Myosins: a diverse superfamily

A B-cell actomyosin arc network couples integrin co-stimulation to mechanical force-dependent immune synapse formation

B-cell activation and immune synapse (IS) formation with membrane-bound antigens are actin-dependent processes that scale positively with the strength of antigen-induced signals. Importantly, ligating the B-cell integrin, LFA-1, with ICAM-1 promotes IS formation when antigen is limiting. Whether the actin cytoskeleton plays a specific role in integrin-dependent IS formation is unknown. Here, we show using super-resolution imaging of mouse primary B cells that LFA-1:ICAM-1 interactions promote the formation of an actomyosin network that dominates the B-cell IS. This network is created by the formin mDia1, organized into concentric, contractile arcs by myosin 2A, and flows inward at the same rate as B-cell receptor (BCR):antigen clusters. Consistently, individual BCR microclusters are swept inward by individual actomyosin arcs. Under conditions where integrin is required for synapse formation, inhibiting myosin impairs synapse formation, as evidenced by reduced antigen centralization, diminished BCR signaling, and defective signaling protein distribution at the synapse. Together, these results argue that a contractile actomyosin arc network plays a key role in the mechanism by which LFA-1 co-stimulation promotes B-cell activation and IS formation.

Genetic Basis of Dorper Sheep (Ovis aries) Revealed by Long-Read De Novo Genome Assembly

Dorper sheep (Ovis aries) (DPS), developed in the 1930s by crossing Dorset Horn and Blackhead Persian sheep in South Africa, is a world-famous composite breed for mutton production. The genetic basis underlying this breed is yet to be elucidated. Here, we report the sequencing and assembly of a highly contiguous Dorper sheep genome via integration of Oxford Nanopore Technology (ONT) sequencing and Hi-C (chromatin conformation capture) approaches. The assembled genome was around 2.64 Gb with a contig N50 of 73.33 Mb and 140 contigs in total. More than 99.5% of the assembled sequences could be anchored to 27 chromosomes and they were annotated with 20,450 protein-coding genes. Allele-specific expression (ASE) genes of Dorper sheep were revealed through ASE analysis and they were involved in the immune system, lipid metabolism, and environmental adaptation. A total of 5,701 and 456 allelic sites were observed in the SNP and indels loci identified from relevant whole-genome resequencing data. These allelic SNP and INDEL sites were annotated in 1,002 and 294 genes, respectively. Moreover, we calculated the number of variant sites and related genes derived from the maternal and paternal ancestors, revealing the genetic basis of outstanding phenotypic performance of Dorper sheep. In conclusion, this study reports the first reference genome of Dorper sheep and reveals its genetic basis through ASE. This study also provides a pipeline for mining genetic information of composite breeds, which has an implication for future hybrid-breeding practices.

High-resolution structures of malaria parasite actomyosin and actin filaments

Malaria is responsible for half a million deaths annually and poses a huge economic burden on the developing world. The mosquito-borne parasites (Plasmodium spp.) that cause the disease depend upon an unconventional actomyosin motor for both gliding motility and host cell invasion. The motor system, often referred to as the glideosome complex, remains to be understood in molecular terms and is an attractive target for new drugs that might block the infection pathway. Here, we present the high-resolution structure of the actomyosin motor complex from Plasmodium falciparum. The complex includes the malaria parasite actin filament (PfAct1) complexed with the class XIV myosin motor (PfMyoA) and its two associated light-chains. The high-resolution core structure reveals the PfAct1:PfMyoA interface in atomic detail, while at lower-resolution, we visualize the PfMyoA light-chain binding region, including the essential light chain (PfELC) and the myosin tail interacting protein (PfMTIP). Finally, we report a bare PfAct1 filament structure at improved resolution.

Contractile apparatus in CNS capillary pericytes

Significance: Whether or not capillary pericytes contribute to blood flow regulation in the brain and retina has long been debated. This was partly caused by failure of detecting the contractile protein α -smooth muscle actin ( α -SMA) in capillary pericytes. Aim: The aim of this review is to summarize recent developments in detecting α -SMA and contractility in capillary pericytes and the relevant literature on the biology of actin filaments. Results: Evidence suggests that for visualization of the small amounts of α -SMA in downstream mid-capillary pericytes, actin depolymerization must be prevented during tissue processing. Actin filaments turnover is mainly based on de/re-polymerization rather than transcription of the monomeric form, hence, small amounts of α -SMA mRNA may evade detection by transcriptomic studies. Similarly, transgenic mice expressing fluorescent reporters under the α -SMA promoter may yield low fluorescence due to limited transcriptional activity in mid-capillary pericytes. Recent studies show that pericytes including mid-capillary ones express several actin isoforms and myosin heavy chain type 11, the partner of α -SMA in mediating contraction. Emerging evidence also suggests that actin polymerization in pericytes may have a role in regulating the tone of downstream capillaries. Conclusions: With guidance of actin biology, innovative labeling and imaging techniques can reveal the molecular machinery of contraction in pericytes.

Functional Characterization of the MYO6 Variant p.E60Q in Non-Syndromic Hearing Loss Patients

Hereditary hearing loss (HHL) is a common genetic disorder accounting for at least 60% of pre-lingual deafness in children, of which 70% is inherited in an autosomal recessive pattern. The long tradition of consanguinity among the Qatari population has increased the prevalence of HHL, which negatively impacts the quality of life. Here, we functionally validated the pathogenicity of the c.178G>C, p.E60Q mutation in the MYO6 gene, which was detected previously in a Qatari HHL family, using cellular and animal models. In vitro analysis was conducted in HeLa cells transiently transfected with plasmids carrying MYO6WT or MYO6p.E60Q, and a zebrafish model was generated to characterize the in vivo phenotype. Cells transfected with MYO6WT showed higher expression of MYO6 in the plasma membrane and increased ATPase activity. Modeling the human MYO6 variants in zebrafish resulted in severe otic defects. At 72 h post-injection, MYO6p.E60Q embryos demonstrated alterations in the sizes of the saccule and utricle. Additionally, zebrafish with MYO6p.E60Q displayed super-coiled and bent hair bundles in otic hair cells when compared to control and MYO6WT embryos. In conclusion, our cellular and animal models add support to the in silico prediction that the p.E60Q missense variant is pathogenic and damaging to the protein. Since the c.178G>C MYO6 variant has a 0.5% allele frequency in the Qatari population, about 400 times higher than in other populations, it could contribute to explaining the high prevalence of hearing impairment in Qatar.

