MYH7 Research Articles

Clinical and genetic characterisation of hereditary distal myopathies in a series of Colombian patients

Hereditary distal myopathies represent a heterogeneous group of rare genetic disorders characterized by progressive distal muscle weakness. The objective of this study was to describe the clinical spectrum and genetic findings in a series of patients with distal myopathy from Colombia. A retrospective review of the medical records of 12 patients with distal myopathy seen at a neuromuscular center in Bogota, Colombia, between 2015 and 2023 was performed. Clinical data, family history, diagnostic studies and genetic test results were obtained. The mean age of onset was 15.7 years. Patterns of limb weakness included distal involvement in the upper and lower extremities (50%), distal involvement in the lower extremities in isolation (33.3%), and proximal and distal involvement in the upper and lower extremities (8.3%). Additional weakness was observed in the face (8.3%) and paraspinal muscles (25.0%). Creatine kinase levels were elevated in 58.3% of cases. Electromyography revealed a myopathic pattern in 91.6% of cases. Variants identified included MYH7, ANO5, TTN, HNRNPA1, DES, DYSF and CAV3 genes. This case series describes the clinical and genetic spectrum of inherited distal myopathies in Colombia. Findings demonstrate phenotypic and genotypic heterogeneity, with variants in genes encoding structural proteins. There is a need to expand access to genetic testing in Latin America to enable more accurate comprehensive diagnosis and treatment.

Association of polymorphisms in FBN1, MYH11, and TGF-β signaling-related genes with susceptibility of sporadic thoracic aortic aneurysm and dissection in the Zhejiang Han population.

Sporadic thoracic aortic aneurysm and dissection (sTAAD) is a complicated vascular disease with a high mortality rate. And its genetic basis has not been fully explored. Here, 122 sTAAD patients and 98 healthy individuals were recruited, and 10 single nucleotide polymorphisms were selected and analyzed (FBN1 rs10519177, rs1036477, rs2118181, MYH11 rs115364997, rs117593370, TGFβ1 rs1800469, TGFβ2 rs900, TGFβR2 rs764522, rs1036095, and rs6785385). Moreover, multiple logistic regression analysis was used to evaluate gene-environment interactions. We identified that TGFβR2 rs1036095 dominant model CC + CG genotype (GT) (P = 0.004) may be a factor of increased risk of sTAAD, especially for women. FBN1 rs1036477 recessive model AA GT (P = 0.009) and FBN1 rs2118181 dominant model CC + CT GT (P = 0.009) were correlated to an increased death rate in sTAAD men patients. Gene-environment interactions indicated TGFβR2 rs1036095 dominant model (CC + CG)/GG to be a higher-risk factor for sTAAD (odds ratio = 3.255; 95% confidence interval: 1.324-8.000, P = 0.01). TGFβR2 rs1036095, FBN1 rs1036477, and FBN1 rs2118181 were identified as factors of increased risk of sTAAD. Gene-environment interactions were associated with the risk of sTAAD.

Human Genetics of Tricuspid Atresia and Univentricular Heart.

Tricuspid atresia (TA) is a rare congenital heart condition that presents with a complete absence of the right atrioventricular valve. Because of the rarity of familial and/or isolated cases of TA, little is known about the potential genetic abnormalities contributing to this condition. Potential responsible chromosomal abnormalities were identified in exploratory studies and include deletions in 22q11, 4q31, 8p23, and 3p as well as trisomies 13 and 18. In parallel, potential culprit genes include the ZFPM2, HEY2, NFATC1, NKX2-5, MYH6, and KLF13 genes. The aim of this chapter is to expose the genetic components that are potentially involved in the pathogenesis of TA in humans. The large variability in phenotypes and genotypes among cases of TA suggests a genetic network that involves many components yet to be unraveled.

Prenatal diagnosis of Freeman-Sheldon syndrome using ultrasound and genetic testing. Case report

To describe a case of prenatal diagnosis of Freeman-Sheldon syndrome based on ultrasound findings and complete fetal exome sequencing. A 33-year-old patient currently on treatment for hypothyroidism in whom a 19-week detailed anatomical ultrasound scan showed fetal deformities in more than two body areas (upper and lower limbs), suggesting a diagnosis of arthrogryposis. Genetic counseling was provided and amniocentesis was performed at 20 weeks for fluorescence in situ hybridization (FISH) analysis and complete fetal exome sequencing, with the latter allowing the identification of a heterozygous pathogenic variant of the MYH3 gene which is associated with type 2A distal arthrogryposis. Complete fetal exome sequencing was a key factor in identifying the MYH3 gene mutation and confirmed that the deformities seen on ultrasound were associated with type 2A distal arthrogryposis. It is important to perform complete fetal exome sequencing in cases of joint malformations seen on prenatal ultrasound.

