c.4404-1G>A and c.4041+5G>T, for which the latter was unreported previously. Based on the guidelines from the American College of Medical Genetics and Genomics, the variants were classified as likely pathogenic (PVS1+PM2_Supporting) and variant of unknown significance (PM2_Supporting+PM3+PP3), respectively. The result of CNV-seq was negative. And the minigene splicing assay has further verified that both variants can result in alternative splicing. For pyrexia with unknown causes and refractory to conventional treatment, it is necessary to recommend early genetic testing to avoid missed diagnosis of GACI.

Cross-Sectional Analysis of Exome Sequencing Diagnosis in Patients With Neurologic Phenotypes Facing Barriers to Clinical Testing.

Exome sequencing (ES) demonstrates a 20-50 percent diagnostic yield for patients with a suspected monogenic neurologic disease. Despite the proven efficacy in achieving a diagnosis for such patients, multiple barriers for obtaining exome sequencing remain. This study set out to assess the efficacy of ES in patients with primary neurologic phenotypes who were appropriate candidates for testing but had been unable to pursue clinical testing. A total of 297 patients were identified from the UCLA Clinical Neurogenomics Research Center Biobank, and ES was performed, including bioinformatic assessment of copy number variation and repeat expansions. Information regarding demographics, clinical indication for ES, and reason for not pursuing ES clinically were recorded. To assess diagnostic efficacy, variants were interpreted by a multidisciplinary team of clinicians, bioinformaticians, and genetic counselors in accordance with the American College of Medical Genetics and Genomics variant classification guidelines. We next examined the specific barriers to testing for these patients, including how frequently insurance-related barriers such as coverage denials and inadequate coverage of cost were obstacles to pursuing exome sequencing. The cohort primarily consisted of patients with sporadic conditions (n = 126, 42.4%) of adult-onset (n = 239, 80.5%). Cerebellar ataxia (n = 225, 75.8%) was the most common presenting neurologic phenotype. Our study found that in this population of mostly adult patients with primary neurologic phenotypes that were unable to pursue exome sequencing clinically, 47 (15.8%) had diagnostic results while an additional 24 patients (8.1%) had uncertain results. Of the 297 patients, 206 were initially recommended for clinical exome but 88 (42.7%) could not pursue ES because of insurance barriers, of whom 14 (15.9%) had diagnostic findings, representing 29.8% of all patients with diagnostic findings. In addition, the incorporation of bioinformatic repeat expansion testing was valuable, identifying a total of 8 pathogenic repeat expansions (17.0% of all diagnostic findings) including 3 of the common spinocerebellar ataxias and 2 patients with Huntington disease. These findings underscore the importance and value of clinical ES as a diagnostic tool for neurogenetic disease and highlight key barriers that prevent patients from receiving important clinical information with potential treatment and psychosocial implications for patients and family members.

Myotonic dystrophy type 1 testing, 2024 revision: Atechnical standard of the American College of Medical Genetics and Genomics (ACMG).

Myotonic dystrophy type 1 (DM1) is a form of muscular dystrophy causing progressive muscle loss and weakness. Although clinical features can manifest at any age, it is the most common form of muscular dystrophy with onset in adulthood. DM1 is an autosomal dominant condition, resulting from an unstable CTG expansion in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. The age of onset and the severity of the phenotype are roughly correlated with the size of the CTG expansion. Multiple methodologies can be used to diagnose affected individuals with DM1, including polymerase chain reaction, Southern blot, and triplet repeat-primed polymerase chain reaction. Recently, triplet repeat interruptions have been described, which may affect clinical outcomes of a fully-variable allele in DMPK. This document supersedes the Technical Standards and Guidelines for Myotonic Dystrophy originally published in 2009 and reaffirmed in 2015. It is designed for genetic testing professionals who are already familiar with the disease and the methods of analysis.

Specifications of the ACMG/AMP variant curation guidelines for the analysis of germline ATM sequence variants.

