Nonmuscle Myosin Heavy Chain IIA Mutation Predicts Severity and Progression of Sensorineural Hearing Loss in Patients With MYH9-Related Disease

Unraveling MYH9-related disease: A case study on misdiagnosis with idiopathic thrombocytopenic purpura, confirmed through genetic

This paper presents a detailed analysis of a case initially misdiagnosed as Idiopathic Thrombocytopenic Purpura (ITP), which was later correctly identified as MYH9-related disease (MYH9-RD), a rare genetic disorder characterized by thrombocytopenia, large platelets, and Döhle-like inclusion bodies in neutrophils. Using advanced slide reading technology, our team identified hallmark features of MYH9-RD in the patient's blood samples, leading to genetic testing that confirmed a spontaneous mutation in the MYH9 gene. This report highlights the diagnostic journey, emphasizing the crucial role of recognizing specific hematologic signs to accurately diagnose MYH9-RD. By comparing our findings with existing literature, we highlight the genetic underpinnings and clinical manifestations of MYH9-RD, emphasizing the necessity for heightened awareness and diagnostic precision in clinical practice to prevent similar cases of misdiagnosis. This case demonstrates the importance of integrating genetic testing into routine diagnostic protocols for unexplained thrombocytopenia, paving the way for improved patient care and treatment outcomes.

MYH9-related inherited thrombocytopenia: the genetic spectrum, underlying mechanisms, clinical phenotypes, diagnosis, and management approaches

Inherited thrombocytopenias have been considered exceedingly rare for a long time, but recent advances have facilitated diagnosis and greatly enabled the discovery of new causative genes. MYH9-related disease (MYH9-RD) represents one of the most frequent forms of inherited thrombocytopenia, usually presenting with nonspecific clinical manifestations, which renders it difficult to establish an accurate diagnosis. MYH9-RD is an autosomal dominant-inherited thrombocytopenia caused by deleterious variants in the MYH9 gene encoding the heavy chain of nonmuscle myosin IIA. Patients with MYH9-RD usually present with thrombocytopenia and platelet macrocytosis at birth or in infancy, and most of them may develop one or more extrahematologic manifestations of progressive nephritis, sensorial hearing loss, presenile cataracts, and elevated liver enzymatic levels during childhood and adult life. Here, we have reviewed recent advances in the study of MYH9-RD, which aims to provide an updated and comprehensive summary of the current knowledge and improve our understanding of the genetic spectrum, underlying mechanisms, clinical phenotypes, diagnosis, and management approaches of this rare disease. Importantly, our goal is to enable physicians to better understand this rare disease and highlight the critical role of genetic etiologic analysis in ensuring accurate diagnosis, clinical management, and genetic counseling while avoiding ineffective and potentially harmful therapies for MYH9-RD patients.

Heterozygous MYH9 Mutations in 2 Children With Cochlear Nerve Canal Stenosis

MYH9 is a gene that encodes for a subunit of the myosin heavy chain IIA protein. Mutations in MYH9 are associated with hematologic abnormalities, renal dysfunction, and hearing loss. Bony cochlear nerve canal stenosis (CNCS), which is diagnosed on computed tomography (CT) imaging, has been associated with congenital deafness, cochlear nerve aplasia/hypoplasia, and inner ear malformations. We report two cases of CNCS presenting with profound congenital hearing loss whom we diagnosed with mutations in MYH9 and discuss the genotype-phenotype association and implications for management.

Defective VWF secretion due to the expression of MYH9-RD E1841K mutant in endothelial cells disrupts hemostasis

Mutations in MYH9, the gene encoding the heavy chain of non-muscle myosin IIa (NMII-A), cause MYH9-related disease (MYH9-RD) that is an autosomal-dominant thrombocytopenia with bleeding tendency. Previously, we showed that NMII-A in endothelial cells (ECs) is critical for hemostasis via regulating von Willebrand factor (VWF) release from Weibel-Palade bodies (WPBs). The aim of this study was to determine the role of the expression of MYH9 mutants in ECs in the pathogenesis of the MYH9-RD bleeding symptom. First, we expressed the 5 most common NMII-A mutants in ECs, and found that E1841K mutant-expressing ECs secreted less VWF than the controls in response to a cAMP signaling agonist. Then, we generated 2 knockin mouse lines, one with Myh9 E1841K in ECs and the other in megakaryocytes. Endothelium-specific E1841K mice exhibited impaired cAMP-induced VWF release and a prolonged bleeding time with normal platelets, while megakaryocyte-specific E1841K mice exhibited macrothrombocytopenia and a prolonged bleeding time with normal VWF release. Finally, we present mechanistic findings that E1841K mutation not only interferes with S1943 phosphorylation and impairs the peripheral distribution of Rab27a positive WPBs in ECs under quiescent condition, but also interferes with S1916 phosphorylation by disrupting the interaction with zyxin and CKIIα, and reduces actin framework formation around WPBs and subsequent VWF secretion under the stimulation by a cAMP agonist. Altogether, our results suggest that impaired cAMP-induced endothelial VWF secretion by E1841K mutant expression may contribute to the MYH9-RD bleeding phenotype.