Gene-Specific Discriminative Echocardiogram Findings in Hypertrophic Cardiomyopathy Determined Using Artificial Intelligence: A Pilot Study

Hypertrophic cardiomyopathy (HCM) is among the most common forms of cardiomyopathies, with a prevalence of 1:200 to 1:500 people. HCM is caused by variants in genes encoding cardiac sarcomeric proteins, of which a majority reside in MYH7, MYBPC3, and TNNT2. Up to 40% of the HCM cases do not have any known HCM variant. Genotype–phenotype associations in HCM remain incompletely understood. This study involved two visits of 46 adult patients with a confirmed diagnosis of HCM. In total, 174 genes were analyzed on the Next-Generation Sequencing platform, and transthoracic echocardiography was performed. Gene-specific discriminative echocardiogram findings were identified using the computer vision library Fast AI. This was accomplished with the generation of deep learning models for the classification of ultrasonic images based on the underlying genotype and a later analysis of the most decisive image regions. Gene-specific echocardiogram findings were identified: for variants in the MYH7 gene (vs. variant not detected), the most discriminative structures were the septum, left ventricular outflow tract (LVOT) segment, anterior wall, apex, right ventricle, and mitral apparatus; for variants in MYBPC3 gene (vs. variant not detected) these were the septum, left ventricle, and left ventricle/chamber; while for variants in the TNNT2 gene (vs. variant not detected), the most discriminative structures were the septum and right ventricle.

Tetralogy of Fallot: variants of MYH6 gene promoter and cellular functional analyses.

Tetralogy of Fallot (TOF) is a common form of congenital heart disease. The MYH6 gene has important effects on cardiovascular growth and development. In 608 subjects, including 315 TOF patients, we investigated the MYH6 gene promoter variants and verified the effect on gene expression by using cellular functional experiments with three cell lines (HEK-293, HL-1, and H9C2 cells) and bioinformatics analysis. In the MYH6 gene promoter, 12 variants were identified from 608 subjects. Five variants were found only in patients with TOF and two of them (g.3384G>T and g.4518T>C) were novel. Electrophoretic mobility shift assay with three cell lines (HEK-293, HL-1, and H9C2) showed significant changes in the transcription factors bound by the promoter variants compared to the wild-type. Dual luciferase reporter showed that four of the five variants reduced the transcriptional activity of the MYH6 gene promoter (p < 0.05). This study is the first to test the cellular function of variants in the promoter region of the MYH6 gene in patients with TOF, which provides new insights into the genetic basis of TOF and provides a basis for further study of the mechanism of TOF formation. DNA from 608 human subjects was sequenced for MYH6 gene promoter region variants with five variants found only in TOF patients and two were novel. EMSA and dual luciferase reporter experiments in three cell lines found these variants pathological. Prediction by JASPAR database indicated that these variants alter the transcription factor binding sites. The study, for the first time, confirmed that there are variants at the MYH6 gene promoter region and these variants alter the cellular function. The variants found in this study suggest the possible pathological role in the formation of TOF.

Identification of common genes and pathways underlying imatinib and nilotinib treatment in CML: a Bioinformatics Study

