C3 Mutation Research Articles

Echocardiographic Strain Abnormalities Precede Left Ventricular Hypertrophy Development in Hypertrophic Cardiomyopathy Mutation Carriers.

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by unexplained left ventricular hypertrophy (LVH), diastolic dysfunction, and increased sudden-death risk. Early detection of the phenotypic expression of the disease in genetic carriers without LVH (Gen+/Phen-) is crucial for emerging therapies. This clinical study aims to identify echocardiographic predictors of phenotypic development in Gen+/Phen-. Sixteen Gen+/Phen- (one subject with troponin T, six with myosin heavy chain-7, and nine with myosin-binding protein C3 mutations), represented the study population. At first and last visit we performed comprehensive 2D speckle-tracking strain echocardiography. During a follow-up of 8 ± 5 years, five carriers developed LVH (LVH+). At baseline, these patients were older than those who did not develop LVH (LVH-) (30 ± 8 vs. 15 ± 8 years, p = 0.005). LVH+ had reduced peak global strain rate during the isovolumic relaxation period (SRIVR) (0.28 ± 0.05 vs. 0.40 ± 0.11 1/s, p = 0.048) and lower global longitudinal strain (GLS) (-19.8 ± 0.4 vs. -22.3 ± 1.1%; p < 0.0001) than LVH- at baseline. SRIVR and GLS were not correlated with age (overall, p > 0.08). This is the first HCM study investigating subjects before they manifest clinically significant or relevant disease burden or symptomatology, comparing at baseline HCM Gen+/Phen- subjects who will develop LVH with those who will not. Furthermore, we identified highly sensitive, easily obtainable, age- and load-independent echocardiographic predictors of phenotype development in HCM gene carriers who may undergo early preventive treatment.

#623 One-year outcome of kidney transplant recipients harbouring complement regulatory gene mutation

Abstract Background and Aims Thrombotic Microangiopathy (TMA) is associated with genetic abnormalities in complement regulatory pathways. The impact of complement regulatory gene (CRG) mutation on post-transplant TMA in Indian kidney transplant recipients (KTR) is unknown. This study was conducted to ascertain an association between post-transplant renal limited TMA and the risk of graft failure in KTRs harbouring mutations in genes encoding complement-regulatory proteins. Method A Single Centre, Prospective Cohort Study was undertaken to assess the incidence of post-transplant renal limited TMA in KTRs with mutations in genes encoding complement regulatory proteins. Patients enrolled over one year were followed up for one-year post-transplantation. Genetic testing was performed with MLPA and Clinical exome sequencing. Results 138 KTRs with a mean age of 36.39 ± 12.39 years were enrolled. CRG mutation was seen in 96/138 (69.6%) KTRs. Duplication of the CFHR gene (n = 72) was most prevalent followed by mutations in CFH (n = 6), CFI (n = 2), MCP (n = 2), and DGKE (n = 1). Mutations in CFB, C3, and THBD genes were not detected. The Incidence of Post transplant renal limited TMA in KTRs with CRG mutations is 9.37% (9/96). Mutation related to aHUS was seen in 9 out of 11 patients who developed TMA. There was no significant difference in eGFR of patients with or without CRG mutation at the end of 1 year. Conclusion The prevalence of CRG mutation in KTRs is high and the majority of patients with post-transplant de novo TMA had CRG mutations. The graft functions at the end of 1 year were similar in patients with or without CRG gene mutation. This study suggests that the presence of CRG mutation should not preclude the option of Kidney transplantation in a patient with ESRD.

