Database gnomAD Research Articles

Genomic Landscape of Chromosome X Factor VIII: From Hemophilia A in Males to Risk Variants in Females

Background: Variants within factor VIII (F8) are associated with sex-linked hemophilia A and thrombosis, with gene therapy approaches being available for pathogenic variants. Many variants within F8 remain variants of uncertain significance (VUS) or are under-explored as to their connections to phenotypic outcomes. Methods: We assessed data on F8 expression while screening the UniProt, ClinVar, Geno2MP, and gnomAD databases for F8 missense variants; these collectively represent the sequencing of more than a million individuals. Results: For the two F8 isoforms coding for different protein lengths (2351 and 216 amino acids), we observed noncoding variants influencing expression which are also associated with thrombosis risk, with uncertainty as to differences in females and males. Variant analysis identified a severe stratification of potential annotation issues for missense variants in subjects of non-European ancestry, suggesting a need for further defining the genetics of diverse populations. Additionally, few heterozygous female carriers of known pathogenic variants have sufficiently confident phenotyping data, leaving researchers unable to determine subtle, less defined phenotypes. Using structure movement correlations to known pathogenic variants for the VUS, we determined seven clusters of likely pathogenic variants based on screening work. Conclusions: This work highlights the need to define missense variants, especially those for VUS and from subjects of non-European ancestry, as well as the roles of these variants in women’s physiology.

Carrier Frequency and Incidence of MUTYH-Associated Polyposis Based on Database Analysis in East Asians and Koreans.

MUTYH-associated polyposis is an autosomal recessive disorder associated with an increased lifetime risk of colorectal cancer and a moderately increased risk of ovarian, bladder, breast, and endometrial cancers. We analyzed the carrier frequency and estimated the incidence of MUTYH-associated polyposis in East Asian and Korean populations, for which limited data were previously available. We examined 125,748 exomes from the gnomAD database, including 9,197 East Asians, and additional data from 5,305 individuals in the Korean Variant Archive and 1,722 in the Korean Reference Genome Database. All MUTYH variants were interpreted according to the American College of Medical Genetics and Genomics and Association for Molecular Pathology guidelines and the Sequence Variant Interpretation guidelines from ClinGen. The global carrier frequency of MUTYH-associated polyposis was 1.29%, with Europeans (non-Finnish) having the highest frequency of 1.86% and Ashkenazi Jews the lowest at 0.06%. East Asians and Koreans had a carrier frequency of 0.35% and 0.37% and an estimated incidence of 1 in 330,409 and 1 in 293,304 in Koreans, respectively, which were substantially lower than the global average of 1 in 24,160 and the European (non-Finnish) incidence of 1 in 11,520. This was the first study to investigate the frequency of carriers of MUTYH-associated polyposis in East Asians, including specific subgroups, utilizing gnomAD and a Korean genome database. Our data provide valuable reference information for future investigations of MUTYH-associated polyposis to understand the genetic diversity and specific variants associated with this condition in East Asian populations.

An estimation of global genetic prevalence of PLA2G6-associated neurodegeneration

BackgroundPLA2G6-associated neurodegeneration (PLAN) comprises three diseases with overlapping features: infantile neuroaxonal dystrophy (INAD), atypical neuroaxonal dystrophy (atypical NAD), and PLA2G6-related dystonia-parkinsonism. INAD is an early onset disease characterized by progressive loss of vision, muscular control, and mental skills. The prevalence of PLA2G6-associated diseases has not been previously calculated.MethodsTo provide the most accurate prevalence estimate, we utilized two independent approaches: database-based approach which included collecting variants from ClinVar, Human Gene Mutation Database (HGMD) and high confidence predicted loss-of-function (pLoF) from gnomAD (Rare Genomes Project Genetic Prevalence Estimator; GeniE), and literature-based approach which gathered variants through Mastermind Genomic Search Engine (Genomenon, Inc). Genetic prevalence of PLAN was calculated based on allele frequencies from gnomAD, assuming Hardy–Weinberg equilibrium.ResultsIn the PLA2G6 gene, our analysis found 122 pathogenic, 82 VUS, and 15 variants with conflicting interpretations (pathogenic vs VUS) between two approaches. Allele frequency was available for 58 pathogenic, 42 VUS, and 15 conflicting variants in gnomAD database. If pathogenic and/or conflicting variants are included, the overall genetic prevalence was estimated to be between 1 in 987,267 to 1 in 1,570,079 pregnancies, with the highest genetic prevalence in African/African-American (1 in 421,960 to 1 in 365,197) and East-Asian (1 in 683,978 to 1 in 190,771) populations.ConclusionOur estimates highlight the significant underdiagnosis of PLA2G6-associated neurodegeneration and underscores the need for increased awareness and diagnostic efforts. Furthermore, our study revealed a higher carrier frequency of PLA2G6 variants in African and Asian populations, stressing the importance of expanded genetic sequencing in non-European populations to ensure accurate and comprehensive diagnosis. Future research should focus on confirming our findings and implementing expanded sequencing strategies to facilitate maximal and accurate diagnosis, particularly in non-European populations.