Imatinib (IMA) and nilotinib are the first and second generations of BCR-ABL tyrosine kinase inhibitors, which widely applied in chronic myeloid leukemia (CML) treatment. Here we aimed to provide new targets for CML treatment by transcriptome analysis. Microarray data GSE19567 was downloaded and analyzed from Gene Expression Omnibus (GEO) to identify common genes, which are downregulated or upregulated in K562-imatinib and K562-nilotinib treated cells. The differentially expressed genes (DEGs) were assessed, and STRING and Cytoscape were used to create the protein–protein interaction (PPI) network. In imatinib and nilotinib treated groups’ comparison, there were common 626 upregulated and 268 downregulated genes, which were differentially expressed. The GO analysis represented the enrichment of DEGs in iron ion binding, protein tyrosine kinase activity, transcription factor activity, ATP binding, sequence-specific DNA binding, cytokine activity, the mitochondrion, sequence-specific DNA binding, plasma membrane and cell-cell adherens junction. KEGG pathway analysis revealed that downregulated DEGs were associated with pathways including microRNAs in cancer and PI3K-Akt signaling pathway. Furthermore, upregulated DEGs were involved in hematopoietic cell lineage, lysosome and chemical carcinogenesis. Among the upregulated genes, MYH9, MYH14, MYL10, MYL7, MYL5, RXRA, CYP1A1, FECH, AKR1C3, ALAD, CAT, CITED2, CPT1A, CYP3A5, CYP3A7, FABP1, HBD, HMBS and PPOX genes were found as hub genes. Moreover, 20 downregulated genes, YARS, AARS, SARS, GARS, CARS, IARS, RRP79, CEBPB, RRP12, UTP14A, PNO1, CCND1, DDX10, MYC, WDR43, CEBPG, DDIT3, VEGFA, PIM1 and TRIB3 were identified as hub genes. These genes have the potential to become target genes for diagnosis and therapy of CML patients.

Efficient selection of knocked-in pluripotent stem cells using a dual cassette cellular elimination system

Although recent advances in genome editing technology with homology-directed repair have enabled the insertion of various reporter genes into the genome of mammalian cells, the efficiency is still low due to the random insertion of donor vectors into the host genome. To efficiently select knocked-in cells without random insertion, we developed the "double-tk donor vector system," in which the expression units of the thymidine kinase of herpes simplex virus (HSV-tk) are placed on both outer sides of homology arms. This system is superior in enriching knocked-in human induced pluripotent stem cells (hiPSCs) than conventional donor vector systems with a single or no HSV-tk cassette. Using this system, we efficiently generated fluorescent reporter knockin hiPSCs targeting POU5F1 (OCT3/4), EEF1A1, H2BC21 (H2B clustered histone 21), ISL1, and MYH7 genes. These results indicate that the double-tk donor vector system enables efficient selection of knocked-in hiPSCs carrying reporter proteins.

неЩасливий випадок як поштовх до діагностики хвороби у 16-річного хлопця, пов’язаної з MYH9. Сюжет із практики гематолога

MYH9-related disease (MYH9-RD) is an autosomal dominant hereditary thrombocytopenia caused by mutations in the MYH9 gene with characteristic laboratory features - the presence of giant platelets and basophilic cytoplasmic inclusions in neutrophils (similar to Dele bodies). Patients with MYH9-RD are at high risk for deafness, cataracts, and renal dysfunction, most often occurring in adulthood. Platelet counts in patients with MYH9-RD range from severe thrombocytopenia to near-normal values, although they are usually stable. Propensity for hemorrhagic Complications correlate with platelet count and are usually absent or limited to minor bleeding in patients with mild thrombocytopenia, but may lead to spontaneous and potentially life-threatening bleeding with persistent platelet counts &lt;50×109/l. Purpose - to describe a clinical case of a disease caused by a heterozygous mutation in the MYH9 gene with an emphasis on the importance of genetic tests for the final verification of the disease. Clinical case. Features of diagnosis caused by a heterozygous mutation in the MYH9 gene in a 16-year-old boy are described. Throughout the child's life, the manifestations of the hemorrhagic syndrome were moderate (periodically a small number of bruises on the skin, to which the parents did not pay much attention, bleeding from the gums when brushing the teeth), the child’s blood tests were performed occasionally without determining the number of platelets. The boy suffered a displaced radius fracture as a result of the injury. The orthopedic traumatologist performed an operation of limited reposition of bone fragments followed by implantation of a needle for proper bone fusion without complications. During a general blood test, thrombocytopenia was detected, which prompted the child to be consulted by a hematologist. During the examination at the Western Ukrainian Specialized Pediatric Medical Center, Lviv, it was noted in the hardware count of the hemogram that the number of platelets was 22.0-30.0×109/l, the microscopic count of platelets was 147.0-156.0×109/l, the entire population of platelets was represented by macroforms with mean platelet volume 14.9 fl. We found good aggregation of platelets with ristocytin, and reduced aggregation with epinephrine, arachidonic acid, and adenosine. Verification of the final diagnosis of MYH9-RD caused by a heterozygous mutation in the MYH9 gene occurred by genome sequencing. Therefore, the application of the genome sequencing technique can contribute to the early diagnosis of hereditary macrothrombocytopenia caused by a heterozygous mutation in the MYH9 gene. The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