#1276 Clinical practice of complement inhibitor use in hemolytic uremic syndrome: findings from the European rare kidney disease registry

Abstract Background and Aims Over the last decade, significant advancements have emerged in the field of rare kidney diseases, notably the introduction of C5 inhibitor therapy. The C5 inhibition has transformed the prognosis for atypical Hemolytic Uremic Syndrome (aHUS), offering improved clinical outcomes. However, despite these advancements, the utilization of C5 inhibitor therapy varies significantly, with disparities in treatment duration, reasons for discontinuation, and consideration of extending treatment to patients with infectious HUS (iHUS). This variability is further compounded by the considerable cost associated with C5 inhibitor treatment. Method This retrospective cohort study utilized data from the ERKNet Registry. The study cohort comprised 608 HUS patients enrolled in the ERKNet Registry between November 2018 and September 2023. The dataset encompassed patient demographics, disease and diagnostic records, medication profiles, dialysis or transplantation requirements, kidney function monitoring at the last visit, and clinical outcomes. Results Among 230 aHUS patients, 23 underwent kidney transplantation. 11 received C5 inhibitor therapy before kidney failure. The majority of these patients had genetic aHUS with various mutations (3 CFH, 2 CFI, and 1 CD46). The only death in the study was from this group of patients, unresponsive to C5 Inhibition. Out of 175 aHUS patients treated with Eculizumab, 23 (13%) transitioned to Ravulizumab. Among 104 patients who discontinued C5 inhibitors, 14 (14%) had to resume treatment, half of them with genetic aHUS, with 3 cases of CD46 mutations, 2 cases CFHR5 mutations, and one each involving mutations in CFI and C3. Only two patients required dialysis.. Among 371 iHUS patients, 82 (22%) received C5 Inhibitor treatment. Conclusion In the context of aHUS, we found that discontinuing C5 inhibitors is generally safe, with a slightly higher relapse rate in patients with complement gene variants, though most relapses were mild, requiring dialysis in only a few cases. Long-term follow-up revealed a return to normal kidney function following TMA relapses. Transitioning from Eculizumab to Ravulizumab exhibited promising outcomes, with no relapses or kidney failures in 23 patients. Our analysis of C5 inhibitor use in iHUS emphasized its association with more severe disease progression. While some studies question C5 inhibitors' acute-phase efficacy, others report remarkable improvements in patients unresponsive to other treatments. Overall, our findings underscore the safety of discontinuation practices, the potential benefits of Ravulizumab, and the ongoing need for further research on C5 inhibitor treatment in iHUS.

Complement-mediated thrombotic microangiopathy treated with anticomplement protein 5 therapy, a retrospective study.

Complement-mediated thrombotic microangiopathy (CM-TMA), also called atypical hemolytic uremic syndrome (aHUS), is a difficult-to-diagnose rare disease that carries severe morbidity and mortality. Anti-C5 monoclonal antibodies (aC5-mab) are standard treatments, but large studies and long-term data are scarce. Here, we report our single institution experience to augment the knowledge of CM-TMA treated with aC5-mab therapy. We aimed to assess the short and long-term effects of aC5-mab in patients diagnosed with CM-TMA treated outside of a clinical trial. This was a retrospective study. We included all patients diagnosed with CM-TMA and treated with aC5-mab at our institution. There were no exclusion criteria. Endpoints included complete TMA response (CR) defined as normalization of hematological parameters and ≥25% improvement in serum creatinine (Cr) from baseline in patients with renal disease, relapse defined as losing the previously achieved CR, morbidity, adverse events, and survival. We found 28 patients with CM-TMA treated with aC5-mab. The median age was 50 years. Baseline laboratories: platelet counts 93 × 109 /L, hemoglobin 8.6 g/dL, lactate dehydrogenase 1326 U/L, serum Cr 4.7 mg/dL, and estimated glomerular filtration rate 19 mL/min. One individual was on renal replacement therapy (RRT) and 10 initiated RRT within 5 days of the first dose of aC5-mab. Genetic variants associated with CM-TMA included mutations in C3, CFB, CFH, CFHR1/3, CFI, and MCP. The mean duration of hospitalization was 24 days. The median time to initiation of aC5-mab was 10 days. Sixteen subjects received RRT. At the time of hospital discharge, 27 were alive, 14 remained on RRT, and 4 had a CR. At 6 months, 23 patients were alive, 18 continued aC5-mab, 8 remained on RRT, and 9 had a CR. At the last follow-up visit past 6 months, 20 were alive, 14 continued aC5-mab, 5 remained on RRT, 12 had a CR, and 1 was lost to follow-up. Our study provides real-world experience and insight into the long-term outcomes of CM-TMA treated with aC5-mab. Our findings validate that CM-TMA is an aggressive disease with significant morbidity and mortality, and confirm that aC5-mab is a relatively effective therapy for CM-TMA. Our study adds practical, real-world experience to the literature, but future research remains imperative.