The ClinGen Hereditary Breast, Ovarian and Pancreatic Cancer (HBOP) Variant Curation Expert Panel (VCEP) is composed of internationally recognized experts in clinical genetics, molecular biology and variant interpretation. This VCEP made specifications for ACMG/AMP guidelines for the ataxia telangiectasia mutated (ATM) gene according to the Food and Drug Administration (FDA)-approved ClinGen protocol. These gene-specific rules for ATM were modified from the American College of Medical Genetics and Association for Molecular Pathology (ACMG/AMP) guidelines and were tested against 33 ATM variants of various types and classifications in a pilot curation phase. The pilot revealed a majority agreement between the HBOP VCEP classifications and the ClinVar-deposited classifications. Six pilot variants had conflicting interpretations in ClinVar and reevaluation with the VCEP's ATM-specific rules resulted in four that were classified as benign, one as likely pathogenic and one as a variant of uncertain significance (VUS) by the VCEP, improving the certainty of interpretations in the public domain. Overall, 28 the 33 pilot variants were not VUS leading to an 85% classification rate. The ClinGen-approved, modified rules demonstrated value for improved interpretation of variants in ATM.

Variant classification changes over time in the clinical molecular diagnostic laboratory setting

BackgroundVariant classification in the setting of germline genetic testing is necessary for patients and their families to receive proper care. Variants are classified as pathogenic (P), likely pathogenic (LP), uncertain...

De novo variation in ARID1B gene causes Coffin-Siris syndrome 1 in a Chinese family with excessive early-onset high myopia

Coffin-Siris syndrome (CSS) is a rare autosomal dominant inheritance disorder characterized by distinctive facial features, hypoplasia of the distal phalanx or nail of the fifth and additional digits, developmental or cognitive delay of varying degree, hypotonia, hirsutism/hypertrichosis, sparse scalp hair and varying kind of congenital anomalies. CSS can easily be misdiagnosed as other syndromes or disorders with a similar clinical picture because of their genetic and phenotypic heterogeneity. We describde the genotype-phenotype correlation of one patient from a healthy Chinese family with a novel genotype underlying CSS, who was first diagnosed in the ophthalmology department as early-onset high myopia (eoHM). Comprehensive ophthalmic tests as well as other systemic examinations were performed on participants to confirm the phenotype. The genotype was identified using whole exome sequencing, and further verified the results among other family members by Sanger sequencing. Real-time quantitative PCR (RT-qPCR) technology was used to detect the relative mRNA expression levels of candidate genes between proband and normal family members. The pathogenicity of the identified variant was determined by The American College of Medical Genetics and Genomics (ACMG) guidelines. STRING protein-protein interactions (PPIs) network analysis was used to detect the interaction of candidate gene-related proteins with high myopia gene-related proteins. The patient had excessive eoHM, cone-rod dystrophy, coarse face, excessive hair growth on the face, sparse scalp hair, developmental delay, intellectual disability, moderate hearing loss, dental hypoplasia, patent foramen ovale, chronic non-atrophic gastritis, bilateral renal cysts, cisterna magna, and emotional outbursts with aggression. The genetic assessment revealed that the patient carries a de novo heterozygous frameshift insertion variant in the ARID1B c.3981dup (p.Glu1328ArgfsTer5), which are strongly associated with the typical clinical features of CSS patients. The test results of RT-qPCR showed that mRNA expression of the ARID1B gene in the proband was approximately 30% lower than that of the normal control in the family, suggesting that the variant had an impact on the gene function at the level of mRNA expression. The variant was pathogenic as assessed by ACMG guidelines. Analysis of protein interactions in the STRING online database revealed that the ARID1A protein interacts with the high myopia gene-related proteins FGFR3, ASXL1, ERBB3, and SOX4, whereas the ARID1A protein antagonizes the ARID1B protein. Therefore, in this paper, we are the first to report a de novo heterozygous frameshift insertion variant in the ARID1B gene causing CSS with excessive eoHM. Our study extends the genotypic and phenotypic spectrums for ARID1B-CSS and supplies evidence of significant association of eoHM with variant in ARID1B gene. As CSS has high genetic and phenotypic heterogeneity, our findings highlight the importance of molecular genetic testing and an interdisciplinary clinical diagnostic workup to avoid misdiagnosis as some disorders with similar manifestations of CSS.