MYH9 binds to dNTPs via deoxyribose moiety and plays an important role in DNA synthesis

The accepted notion of dNTP transport following cytoplasmic biosynthesis is 'facilitated diffusion'; however, whether this alone is sufficient for moving dNTPs for DNA synthesis remains an open question. The data presented here show that the MYH9 gene encoded heavy chain of non-muscle myosin IIA binds dNTPs potentially serving as a 'reservoir'. Pull-down assays showed that MYH9 present in the cytoplasmic, mitochondrial and nuclear compartments bind to DNA and this interaction is inhibited by dNTPs and 2-deoxyribose-5-phosphate (dRP) suggesting that MYH9-DNA binding is mediated via pentose sugar recognition. Direct dNTP-MYH9 binding was demonstrated by ELISA and a novel PCR-based method, which showed that all dNTPs bind to MYH9 with varying efficiencies. Cellular thermal shift assays showed that MYH9 thermal stability is enhanced by dNTPs. MYH9 siRNA transfection or treatment with myosin II selective inhibitors ML7 or blebbistatin decreased cell proliferation compared to controls. EdU labeling and cell cycle analysis by flow cytometry confirmed MYH9 siRNA and myosin II inhibitors decreased progression to S-phase with accumulation of cells in G0/G1 phase. Taken together, our data suggest a novel role for MYH9 in dNTP binding and DNA synthesis.

Comparison of Different Mass Spectrometry Workflows for the Proteomic Analysis of Tear Fluid

The tear film is a multi-layer fluid that covers the corneal and conjunctival epithelia of the eye and provides lubrication, nutrients, and protection from the outside environment. Tear fluid contains a high concentration of proteins and has thus been recognized as a potential source of biomarkers for ocular disorders due to its proximity to disease sites on the ocular surface and the non-invasive nature of its collection. This is particularly true in the case of dry eye disease, which directly impacts the tear film and its components. Proteomic analysis of tear fluid is challenging mainly due to the wide dynamic range of proteins and the small sample volumes. However, recent advancements in mass spectrometry have revolutionized the field of proteomics enabling unprecedented depth, speed, and accuracy, even with small sample volumes. In this study using the Orbitrap Fusion Tribrid mass spectrometer, we compared four different mass spectrometry workflows for the proteomic analysis of tear fluid collected via Schirmer strips. We were able to establish a method of in-strip protein digestion that identified >3000 proteins in human tear samples from 11 healthy subjects. Our method offers a significant improvement in the number of proteins identified compared to previously reported methods without pooling samples.

Myosin 1g and 1f: A Prospective Analysis in NK Cell Functions

NK cells are contained in the ILC1 group; they are recognized for their antiviral and antitumor cytotoxic capacity; NK cells also participate in other immune response processes through cytokines secretion. However, the mechanisms that regulate these functions are poorly understood since NK cells are not as abundant as other lymphocytes, which has made them difficult to study. Using public databases, we identified that NK cells express mRNA encoding class I myosins, among which Myosin 1g and Myosin 1f are prominent. Therefore, this mini-review aims to generate a model of the probable participation of Myosin 1g and 1f in NK cells, based on information reported about the function of these myosins in other leukocytes.

Cryo-EM structure of the autoinhibited state of myosin-2

We solved the near-atomic resolution structure of smooth muscle myosin-2 in the autoinhibited state (10S) using single-particle cryo–electron microscopy. The 3.4-Å structure reveals the precise molecular architecture of 10S and the structural basis for myosin-2 regulation. We reveal the position of the phosphorylation sites that control myosin autoinhibition and activation by phosphorylation of the regulatory light chain. Further, we present a previously unidentified conformational state in myosin-2 that traps ADP and Pi produced by the hydrolysis of ATP in the active site. This noncanonical state represents a branch of the myosin enzyme cycle and explains the autoinhibition of the enzyme function of 10S along with its reduced affinity for actin. Together, our structure defines the molecular mechanisms that drive 10S formation, stabilization, and relief by phosphorylation of the regulatory light chain.

Nonmuscle myosin heavy chain IIA facilitates SARS-CoV-2 infection in human pulmonary cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), binds to host receptor angiotensin-converting enzyme 2 (ACE2) through its spike (S) glycoprotein, which mediates membrane fusion and viral entry. However, the expression of ACE2 is extremely low in a variety of human tissues, especially in the airways. Thus, other coreceptors and/or cofactors on the surface of host cells may contribute to SARS-CoV-2 infection. Here, we identified nonmuscle myosin heavy chain IIA (MYH9) as an important host factor for SARS-CoV-2 infection of human pulmonary cells by using APEX2 proximity-labeling techniques. Genetic ablation of MYH9 significantly reduced SARS-CoV-2 pseudovirus infection in wild type (WT) A549 and Calu-3 cells, and overexpression of MYH9 enhanced the pseudovirus infection in WT A549 and H1299 cells. MYH9 was colocalized with the SARS-CoV-2 S and directly interacted with SARS-CoV-2 S through the S2 subunit and S1-NTD (N-terminal domain) by its C-terminal domain (designated as PRA). Further experiments suggested that endosomal or myosin inhibitors effectively block the viral entry of SARS-CoV-2 into PRA-A549 cells, while transmembrane protease serine 2 (TMPRSS2) and cathepsin B and L (CatB/L) inhibitors do not, indicating that MYH9 promotes SARS-CoV-2 endocytosis and bypasses TMPRSS2 and CatB/L pathway. Finally, we demonstrated that loss of MYH9 reduces authentic SARS-CoV-2 infection in Calu-3, ACE2-A549, and ACE2-H1299 cells. Together, our results suggest that MYH9 is a candidate host factor for SARS-CoV-2, which mediates the virus entering host cells by endocytosis in an ACE2-dependent manner, and may serve as a potential target for future clinical intervention strategies.

HMGA1 stimulates MYH9-dependent ubiquitination of GSK-3β via PI3K/Akt/c-Jun signaling to promote malignant progression and chemoresistance in gliomas

Myosin heavy chain 9 (MYH9) plays an essential role in human diseases, including multiple cancers; however, little is known about its role in gliomas. In the present study, we revealed that HMGA1 and MYH9 were upregulated in gliomas and their expression correlated with WHO grade, and HMGA1 promoted the acquisition of malignant phenotypes and chemoresistance of glioma cells by regulating the expression of MYH9 through c-Jun-mediated transcription. Moreover, MYH9 interacted with GSK-3β to inhibit the expression of GSK-3β protein by promoting its ubiquitination; the downregulation of GSK-3β subsequently promoted the nuclear translocation of β-catenin, enhancing growth, invasion, migration, and temozolomide resistance in glioma cells. Expression levels of HMGA1 and MYH9 were significantly correlated with patient survival and should be considered as independent prognostic factors. Our findings provide new insights into the role of HMGA1 and MYH9 in gliomagenesis and suggest the potential application of HMGA1 and MYH9 in cancer therapy in the future.