Clinical and Genetic Characteristics of 30 Patients Misdiagnosed As Having ITP with Non-Muscle Myosin Heavy Chain 9-Related Disease (MYH9-RD): A Retrospective Analysis in China

Introduction : Non-muscle myosin heavy chain 9-related diseases (MYH9-RD) are rare autosomal dominant platelet (PLT) disorders presenting as nonsyndromic forms characterized by macrothrombocytopenia with giant PLTs and leukocyte inclusion bodies or as syndromic forms combining these hematological features with deafness, nephropathy, or cataracts. Owing to its low incidence and similar clinical manifestations, it is easily misdiagnosed as immune thrombocytopenia (ITP), leading to inappropriate treatment. To improve the diagnosis of this rare thrombocytopenic disease and minimize the misdiagnosis rate, we retrospectively analyzed the clinical, treatment, and genetic characteristics of patients with MYH9-RD who were initially misdiagnosed with ITP and compared the differences between pediatric and adult patients. Methods: Patients from various sites in China were enrolled. The inclusion criteria were macrothrombocytopenia on peripheral blood smear, MYH9 gene mutation detected by next-generation sequencing or whole exon sequencing and verified by Sanger sequencing, and absence of other acquired thrombocytopenia diseases. We collected basic information, clinical manifestations, and laboratory test results via medical records and telephone interviews. Results: Of the 30 patients, 17 were male, 13 were female, 14 were children, and 16 were adults. There was no significant difference in the mean PLT count (×10 9/L) at the time of diagnosis between children and adults (50.5 vs. 33.4, P=0.188). However, the median duration of misdiagnosis was significantly shorter in children (0.1 y vs. 9 y, P=0.000) (Table 1). Overall, 5 patients showed no signs of bleeding, while 25 presented with bleeding manifestations: 11 with skin bleeding spots and ecchymosis, 15 with epistaxis, 6 with gingival bleeding, and 3 with increased menstrual volume. Moreover, 21 patients showed no non-hematological manifestations, while 9 presented with non-hematological manifestations, which occurred exclusively in adult patients. Among the latter, 6 patients had nephropathy (2 underwent renal transplantation, and 2 underwent regular dialysis), 5 had hearing impairment (4 underwent high-frequency hearing impairment, and 1 received a cochlear implant due to deafness), and 1 had a congenital cataract. All patients received first- or second-line treatment for ITP. The most common treatment in children was immunoglobulins (12/14), followed by steroids (5/14) and traditional Chinese medicine (2/14). No children received &amp;gt;3 types of treatment, 4 children received &amp;gt;1, and 6 adult patients received &amp;gt;3. The highest number of treatment type for a single patient was up to 7. The median duration of ITP treatment was 1.5 y for adults and 0.1 y for children ( P=0.002). All patients presented heterozygous missense mutations in MYH9; 17/30 were spontaneous mutations, 7/30 were familial mutations (involving 6 paternal and 1 maternal origin), and 6/30 cases had an unknown inherited type. Fourteen cases were located in the N-terminal globular head region, and 16 cases were located in the C-terminal tail domain (Figure 1). Two novel mutations (not recorded in the Global Variome database), p. G1517V and p. K1674Q, were identified. In 2 adult patients with p.R702C mutations, proteinuria occurred in adolescence, followed by chronic renal failure (CRF), end-stage renal failure, and hearing loss. The 3 children with p.R702C mutation were aged &amp;lt;4 years and exhibited no non-hematological symptoms. Three of the 5 adults with p.E1841K mutations had CRF and underwent kidney transplantation. Conclusion s : Compared with pediatric patients, adult patients are more likely to be misdiagnosed with ITP, receive more types of inappropriate treatment for a longer period of time, and have more common non-hematological manifestations. To improve diagnostic accuracy and reduce the misdiagnosis rate for patients with thrombocytopenia, especially those with a poor response to ITP treatments, attention should be paid to mean PLT volume, family history, and genetic screening. Consistent with previous reports, patients with the p.R702C mutation showed early-stage kidney injury and hearing loss. The incidence of spontaneous mutations (56.7%) was significantly higher than previously reported (25-35%). The genetic characteristics of MYH9-RD and genotype-phenotype relationships in China require further clarification.