#1723 Genetic landscape of polycystic kidney disease in a Chinese cohort – experience using whole genome sequencing in a tertiary renal unit

Abstract Background and Aims Genetic testing has increasingly been employed to provide definitive diagnoses and prognostic information in patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD). We aim to explore the genetic landscape of ADPKD in a Chinese cohort utilizing whole genome sequencing and study its real-world clinical utility. Method From 1st January 2022 to 31st March 2023, we recruited 50 adult Chinese patients who had the clinical diagnosis of ADPKD followed up at Queen Mary Hospital and consented to the study protocol. The study was approved by the University Institution Review Board and local ethics committees. Genomic DNA was isolated from samples obtained from patients per standard protocol. Whole-genome sequencing was performed and analysed through the germline analysis pipeline. Diagnostic analysis was performed per American College of Medical Genetics (ACMG) guidelines and ClinGen variant curation expert panel specifications. Diagnostic variants were defined as those classified as ‘pathogenic’ or ‘likely pathogenic’. Potential clinical utility of genetic findings were studied case-by-case based on the Kidney Disease Improving Global Outcomes (KDIGO) 2023 Clinical Practice Guideline for the Evaluation, Management and Treatment of ADPKD. Results Among the 50 unrelated probands with ADPKD, half were males and the mean age at presentation was 38. 38% patients had incidental finding of kidney cysts on abdominal imaging performed for unrelated symptoms or health screening, 32% presented for screening due to positive family history and only 30% presented with typical symptoms of ADPKD. Cystic complications were present in 30%, with cyst haemorrhage being the most common, followed by kidney stones, cyst rupture and infection. 80% patients also had liver cysts and none had a history of cerebral aneurysms. The majority of our cohort (72%) had a family history of ADPKD. We identified diagnostic variants in 35 individuals, reaching a diagnostic yield of 70%. Diagnostic variants were identified in PKD1 (20/35), PKD2 (11/35), IFT140 (3/35) and ALG9 (1/35). The majority of diagnostic variants were protein-truncating (32/35), while non-truncating variants consisted of 1 in-frame deletion and 2 missense variants in PKD1. We identified 3 copy number variation:NC_000016.10:g.2110587_2111851del,NC_000016.10:g.2132339_2137621del,NC_000016.10:g.2036427_2101117del. The genetic findings allowed physicians to make definitive diagnosis in 9 patients with negative family history of ADPKD. The genetic findings provided important prognostic information as protein-truncating variants in PKD1 or PKD2 were associated with more severe disease compared to non-truncating variants. For the 3 patients harbouring heterozygous pathogenic variants in IFT140 (NM_014714.4:c.2659G>T, NM_014714.4:c.3780del, NM_014714.4:c.1035_1036del), they demonstrated a milder PKD phenotype with stable kidney function, normal kidneys size and absence of liver cysts 10 years after the diagnosis. The patient with heterozygous likely pathogenic ALG9 variant (NM_024740.2:c.1225del) also had milder PKD phenotype with normal kidney function and normal sized kidneys on USG 5 years after the diagnosis. In another male patient with young hypertension who was classified as Mayo Class 1C according to kidney imaging, identifying the pathogenic protein-truncating variant in PKD1 (NM_001009944.3:c.7288C>T) would render him eligible to tolvaptan treatment in view of the high PROPKD score (7). Furthermore, the genetic findings enabled an earlier diagnosis in a number of family members by cascade testing and genetic results were important to identify suitable living-related kidney donors. Conclusion Genetic testing utilizing whole genome sequencing has multiple clinical utility in ADPKD patients. It could provide a definitive diagnosis in those with atypical presentation or without family history, inform prognosis, guide treatment, determine living-related donor suitability and allow earlier diagnosis in other family members.

#2438 ADPKD and collagen genes (COL4A3, COL4A4, COL4A5)