Endogenous protein tagging in medaka using a simplified CRISPR/Cas9 knock-in approach

The CRISPR/Cas9 system has been used to generate fluorescently labelled fusion proteins by homology-directed repair in a variety of species. Despite its revolutionary success, there remains an urgent need for increased simplicity and efficiency of genome editing in research organisms. Here, we establish a simplified, highly efficient, and precise strategy for CRISPR/Cas9-mediated endogenous protein tagging in medaka (Oryzias latipes). We use a cloning-free approach that relies on PCR-amplified donor fragments containing the fluorescent reporter sequences flanked by short homology arms (30–40 bp), a synthetic single-guide RNA and Cas9 mRNA. We generate eight novel knock-in lines with high efficiency of F0 targeting and germline transmission. Whole genome sequencing results reveal single-copy integration events only at the targeted loci. We provide an initial characterization of these fusion protein lines, significantly expanding the repertoire of genetic tools available in medaka. In particular, we show that the mScarlet-pcna line has the potential to serve as an organismal-wide label for proliferative zones and an endogenous cell cycle reporter.

High-resolution structures of the actomyosin-V complex in three nucleotide states provide insights into the force generation mechanism

The molecular motor myosin undergoes a series of major structural transitions during its force-producing motor cycle. The underlying mechanism and its coupling to ATP hydrolysis and actin binding are only partially understood, mostly due to sparse structural data on actin-bound states of myosin. Here, we report 26 high-resolution cryo-EM structures of the actomyosin-V complex in the strong-ADP, rigor, and a previously unseen post-rigor transition state that binds the ATP analog AppNHp. The structures reveal a high flexibility of myosin in each state and provide valuable insights into the structural transitions of myosin-V upon ADP release and binding of AppNHp, as well as the actomyosin interface. In addition, they show how myosin is able to specifically alter the structure of F-actin.

Striated muscle proteins are regulated both by mechanical deformation and by chemical post-translational modification

All cells sense force and build their cytoskeleton to optimize function. How is this achieved? Two major systems are involved. The first is that load deforms specific protein structures in a proportional and orientation-dependent manner. The second is post-translational modification of proteins as a consequence of signaling pathway activation. These two processes work together in a complex way so that local subcellular assembly as well as overall cell function are controlled. This review discusses many cell types but focuses on striated muscle. Detailed information is provided on how load deforms the structure of proteins in the focal adhesions and filaments, using α-actinin, vinculin, talin, focal adhesion kinase, LIM domain-containing proteins, filamin, myosin, titin, and telethonin as examples. Second messenger signals arising from external triggers are distributed throughout the cell causing post-translational or chemical modifications of protein structures, with the actin capping protein CapZ and troponin as examples. There are numerous unanswered questions of how mechanical and chemical signals are integrated by muscle proteins to regulate sarcomere structure and function yet to be studied. Therefore, more research is needed to see how external triggers are integrated with local tension generated within the cell. Nonetheless, maintenance of tension in the sarcomere is the essential and dominant mechanism, leading to the well-known phrase in exercise physiology: "use it or lose it."

Post-translational modifications of proteins associated with yeast peroxisome membrane: An essential mode of regulatory mechanism

Peroxisomes are single membrane‐bound organelles important for the optimum functioning of eukaryotic cells. Seminal discoveries in the field of peroxisomes are made using yeast as a model. Several proteins required for the biogenesis and function of peroxisomes are identified to date. As with proteins involved in other major cellular pathways, peroxisomal proteins are also subjected to regulatory post‐translational modifications. Identification, characterization and mapping of these modifications to specific amino acid residues on proteins are critical toward understanding their functional significance. Several studies have tried to identify post‐translational modifications of peroxisomal proteins and determine their impact on peroxisome structure and function. In this manuscript, we provide an overview of the various post‐translational modifications that govern the peroxisome dynamics in yeast.

Motor Skills: Recruitment of Kinesins, Myosins and Dynein during Assembly and Egress of Alphaherpesviruses

The alphaherpesviruses are pathogens of the mammalian nervous system. Initial infection is commonly at mucosal epithelia, followed by spread to, and establishment of latency in, the peripheral nervous system. During productive infection, viral gene expression, replication of the dsDNA genome, capsid assembly and genome packaging take place in the infected cell nucleus, after which mature nucleocapsids emerge into the cytoplasm. Capsids must then travel to their site of envelopment at cytoplasmic organelles, and enveloped virions need to reach the cell surface for release and spread. Transport at each of these steps requires movement of alphaherpesvirus particles through a crowded and viscous cytoplasm, and for distances ranging from several microns in epithelial cells, to millimeters or even meters during egress from neurons. To solve this challenging problem alphaherpesviruses, and their assembly intermediates, exploit microtubule- and actin-dependent cellular motors. This review focuses upon the mechanisms used by alphaherpesviruses to recruit kinesin, myosin and dynein motors during assembly and egress.

Dictyostelium myosin 1F and myosin 1E inhibit actin waves in a lipid-binding-dependent and motor-independent manner

Actin waves are F-actin-rich entities traveling on the ventral plasma membrane by the treadmilling mechanism. Actin waves were first discovered and are best characterized in Dictyostelium. Class I myosins are unconventional monomeric myosins that bind lipids through their tails. Dictyostelium has seven class I myosins, six of these have tails (Myo1A-F) while one has a very short tail (Myo1K), and three of them (Myo1D, Myo1E and Myo1F) bind PIP3 with high affinity. Localization of five Dictyostelium Class I myosins synchronizes with localization and propagation of actin waves. Myo1B and Myo1C colocalize with actin in actin waves, whereas Myo1D, E and F localize to the PIP3-rich region surrounded by actin waves. Here, we studied the effect of overexpression of the three PIP3 specific Class I myosins on actin waves. We found that ectopic expression of the short-tail Myo1F inhibits wave formation, short-tail Myo1E has similar but weaker inhibitory effect, but long-tail Myo1D does not affect waves. A study of Myo1F mutants shows that its membrane-binding site is absolutely required for wave inhibition, but the head portion is not. The results suggest that PIP3 specificity and the presence of two membrane-binding sites are required for inhibition of actin waves, and that inhibition may be caused by crosslinking of PIP3 heads groups.

Pushing the Limits of Medical Management in HCM: A Review of Current Pharmacological Therapy Options

Hypertrophic cardiomyopathy (HCM) is the most common monogenic cardiac disease with a highly variable phenotypic expression, ranging from asymptomatic to drug refractory heart failure (HF) presentation. Pharmacological therapy is the first line of treatment, but options are currently limited to nonspecific medication like betablockers or calcium channel inhibitors, with frequent suboptimal results. While being the gold standard practice for the management of drug refractory HCM patients, septal reduction therapy (SRT) remains an invasive procedure with associated surgical risks and it requires the expertise of the operating centre, thus limiting its accessibility. It is therefore with high interest that researchers look for pharmacological alternatives that could provide higher rates of success. With new data gathering these past years as well as the development of a new drug class showing promising results, this review provides an up-to-date focused synthesis of existing medical treatment options and future directions for HCM pharmacological treatment.