Analyzing the Mutational Landscape of Prostate Cancer Susceptibility Genes through Next-Generation Sequencing (NGS) Analysis

Prostate cancer, a significant public health concern, exhibits a complex genetic landscape influenced by a variety of susceptibility genes. This study deciphers the intricate genetic makeup of prostate cancer by examining mutations in 14 prostate cancer susceptibility genes. The Next-Generation Sequencing (NGS) approach was employed on a cohort of 45 prostate cancer patients to detect mutations. The gnomAD database was used to analyze mutational frequencies in the Asian population suffering from prostate cancer. The cBioPortal database was employed to check the presence of observed mutations in The Cancer Genome Atlas (TCGA) dataset. In addition, this study employed RT-qPCR and Immunohistochemistry (IHC) techniques were utilized to check the functional consequences of the observed pathogenic mutations. Finally, Metascape and DrugBank resources were used for gene enrichment and drug prediction analyses. Results of the NGS analysis revealed a total of 29 mutations (pathogenic and benign) within the examined prostate cancer cohort, distributed across four key genes (BRCA1/2, TP53, and PMS2) out of the total analyzed 14 genes. Pathogenic mutations in BRCA1/2 and TP53 genes are of particular interest due to their fundamental roles in DNA repair, cell cycle regulation, and tumor suppression. Functional consequence analyses (RT-qPCR and IHC) demonstrated the down-regulation of BRCA1/2 and TP53 genes in prostate cancer samples with pathogenic mutations, reinforcing the disruption of their tumor suppressor roles. Lastly, drug prediction analysis uncovered promising therapeutic options by identifying drugs capable of enhancing the mRNA expression of these genes. This opens new avenues for tailored treatment strategies aimed at restoring normal cellular functions of the BRCA1/2 and TP53 genes. In conclusion, this study provides a comprehensive view of genetic mutations in prostate cancer susceptibility genes, ranging from benign to pathogenic. It emphasizes the genetic complexity of prostate cancer and offers insights into potential mechanisms driving this malignancy. These findings lay the groundwork for further research, personalized treatment approaches, and enhanced clinical management of prostate cancer.

Heterozygous variants in USP25 cause genetic generalized epilepsy.