Clinical phenotype and genetic analysis of patients with left ventricular noncompaction caused by the biallelic mutation of MYBPC3 and MYH7

Objective: To explore the relationship between pathogenic gene, mutation and phenotype of left ventricular noncompaction (LVNC) patients and their family members. Methods: The subjects were the proband with LVNC and her family members. The medical history including electrocardiogram, echocardiography and cardiac magnetic resonance examination of the proband and family members were collected. Whole exome sequencing of the proband was performed, bioinformatics analysis focused on the genes related to hereditary cardiomyopathy. Candidate pathogenic sites were validated by Sanger sequencing. The clinical interpretation of sequence variants were classified according to American College of Medical Genetics and Genomics (ACMG) guidelines. Results: The proband carried a heterozygous variation of the MYBPC3 gene c.C2827T and the MYH7 gene c.G2221C. The proband's sister carried heterozygous variation of MYBPC3 gene c.C2827T. According to the ACMG guidelines, the variant was determined to be pathogenic. Conclusion: The missense variant of MYBPC3 gene c.C2827T and MYH7 gene c.G2221C are identified from the proband with LVNC and her family member, which provides a genetic basis for clinical diagnosis and genetic counseling of the patients and the family members with LVNC.

Qualitative platelet alterations in May — Hegglin anomaly

Introduction: May — Hegglin anomaly is an autosomal dominant mutation in the MYH9 gene that disrupts the dynamics of the cytoskeleton in megakaryocytes. Megakaryocyte dysfunction entails a violation of thrombocytopoiesis, which is manifested by macrothrombocytopenia, sometimes associated with bleeding. Aim: to study the structure and function of platelets in the family members with documented May — Hegglin anomaly. Patients and methods. The proband, her sister and their mother who all had a heterozygous mutation R1933X in the MYH9 gene were examined. The examination included complete blood count, peripheral blood microscopy, platelet flow cytometry, blood clot contraction kinetics, scanning and transmission electron microscopy of platelets. The control group included10 healthy donors. Results. In the proband and her sister the degree of contraction of blood clots was reduced. Unstimulated platelets displayed overexpression of P-selectin and active αIIbβ3 integrin. After TRAP-induced stimulation the proportion of platelets expressing P-selectin in the patients was below normal, indicating partial platelet refractoriness. Electron microscopy of the unstimulated platelets revealed macrothrombocytosis and multiple filopodia, as well as enlargement of the open canalicular system. Conclusion. The May — Hegglin anomaly caused by a heterozygous mutation R1933X in the MYH9 gene is accompanied by thrombocytopenia associated with structural and functional platelet defects. Partial platelet refractoriness and contractile dysfunction can impair the retraction of hemostatic clots, predisposing patients with MYH9-related disorders to bleeding.

Phenotype and genotype characteristics of children with cardiomyopathy associated with MYH7 gene mutation: a retrospective analysis

To investigate the clinical phenotype and genotype characteristics of children withcardiomyopathy (CM) associated with MYH7 gene mutation. A retrospective analysis was conducted on the medical data of five children with CM caused by MYH7 gene mutation who were diagnosed and treated in the Department of Cardiology, Hebei Children's Hospital. Among the five children with CM, there were three girls and two boys, all of whom carried MYH7 gene mutation. Seven mutation sites were identified, among which five were not reported before. Among the five children, there were three children with hypertrophic cardiomyopathy, one child with dilated cardiomyopathy, and one child with noncompaction cardiomyopathy. The age ranged from 6 to 156 months at the initial diagnosis. At the initial diagnosis, two children had the manifestations of heart failure such as cough, shortness of breath, poor feeding, and cyanosis of lips, as well as delayed development; one child had palpitation, blackness, and syncope; one child had fever, runny nose, and abnormal liver function; all five children had a reduction in activity endurance. All five children received pharmacotherapy for improving cardiac function and survived after follow-up for 7-24 months. The age of onset varies in children with CM caused by MYH7 gene mutation, and most children lack specific clinical manifestations at the initial diagnosis and may have the phenotype of hypertrophic cardiomyopathy, dilated cardiomyopathy or noncompaction cardiomyopathy. The children receiving early genetic diagnosis and pharmacological intervention result in a favorable short-term prognosis.