672 - Complete response to eculizumab in atypical hemolytic uremic syndrome with homozygous C3 mutation.

672 - Complete response to eculizumab in atypical hemolytic uremic syndrome with homozygous C3 mutation.

A case of malignant hypertension as a presentation of atypical hemolytic uremic syndrome

Malignant hypertension (mHTN) damages multiple target organs, including the kidneys. mHTN has been regarded as one of the causes of secondary thrombotic microangiopathy (TMA); however, a high prevalence of complement gene abnormalities was recently reported in cohorts of mHTN. We herein describe a 47-year-old male who presented with severe hypertension, renal failure (serum creatinine (sCr): 11.6 mg/dL), heart failure, retinal hemorrhage, hemolytic anemia, and thrombocytopenia. Renal biopsy findings were consistent with acute hypertensive nephrosclerosis. The patient was diagnosed with secondary TMA associated with mHTN. However, his previous medical history of TMA of unknown origin and family history of atypical hemolytic uremic syndrome (aHUS) suggested as aHUS presenting mHTN, and genetic testing revealed a pathogenic C3 mutation (p.I1157T). The patient required plasma exchange and hemodialysis for 2 weeks and was able to withdraw from dialysis by antihypertensive therapy without eculizumab. Renal function gradually improved to a sCr level of 2.7mg/dL under antihypertensive therapy for 2 years after the event. There was no recurrence, and renal function was preserved throughout a 3-year follow-up. mHTN is a common presentation of aHUS. In cases of mHTN, abnormalities in complement-related genes may be involved in the development of the disease.

Establishment of an induced pluripotent stem cell line (ZJULLi004-A) from a hypertrophic cardiomyopathy patient carrying MYBPC3/c.3764C>A mutation

Hypertrophic cardiomyopathy (HCM) is an inherited cardiovascular disease characterized by left ventricular hypertrophy and a high risk of sudden death. In this study, a skin biopsy was obtained from a HCM patient harboring a heterozygous missense mutation (c.3764C>A; p.A1225D) in the myosin binding protein C3 (MYBPC3) gene. The isolated fibroblasts were reprogrammed using non-integrated Sendai viral method to establish the patient-specific induced pluripotent stem cell (iPSC) line. The established iPSC line displayed normal morphology and karyotype, expressed pluripotency markers, and can differentiate into three germ layers in vivo.

Psoriatic Dermal-Derived Mesenchymal Stem Cells Induced C3 Expression in Keratinocytes.