The C-terminal tail extension of myosin 16 acts as a molten globule, including intrinsically disordered regions, and interacts with the N-terminal ankyrin

The lesser-known unconventional myosin 16 protein is essential in proper neuronal functioning and has been implicated in cell cycle regulation. Its longer Myo16b isoform contains a C-terminal tail extension (Myo16Tail), which has been shown to play a role in the neuronal phosphoinositide 3-kinase signaling pathway. Myo16Tail mediates the actin cytoskeleton remodeling, downregulates the actin dynamics at the postsynaptic site of dendritic spines, and is involved in the organization of the presynaptic axon terminals. However, the functional and structural features of this C-terminal tail extension are not well known. Here, we report the purification and biophysical characterization of the Myo16Tail by bioinformatics, fluorescence spectroscopy, and CD. Our results revealed that the Myo16Tail is functionally active and interacts with the N-terminal ankyrin domain of myosin 16, suggesting an intramolecular binding between the C and N termini of Myo16 as an autoregulatory mechanism involving backfolding of the motor domain. In addition, the Myo16Tail possesses high structural flexibility and a solvent-exposed hydrophobic core, indicating the largely unstructured, intrinsically disordered nature of this protein region. Some secondary structure elements were also observed, indicating that the Myo16Tail likely adopts a molten globule-like structure. These structural features imply that the Myo16Tail may function as a flexible display site particularly relevant in post-translational modifications, regulatory functions such as backfolding, and phosphoinositide 3-kinase signaling.

Mechanical processes underlying precise and robust cell matching

During the development of complicated multicellular organisms, the robust formation of specific cell-cell connections (cell matching) is required for the generation of precise tissue structures. Mismatches or misconnections can lead to various diseases. Diverse mechanical cues, including differential adhesion and temporally varying cell contractility, are involved in regulating the process of cell-cell recognition and contact formation. Cells often start the process of cell matching through contact via filopodia protrusions, mediated by specific adhesion interactions at the cell surface. These adhesion interactions give rise to differential mechanical signals that can be further perceived by the cells. In conjunction with contractions generated by the actomyosin networks within the cells, this differentially coded adhesion information can be translated to reposition and sort cells. Here, we review the role of these different cell matching components and suggest how these mechanical factors cooperate with each other to facilitate specificity in cell-cell contact formation.

Unravelling the molecular basis of the dominant negative effect of myosin XI tails on P-bodies

The directional movement and positioning of organelles and macromolecules is essential for regulating and maintaining cellular functions in eukaryotic cells. In plants, these processes are actin-based and driven by class XI myosins, which transport various cargos in a directed manner. As the analysis of myosin function is challenging due to high levels of redundancy, dominant negative acting truncated myosins have frequently been used to study intracellular transport processes. A comparison of the dominant negative effect of the coiled-coil domains and the GTD domains revealed a much stronger inhibition of P-body movement by the GTD domains. In addition, we show that the GTD domain does not inhibit P-body movement when driven by a hybrid myosin in which the GTD domain was replaced by DCP2. These data suggest that the dominant negative effect of myosin tails involves a competition of the GTD domains for cargo binding sites.

Genetics of Familial Non-Medullary Thyroid Carcinoma (FNMTC)

Non-medullary thyroid carcinoma (NMTC) is the most frequent endocrine tumor and originates from the follicular epithelial cells of the thyroid. Familial NMTC (FNMTC) has been defined in pedigrees where two or more first-degree relatives of the patient present the disease in absence of other predisposing environmental factors. Compared to sporadic cases, FNMTCs are often multifocal, recurring more frequently and showing an early age at onset with a worse outcome. FNMTC cases show a high degree of genetic heterogeneity, thus impairing the identification of the underlying molecular causes. Over the last two decades, many efforts in identifying the susceptibility genes in large pedigrees were carried out using linkage-based approaches and genome-wide association studies, leading to the identification of susceptibility loci and variants associated with NMTC risk. The introduction of next-generation sequencing technologies has greatly contributed to the elucidation of FNMTC predisposition, leading to the identification of novel candidate variants, shortening the time and cost of gene tests. In this review we report the most significant genes identified for the FNMTC predisposition. Integrating these new molecular findings in the clinical data of patients is fundamental for an early detection and the development of tailored therapies, in order to optimize patient management.

Cofilin Loss in Drosophila Muscles Contributes to Muscle Weakness through Defective Sarcomerogenesis during Muscle Growth

Sarcomeres, the fundamental contractile units of muscles, are conserved structures composed of actin thin filaments and myosin thick filaments. How sarcomeres are formed and maintained is not well understood. Here, we show that knockdown of Drosophila cofilin (DmCFL), an actin depolymerizing factor, disrupts both sarcomere structure and muscle function. The loss of DmCFL also results in the formation of sarcomeric protein aggregates and impairs sarcomere addition during growth. The activation of the proteasome delays muscle deterioration in our model. Furthermore, we investigate how a point mutation in CFL2 that causes nemaline myopathy (NM) in humans affects CFL function and leads to the muscle phenotypes observed in vivo. Our data provide significant insights to the role of CFLs during sarcomere formation, as well as mechanistic implications for disease progression in NM patients.

How sarcomeres are added and maintained in a growing muscle cell is unclear. Balakrishnan et al. observed that DmCFL loss in growing muscles affects sarcomere size and addition through unregulated actin polymerization. This results in a collapse of sarcomere and muscle structure, formation of large protein aggregates, and muscle weakness.

Molecular Pumps and Motors

Pumps and motors are essential components of the world as we know it. From the complex proteins that sustain our cells, to the mechanical marvels that power industries, much we take for granted is only possible because of pumps and motors. Although molecular pumps and motors have supported life for eons, it is only recently that chemists have made progress toward designing and building artificial forms of the microscopic machinery present in nature. The advent of artificial molecular machines has granted scientists an unprecedented level of control over the relative motion of components of molecules through the development of kinetically controlled, away-from-thermodynamic equilibrium chemistry. We outline the history of pumps and motors, focusing specifically on the innovations that enable the design and synthesis of the artificial molecular machines central to this Perspective. A key insight connecting biomolecular and artificial molecular machines is that the physical motions by which these machines carry out their function are unambiguously in mechanical equilibrium at every instant. The operation of molecular motors and pumps can be described by trajectory thermodynamics, a theory based on the work of Onsager, which is grounded on the firm foundation of the principle of microscopic reversibility. Free energy derived from thermodynamically non-equilibrium reactions kinetically favors some reaction pathways over others. By designing molecules with kinetic asymmetry, one can engineer potential landscapes to harness external energy to drive the formation and maintenance of geometries of component parts of molecules away-from-equilibrium, that would be impossible to achieve by standard synthetic approaches.