Abstract Background and Aims Familial hematuria diseases are a heterogeneous group of monogenic conditions caused by mutations in one of the collagen IV genes: COL4A3 (2q36.3), COL4A4 (2q36.3), and COL4A5 (Xq22.3) that are expressed in the glomerular basement membranes (GBM) and are responsible for the most frequent forms of microscopic hematuria (MH), Alport syndrome, and thin basement membrane nephropathy (TBMN). Recent data suggest that about 1% (1 in 106 individuals) of the world population may have heterozygous predicted pathogenic COL4A3 or COL4A4 variants, a frequency that leads to the occasional superimposition of TBMN with other glomerulopathies. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major genetic disorder affecting up to 12.5 million individuals worldwide and it is the fourth most common global cause of renal replacement therapy. Two are the principal causative genes: PKD1(16p13.3) and PKD2 (4q22.1). The aim of the study was to describe a cohort of clinically ADPKD patients studying collagen IV genes COL4A3, COL4A4, and COL4A5. Method We performed NGS with Sophia Genetic “Nephropathies Solution” Panel on clinically ADPKD patients (pts). This panel includes 44 genes (target region 105.8 kb) involved in different types of nephropathies. We considered variants that are categorized as Variant of Uncertain Significance (Vus), likely pathogenic, or pathogenic (Class 3,4, or 5 of American College of Medical Genetics (ACMG)) in COL4A3, COL4A4, and COL4A5 genes. Results We analyzed 250 consecutive clinically ADPKD pts (consecutive in the outpatient clinic). We found 13 (6.3%) clinically potentially interesting (Class 3,4 or 5 of ACMG) variants in collagen genes. We found 2 pts that were negative for PKD1, PKD2, PKHD1 analysis: 1 pt carrier COL4A4 NM_000092.5: c.2908C>T (p.Gln970Ter), Pathogenic and c.2756A>G (p.Glu919Gly) Vus; 1 male pt carrier COL4A3 NM_000091.5: c.609+3_609+6del, Vus and COL4A5 NM_000495:c.169G>A p.(Gly57Arg), likely pathogenic. We also found 4 pts with 4 Vus variants in collagens genes combined with at least 1 pathogenic or likely pathogenic variant in PKD1 or PKD2 genes. We found 3 pts with likely pathogenic variants in COL4A4 or COL4A3 genes combined with Vus or likely benign variants in PKD1 or PKD2 genes and 1 patient with 1 likely pathogenic variant in COL4A3 and 1 likely pathogenic variant in PKD1. Conclusion Variants in collagen genes are very frequent and the associated phenotype is varied, sometimes very mild such as microhematuria. Furthermore, penetrance has to be considered. The study outlines the importance of considering also collagen genes, even if we have a clear clinical manifestation of ADPKD. An additional variant in a kidney already compromised can have an impact on the phenotype. Analysis of genes involved in these 2 pathologies could lead to a better understanding of the phenotype-genotype correlation at least in patients with both conditions.

#958 Development and Validation of a Score Estimating the Probability of obtaining a genetic diagnosis in adults with CKD of uncertain origin

Abstract Background and Aims We aim to derive and validate a score estimating the probability of identifying a variant explicative of the renal phenotype using Exome Sequencing (ES) in adults with CKD of uncertain origin. Method Participants: prospective cohort study including all consecutive index patients with a CKD from uncertain origin in three French nephrology units (metropolitan: Sorbonne University Hospitals, Paris, and Conception Hospital, Marseille; overseas: La Réunion University Hospital, Réunion island) who underwent ES between October 11th, 2017 and May 31st, 2023. Outcome measure: identification of a causal variant using ES data, according to the American College of Medical Genetics and Genomics diagnostic criteria. Candiate variables and feature engineering: raw data regarding patients’ phenotypes was prospectively entered in a collection form at the time of ES by the prescribing physician. Structured data (yes/no questions and lists) was mapped to Human Phenotype Ontology (HPO) terms. Unstructured data (free text) was manually translated into HPO terms by the same investigator (nephrologist), which was blinded to ES results. First, second and third-order ancestor HPO terms were included in the analysis. Score's derivation: an optimal weighted average of multiple models (“ensemble model”) was specified, following guidelines provided in a recently published article (PMID:36905602). Score's validation: internal validation using 10-fold cross validation, followed by internal-external validation (data from 2/3 centers was used to develop a model which was then tested using data from the remaining center; this process was repeated in each center). Results We included 2,490 patients, 560/2,490 (22.5%) of whom had a causal variant identified by ES. We collected 1,028 distinct HPO terms describing the patients’ phenotypes. The most common term was “Hypertension”, occurring in 2,079/2,490 (83.5%) patients. In internal validation, the score showed accurate calibration and discrimination (area under the receiver operating characteristics curve (AUC): 0.71, 95% CI 0.68 to 0.73; index of precision accuracy (IPA): 0.11, 95% CI 0.09 to 0.13). Performances were moderately diminished in internal-external validation but remained satisfactory (Tenon: AUC 0.64, IPA 0.04; Marseille: AUC 0.67, IPA 0.04; La Réunion: 0.68, IPA 0.09). Conclusion We derived, internally and internally-externally validated a clinical score which accurately predicts the probability of obtaining a genetic diagnosis using Exome Sequencing. Feature engineering could further increase the score's performances. Automatic computation by clinicians using an interactive tool is achievable and could be of clinical utility, especially to guide resource allocation in case of a low pretest probability.