PurposeOur recent studies found a splice region mutation in C3 accompanied by a significantly increased C3 in psoriatic peripheral blood. Mesenchymal stem cells (MSCs) are a key immunological suppression cell. We further investigate the regulation of MSCs on C3 in psoriasis.Patients and MethodsWe analyzed the C3 and its upstream S100A9, S100A8 and downstream MCP1 in psoriatic and control skin, and in normal human epidermal keratinocytes (NHEKs) co-cultured with psoriatic versus control dermal-derived mesenchymal stem cells (DMSCs) by mRNA, iTRAQ (isobaric tags for relative and absolute quantitative) and simple Western analysis.ResultsThe mRNA and Simple Western analysis showed that the expression of C3, S100A8 and S100A9 are upregulated in psoriatic lesion (C3: mRNA, 9.23-fold, p = 0.0092; protein, 3.56-fold, p = 0.0244. S100A8: mRNA, 28.35-fold, p = 0.0015; protein, 4.68-fold, p = 0.0215. S100A9: mRNA, 79.45-fold, p = 0.0066; protein, 12.42-fold, p > 0.05). Moreover, the iTRAQ showed that C3 and S100A9 were significantly increased in NHEKs after co-cultured with psoriatic DMSCs compared to that of control DMSCs (C3: 3.40-fold, p = 0, FDR = 0; S100A9: 2.30-fold, p = 9.86E-241, FDR = 6.50E-239), verified by Simple Western. However, the expression of S100A8 and MCP1 was slightly different between the two groups.ConclusionOur results suggest that psoriatic DMSCs contribute to the increased C3 expression in psoriatic lesion via upregulating S100A9, providing the theoretical basis for the role of C3 and DMSCs in the pathogenesis of psoriasis.

Prevalence of cardiac myosin-binding protein C3 mutations in Maine Coon cats with hypertrophic cardiomyopathy.

Background and Aim:Hypertrophic cardiomyopathy (HCM) is a common heart problem that affects many cats. Although cats with HCM are symptomatic, some die suddenly or develop congestive heart failure. Therefore, this study aimed to estimate the prevalence of myosin-binding protein C3 (MYBPC3), A31P, and A74T polymorphisms in Maine Coon cats to assess risk factors for diagnosing HCM in cats.Materials and Methods:Forty-nine Maine Coon cats of at least 10 months of age were enrolled in this study. First, clinical parameters, such as heart rate, systolic blood pressure, and echocardiography, were evaluated. Then, polymerase chain reaction, followed by DNA sequencing, was conducted using specific primers for amino acid substitutions caused by genetic variants of MYBPC3-A31P and -A74T polymorphisms.Results:Investigations showed that the prevalence of MYBPC3-A31P and -A74T mutations in this study was 16.33% and 24.45%, respectively. Moreover, HCM in cats with MYBPC3-A31P and A74T mutations increased with age, body weight, high heart rate, and prolonged isovolumic relaxation time.Conclusion:Therefore, we propose that Maine Coon cats develop HCM due to multiple genetic factors and underlying clinical characteristics in individual cats. Furthermore, relaxation time assessments can be a sensitive technique for HCM screening during its preclinical phase and can help identify the risk of developing HCM. However, further studies are warranted to evaluate the effect of MYBPC3 mutations on the phenotypic expression of HCM.

Complement Protein Levels Decrease with Tumour Severity in Pancreatic Ductal Adenocarcinoma

Introduction: Pancreatic ductal adenocarcinoma (PDAC) has poor prognosis and is resistant to various treatments including immunotherapy. The complement system is a major component of innate immunity and plays a major role in immunosurveillance and homeostasis although pancreatic cancer hijacks the innate immune response to evade detection. Despite advances, immunotherapy is still ineffective in PDAC treatment. This study aimed to elucidate the expression of complement proteins, C3 and C5, in South African PDAC patients. Methods: Following ethical approval (Ethics-M190734), twenty-five confirmed PDAC patients, 6 chronic pancreatitis, and 3 healthy controls were recruited and ELISA performed. Statistical analysis was conducted (Statistica V13.5), reported as mean±SEM, with p<0.05 considered as significant. Furthermore, we interrogated online databases (GENT2 & COSMIC V.92) to observe expression and mutation data of C3 and C5 for comparison purposes. Results: C3 plasma levels decreased in locally-advanced and metastatic disease 0.71±0.15μg/mL) compared to resectable cancer (0.97±0.09μg/mL;p<0.05). C5 was lower in healthy controls compared to patients with pancreatic cancer (p<0.05) and correlated with the inflammatory marker, C-reactive protein (CRP; p=0.0098). online databases showed both C3 and C5 were overexpressed in pancreatic tumours compared to normal tissues. Missense mutations were the most commonly occurring mutations in both C3 and C5 in PDAC. Conclusion: The decrease in C3 with disease severity in PDAC may indicate the loss of innate immune response and thus a compromised immunity. The correlation of C5 with CRP may imply potential roles in inflammation that might affect immune response, however, this needs to be further investigated.