Targeting the cytoskeleton against metastatic dissemination

Cancer is a pathology characterized by a loss or a perturbation of a number of typical features of normal cell behaviour. Indeed, the acquisition of an inappropriate migratory and invasive phenotype has been reported to be one of the hallmarks of cancer. The cytoskeleton is a complex dynamic network of highly ordered interlinking filaments playing a key role in the control of fundamental cellular processes, like cell shape maintenance, motility, division and intracellular transport. Moreover, deregulation of this complex machinery contributes to cancer progression and malignancy, enabling cells to acquire an invasive and metastatic phenotype. Metastasis accounts for 90% of death from patients affected by solid tumours, while an efficient prevention and suppression of metastatic disease still remains elusive. This results in the lack of effective therapeutic options currently available for patients with advanced disease. In this context, the cytoskeleton with its regulatory and structural proteins emerges as a novel and highly effective target to be exploited for a substantial therapeutic effort toward the development of specific anti-metastatic drugs. Here we provide an overview of the role of cytoskeleton components and interacting proteins in cancer metastasis with a special focus on small molecule compounds interfering with the actin cytoskeleton organization and function. The emerging involvement of microtubules and intermediate filaments in cancer metastasis is also reviewed.

Improved Inhibitory and Absorption, Distribution, Metabolism, Excretion, and Toxicology (ADMET) Properties of Blebbistatin Derivatives Indicate That Blebbistatin Scaffold Is Ideal for drug Development Targeting Myosin-2

Blebbistatin, para-nitroblebbistatin (NBleb), and para-aminoblebbistatin (AmBleb) are highly useful tool compounds as they selectively inhibit the ATPase activity of myosin-2 family proteins. Despite the medical importance of the myosin-2 family as drug targets, chemical optimization has not yet provided a promising lead for drug development because previous structure-activity-relationship studies were limited to a single myosin-2 isoform. Here we evaluated the potential of blebbistatin scaffold for drug development and found that D-ring substitutions can fine-tune isoform specificity, absorption-distribution-metabolism-excretion, and toxicological properties. We defined the inhibitory properties of NBleb and AmBleb on seven different myosin-2 isoforms, which revealed an unexpected potential for isoform specific inhibition. We also found that NBleb metabolizes six times slower than blebbistatin and AmBleb in rats, whereas AmBleb metabolizes two times slower than blebbistatin and NBleb in human, and that AmBleb accumulates in muscle tissues. Moreover, mutagenicity was also greatly reduced in case of AmBleb. These results demonstrate that small substitutions have beneficial functional and pharmacological consequences, which highlight the potential of the blebbistatin scaffold for drug development targeting myosin-2 family proteins and delineate a route for defining the chemical properties of further derivatives to be developed. SIGNIFICANCE STATEMENT: Small substitutions on the blebbistatin scaffold have beneficial functional and pharmacological consequences, highlighting their potential in drug development targeting myosin-2 family proteins.

Walking the line: mechanisms underlying directional mRNA transport and localisation in neurons and beyond

Messenger RNA (mRNA) localisation enables a high degree of spatiotemporal control on protein synthesis, which contributes to establishing the asymmetric protein distribution required to set up and maintain cellular polarity. As such, a tight control of mRNA localisation is essential for many biological processes during development and in adulthood, such as body axes determination in Drosophila melanogaster and synaptic plasticity in neurons. The mechanisms controlling how mRNAs are localised, including diffusion and entrapment, local degradation and directed active transport, are largely conserved across evolution and have been under investigation for decades in different biological models. In this review, we will discuss the standing of the field regarding directional mRNA transport in light of the recent discovery that RNA can hitchhike on cytoplasmic organelles, such as endolysosomes, and the impact of these transport modalities on our understanding of neuronal function during development, adulthood and in neurodegeneration.

Filament evanescence of myosin II and smooth muscle function

Smooth muscle is an integral part of hollow organs. Many of them are constantly subjected to mechanical forces that alter organ shape and modify the properties of smooth muscle. To understand the molecular mechanisms underlying smooth muscle function in its dynamic mechanical environment, a new paradigm has emerged that depicts evanescence of myosin filaments as a key mechanism for the muscle’s adaptation to external forces in order to maintain optimal contractility. Unlike the bipolar myosin filaments of striated muscle, the side-polar filaments of smooth muscle appear to be less stable, capable of changing their lengths through polymerization and depolymerization (i.e., evanescence). In this review, we summarize accumulated knowledge on the structure and mechanism of filament formation of myosin II and on the influence of ionic strength, pH, ATP, myosin regulatory light chain phosphorylation, and mechanical perturbation on myosin filament stability. We discuss the scenario of intracellular pools of monomeric and filamentous myosin, length distribution of myosin filaments, and the regulatory mechanisms of filament lability in contraction and relaxation of smooth muscle. Based on recent findings, we suggest that filament evanescence is one of the fundamental mechanisms underlying smooth muscle’s ability to adapt to the external environment and maintain optimal function. Finally, we briefly discuss how increased ROCK protein expression in asthma may lead to altered myosin filament stability, which may explain the lack of deep-inspiration–induced bronchodilation and bronchoprotection in asthma.

Cardiac myosin super relaxation (SRX): a perspective on fundamental biology, human disease and therapeutics

The fundamental basis of muscle contraction 'the sliding filament model' (Huxley and Niedergerke, 1954; Huxley and Hanson, 1954) and the 'swinging, tilting crossbridge-sliding filament mechanism' (Huxley, 1969; Huxley and Brown, 1967) nucleated a field of research that has unearthed the complex and fascinating role of myosin structure in the regulation of contraction. A recently discovered energy conserving state of myosin termed the super relaxed state (SRX) has been observed in filamentous myosins and is central to modulating force production and energy use within the sarcomere. Modulation of myosin function through SRX is a rapidly developing theme in therapeutic development for both cardiovascular disease and infectious disease. Some 70 years after the first discoveries concerning muscular function, modulation of myosin SRX may bring the first myosin targeted small molecule to the clinic, for treating hypertrophic cardiomyopathy (Olivotto et al., 2020). An often monogenic disease HCM afflicts 1 in 500 individuals, and can cause heart failure and sudden cardiac death. Even as we near therapeutic translation, there remain many questions about the governance of muscle function in human health and disease. With this review, we provide a broad overview of contemporary understanding of myosin SRX, and explore the complexities of targeting this myosin state in human disease.This article has an associated Future Leaders to Watch interview with the authors of the paper.