Rare Case of Dense Deposition Disease with Combined C3 and C4d Deposits with MYH9-related Mutation

Background: The C3 glomerulopathies are a group of rare forms of glomerulonephritis with an incidence of 1-2 cases per million. It is mainly characterized by dysregulation of the alternative complement pathway. It is further classified morphologically based on electron microscopy ultrastructural findings into Dense Deposition Disease (DDD) and C3 glomerulonephritis. DDD is normally characterised by C3 Deposits. Case: We report a rare case of a young Emirati male who presented with sub nephrotic proteinuria and microscopic haematuria on routine evaluation. Renal biopsy showed features of DDD with combined C3 and C4 deposits. The retinal evaluation showed features of Drusen classically seen in DDD. Genomic study showed heterozygous mutation in c.5842G&gt;C (p.Asp1948His) variant of uncertain significance in MYH9 gene. Discussion: C3 Glomerulopathy is a type of immune mediated disease previously classified as membranoproliferative glomerulonephritis. DDD is mainly characterised by C3 deposits in the glomerular basement Membrane. Our case has both C3 and C4d deposits, which is a rare entity. It shows the activation of both classical and alternate pathways. Conclusion: Dense deposition disease is a rare complement mediated glomerulopathy. It is characterised by C3 deposits. Dense deposition disease with combined C3 and C4d deposits is a new entity. The treatment and prognosis of such cases will be different and unique compared to the normal cases of DDD.

Genetic testing in presumed cardiac sarcoidosis

Abstract Background Cardiac sarcoidosis (CS) is a difficult to diagnose inflammatory heart disease. Certain types of genetic cardiomyopathy have been reported to masquerade as inflammatory cardiomyopathy. The utility of genetic testing in the evaluation of inflammatory cardiomyopathy is not completely explored and data regarding the prevalence of genetic cardiomyopathies in patients with presumed CS is limited. Methods We retrospectively analyzed patients evaluated from May 2020 to October 2022 in our Cardiac Sarcoid Clinic diagnosed with presumed CS as inferred by either fluorodeoxyglucose positron emission tomography (FDG-PET) - computed tomography (CT) or cardiac magnetic resonance (CMR) or both. Pertinent demographic, genetic, electrocardiographic, and imaging data for these patients was extracted from the electronic medical record. Results Genetic testing was obtained in 47 (22%) of the 213 presumed CS patients, among whom 43 (91%) presented with suspected isolated CS, and 4 (9%) with possible cardiac involvement in the setting of systemic sarcoidosis. Among the patients who underwent genetic testing, 10 (21 %) had a pathogenic or likely pathogenic (P/LP) variant(s) in a genetic cardiomyopathy-susceptibility gene, including DSP (n=2), LMNA, FHL1, TPM1, MYBPC3, NRAS, MYH7 (n=2) and TTN (n= 2) genes. All P/LP patients had FDG uptake, and in those with CMR data, 100% had late gadolinium enhancement. The seven patients with P/LP who underwent endomyocardial biopsy had no evidence of granulomatous inflammation. Immunosuppression was initiated in 60% of the P/LP patients before knowledge of genetic results. Conclusion Patients suspected to have CS may have concomitant or primarily genetic cardiomyopathy that may masquerade as an inflammatory phenotype Genetic testing should be considered in these patients, not only to clarify the diagnosis and its prognostic and therapeutic implications, but also to offer cascade screening for the family of patients with P/LP variants who otherwise would not have been considered to have a heritable disease.

Enhanced myofilament calcium sensitivity aggravates abnormal calcium handling and diastolic dysfunction in patient-specific induced pluripotent stem cell-derived cardiomyocytes with MYH7 mutation

Hypertrophic cardiomyopathy (HCM), the most common inherited heart disease, is frequently caused by mutations in the β-cardiac myosin heavy chain gene (MYH7). Abnormal calcium handling and diastolic dysfunction are archetypical features of HCM caused by MYH7 gene mutations. However, the mechanism of how MYH7 mutations leads to these features remains unclear, which inhibits the development of effective therapies. Initially, cardiomyocytes were generated from induced pluripotent stem cells from an eight-year-old girl diagnosed with HCM carrying a MYH7(C.1063 G>A) heterozygous mutation(mutant-iPSC-CMs) and mutation-corrected isogenic iPSCs(control-iPSC-CMs) in the present study. Next, we compared phenotype of mutant-iPSC-CMs to that of control-iPSC-CMs, by assessing their morphology, hypertrophy-related genes expression, calcium handling, diastolic function and myofilament calcium sensitivity at days 15 and 40 respectively. Finally, to better understand increased myofilament Ca2+ sensitivity as a central mechanism of central pathogenicity in HCM, inhibition of calcium sensitivity with mavacamten can improveed cardiomyocyte hypertrophy. Mutant-iPSC-CMs exhibited enlarged areas, increased sarcomere disarray, enhanced expression of hypertrophy-related genes proteins, abnormal calcium handling, diastolic dysfunction and increased myofilament calcium sensitivity at day 40, but only significant increase in calcium sensitivity and mild diastolic dysfunction at day 15. Increased calcium sensitivity by levosimendan aggravates cardiomyocyte hypertrophy phenotypes such as expression of hypertrophy-related genes, abnormal calcium handling and diastolic dysfunction, while inhibition of calcium sensitivity significantly improves cardiomyocyte hypertrophy phenotypes in mutant-iPSC-CMs, suggesting increased myofilament calcium sensitivity is the primary mechanisms for MYH7 mutations pathogenesis. Our studies have uncovered a pathogenic mechanism of HCM caused by MYH7 gene mutations through which enhanced myofilament calcium sensitivity aggravates abnormal calcium handling and diastolic dysfunction. Correction of the myofilament calcium sensitivity was found to be an effective method for treating the development of HCM phenotype in vitro.