Inherited thrombocytopenias: an updated guide for clinicians

The great advances in the knowledge of inherited thrombocytopenias (ITs) made since the turn of the century have significantly changed our view of these conditions. To date, ITs encompass 45 disorders with different degrees of complexity of the clinical picture and very wide variability in the prognosis. They include forms characterized by thrombocytopenia alone, forms that present with other congenital defects, and conditions that predispose to acquire additional diseases over the course of life. In this review, we recapitulate the clinical features of ITs with emphasis on the forms predisposing to additional diseases. We then discuss the key issues for a rational approach to the diagnosis of ITs in clinical practice. Finally, we aim to provide an updated and comprehensive guide to the treatment of ITs, including the management of hemostatic challenges, the treatment of severe forms, and the approach to the manifestations that add to thrombocytopenia.

Successful cochlear implantation in a patient with Epstein syndrome during long-term follow-up

Epstein syndrome is a rare disease characterized by macrothrombocytopenia, nephritis and progressive sensorineural hearing loss (SNHL). This syndrome is presently recognized as an autosomal dominant disease caused by mutations of non-muscle myosin heavy chain 9 (MYH9). Little information is available about the progress of SNHL, the efficacy of cochlear implants (CI) or the perioperative management of thrombocytopenia in patients with Epstein syndrome. We herein report a case of a patient with Epstein syndrome with the MYH9:c.2105G>A:p.R702H variant who underwent cochlear implantation after 27 years of follow-up for her progressive SNHL. The deterioration rates of hearing were 3.48 dB/year on the right ear and 2.46 dB/year on the left ear. The patient derived benefits from CI and had a speech recognition test result (for sentences) of 93% at 6-months postoperatively. Thrombocytopenia was successfully managed without any bleeding complications by using eltrombopag, an oral thrombopoietic agent, making transfusion of platelets unnecessary. The accurate diagnosis of Epstein syndrome was made only after long-term follow-up as the thrombocytopenia was initially diagnosed as idiopathic thrombocytopenic purpura. This case report highlights the perioperative management of thrombocytopenia, the progress of SNHL and the potential pitfalls of diagnosis.

A New Pathogenic Variant in the TRIOBP Associated with Profound Deafness Is Remediable with Cochlear Implantation

BACKGROUND AND OBJECTIVES

A rare type of nonsyndromic autosomal recessive hereditary hearing loss is caused by pathogenic mutations in the TRIOBP gene mostly involving exons 6 and 7. These mutations cause hearing loss originating from dysfunction of sensory inner ear hair cells. Of all the affected siblings, 2 brothers and 1 sister, part of an Afghan family, were referred to our clinic for diagnostic workup and candidacy selection for cochlear implantation (CI).

METHODS

Molecular analysis showed a homozygous c.1342C > T p. (Arg448*) pathogenic variant in exon 7 of the TRIOBP gene (reference sequence NM_001039141.2) in all 3 affected siblings. Clinical audiometry demonstrated profound sensorineural hearing loss in all 3 affected siblings (2 males and 1 female), and they were implanted unilaterally.

RESULTS

One month after activation, the pure-tone averages with the CI processor were between 30 and 23 dBHL. Ten months after the first activation of the implant, open-set speech audiometry test could be performed for the first time in the 2 younger CI recipients (S5 and S9), and they could identify up to a maximum 77% phonemes correctly. The oldest brother (S12) could not yet perform open-set speech audiometry at that moment.

CONCLUSIONS

Implant outcomes are better with normal inner ear anatomy in general. The earlier congenital patients are implanted, the better their outcomes. Here, we demonstrate both statements are true in a homozygous c.1342C > T p. (Arg448*) pathogenic variant in the TRIOBP gene in all 3 affected siblings.