#1049 Genetic characteristics of autosomal dominant polycystic kidney disease in a Greek population

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the predominant monogenic renal genetic disorder, and the fourth leading cause of end stage kidney disease. Confirmatory genetic testing defines the disease, provides prognostic information and may support therapeutic management. This study aims to investigate the genetic characteristics of a substantial cohort of ADPKD patients from a single Greek center. Method Ninety-three patients (46 females, 47 males with a mean age of 34 ± 15 years) were enrolled from 59 distinct families attending the outpatient ADPKD clinic at the Nephrology Department of the General Hospital of Athens “G. Gennimatas.” Genetic analysis included targeted next-generation sequencing (tNGS) of over 600 clinically relevant genes, Sanger sequencing, and Multiplex ligation-dependent probe amplification (MLPA). Whole exome and whole genome sequencing (WES and WGS) studies were conducted in 3 patients with negative results. Magnetic Resonance Imaging (MRI) was performed in 74 out of 93 patients, revealing more than 10 renal cysts in all but one patient. Children with a positive family history (FH) displayed at least one cyst in echography, while two without FH had multiple renal cysts. Results Genetic diagnosis was established in 88 of 93 patients (94.5%). Seventy patients (75%), demonstrated single nucleotide variants (SNVs) and large deletions (4 patients) in the PKD1 gene, whereas SNVs and large deletions (5 patients) in the PKD2 gene were identified in 15 (16%) patients. Additionally, mutations in genes other than PKD1 and PKD2 were identified in 3 patients (3.5%). Two cases, involving a father and son, revealed the presence of a SEC61B variant; the father exhibited more than 10 renal cysts and liver cysts in the MRI, while the son displayed only liver cysts. Additionally, a third patient, a woman with nephrolithiasis and over 10 renal cysts in the MRI, exhibited a SLC3A1 variant. Notably, 5 patients (5.5%) with ADPKD phenotype had negative genetic analyses, despite the application of both WES and WGS in three of these patients. Truncating mutations in PKD1 were observed in 43 of 70 cases, (61%), while the rest (39%) had non-truncating mutations. Detected variants were classified as Pathogenic (45.5%), Likely Pathogenic (36%), and Variants of Uncertain Significance (VUS-13.5%, 12 cases), according to the guidelines of the American College of Medical Genetics and Genomics. Reclassification to Likely Pathogenic could be proposed for 6 out of 12 cases with VUS variants for which family segregation was noted. Finally, 52% and 82% of the detected variants have not been previously reported in ClinVar and gnomAD databases, respectively. Conclusion In this ethnically homogenous population, truncating mutations in the PKD1 gene were the predominant genetic cause of ADPKD, followed by PKD1 non-truncating mutations, PKD2 gene variants and other rare or undefined genetic etiologies.

#2412 Monoallelic NEK8-related polycystic kidney disease in an Irish ADPKD cohort