Eculizumab therapy on a patient with co\u2010existent lupus nephritis and C3 mutation\u2010related atypical haemolytic uremic syndrome: a case report

BackgroundThrombotic microangiopathy (TMA), a rare but serious complication of systemic lupus erythematosus (SLE), is associated with poor outcomes to conventional immunosuppressive therapy. Recently, eculizumab, a humanised monoclonal antibody that blocks the complement factor 5, has been known to effectively treat atypical haemolytic uremic syndrome (aHUS). Here, we report a case of aHUS co-existing with lupus nephritis that was successfully treated with eculizumab.Case presentationA 23-year-old man presented with abdominal pain and diarrhoea. Initial laboratory tests have shown thrombocytopaenia, microangiopathic haemolytic anaemia, and acute kidney injury. Immunologic tests were consistent with SLE. Kidney biopsy have revealed lupus nephritis class IV-G with TMA. Genetic analysis have shown complement C3 gene mutations, which hints the co-existence of lupus nephritis with aHUS, a form of complement-mediated TMA. Although initial treatment with haemodialysis, plasma exchange, and conventional immunosuppressive therapy (steroid and cyclophosphamide) did not appreciably improve kidney function and thrombocytopaenia, the patient was able to respond to eculizumab therapy.ConclusionsDue to the similar features of TMA and SLE, clinical suspicion of aHUS in patients with lupus nephritis is important for early diagnosis and prompt management. Timely administration of eculizumab should be considered as a treatment option for aHUS in lupus nephritis patients to yield optimal therapeutic outcomes.

Expression of complement proteins C3 &amp; C5 in South African pancreatic ductal adenocarcinoma patients and their potential roles in PDAC progression

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and deadliest of human malignancies. PDAC cells have developed mechanisms to evade and suppress immune function. Despite advances, immunotherapy is still ineffective for the treatment of PDAC.We aimed to identify novel potential immune targets in South African PDAC patients. Method: Total RNA was isolated from 15 tumours and 15 adjacent corresponding “normal” tissues (Ethics-M190734). A PCR Array immune focused panel was used to identify differentially expressed genes and qPCR used for verification. ELISA was further performed on 25 PDAC, 6 chronic pancreatitis, and 3 controls. Statistical analysis was conducted using Statistica V13.5, reported as mean±SEM, with a p<0.05 considered as significant. Online databases were accessed for C3 and C5 gene/protein expression and mutation data. Results: We found 13 upregulated and 62 downregulated genes. C3 was the most overexpressed gene in tumours (fold change=562,22). Furthermore, C3 plasma levels decreased in locally-advanced and metastatic disease 0.71±0.15μg/mL) compared to resectable cancer (0.97±0.09μg/mL;p<0.05). C5 was lower in healthy controls compared to patients with pancreatic disease (chronic + cancer; p<0.05) and correlated with the inflammatory marker, C-reactive protein (CRP; p=0.0098). Missense mutations were the most commonly occurring mutations in both C3 and C5 in PDAC. Conclusion: The decrease in C3 with disease severity in PDAC may indicate the loss of innate immune response and thus a compromised immunity as the complement system plays a major role in immunosurveillance. C5 may play a role in inducing inflammation in pancreatic cancer, therefore may be a potential therapeutic target.