The intragenic microRNA miR199A1 in the dynamin 2 gene contributes to the pathology of X-linked centronuclear myopathy

Mutations in the myotubularin 1 (MTM1) gene can cause the fatal disease X-linked centronuclear myopathy (XLCNM), but the underlying mechanism is incompletely understood. In this report, using an Mtm1 ^-/y disease model, we found that expression of the intragenic microRNA miR-199a-1 is up-regulated along with that of its host gene, dynamin 2 (Dnm2), in XLCNM skeletal muscle. To assess the role of miR-199a-1 in XLCNM, we crossed miR-199a-1 ^-/- with Mtm1 ^-/y mice and found that the resultant miR-199a-1-Mtm1 double-knockout mice display markers of improved health, as evidenced by lifespans prolonged by 30% and improved muscle strength and histology. Mechanistic analyses showed that miR-199a-1 directly targets nonmuscle myosin IIA (NM IIA) expression and, hence, inhibits muscle postnatal development as well as muscle maturation. Further analysis revealed that increased expression and phosphorylation of signal transducer and activator of transcription 3 (STAT3) up-regulates Dnm2/miR-199a-1 expression in XLCNM muscle. Our results suggest that miR-199a-1 has a critical role in XLCNM pathology and imply that this microRNA could be targeted in therapies to manage XLCNM.

Whole exome sequencing in the diagnostic workup of patients with a bleeding diathesis

INTRODUCTION

Bleeding assessment tools and laboratory phenotyping often remain inconclusive in patients with a haemorrhagic diathesis.

AIM

To describe the phenotype and genetic profile of patients with a bleeding tendency.

METHODS

Whole exome sequencing (WES) was incorporated in the routine diagnostic pathway of patients with thrombocytopenia (n = 17), platelet function disorders (n = 19) and an unexplained bleeding tendency (n = 51). The analysis of a panel of 126 OMIM (Online Mendelian Inheritance in Man) genes involved in thrombosis and haemostasis was conducted, and if negative, further exome-wide analysis was performed if informed consent given.

RESULTS

Eighteen variants were detected in 15 patients from a total of 87 patients (17%). Causative variants were observed in MYH9 (two cases), SLFN14, P2RY12 and GP9. In addition, one case was considered solved due to combined carriership of F7 and F13A1 variants and one with combined carriership of F2, F8 and VWF, all variants related to secondary haemostasis protein aberrations. Two variants of uncertain significance (VUS) were found in two primary haemostasis genes: GFI1B and VWF. Eight patients were carriers of autosomal recessive disorders. Exome-wide analysis was performed in 54 cases and identified three variants in candidate genes.

CONCLUSION

Based on our findings, we conclude that performing WES at the end of the diagnostic trajectory can be of additive value to explain the complete bleeding phenotype in patients without a definite diagnosis after conventional laboratory tests. Discovery of combinations of (novel) genes that predispose to bleeding will increase the diagnostic yield in patients with an unexplained bleeding diathesis.

MYH9: Structure, functions and role of non-muscle myosin IIA in human disease

The MYH9 gene encodes the heavy chain of non-muscle myosin IIA, a widely expressed cytoplasmic myosin that participates in a variety of processes requiring the generation of intracellular chemomechanical force and translocation of the actin cytoskeleton. Non-muscle myosin IIA functions are regulated by phosphorylation of its 20 kDa light chain, of the heavy chain, and by interactions with other proteins. Variants of MYH9 cause an autosomal-dominant disorder, termed MYH9-related disease, and may be involved in other conditions, such as chronic kidney disease, non-syndromic deafness, and cancer. This review discusses the structure of the MYH9 gene and its protein, as well as the regulation and physiologic functions of non-muscle myosin IIA with particular reference to embryonic development. Moreover, the review focuses on current knowledge about the role of MYH9 variants in human disease.

Identification and characterization of MYH9 locus for high efficient gene knock-in and stable expression in mouse embryonic stem cells

Targeted integration of exogenous genes into so-called safe harbors/friend sites, offers the advantages of expressing normal levels of target genes and preventing potentially adverse effects on endogenous genes. However, the ideal genomic loci for this purpose remain limited. Additionally, due to the inherent and unresolved issues with the current genome editing tools, traditional embryonic stem (ES) cell-based targeted transgenesis technology is still preferred in practical applications. Here, we report that a high and repeatable homologous recombination (HR) frequency (>95%) is achieved when an approximate 6kb DNA sequence flanking the MYH9 gene exon 2 site is used to create the homology arms for the knockout/knock-in of diverse nonmuscle myosin II (NM II) isoforms in mouse ES cells. The easily obtained ES clones greatly facilitated the generation of multiple NM II genetic replacement mouse models, as characterized previously. Further investigation demonstrated that though the targeted integration site for exogenous genes is shifted to MYH9 intron 2 (about 500bp downstream exon 2), the high HR efficiency and the endogenous MYH9 gene integrity are not only preserved, but the expected expression of the inserted gene(s) is observed in a pre-designed set of experiments conducted in mouse ES cells. Importantly, we confirmed that the expression and normal function of the endogenous MYH9 gene is not affected by the insertion of the exogenous gene in these cases. Therefore, these findings suggest that like the commonly used ROSA26 site, the MYH9 gene locus may be considered a new safe harbor for high-efficiency targeted transgenesis and for biomedical applications.