Skeletal muscle myosin and cardiac myosin attenuate heparin's antithrombin-dependent anticoagulant activity

BACKGROUND

Heparin enhances the ability of the plasma protease inhibitor, antithrombin, to neutralize coagulation factor Xa and thrombin. Skeletal muscle myosin binds unfractionated heparin.

OBJECTIVES

The aim of this study was to investigate the influence of myosin binding to heparin on antithrombin's anticoagulant activity.

METHODS

Inhibition of factor Xa and thrombin by antithrombin in the presence of different heparins and skeletal muscle myosin or cardiac myosin was studied by measuring inhibition of each enzyme's chromogenic substrate hydrolysis.

RESULTS AND CONCLUSIONS

Skeletal muscle myosin and cardiac myosin neutralized unfractionated heparin's enhancement of antithrombin's inhibition of purified factor Xa and thrombin. Skeletal muscle myosin also reduced the inhibition of factor Xa and thrombin by antithrombin in the presence of heparan sulfate. These two myosins did not protect factor Xa from antithrombin inhibition when tested in the presence of smaller heparins (eg, low molecular weight heparin, heparin pentasaccharide). This chain length dependence for skeletal muscle myosin's ability to reduce heparin's anticoagulant activity might have potential implications for therapy for patients who experience increases in plasma myosin levels (eg, acute trauma patients). In addition to the chain length, the type and extent of sulfation of glycosaminoglycans influenced the ability of skeletal muscle myosin to neutralize the polysaccharide's ability to enhance antithrombin's activity. In summary, these studies show that skeletal muscle myosin and cardiac myosin can influence antithrombin's anticoagulant activity against factor Xa and thrombin, implying that they may significantly influence the hemostatic balance involving bleeding vs clotting.

Specification of the patterning of a ductal tree during branching morphogenesis of the submandibular gland

The development of ductal structures during branching morphogenesis relies on signals that specify ductal progenitors to set up a pattern for the ductal network. Here, we identify cellular asymmetries defined by the F-actin cytoskeleton and the cell adhesion protein ZO-1 as the earliest determinants of duct specification in the embryonic submandibular gland (SMG). Apical polarity protein aPKCζ is then recruited to the sites of asymmetry in a ZO-1-dependent manner and collaborates with ROCK signaling to set up apical-basal polarity of ductal progenitors and further define the path of duct specification. Moreover, the motor protein myosin IIB, a mediator of mechanical force transmission along actin filaments, becomes localized to vertices linking the apical domains of multiple ductal epithelial cells during the formation of ductal lumens and drives duct maturation. These studies identify cytoskeletal, junctional and polarity proteins as the early determinants of duct specification and the patterning of a ductal tree during branching morphogenesis of the SMG.

The effect of sport and physical activity on transport proteins: implications for cancer prevention and control

The present contribution briefly overviews the major biological functions of the plasma membrane and of the transport proteins (transporters), which enable the movement of different molecules and substrates (either charged or uncharged) by passive (facilitated diffusion) or active transport. In particular, transporters are overviewed at the level of the skeletal muscles, which represent a highly complex, heterogeneous, plastic and dynamic tissue and are one of the most abundant tissues in humans, accounting for up to 40% of their total weight and containing up to 50%-75% of all body proteins. Moreover, it is shown how sport and physical activity finely tune and modulate human proteome, especially in terms of structural and functional improvements concerning the density of the transport proteins. These changes are among the factors responsible for the positive outcomes of training, which involve mainly the cardiovascular and the endocrine/metabolic systems. Different kinds of training (strength and endurance) enable to achieve such improvements, even though there seems to exist a dose-relationship intensity-dependent effect, with responses after 6-8 weeks of exercise and disappearing in the chronic period (years of training). Finally, exercise-induced changes at the level of transporters can play a role in terms of cancer prevention and management. Regular physical activity and exercise can, indeed, counteract the side-effects of chemotherapy drugs, including doxorubicin and other anthracycline derivatives, which may impair the functions of cardiac and skeletal muscles, probably modulating the expression of multidrug resistance proteins.

Novel blood coagulation molecules: Skeletal muscle myosin and cardiac myosin

Essentials Striated muscle myosins can promote prothrombin activation by FXa or FVa inactivation by APC. Cardiac myosin and skeletal muscle myosin are pro-hemostatic in murine tail cut bleeding models. Infused cardiac myosin exacerbates myocardial injury caused by myocardial ischemia reperfusion. Skeletal muscle myosin isoforms that circulate in human plasma can be grouped into 3 phenotypes. ABSTRACT: Two striated muscle myosins, namely skeletal muscle myosin (SkM) and cardiac myosin (CM), may potentially contribute to physiologic mechanisms for regulation of thrombosis and hemostasis. Thrombin is generated from activation of prothrombin by the prothrombinase (IIase) complex comprising factor Xa, factor Va, and Ca++ ions located on surfaces where these factors are assembled. We discovered that SkM and CM, which are abundant motor proteins in skeletal and cardiac muscles, can provide a surface for thrombin generation by the prothrombinase complex without any apparent requirement for phosphatidylserine or lipids. These myosins can also provide a surface that supports the inactivation of factor Va by activated protein C/protein S, resulting in negative feedback downregulation of thrombin generation. Although the physiologic significance of these reactions remains to be established for humans, substantive insights may be gleaned from murine studies. In mice, exogenously infused SkM and CM can promote hemostasis as they are capable of reducing tail cut bleeding. In a murine myocardial ischemia-reperfusion injury model, exogenously infused CM exacerbates myocardial infarction damage. Studies of human plasmas show that SkM antigen isoforms of different MWs circulate in human plasma, and they can be used to identify three plasma SkM phenotypes. A pilot clinical study showed that one SkM isoform pattern appeared to be linked to isolated pulmonary embolism. These discoveries enable multiple preclinical and clinical studies of SkM and CM, which should provide novel mechanistic insights with potential translational relevance for the roles of CM and SkM in the pathobiology of hemostasis and thrombosis.

A De Novo Mutation in MYH9 in a Child With Severe and Prolonged Macrothrombocytopenia

Congenital macrothrombocytopenia is a diverse group of hereditary disorders caused by mutations in the MYH9 gene, which encodes the nonmuscle myosin heavy chain-A, an important motor protein in hemopoietic cells. Thus, the term MYH9-related disease has been proposed, but the clinicopathologic basis of MYH9 mutations has been poorly investigated. Here, we report a sporadic case of Epstein syndrome, an MYH9 disorder, in a 4-year-old Chinese boy who presented with macrothrombocytopenia. He had no family history of thrombocytopenia, hearing loss, or renal failure. A de novo heterozygous MYH9 mutation, c.287C>T; p. (Ser96Leu), was found in this patient. Genotype-phenotype analysis of all reported mutations suggested a domain-specific relationship between the location of the MYH9 mutation and the penetrance of the nonhematologic characteristics of MYH9-related disorders. Our study highlights the importance of suspecting MYH9-related disease even in cases of chronic macrothrombocytopenia without a family history or extrahematologic symptoms.