Atypical hemolytic and uremic syndrome due to C3 mutation in pancreatic islet transplantation: a case report

BackgroundWe here report on the first observation of a C3 mutation that is related to atypical hemolytic and uremic syndrome (aHUS), which occurred in a pancreatic islet transplant patient. Immunosuppressive treatments, such as calcineurin inhibitors, have been linked to undesirable effects like nephrotoxicity.Case presentationA 40-year-old man with brittle diabetes, who was included in the TRIMECO trial, became insulin-independent 2 months after pancreatic islet transplantation. About 15 months after islet transplantation, the patient exhibited acute kidney injury due to aHUS. Despite plasma exchange and eculizumab treatment, the patient developed end-stage renal disease.A genetic workup identified a missense variant (p.R592Q) in the C3 gene. In vitro, this C3 variant had defective Factor I proteolytic activity with membrane proteins as cofactor proteins, which was thus classified as pathogenic. About 1 year after the aHUS episode, kidney transplantation was carried out under the protection of the specific anti-C5 monoclonal antibody eculizumab. The patient had normal kidney function, with preserved pancreatic islet function 4 years later.ConclusionsPancreatic islet transplantation could have triggered this aHUS episode, but this link needs to be clarified. Although prophylactic eculizumab maintains kidney allograft function, its efficacy still needs to be studied in larger populations.

Common APOC3 variants are associated with circulating ApoC-III and VLDL cholesterol but not with total apolipoprotein B and coronary artery disease

Background and aimsVery rare loss-of-function mutations in the apolipoprotein C3 (APOC3) gene have been associated with low circulating apoC-III, low triglycerides, and reduced cardiovascular risk. We aimed to analyze the impact of common APOC3 variants on key parameters of lipid metabolism and coronary artery disease in the largest sample so far. MethodsCommon variants in APOC3 were tested for associations with circulating apoC-III, lipids, and apolipoprotein B (apoB) in 3041 participants of the LUdwigshafen RIsk and Cardiovascular health study (LURIC). These variants were then tested for associations with coronary artery disease in a meta-analysis comprising up to 332,389 participants of the CARDIOGRAMplusC4D consortium and the UK Biobank. ResultsThe mean (standard deviation) apoC-III concentration was 14.6 (5.1) mg/dl. Seven common variants in APOC3 (rs734104, rs4520, rs5142, rs5141, rs5130, rs5128, and rs4225) were associated with circulating apoC-III (all p < 0.05). The alleles that modestly raised apoC-III were also associated with markedly higher total triglycerides and very low density lipoprotein (VLDL) triglycerides and cholesterol (all p < 0.05), but not with low density lipoprotein (LDL) cholesterol and total apoB (all p > 0.05). These variants were not associated with coronary artery disease in the CARDIOGRAMplusC4D consortium and the UK Biobank (all p > 0.1). ConclusionsModest, genetically caused elevations of apoC-III are associated with a marked increase of triglyceride-rich lipoproteins but not with an increase of LDL cholesterol, total apoB, and coronary artery disease. Whether effective inhibition of apoC-III production with antisense oligomers will be instrumental to reduce cardiovascular risk remains to be demonstrated.

The Relevance of the MCP Risk Polymorphism to the Outcome of aHUS Associated With C3 Mutations. A Case Report

Thrombotic microangiopathy (TMA) has different etiological causes, and not all of them are well understood. In atypical hemolytic uremic syndrome (aHUS), the TMA is caused by the complement dysregulation associated with pathogenic mutations in complement components and its regulators. Here, we describe a pediatric patient with aHUS in whom the relatively benign course of the disease confused the initial diagnosis. A previously healthy 8-year-old boy developed jaundice, hematuria, hemolytic anemia, thrombopenia, and mild acute kidney injury (AKI) in the context of a diarrhea without hypertension nor oliguria. Spontaneous and complete recovery was observed from the third day of admission. Persistent low C3 plasma levels after recovery raised the suspicion for aHUS, which prompted clinicians to discard the initial diagnosis of Shigatoxin-associated HUS (STEC-HUS). A thorough genetic and molecular study of the complement revealed the presence of an isolated novel pathogenic C3 mutation. The relatively benign clinical course of the disease as well as the finding of a de novo pathogenic C3 mutation are remarkable aspects of this case. The data are discussed to illustrate the benefits of identifying the TMA etiological factor and the relevant contribution of the MCP aHUS risk polymorphism to the disease severity.