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD), commonly caused by pathogenic variants in PKD1 and PKD2 genes, leads to enlarged cystic kidneys and typically present in adulthood where ∼70% of affected patients progress to kidney failure by their 7th decade of life. Recently, new genes have been reported that appear to explain some of the previously unresolved ADPKD-like cases. An example is the NEK8 gene, where monoallelic variants are reported to cause early-onset ADPKD with progressive phenotype. We are reporting 4 Irish families with monoallelic NEK8 variants. Method In-depth clinical and radiological evaluations were conducted on 250 families with polycystic kidney disease referred to the Irish Kidney Gene Project. All patients underwent genomic testing using gene-panel and exome Next Generation Sequencing (NGS), while multiple ligation probe amplification analysis of PKD1 or PKD2 was utilized in genetically unresolved families. The American College of Medical Genetics and Genomics guidelines were applied to assess variant pathogenicity. Results To date, 471 individuals representing 250 distinct families (F) have been studied, including 105 (42%) families with two or more individuals (326 individuals). 55.2% have reached end-stage kidney failure, with an average age of 49.1 ± 14.3 years. We identified pathogenic / likely pathogenic variants in 76% (190/250) of families, with variants in PKD1 accounting for 76.8% (146/190) and PKD2 accounting for 15.3% (29/190) of families, respectively. In familial cases with non-PKD1/PKD2 variants, we identified pathogenic variants in a small proportion of families with ADPKD-like phenotypes: IFT140 variants (n = 4), ALG5 (n = 2), 17q12 microdeletion (n = 2) and DNAJB11, ALG8, and ALG9 variants (n = 1 each). Upon thorough review of all genetically unresolved PKD families, 4 (6.7%) families were identified with monoallelic protein-kinase domain NEK8 variants [NM_178170.3]: p.R45W (in 2 families) and two other missense variants: p.N69D and p.R140L, none of which contained a second NEK8 variant despite extensive analysis. Autosomal dominant segregation was confirmed in two parent-child pairs, whereas the remaining two index patients reported no family history of kidney disease. The median age at the initial presentation was 12 years (IQR: 2.5–27.3), with a median follow-up period of 22.5 years at the last evaluation. The phenotype of all patients was consistent with polycystic kidney disease with the absence of liver and pancreatic cysts. All patients were diagnosed with hypertension at an average age of 15.3 ± 12.2 years. Cerebral aneurysms were detected in two patients (F1: at age 61 years and F4: at age 54 years), while F3 was reported to have childhood-onset frontal bossing, prominence cerebrospinal fluid, and large arachnoid cysts. Approximately 67% [4/6] patients progressed to end-stage kidney failure by the 3rd decade of life. Compared to families with PKD1/PKD2 variants, families with NEK8 variants were characterized by earlier average age at initial presentation (14.5 versus 29.9 years; p 0.01) and progression to end-stage kidney failure (15.5 versus 49.6 years; p < 0.0001). Table 1 summarizes the clinical and genetic characteristics of the reported families. Conclusion We provide further evidence that monoallelic NEK8 variants cause early presentation and progressive ADPKD-like phenotype. Sequencing for monoallelic NEK8 variants in patients with childhood and early-adulthood cystic kidney disease can inform renal prognosis, treatment planning, familial screening and reproductive choices.

Whole-exome sequencing in a cohort of Chinese patients with isolated cervical dystonia

BackgroundDystonia is a kind of movement disorder but its pathophysiological mechanisms are still largely unknown. Recent evidence reveals that genetical defects may play important roles in the pathogenesis of dystonia. Objectives and Methods-To explore possible causative genes in Chinese dystonia patients, DNA samples from 42 sporadic patients with isolated cervical dystonia were subjected to whole-exome sequencing. Rare deleterious variants associated with dystonia phenotype were screened out and then classified according to the American College of Medical Genetics and Genomics (ACMG) criteria. Phenolyzer was used for analyzing the most probable candidates correlated with dystonia phenotype, and SWISS-MODEL server was for predicting the 3D structures of variant proteins. ResultsAmong 42 patients (17 male and 25 female) recruited, a total of 36 potentially deleterious variants of dystonia-associated genes were found in 30 patients (30/42, 71.4 %). Four disease-causing variants including a pathogenic variant in PLA2G6 (c.797G > C) and three likely pathogenic variants in DCTN1 (c.73C > T), SPR (c.1A > C) and TH (c.56C > G) were found in four patients separately. Other 32 variants were classified as uncertain significance in 26 patients. Phenolyzer prioritized genes TH, PLA2G6 and DCTN1 as the most probable candidates correlated with dystonia phenotype. Although 3D prediction of DCTN1 and PLA2G6 variant proteins detected no obvious structural alterations, the mutation in DCTN1 (c.73C > T:p.Arg25Trp) was closely adjacent to its key functional domain. ConclusionOur whole-exome sequencing results identified a novel variant in DCTN1 in sporadic Chinese patients with isolated cervical dystonia, which however, needs our further study on its exact role in dystonia pathogenesis.

Familial communication and cascade testing following elective genomic testing.