USP25 encodes ubiquitin-specific protease 25, a key member of the deubiquitinating enzyme family that is involved in neural fate determination. Although abnormal expression in Down's syndrome was reported previously, the specific role of USP25 in human diseases has not been defined. In this study, we performed trio-based whole exome sequencing in a cohort of 319 cases (families) with generalized epilepsy of unknown aetiology. Five heterozygous USP25 variants, including two de novo and three co-segregated variants, were determined in eight individuals affected by generalized seizures and/or febrile seizures from five unrelated families. The frequency of USP25 variants showed a significantly high aggregation in this cohort compared with the East Asian population and all populations in the gnomAD database. The mean age at onset of febrile and afebrile seizures were 10 months (infancy) and 11.8 years (juvenile), respectively. The patients achieved seizure freedom, except that one had occasional nocturnal seizures at the last follow-up. Two patients exhibited intellectual disability. Usp25 was expressed ubiquitously in mouse brain with two peaks, on embryonic Days 14-16 and postnatal Day 21, respectively. In human brain, likewise, USP25 is expressed in the fetus/early childhood stage and with a second peak at ∼12-20 years old, consistent with the seizure onset age in patients during infancy and in juveniles. To investigate the functional impact of USP25 deficiency in vivo, we established Usp25 knockout mice, which showed increased seizure susceptibility compared with wild-type mice in a pentylenetetrazol-induced seizure test. To explore the impact of USP25 variants, we used multiple functional detections. In HEK293 T cells, the variant associated with a severe phenotype (p.Gln889Ter) led to a significant reduction of mRNA and protein expressions but formed stable truncated dimers with an increment of deubiquitinating enzyme activities and abnormal cellular aggregations, indicating a gain-of-function effect. The p.Gln889Ter and p.Leu1045del variants increased neuronal excitability in mouse brain, with a higher firing ability in p.Gln889Ter. These functional impairments align with the severity of the observed phenotypes, suggesting a genotype-phenotype correlation. Hence, a moderate association between USP25 and epilepsy was noted, indicating that USP25 is potentially a predisposing gene for epilepsy. Our results from Usp25 null mice and the patient-derived variants indicated that USP25 would play an epileptogenic role via loss-of-function or gain-of-function effects. The truncated variant p.Gln889Ter would have a profoundly different effect on epilepsy. Together, our results underscore the significance of USP25 heterozygous variants in epilepsy, thereby highlighting the critical role of USP25 in the brain.

Prevalence Estimation of the PALB2 Germline Variant in East Asians and Koreans through Population Database Analysis.

PALB2 is a tumor suppressor gene. Heterozygous germline pathogenic variants of PALB2 significantly increase the lifetime risk of breast cancer and moderately increase the risk of ovarian and pancreatic cancers. This study analyzed the estimated prevalence of PALB2 variants globally, focusing on East Asian and Korean populations, where limited data were previously available. We examined 125,748 exomes from the Genome Aggregation Database (gnomAD), including 9197 East Asians, and additional data from 5305 individuals in the Korean Variant Archive and 1722 in the Korean Reference Genome Database. All PALB2 variants were interpreted according to guidelines from the American College of Medical Genetics and Genomics and the Clinical Genome Resource. The global prevalence of PALB2 variants was 0.18%, with the highest prevalence in Finnish populations (0.41%) and the lowest in Ashkenazi Jewish populations (0.04%). East Asians had a prevalence of 0.09%. By combining data from Korean genome databases and gnomAD totaling 8936 individuals, the overall prevalence of PALB2 variants in the Korean population was determined to be 0.13%. This study is the first comprehensive investigation of PALB2 variant prevalence in East Asians and Koreans using gnomAD and Korean genome databases. These findings provide essential reference data for future research and highlight the importance of region-specific genetic studies that will inform genetic counseling and hereditary cancer risk management.

Allele frequency of genetic variations related to the UGT1A1 gene-drug pair in a group of Iranian population.

The efficacy and safety of drug treatments vary widely due to genetic variations. Pharmacogenomics investigates the impact of genetic variations on patient drug response. This research investigates the frequency of UGT1A1 genetic variations in the Iranian population, comparing them with global data to provide insights into the pharmacogenomic approach in the Iranian population. The study was conducted using the data of the Bushehr Elderly Health (BEH) program, a population-based cohort study of the elderly population aged ≥ 60 years. Genotyping of three UGT1A1 variant alleles (UGT1A1*6, UGT1A1*27, and UGT1A1*80) was performed on a group of 2730 elderly Iranian participants with the Infinium Global Screening Array. The genotyping analysis revealed significant differences compared to major global populations that were addressed in the gnomAD database. UGT1A1*80 was found at a high frequency (32.34%), and followed by UGT1A1*6 (0.76%) and UGT1A1*27 (0.018) at a low frequency in the Iranian group. The UGT1A1*80 was the more prevalent allele between investigated alleles in the present study which can be considered as an important allele for pharmacogenomic testing.

Expanding the Spectrum of Endocrine Abnormalities Associated with SOX11-related Disorders.