Sudden Cardiac Death in Biventricular Arrhythmogenic Cardiomyopathy: A New Undescribed Variant of the MYH6 Gene

Arrhythmogenic cardiomyopathy (ACM) may present with sudden cardiac arrest (SCA), and demonstration of a pathogenic variant in ACM-related genes is crucial for its definitive diagnosis. A 42-year-old female patient with family history of sudden cardiac death (SCD) was referred to the cardiomyopathy clinic after two episodes of aborted SCA. In the second episode, the patient was transported under cardiopulmonary resuscitation (downtime of 57 min) until extracorporeal membrane oxygenation was implanted. A thorough diagnostic work-up led to a diagnosis of biventricular ACM. Genetic testing revealed a previously undescribed variant in ACM patients in the MYH6 gene, c.3673G&gt;T p.(Glu 1225*), which inserts a premature stop codon. This was considered a possible pathogenic variant originating a truncated protein, previously undescribed in ACM. The patient’s 23-year-old daughter was positive for the MYH6 variant and had ECG abnormalities suggestive of ACM. This case details the complex differential diagnosis of SCA and explores the current recommendations for the diagnosis of biventricular ACM. The identification of a MYH6 variant in a patient with ACM, recurrent SCA, and family history of SCD appears to support the hypothesis of the pathogenicity of MYH6 variants in ACM, in which the association of phenotype with sarcomere variants is still unclear.

Analysis of clinical phenotype and gene mutation characteristics of MYH9-related disorder

Objective: To investigate the clinical phenotype and gene mutation characteristics of MYH9-related disorder (MYH9-RD). Methods: The clinical data of 66 patients with MYH9-RD in the First Affiliated Hospital of Soochow University from January 2010 to December 2022 were retrospectively analyzed. According to the bleeding symptom, the patients were divided into bleeding and non-bleeding group, and according to the mutation sites, the patients were divided into non-muscle myosin heavy chain ⅡA head region (MD) and tail region (TD) mutation group. Statistical analysis was made to explore the clinical features in different groups such as platelet counts, bleeding, renal function, cataracts and hearing as well as MYH9 gene mutations. Results: A total of 66 MYH9-RD patients were included, with 28 males and 38 females, diagnosis age of 1-63(26±2) years. And 41% (27/66) of the patients had no family history. All patients presented with macrothrombocytopenia and normal platelet aggregation(10/10), 92% (54/59) of the patients had visible blue inclusion bodies in neutrophils, 30% (20/66) had bleeding symptoms, 45% (22/49) had proteinuria or glomerulonephropathy, 20% (8/41) had bilateral hearing impairment, and 10% (4/42) had bilateral cataracts. 18 mutation sites were identified in total, including 15 missense, 1 splicing and 2 termination mutations. Among them, p.Asp1424Asn, p.Arg1933* and p.Arg702His/Cys mutations were identified in 56% (29/52) of the patients, and p.Ser96Leu, Arg1165Cys and p.Glu1841Lys mutations were recurrent mutations, while p.Ala44Thr, p.Asp1447Ala and c.3838-2A>G mutations were novel mutations. The average platelet count of patients in bleeding group was (19±3)×109/L, which was significantly less than (36±3)×109/L in non-bleeding group (P<0.001). Compared with TD mutation group, patients of MD mutation group were presented with lower platelet count and higher risk of bleeding, as well as more severe clinical presentations including renal and hearing impairment and cataracts (all P<0.05). Conclusion: Mutations of p.Asp1424Asn, p.Arg1933* and p.Arg702His/Cys in MYH9 gene are hotspot mutations for MYH9-RD patients, Compared with TD mutation group, patients of MD mutation group were presented with lower platelet count and higher risk of bleeding, as well as more severe clinical presentations including renal and hearing impairment and cataracts.