Utility and limitations of exome sequencing in the molecular diagnosis of pediatric inherited platelet disorders

Inherited platelet disorders (IPD) are a heterogeneous group of rare disorders that affect platelet number and function and often predispose to other significant medical complications. In spite of the identification of over 50 IPD disease-associated genes, a molecular diagnosis is only identified in a minority (10%) of affected patients without a clinically suspected etiology. We studied a cohort of 21 pediatric patients with suspected IPDs by exome sequencing (ES) to: (1) examine the performance of the exome test for IPD genes, (2) determine if this exome-wide diagnostic test provided a higher diagnostic yield than has been previously reported, (3) to evaluate the frequency of variants of uncertain significance identified, and (4) to identify candidate variants for functional evaluation in patients with an uncertain or negative diagnosis. We established a high priority gene list of 53 genes, evaluated exome capture kit performance, and determined the coverage for these genes and disease-related variants. We identified likely disease causing variants in 5 of the 21 probands (23.8%) and variants of uncertain significance in 52% of patients studied. In conclusion, ES has the potential to molecularly diagnose causes of IPD, and to identify candidate genes for functional evaluation. Robust exome sequencing also requires that coverage of genes known to be associated with clinical findings of interest need to be carefully examined and supplemented if necessary. Clinicians who undertake ES should understand the limitations of the test and the full significance of results that may be returned.

Hereditary thrombocytopenias: a growing list of disorders

The introduction of high throughput sequencing (HTS) techniques greatly improved the knowledge of inherited thrombocytopenias (ITs) over the last few years. A total of 33 different forms caused by molecular defects affecting at least 32 genes have been identified; along with the discovery of new disease-causing genes, pathogenetic mechanisms of thrombocytopenia have been better elucidated. Although the clinical picture of ITs is heterogeneous, bleeding has been long considered the major clinical problem for patients with IT. Conversely, the current scenario indicates that patients with some of the most common ITs are at risk of developing additional disorders more dangerous than thrombocytopenia itself during life. In particular, MYH9 mutations result in congenital macrothrombocytopenia and predispose to kidney failure, hearing loss, and cataracts, MPL and MECOM mutations cause congenital thrombocytopenia evolving into bone marrow failure, whereas thrombocytopenias caused by RUNX1, ANKRD26, and ETV6 mutations are characterized by predisposition to hematological malignancies. Making a definite diagnosis of these forms is crucial to provide patients with the most appropriate treatment, follow-up, and counseling. In this review, the ITs known to date are discussed, with specific attention focused on clinical presentations and diagnostic criteria for ITs predisposing to additional illnesses. The currently available therapeutic options for the different forms of IT are illustrated.

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA "on" and "off" motifs. Proteomics analysis was performed on AGS cell pre-infection and postinfection with H. pylori oipA "on" and "off" strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down-regulated postinfection with oipA "off" strains comparing to oipA "on" strains. Furthermore, oipA "off" and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell-cycle arrest than oipA "on" strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA "on" strains predominates.

The expression of MYH9 in osteosarcoma and its effect on the migration and invasion abilities of tumor cell

OBJECTIVE

To determine the expression of non-muscle myosin heavy chain 9 (MYH9) in osteosarcoma and its effect on the migration and invasion abilities of tumor cell.

METHODS

A total of 65 cases of osteosarcoma and 20 cases with benign osteochondroma who underwent resection operation in the Orthopaedics Department of our hospital from January 1st 2009 to January 1st 2015 were selected. Their mRNA levels of MYH9 were tested by qrt-PCR. Immunohistochemical method was used to examine the expression of MYH9 in osteosarcoma and the correlation between the positive expression of MYH9 and the clinicopathological features of patients was illustrated by statistical analysis. MYH9 was compounded artificially. The expression of MYH9 in SAOS2 osteosarcoma cells was decreased by siRNA. Scratch test was used to determine the change of SAOS2 cell migration ability after MYH9 silence. Transwell assay was employed to detect the change of cell invasion ability after MYH9 silence.

RESULTS

The expression levels of mRNA of MYH9 and protein in osteosarcoma tissues were significantly higher than those in benign osteochondroma tissues. The high expression of MYH9 in osteosarcoma tissues was apparently related to the high Enneking classification (III classification) and lung metastasis. SiRNA of MYH9 could evidently decrease the expression level of MYH9 in SAOS2. The down-regulated expression of MYH9 could inhibit the migration and invasion abilities of SAOS2 cells.

CONCLUSIONS

MYH9 shows a trend of high expression in osteosarcoma tissues, and its high expression is associated with features such as tumor invasion and metastasis. The down-regulated MYH9 can realize an anti-tumor effect by inhibiting the migration and invasion of osteosarcoma cells.