SOX11 variants cause Coffin-Siris Syndrome (CSS), characterized by developmental delay, hypogonadotropic hypogonadism (HH), skeletal and facial defects. To examine the contribution of SOX11 variants to the pathogenesis of Idiopathic Hypogonadotropic Hypogonadism (IHH), a disorder caused by hypothalamic GnRH deficiency. The Reproductive Endocrine Unit and the Pediatric Endocrinology Division, Massachusetts General Hospital. A cohort of 1810 unrelated IHH probands. Exome sequencing data from the entire cohort were examined for SOX11 rare single nucleotide variants (SNVs) [minor allele frequency in the gnomAD database <0.1%]. Rare SOX11 variant association testing was performed between the IHH and gnomAD population. Phenotyping of individuals harboring pathogenic/likely pathogenic SNVs (determined by the ACMG criteria) was performed. Four pathogenic SOX11 SNVs were identified in 5 IHH probands. The IHH cohort was enriched for SOX11 protein truncating SNVs (frameshift/nonsense) across the entire protein (2 SNVs in 3 IHH cases [p.S303X (de-novo); p.S345Afs*13]; p 0.0004981) and for SOX11 missense SNVs within the SOX11-high-mobility group (HMG) domain (2 SNVs in 2 IHH cases p.G84D[de-novo]; p.P114S; p=0.00313922). The phenotypic spectrum of SOX11 variant carriers revealed additional endocrine defects including anosmic and normosmic forms of IHH, growth-hormone deficiency, pituitary and hypothalamic structural defects, and hypothyroidism. A pathogenic SOX11 SNV was also identified in a patient with functional HH (FHH, p.R100Q). CSS-associated features were present in 4/5 probands. Deleterious SOX11 variants cause IHH and other pituitary hormone deficiencies, suggesting that the human SOX11-associated disorder may stem from both hypothalamic and pituitary level defects.

Estimating carrier rates and prevalence of porphyria-associated gene variants in the Chinese population based on genetic databases

Porphyria is a group of rare metabolic disorders caused by mutations in the genes encoding crucial enzymes in the heme biosynthetic pathway. However, the lack of comprehensive genetic analysis of porphyria patients in the Chinese population makes identifying and diagnosing carriers of the condition challenging. Using the ChinaMAP database, we determined the frequencies of P/LP porphyria-associated gene variants according to the ACMG guidelines. We also calculated the carrier rates and prevalence of each type of porphyria in the Chinese population under Hardy–Weinberg equilibrium. Compared with the variants in the gnomAD database, the genetic spectrum of porphyria-related P/LP variants in the Chinese population is distinct. In the ChinaMAP database, we identified 23 variants. We estimated the carrier rates for autosomal dominant porphyrias (AIP, HCP, VP, PCT) in the Chinese population to be 1/1059, 1/1513, 1/10588, and 1/1765, respectively. For autosomal recessive porphyrias (ADP, EPP, HEP, CEP), the estimated carrier rates were 1/5294, 1/2117, 1/1765, and 1/2647, respectively, with predicted prevalence rates of 8.92 × 10−9, 7.51 × 10−5, 8.02 × 10−8, and 3.57 × 10−8, respectively. Notably, 12 of the variants we identified were unique to the Chinese population. The predicted prevalence rate of EPP was the highest among the various types of porphyria in the Chinese population, while the others were moderate to low. This is the first comprehensive genetic study on porphyria in the Chinese population. Clarifying the genetic characteristics of various porphyria types among the Chinese population provides scientifically sound reference data for both research and genetic screening to identify porphyria carriers.

Nonamyloidogenic TTR gene variants c.76G>A and c.337-18G>C are not associated with idiopathic small-fiber neuropathy.

Small-fiber neuropathy (SFN) affects only unmyelinated and thin myelinated fibers. It may be caused by amyloidogenic mutations of the transthyretin (TTR) gene, but not all TTR gene variants are pathogenic. The nonamyloidogenic c.76G>A (rs1800458) and c.337-18G>C (rs36204272) variants of TTR were recently reported to be associated with SFN. We investigated this putative association by analyzing TTR gene sequencing data retrospectively for two cohorts of patients, one with SFN and a control group. In this retrospective single-center study, we analyzed the frequency of the c.76G>A and c.337-18G>C TTR gene variants in a cohort of patients meeting a strict definition of SFN, with or without dysautonomia, a control cohort of patients investigated for nonneurological conditions, and the gnomAD international database. We included 55 SFN patients in this study, 17 of whom had dysautonomia. The allelic frequencies of the two variants in our cohort of 55 SFN patients were 7.27% for c.76G>A TTR and 5.25% for c.337-18G>C. The frequencies of both variants were statistically similar in the 337 control patients and the gnomAD database. The c.76G>A and c.337-18G>C TTR gene variants are not associated with SFN.