Familial communication of results and cascade genetic testing (CGT) can extend the benefits of genetic screening beyond the patient to their at-risk relatives. While an increasing number of health systems are offering genetic screening as an elective clinical service, data are limited about how often results are shared and how often results lead to CGT. From 2018 to 2022, the Sanford Health system offered the Sanford Chip, an elective genomic test that included screening for medically actionable predispositions for disease recommended by the American College of Medical Genetics and Genomics for secondary findings disclosure, to its adult primary care patients. We analyzed patient-reported data about familial sharing of results and CGT among patients who received Sanford Chip results at least 1 year previously. Among the patients identified with medically actionable predispositions, 94.6% (53/56) reported disclosing their result to at least one family member, compared with 46.7% (423/906) of patients with uninformative findings (p < 0.001). Of the patients with actionable predispositions, 52.2% (12/23) with a monogenic disease risk and 12.1% (4/33) with a carrier status reported that their relatives underwent CGT. Results suggest that while the identification of monogenic risk during elective genomic testing motivates CGT in many at-risk relatives, there remain untested at-risk relatives who may benefit from future CGT. Findings identify an area that may benefit from increased genetic counseling and the development of tools and resources to encourage CGT for family members.

DEPDC5 plays a vital role in epilepsy: Genotypic and phenotypic features in cohort and literature.

DEPDC5 emerges to play a vital role in focal epilepsy. However, genotype-phenotype correlation in DEPDC5-related focal epilepsies is challenging and controversial. In this study, we aim to investigate the genotypic and phenotypic features in DEPDC5-affected patients. Genetic testing combined with criteria published by the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP), was used to identify pathogenic/likely pathogenic variants in DEPDC5 among the cohort of 479 patients with focal epilepsy. Besides, the literature review was performed to explore the genotype-phenotype correlation and the penetrance in DEPDC5-related focal epilepsies. Eight unrelated probands were revealed to carry different pathogenic/likely pathogenic variants in DEPDC5 and the total prevalence of DEPDC5-related focal epilepsy was 1.67% in the cohort. Sixty-five variants from 28 studies were included in our review. Combined with the cases reported, null variants accounted for a larger proportion than missense variants and were related to unfavorable prognosis (drug resistance or even sudden unexpected death in epilepsy; χ2 = 5.429, p = .020). And, the prognosis of probands with developmental delay/intellectual disability or focal cortical dysplasia was worse than that of probands with simple epilepsy (χ2 = -, p = .006). Besides, the overall penetrance of variants in DEPDC5 was 68.96% (231/335). The study expands the variant spectrum of DEPDC5 and proves that the DEPDC5 variant plays a significant role in focal epilepsy. Due to the characteristics of phenotypic heterogeneity and incomplete penetrance, genetic testing is necessary despite no specific family history. And we propose to adopt the ACMG/AMP criteria refined by ClinGen Sequence Variant Interpretation Working Group, for consistency in usage and transparency in classification rationale. Moreover, we reveal an important message to clinicians that the prognosis of DEPDC5-affected patients is related to the variant type and complications.

A whole-exome sequencing study of patent foramen ovale: investigating genetic variants and their association with cardiovascular disorders.

Patent foramen ovale (PFO) has a genetic predisposition and is closely associated with cryptogenic stroke (CS), migraine, decompression sickness, and hypoxemia. Identifying PFO-related mutant genes through whole-exome sequencing (WES) can help in the early recognition of cardiovascular genetic risk factors, guide timely clinical intervention, and reduce the occurrence of cardiovascular events. We analyzed mutant genes from ClinVar and OMIM databases. WES was performed on 25 PFO patients from Zhejiang Provincial Hospital of Chinese Medicine. Pathogenicity of variants was evaluated using American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology. (AMP) guidelines. In ClinVar (4 Feb 2023), 113 coding gene mutations were found, including 83 associated with PFO. From OMIM (18 Apr 2023), 184 gene mutations were analyzed, with 110 mutant coding genes. WES identified pathogenic mutations in two of 25 PFO patients (8%). LDLR, SDHC, and NKX2-5 genes were linked to PFO and primarily involved in myocardial tissue function. NKX2-5 may play a crucial role in PFO development, interacting with NOTCH1, GATA4, MYH6, SCN5A signaling pathways regulating cardiomyocyte characteristics. We identified pathogenic mutations in LDLR, SDHC, and NKX2-5 genes, implying their role in PFO development. Functional enrichment analysis revealed NKX2-5's interaction with signaling pathways regulating cardiomyocyte function. These findings enhance our understanding of PFO's genetic basis, suggesting potential therapeutic targets for future research.