Tobacco curly shoot virus C3 protein enhances viral replication and gene expression in Nicotiana benthamiana plants

Geminiviruses are single-stranded DNA viruses that cause devastating diseases in many crops worldwide. The replication enhancer proteins (REn), encoded by the C3 (AC3, and AL3) ORFs of geminiviruses, have critical roles in viral DNA accumulation and symptom development in infected plants. In the current study, we have constructed an infectious clone of the Tobacco curly shoot virus (TbCSV) C3 mutant, TbCSVΔC3, that contains two start codon mutations that abrogated C3 ORF expression, but did not alter the amino acid sequence of the C2 ORF. As predicted, the absence of the C3 protein reduced TbCSV DNA accumulation, and over-expression of the C3 protein enhanced TbCSV DNA accumulation in infected leaves of Nicotiana benthamiana. The C3 mutation reduced the expression levels of both virion- and complementary-sense TbCSV genes whereas over-expression of the C3 protein increased TbCSV gene expression. Furthermore, the expression of the wild-type and site-directed mutants of C3 proteins using the potato virus X (PVX) system showed that Y93A mutation reduced the replication enhancement activity of the C3 protein in N. benthamiana. All the available evidence demonstrates that the C3 protein is tightly coupled with TbCSV DNA accumulation. However, the TbCSVΔC3 mutant was nearly as infectious in N. benthamiana as TbCSVWT and only had slightly delayed and attenuated symptom expression. Our findings demonstrate that TbCSV C3 protein enhances viral replication and gene expression, but has only moderate effects on symptom development in N. benthamiana.

Multi-omics study in monozygotic twins confirm the contribution of de novo mutation to psoriasis

BackgroundGenome-wide association studies have identified over 120 risk loci for psoriasis. However, most of the variations are located in non-coding region with high frequency and small effect size. Pathogenetic variants are rarely reported except HLA-C*0602 with the odds ratio being approximately 4.0 in Chinese population. Although rare variations still account for a small proportion of phenotypic variances in complex diseases, their effect on phenotypes is large. Recently, more and more studies focus on the low-frequency functional variants and have achieved a certain amount of success. MethodWhole genome sequencing and sanger sequencing was performed on 8 MZ twin pairs discordant for psoriasis to scan and verified the de novo mutations (DNMs). Additionally, 665 individuals with about 20 years' medical history versus 2054 healthy controls and two published large population studies which had about 8 years’ medical history (including 10,727 cases versus 10,582 controls) were applied to validate the enrichment of rare damaging mutations in two DNMs genes. Besides, to verify the pathogenicity of candidate DNM in C3, RNA-sequencing for CD4+, CD8+ T cells of twins and lesion, non-lesion skin of psoriasis patients were carried out. Meanwhile, the enzyme-linked immunosorbent assay kit was used to detect the level of C3, C3b in the supernatant of peripheral blood. ResultA total of 27 DNMs between co-twins were identified. We found six of eight twins carry HLA-C∗0602 allele which have large effects on psoriasis. And it is interesting that a missense mutation in SPRED1 and a splice region mutation in C3 are found in the psoriasis individuals in the other two MZ twin pairs without carrying HLA-C*0602 allele. In the replication stage, we found 2 loss-of-function (LOF) variants of C3 only in 665 cases with about 20 years' medical history and gene-wise analysis in 665 cases and 2054 controls showed that the rare missense mutations in C3 were enriched in cases (OR = 1.91, P = 0.0028). We further scanned the LOF mutations of C3 in two published studies (about 8 years’ medical history), and found one LOF mutation in the case without carrying HLA-C*0602. In the individual with DNM in C3, RNA sequencing showed the expression level of C3 in skin was significant higher than healthy samples in public database (TPM fold change = 1.40, P = 0.000181) and ELISA showed protein C3 in peripheral blood was higher (~2.2-fold difference) than the other samples of twins without DNM in C3. ConclusionTo the best of our knowledge, this is the first report that DNM in C3 is the likely pathological mutations, and it provided a better understanding of the genetic etiology of psoriasis and additional treatments for this disease.