Association of the rs1042522 SNP with prostate cancer risk: a study of cancer tissues, primary tumor cultures, and serum samples from a Spanish Caucasian population.

Prostate cancer (PCa) is a leading cause of cancer-related deaths in European men, emphasizing the urgent need for effective risk assessment strategies. The TP53 gene, a tumor suppressor gene frequently mutated in cancer, commonly harbors the rs1042522 single nucleotide polymorphism (SNP), known as the P72R SNP, which may influence PCa susceptibility. This study investigated the prevalence of the P72R SNP in European Caucasian PCa samples and its association with PCa risk. Genotyping was conducted on 12 hormone-naïve aggressive PCa cultures (hnPCs) from untreated patients (Gleason ≥8), 11 radical prostatectomies (RP), and 94 serum samples using DNA Sanger sequencing and melting curve analysis. Comparative analysis utilized data from the GnomAD database's European Caucasian non-cancer population. Our results demonstrate a significantly higher frequency of the P72R SNP in PCa samples and serums compared to the general European non-cancer population. A robust and statistically significant association (p < 0.0001) between the SNP and prostate cancer risk was identified, with an odds ratio of 7.937 (95% CI 5.37-11.00). Notably, the G allele (R72) showed a pronounced prevalence in high Gleason score (≥8) patients, although statistical significance was not reached. These results highlight a potential association with undifferentiated and malignant PCa lesions. The compelling association between the P72R SNP and prostate cancer risk underscores the potential utility of this marker for the early identification of patients at risk of aggressive metastatic prostate cancer. This insight could empower further research to intervene at an early stage by offering enhanced opportunities for timely and targeted interventions.

Report of a child with Bainbridge-Ropers syndrome due to a novel variant of ASXL3 gene and a literature review

To explore the clinical phenotype and genetic basis of a child with Bainbridge-Ropers syndrome (BRPS). A child with BRPS who had visited Nanjing Children's Hospital on June 26, 2019 was selected as the study subject. Clinical data of the child was reviewed. Genomic DNA was extracted from peripheral blood samples of the child and her parents. Whole exome sequencing (WES) was carried out, and candidate variant was verified by Sanger sequencing and bioinformatic analysis. The child was a 6-month-old girl with peculiar facial features, feeding difficulties, malnutrition, global developmental delay, hypotonia, mildly elevated aminotransferase and ulnar deviation. Results of WES showed that she has harbored a c.1533_1534del variant of the ASXL3 gene. Sanger sequencing confirmed that neither of her parents has carried the same variant. No similar case had been retrieved from the HGMD and ClinVar databases. No frequency for this variant among Asian populations was available in the ExAC, 1000 Genomes, and gnomAD databases. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c.1533_1534del variant of the ASXL3 gene was determined to be likely pathogenic (PVS1+PS2+PM2_Supporting). The ASXL3 gene c.1533_1534del variant probably underlay the BRPS in this child. Above finding has provided a reference for the clinical diagnosis and genetic counseling for children with similar disorders.

Rare heterozygous variants in paediatric steroid resistant nephrotic syndrome – a population-based analysis of their significance