Clinical features and genotypes of Laing distal myopathy in a group of Chinese patients, with in-frame deletions of MYH7 as common mutations

Background

Laing distal myopathy is a rare autosomal dominant inherited distal myopathy caused by mutations of the MYH7 gene affecting mainly the rod region. We described the clinical features, muscle MRI and pathological changes as well as genetic mutations in a group of Chinese patients with Laing distal myopathy.

Results

Six patients with the confirmed diagnoses of Laing distal myopathy were recruited. Ankle dorsiflexion and finger extension weakness, as well as neck flexion weakness were common in our patients. Myopathic as well as neurogenic lesions were suggested by electromyography in different patients. Respiratory abnormality of sleep apnea was detected in two of our patients stressing the necessity of close respiratory monitoring in this disease. Muscle MRIs showed similar features of concentric fatty infiltration of anterior thigh muscles together with early involvement of tibialis anterior and extensor hallucis longus. However, muscle pathological presentations were varied depending on the biopsied muscles and the severity of the disease. In-frame deletions of the MYH7 gene made up 3/4 of mutations in our patients, suggesting that these are common mutations of Laing distal myopathy.

Conclusions

Our study further expanded the phenotypes and genotypes of Laing distal myopathy. In-frame deletions of the MYH7 gene are common causes of Laing distal myopathy.

Distinct Roles of Smooth Muscle and Non-muscle Myosin Light Chain-Mediated Smooth Muscle Contraction

Both smooth muscle (SM) and non-muscle (NM) myosin II are expressed in hollow organs such as the bladder and uterus, but their respective roles in contraction and corresponding physiological functions remain to be determined. In this report, we assessed their roles by analyzing mice deficient of Myl9, a gene encoding the SM myosin regulatory light chain (SM RLC). We find that global Myl9-deficient bladders contracted with an apparent sustained phase, despite no initial phase. This sustained contraction was mediated by NM myosin RLC (NM RLC) phosphorylation by myosin light chain kinase (MLCK). NM myosin II was expressed abundantly in the uterus and young mice bladders, of which the force was accordingly sensitive to NM myosin inhibition. Our findings reveal distinct roles of SM RLC and NM RLC in SM contraction.

Conditional Myh9 and Myh10 inactivation in adult mouse renal epithelium results in progressive kidney disease

Actin-associated nonmuscle myosin II (NM2) motor proteins play critical roles in a myriad of cellular functions, including endocytosis and organelle transport pathways. Cell type-specific expression and unique subcellular localization of the NM2 proteins, encoded by the Myh9 and Myh10 genes, in the mouse kidney tubules led us to hypothesize that these proteins have specialized functional roles within the renal epithelium. Inducible conditional knockout (cKO) of Myh9 and Myh10 in the renal tubules of adult mice resulted in progressive kidney disease. Prior to overt renal tubular injury, we observed intracellular accumulation of the glycosylphosphatidylinositol-anchored protein uromodulin (UMOD) and gradual loss of Na+ K+ 2Cl- cotransporter from the apical membrane of the thick ascending limb epithelia. The UMOD accumulation coincided with expansion of endoplasmic reticulum (ER) tubules and activation of ER stress and unfolded protein response pathways in Myh9&10-cKO kidneys. We conclude that NM2 proteins are required for localization and transport of UMOD and loss of function results in accumulation of UMOD and ER stress-mediated progressive renal tubulointerstitial disease. These observations establish cell type-specific role(s) for NM2 proteins in regulation of specialized renal epithelial transport pathways and reveal the possibility that human kidney disease associated with MYH9 mutations could be of renal epithelial origin.

Gene-Metabolite Network Linked to Inhibited Bioenergetics in Association With Spaceflight-Induced Loss of Male Mouse Quadriceps Muscle

Prolonged residence of mice in spaceflight is a scientifically robust and ethically ratified model of muscle atrophy caused by continued unloading. Under the Rodent Research Program of the National Aeronautics and Space Administration (NASA), we assayed the large-scale mRNA and metabolomic perturbations in the quadriceps of C57BL/6j male mice that lived in spaceflight (FLT) or on the ground (control or CTR) for approximately 4 weeks. The wet weights of the quadriceps were significantly reduced in FLT mice. Next-generation sequencing and untargeted mass spectroscopic assays interrogated the gene-metabolite landscape of the quadriceps. A majority of top-ranked differentially suppressed genes in FLT encoded proteins from the myosin or troponin families, suggesting sarcomere alterations in space. Significantly enriched gene-metabolite networks were found linked to sarcomeric integrity, immune fitness, and oxidative stress response; all inhibited in space as per in silico prediction. A significant loss of mitochondrial DNA copy numbers in FLT mice underlined the energy deprivation associated with spaceflight-induced stress. This hypothesis was reinforced by the transcriptomic sequencing-metabolomics integrative analysis that showed inhibited networks related to protein, lipid, and carbohydrate metabolism, and adenosine triphosphate (ATP) synthesis and hydrolysis. Finally, we discovered important upstream regulators, which could be targeted for next-generation therapeutic intervention for chronic disuse of the musculoskeletal system. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Non-Muscle Myosin II in Axonal Cell Biology: From the Growth Cone to the Axon Initial Segment

By binding to actin filaments, non-muscle myosin II (NMII) generates actomyosin networks that hold unique contractile properties. Their dynamic nature is essential for neuronal biology including the establishment of polarity, growth cone formation and motility, axon growth during development (and axon regeneration in the adult), radial and longitudinal axonal tension, and synapse formation and function. In this review, we discuss the current knowledge on the spatial distribution and function of the actomyosin cytoskeleton in different axonal compartments. We highlight some of the apparent contradictions and open questions in the field, including the role of NMII in the regulation of axon growth and regeneration, the possibility that NMII structural arrangement along the axon shaft may control both radial and longitudinal contractility, and the mechanism and functional purpose underlying NMII enrichment in the axon initial segment. With the advances in live cell imaging and super resolution microscopy, it is expected that in the near future the spatial distribution of NMII in the axon, and the mechanisms by which it participates in axonal biology will be further untangled.