Clinical and genetic analysis of eight children with Primary hypertrophic cardiomyopathy

To explore the clinical and genetic characteristics of eight children with Primary hypertrophic cardiomyopathy (HCM). Eight children with HCM admitted to the Department of Cardiology of Henan Children's Hospital from January 2018 to December 2021 were selected as the study subjects. Clinical data of the children were collected. Whole exome sequencing was carried out on two children, and trio whole exome sequencing was carried out on the remainder 6 children. Sanger sequencing was used to verify the candidate variants in the children and their parents, and the pathogenicity of the variants was evaluated based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The patients had included 5 males and 3 females, with their ages ranging from 5 to 13 years old. The average age of diagnosis was (7.87 ± 4.8) years old, and the cardiac phenotype showed non-obstructive HCM in all of the patients. WES has identified variants of the MYH7 gene in 4 children, including c.2155C>T (p.Arg719Trp), c.1208G>A (p.Arg403Gln), c.1358G>A (p.Arg453His), and c.1498G>A (p.Glu500Lys). Based on the guidelines from the ACMG, the first 3 variants were classified as pathogenic, while c.1498G>A (p.Glu500Lys) was classified as likely pathogenic (PM1+PM2_Supporting+PM6+PP3), which was also unreported previously. The remaining four children had all harbored maternal variants, including MYL2: c.173G>A (p.Arg58Gln; classified as pathogenic), TPM1: c.574G>A (p.Glu192Lys) and ACTC1: c.301G>A (p.Glu101Lys)(both were classified as likely pathogenic), and MYBPC3: c.146T>G (p.Ile49Ser; classified as variant of uncertain significance). Seven children were treated with 0.5 ~ 3 mg/(kg·d) propranolol, and their symptoms had improved significantly. They were followed up until September 30, 2022 without further cardiac event. Genetic testing can clarify the molecular basis for unexplained cardiomyopathy and provide a basis for clinical diagnosis and genetic counseling. Discovery of the c.1498G>A (p.Glu500Lys) variant has also expanded the spectrum of MYH7 gene mutations underlying HCM.

Successful renal transplantation following hemodialysis as bridging therapy in a patient with Fechtner syndrome: a case report and literature review

BackgroundFechtner syndrome, also referred to as nonmuscle myosin heavy chain 9-related disease (MYH9-RD), is an autosomal-dominant genetic disorder. It is caused by abnormalities in the MYH9 gene, which encodes the nonmuscle conventional (class II) myosin heavy chain A (NMMHC-IIA). Its clinical manifestations include mild macrothrombocytopenia with leukocyte inclusions, hearing loss, cataracts, and renal failure.Case presentationWe present the case of a 34-year-old female patient with Fechtner syndrome in whom end-stage renal disease (ESRD) developed. During childhood, she presented with the typical symptoms of MYH9-RD, including thrombocytopenia, leukocyte inclusion bodies, onset of nephropathy, sensorineural hearing loss, and cataracts, wherein a clinical diagnosis of Fechtner syndrome was established. Her renal function deteriorated during adolescence. Furthermore, the patient underwent renal biopsy at the age of 18 years, which revealed focal segmental glomerulosclerosis. She was started on hemodialysis at the age of 33 years, followed by a living-donor renal transplantation after 5 months. She achieved a target platelet count of 50 × 109/L for arteriovenous fistula creation and 100 × 109/L for renal transplantation via platelet transfusions. Heparin use was avoided as an anticoagulant during hemodialysis. Since the patient expressed a desire for childbearing, genetic testing was performed, revealing an in-frame deletion of 21 nucleotides at 3195–3215 in exon 25 (A1065_A1072 del) of NMMHC-IIA, which has been reported to correlate with mild renal dysfunction. Our patient’s condition progressed into ESRD. Although genetic testing techniques have made great strides in recent years, our case clearly presents the difficulty in assuming an association between genetic abnormalities and clinical manifestations.ConclusionsOur case may provide further understanding of the management of ESRD in patients with MYH9-RD-related thrombocytopenia based on the results of genetic testing.