Genetic testing in nephrotic syndrome may identify heterozygous predicted-pathogenic variants (HPPVs) in autosomal recessive (AR) genes that are known to cause disease in the homozygous or compound heterozygous state. In such cases, it can be difficult to define the variant’s true significance and questions remain about whether a second pathogenic variant has been missed during analysis or whether the variant is an incidental finding. There are now known to be over 70 genes associated with nephrotic syndrome, the majority inherited as an AR trait. Knowledge of whether such HPPVs occur with equal frequency in patients compared to the general population would assist interpretation of their significance. Exome sequencing was performed on 187 Steroid-Resistant Nephrotic Syndrome (SRNS) paediatric patients recruited to a UK rare disease registry plus originating from clinics at Evelina, London. 59 AR podocytopathy linked genes were analysed in each patient and a list of HPPVs created. We compared the frequency of detected HPPVs with a ‘control’ population from the gnomAD database containing exome data from approximately 50,000 individuals. A bespoke filtering process was used for both patients and controls to predict ‘likely pathogenicity’ of variants. In total 130 Caucasian SRNS patients were screened across 59 AR genes and 201 rare heterozygous variants were identified. 17/201 (8.5%) were assigned as ‘likely pathogenic’ (HPPV) using our bespoke filtering method. Comparing each gene in turn, for SRNS patients with a confirmed genetic diagnosis, in 57 of the 59 genes we found no statistically significant difference in the frequency of these HPPVs between patients and controls (In genes ARHGDIA and TP53RK, we identified a significantly higher number of HPPVs in the control population compared with the patients when filtering was performed with ‘high stringency’ settings only). In the SRNS patients without a genetics diagnosis confirmed, there was no statistically significant difference identified in any gene between patient and control. In children with SRNS, we propose that identification of HPPV in AR podocytopathy linked genes is not necessarily representative of pathogenicity, given that the frequency is similar to that seen in controls for the majority. Whilst this may not exclude the presence of genetic kidney disease, this type of heterozygous variant is unlikely to be causal and each result must be interpreted in its clinical context.

Abstract Or107: MyBP-HL nonsense mutations fail in sarcomere incorporation leads to modifications in myocyte contraction trough calcium modifications.

Introduction: Heart function depends on the cardiomyocyte contractile apparatus and proper sarcomere protein expression. Mutations in sarcomere genes cause inherited forms of cardiomyopathy and arrhythmias, including atrial fibrillation. AF is the most common cardiac arrhythmia and is associated with ischemic stroke, heart failure, and substantial morbidity and mortality. Recently, our group described a novel sarcomere component, myosin binding protein-H like (MyBP-HL), that is mainly expressed in the cardiac atria. MyBP-HL is composed of two immunoglobulin domains and one fibronectin domain, with homology to last three C-terminal domains of cardiac myosin binding protein-C (cMyBP-C). cMyBP-C nonsense mutations prevent his incorporation into the sarcomere. C-MyBP-C truncated peptides are identified by cells as poisoning peptides, and they are rapidly degraded. cMyBP-C nonsense mutations are causative of hypertrophic cardiomyopathy (HCM). The MyBP-HL Arg255stop variant has been described in humans and has been linked to ventricular conduction system abnormalities, atrial enlargement, dilated cardiomyopathy, and atrial and ventricular arrhythmias. The gnomAD database reports 9 nonsense mutations for MYBPHL in humans (Gln29, Trp54, Arg113, Tyr123, Trp158, Trp192, Lys250, Arg255, and Tyr307). Hypothesis: MYBPHL nonsense mutations fail to incorporate into the sarcomere will lead to contractile disfunction. Results: We demonstrated that MyBP-HL overexpression showed to be able to incorporate in a similar pattern to cMyBP-C C-zone doublets. Nevertheless, nonsense mutations disrupt normal sarcomere localization. MyBP-HL nonsense mutations promote an increase in contraction amplitude and slower relaxation kinetics. Also, we observed an increase in sarcomere length. Similarly, MyBP-HL nonsense mutations lead to increase in amplitude peak of calcium transients, and reduction in velocity to maximal calcium peak. In accordance with calcium modifications, we observed through mass spectrometry an increase in calpain 6 abundance promoted by MyBP-HL nonsense mutations. Conclusion: Based on these data, we demonstrated that MYBPHL nonsense mutations prevent MyBP-HL incorporation into the thick filament. The failure of MyBP-HL truncating peptides to incorporate into the sarcomere leads to a deficiencies in myocytes contraction patterns, changes in calcium patterns and increase in degradation proteins abundance, which are related to AF prevalence.

A spectrum of clinically-identified cysteine mutations in fibulin-3 (EFEMP1) highlight its disulfide bonding complexity and potential to induce stress response activation.