Common Apoc3 Variants And Coronary Artery Disease

Background and Aims: Very rare loss-of-function mutations in the apolipoprotein C3 (APOC3) gene have been associated with low circulating apoC-III, low triglycerides, and reduced cardiovascular risk. However, these very rare mutations have also been related to low LDL cholesterol. We aimed to precisely analyze the impact of common APOC3 variants on circulating apoC-III, lipids, and on coronary artery disease in the largest sample so far.

A Premature Termination Codon Mutation in MYBPC3 Causes Hypertrophic Cardiomyopathy via Chronic Activation of Nonsense-Mediated Decay.

Hypertrophic cardiomyopathy (HCM) is frequently caused by mutations in myosin-binding protein C3 ( MYBPC3) resulting in a premature termination codon (PTC). The underlying mechanisms of how PTC mutations in MYBPC3 lead to the onset and progression of HCM are poorly understood. This study's aim was to investigate the molecular mechanisms underlying the pathogenesis of HCM associated with MYBPC3 PTC mutations by utilizing human isogenic induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Isogenic iPSC lines were generated from HCM patients harboring MYBPC3 PTC mutations (p.R943x; p.R1073P_Fsx4) using genome editing. Comprehensive phenotypic and transcriptome analyses were performed in the iPSC-CMs. We observed aberrant calcium handling properties with prolonged decay kinetics and elevated diastolic calcium levels in the absence of structural abnormalities or contracile dysfunction in HCM iPSC-CMs as compared to isogenic controls. The mRNA expression levels of MYBPC3 were significantly reduced in mutant iPSC-CMs, but the protein levels were comparable among isogenic iPSC-CMs, suggesting that haploinsufficiency of MYBPC3 does not contribute to the pathogenesis of HCM in vitro. Furthermore, truncated MYBPC3 peptides were not detected. At the molecular level, the nonsense-mediated decay pathway was activated, and a set of genes involved in major cardiac signaling pathways was dysregulated in HCM iPSC-CMs, indicating an HCM gene signature in vitro. Specific inhibition of the nonsense-mediated decay pathway in mutant iPSC-CMs resulted in reversal of the molecular phenotype and normalization of calcium-handling abnormalities. iPSC-CMs carrying MYBPC3 PTC mutations displayed aberrant calcium signaling and molecular dysregulations in the absence of significant haploinsufficiency of MYBPC3 protein. Here we provided the first evidence of the direct connection between the chronically activated nonsense-mediated decay pathway and HCM disease development.

A Contraction Stress Model of Hypertrophic Cardiomyopathy due to Sarcomere Mutations.

SummaryThick-filament sarcomere mutations are a common cause of hypertrophic cardiomyopathy (HCM), a disorder of heart muscle thickening associated with sudden cardiac death and heart failure, with unclear mechanisms. We engineered four isogenic induced pluripotent stem cell (iPSC) models of β-myosin heavy chain and myosin-binding protein C3 mutations, and studied iPSC-derived cardiomyocytes in cardiac microtissue assays that resemble cardiac architecture and biomechanics. All HCM mutations resulted in hypercontractility with prolonged relaxation kinetics in proportion to mutation pathogenicity, but not changes in calcium handling. RNA sequencing and expression studies of HCM models identified p53 activation, oxidative stress, and cytotoxicity induced by metabolic stress that can be reversed by p53 genetic ablation. Our findings implicate hypercontractility as a direct consequence of thick-filament mutations, irrespective of mutation localization, and the p53 pathway as a molecular marker of contraction stress and candidate therapeutic target for HCM patients.