Fibulin-3 (FBLN3), also known as EFEMP1, is a secreted extracellular matrix (ECM) glycoprotein that contains forty cysteine residues. These cysteines, which are distributed across one atypical and five canonical calcium-binding epidermal growth factor (EGF) domains, are important for regulating FBLN3 structure, secretion, and presumably function. As evidence of this importance, a rare homozygous p.C55R mutation in FBLN3 negates its function, alters disulfide bonding, and causes marfanoid syndrome. Additional studies suggest that heterozygous premature stop codon mutations in FBLN3 may also cause similar, albeit less severe, connective tissue disorders. Interestingly, a series of twenty-four cysteine mutations in FBLN3 have been identified in the human population and published in the Clinical Variation (ClinVar) and gnomAD databases. We tested how seven of these cysteine mutants (five loss-of-cysteine variants: C42Y, C190R, C218R, C252F, and C365S, two gain-of-cysteine variants: R358C, Y369C) and two newly developed mutations (G57C and Y397C) altered FBLN3 secretion, disulfide bonding, MMP2 zymography, and stress response activation Surprisingly, we found a wide variety of biochemical behaviors: i) loss-of-cysteine variants correlated with an increased likelihood of disulfide dimer formation, ii) N-terminal mutations were less likely to disrupt secretion, and were less prone to aggregation, iii) in contrast to wild-type FBLN3, multiple, but not all variants failed to induce MMP2 levels in cell culture, and iv) C-terminal mutations (either loss or gain of cysteines) were more prone to significant secretion defects, intracellular accumulation/misfolding, and stress response activation. These results provide molecular and biochemical insight into FBLN3 folding, secretion, and function for many cysteine mutations found in the human population, some of which may increase the likelihood of subclinical connective tissue or other FBLN3-associated haploinsufficiency diseases.

Rare Genetic Variants in Young Adults Requiring Pacemaker Implantation

BackgroundGenetic disease has recently emerged as a cause of cardiac conduction disorders (CCDs), but the diagnostic yield of genetic testing and the contribution of the different genes to CCD is still unsettled. ObjectivesThis study sought to determine the diagnostic yield of genetic testing in young adults with CCD of unknown etiology requiring pacemaker implantation. We also studied the prevalence of rare protein-altering variants across individual genes and functional gene groups. MethodsWe performed whole exome sequencing in 150 patients with CCD of unknown etiology who had permanent pacemaker implanted at age ≤60 years at 14 Spanish hospitals. Prevalence of rare protein-altering variants in patients with CCD was compared with a reference population of 115,522 individuals from gnomAD database (control subjects). ResultsAmong 39 prioritized genes, patients with CCD had more rare protein-altering variants than control subjects (OR: 2.39; 95% CI: 1.75-3.33). Significant enrichment of rare variants in patients with CCD was observed in all functional gene groups except in the desmosomal genes group. Rare variants in the nuclear envelope genes group exhibited the strongest association with CCD (OR: 6.77; 95% CI: 3.71-13.87). Of note, rare variants in sarcomeric genes were also enriched (OR: 1.73; 95% CI: 1.05-3.10). An actionable genetic variant was detected in 21 patients (14%), with LMNA being the most frequently involved gene (4.6%). ConclusionsUnrecognized rare genetic variants increase the risk of CCD in young adults with CCD of unknown etiology. Genetic testing should be performed in patients age ≤60 years with CCD of unknown etiology. The role of genetic variants in sarcomeric genes as a cause of CCD should be further investigated.

Ethnic Variation and Structure‐Function Analysis of Tauopathy‐Associated PERK Alleles

AbstractEIF2AK3, also known as PERK, plays a pivotal role in cellular proteostasis, orchestrating the Unfolded Protein Response (UPR) and Integrated Stress Response (ISR) pathways. In addition to its central position in intracellular stress regulation, human GWAS identify EIF2AK3 as a risk factor in tauopathies, neurodegenerative diseases caused by aberrant tau protein accumulation. Guided by these genomic indicators, our investigation systematically analyzed human PERK variants, focusing on those with potential tauopathy linkages. We assembled a comprehensive data set of human PERK variants associated with Wolcott Rallison Syndrome (WRS), tauopathies, and bioinformatically predicted loss‐of‐function, referencing the gnomAD, Ensembl, and NCBI databases. We found extensive racial/ethnic variation in the prevalence of common PERK polymorphisms linked to tauopathies. Using SWISS‐MODEL, we identified structural perturbations in the ER stress‐sensing luminal domain dimers/oligomers of tauopathy‐associated PERK variants, Haplotypes A and B, in combination with another tauopathy‐linked R240H mutation. Recombinant expression of disease‐associated variants in vitro revealed altered PERK signal transduction kinetics in response to ER stress compared to the predominant non‐disease variant. In summary, our data further substantiates that human PERK variants identified in tauopathy genetic studies negatively impact PERK structure, function, and downstream signaling with significant variations in prevalence among different racial and ethnic groups.

#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.

#1556 An unusually high prevalence of TMEM67 c.1843T&amp;gt;C (p.Cys615Arg) variant in Russia

Abstract Background and Aims A hypomorphic TMEM67 variant c.1843T&amp;gt;C (p.Cys615Arg) (rs201893408) is associated with an autosomal-recessive condition characterized by a combination of nephronophthisis and liver fibrosis, and, in some cases, neurologic manifestations. According to the gnomAD database, it reaches the highest prevalence in Swedish population (MAF=17/26128, 0.00065). In two large European studies of nephronophthisis and related conditions, the contribution of this pathogenic allele to TMEM67-associated disorders reached 15%-27%. The report presents the first evidence for the major contribution of this recurrent variant to nephronophthisis in Russia. Method Blood DNA samples of 29 pediatric patients, undergoing chronic renal replacement therapy in a dialysis department of a large pediatric medical center, were evaluated by targeted (“clinical exome”) sequencing. KAPA HyperCap Heredity Panel (Roche) was used for target enrichment. Sequencing was performed on Illumina Nextseq2000 device. The alignment on GRCh37 reference genome sequence was made using BWA 0.7.12; HaplotypeCaller (GATK 3.3.0) was used for variant calling. Causative variants were verified by Sanger sequencing. Results Among other findings, we have identified two unrelated Russian patients, homozygous for TMEM67 p.Cys615Arg mutation; none of them have previously been diagnosed with nephronophthisis. Patient D, a 11-year-old girl, presented with unexplained chronic kidney disease with unremarkable ultrasound findings. Patient B was an 8-year-old girl with chronic kidney disease linked to bilateral ureterohydronephrosis. In both patients, cholestatic hepatitis of unknown etiology was diagnosed. No neurological involvement was reported. The parents of both girls denied consanguinity. One more Russian patient homozygous for p.Cys615Arg variant had been previously described [Andreeva and Savenkova, 2022; in Russian]: the 2-year-old child born from non-consanguineous parents had prenatally identified multiple renal cysts, nephrogenic arterial hypertension, and laboratory signs of cholestasis. The analysis of Ruseq database (ruseq.ru) confirmed high prevalence of TMEM67 c.1843T&amp;gt;C (p.Cys615Arg) variant in Russian population (MAF=14/10860, 0.0013). Conclusion TMEM67 c.1843T&amp;gt;C (p.Cys615Arg) allele is particularly common in Russian pediatric patients with chronic kidney disease and liver involvement, and, therefore, deserves to be analyzed in other countries with predominantly Slavic population.

Genetic background of primary and familial HLH in Qatar: registry data and population study.

Familial hemophagocytic lymphohistiocytosis (FHLH) is an inherited life-threatening disease. Five types are identified, with the addition of congenital immunodeficiency syndromes in which HLH is a typical manifestation. The literature on this disease is very scarce in the Middle East, with only a few scattered reports. We report detailed demographic, clinical, and genomic data from 28 patients diagnosed with primary and familial HLH over the last decade in Qatar. An evaluation was performed of allele frequencies of deleterious variants from 12 primary and familial HLH causative genes on the Qatar Genome Programme (QGP) cohort of 14,669 Qatari individuals. The genetic diagnosis was obtained in 15 patients, and four novel mutations in Perforin 1 (PRF1), UNC13D, LYST, and RAB27A genes were found. We identified 22,945 low/high/moderate/modifier impact variants significantly enriched in the QGP in those 12 genes. The variants rs1271079313 in PRF1 and rs753966933 in RAB27A found in our patient cohort were significantly more prevalent in the QGP compared to the Genome Aggregation Database (gnomAD) database, with a high carrier frequency in the Qatari population. We established the first primary and familial HLH Registry in the Gulf Region and identified novel possibly pathogenic variants present at higher frequency in the Qatari population, which could be used for screening purposes. Raising awareness about primary and familial HLH and implementing screening activities in the Qatari highly inbred population could stem into more comprehensive premarital and prenatal evaluations and faster diagnosis.