Myosin XVI in the Nervous System

The myosin family is a large inventory of actin-associated motor proteins that participate in a diverse array of cellular functions. Several myosin classes are expressed in neural cells and play important roles in neural functioning. A recently discovered member of the myosin superfamily, the vertebrate-specific myosin XVI (Myo16) class is expressed predominantly in neural tissues and appears to be involved in the development and proper functioning of the nervous system. Accordingly, the alterations of MYO16 has been linked to neurological disorders. Although the role of Myo16 as a generic actin-associated motor is still enigmatic, the N-, and C-terminal extensions that flank the motor domain seem to confer unique structural features and versatile interactions to the protein. Recent biochemical and physiological examinations portray Myo16 as a signal transduction element that integrates cell signaling pathways to actin cytoskeleton reorganization. This review discusses the current knowledge of the structure-function relation of Myo16. In light of its prevalent localization, the emphasis is laid on the neural aspects.

Identification of a novel pathogenic variant in the MYH3 gene in a five-generation family with CPSFS1A (Contractures, Pterygia, and Spondylocarpotarsal Fusion Syndrome 1A)

Background

Distal arthrogryposis (DA) is a group of rare Mendelian conditions that demonstrate heterogeneity with respect to genetics and phenotypes. Ten types of DAs, which collectively involve six genes, have been reported. Among them, the MYH3 gene causes several types of arthrogryposis conditions and therefore has a pivotal role in the skeletal and muscle development of the fetus. For this study, we recruited a five‐generation Chinese family with members presenting DA features and phenotypic variability. Further clinical study characterized it as CPSFS1A (Contractures, Pterygia, and Spondylocarpotarsal Fusion Syndrome 1A).

Methods

Genomic DNA was extracted from eight family members, including one fetus. Whole‐exome sequencing (WES) was then conducted on the proband's sample, followed by Sanger sequencing as validation for each of the participants. In silico analysis was performed. Western blotting (WB) detection and pathological staining were conducted on skeletal muscle tissue of the induced fetus after prenatal diagnosis.

Results

A novel heterozygous pathogenic variant, namely NM_002470.3: c.3044_3047delinsTCAATTTGTT: p.E1015_D1016delinsVNLF in the MYH3 gene, was identified and shown to be cosegregated with the condition in the subject family. This variant resulted in the replacement of amino‐acid residues E1015 and D1016 by a string of VNLFs. The pregnancy was selectively terminated because the fetus was genetically affected. However, the WB and pathological results did not indicate a significant change in the norm.

Conclusions

Our study expanded the variant spectrum of CPSFS1A, in addition to which it provided solid evidence for the appropriateness of genetic counseling and pregnancy management for the family. The results may also provide further insight into the molecular mechanism of MYH3.

Pushing myelination - developmental regulation of myosin expression drives oligodendrocyte morphological differentiation

Oligodendrocytes are the central nervous system myelin-forming cells providing axonal electrical insulation and higher-order neuronal circuitry. The mechanical forces driving the differentiation of oligodendrocyte precursor cells into myelinating oligodendrocytes are largely unknown, but likely require the spatiotemporal regulation of the architecture and dynamics of the actin and actomyosin cytoskeletons. In this study, we analyzed the expression pattern of myosin motors during oligodendrocyte development. We report that oligodendrocyte differentiation is regulated by the synchronized expression and non-uniform distribution of several members of the myosin network, particularly non-muscle myosins 2B and 2C, which potentially operate as nanomechanical modulators of cell tension and myelin membrane expansion at different cell stages.This article has an associated First Person interview with the first author of the paper.

MYL6B drives the capabilities of proliferation, invasion, and migration in rectal adenocarcinoma through the EMT process

Objective

This study was designed to explore the biological significance of myosin light chain 6B (MYL6B) in rectal adenocarcinoma.

Methods

Profiles on the Oncomine dataset, GEPIA website, and UALCAN-TCGA database were searched to assess the MYL6B expression level in rectal adenocarcinoma tissues and normal tissues. After MYL6B knockdown using siRNA strategy, cell counting kit-8 (CCK-8) and transwell assays were conducted to measure cell proliferation, migration and invasion, respectively. Flow cytometry analysis was conducted to assess cell apoptosis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot were performed to detect the expression level of mRNAs and proteins.

Results

The data showed that overexpression of MYL6B was observed in rectal adenocarcinoma tissues and correlated with a poor prognosis of patients. Functional in vitro experiments revealed that MYL6B knockdown could inhibit proliferation, migration, and invasion of rectal adenocarcinoma cells, while promote cell apoptosis. Moreover, western blot analysis suggested that increased expression of E-cadherin and decreased expression of N-cadherin and Vimentin were induced by si-MYL6B.

Conclusion

In summary, this study elaborated on the promoting effect of MYL6B in rectal adenocarcinoma progression, thus providing novel insight for strategies of clinical diagnosis and drug application in the future clinical study.

A novel MYH14 mutation in a Chinese family with autosomal dominant nonsyndromic hearing loss

Background

MYH14 gene mutations have been suggested to be associated with nonsyndromic/syndromic sensorineural hearing loss. It has been reported that mutations in MYH14 can result in autosomal dominant nonsyndromic deafness-4A (DFNA4).

Methods

In this study, we examined a four-generation Han Chinese family with nonsyndromic hearing loss. Targeted next-generation sequencing of deafness genes was employed to identify the pathogenic variant. Sanger sequencing and PCR-RFLP analysis were performed in affected members of this family and 200 normal controls to further confirm the mutation.

Results

Four members of this family were diagnosed as nonsyndromic bilateral sensorineural hearing loss with postlingual onset and progressive impairment. A novel missense variant, c.5417C > A (p.A1806D), in MYH14 in the tail domain of NMH II C was successfully identified as the pathogenic cause in three affected individuals. The family member II-5 was suggested to have noise-induced deafness.

Conclusion

In this study, a novel missense mutation, c.5417C > A (p.A1806D), in MYH14 that led to postlingual nonsyndromic autosomal dominant SNHL were identified. The findings broadened the phenotype spectrum of MYH14 and highlighted the combined application of gene capture and Sanger sequencing is an efficient approach to screen pathogenic variants associated with genetic diseases.

A family with an MYH9-related disorder with different phenotypes masquerading as immune thrombocytopaenia: an underreported disorder in Taiwan

A 66-year-old woman had experienced abnormal bleeding since the age of 7. Thrombocytopenia was not detected until she was 48, and immune thrombocytopenia was diagnosed at age 66. She also reported experiencing hearing disturbance since the age of 30 and acute renal failure since the age of 61 but reported no visual disturbance. Her younger son, who was 40 years old, also experienced abnormal bleeding since the age of 6, but immune thrombocytopenia was diagnosed as late as age 35. He had no other associated disorders. Laboratory examinations of both mother and son revealed a low platelet count (8000 and 29,000 µL, respectively), giant platelets and Döhle body-like granulocyte inclusion bodies. The mother had a high creatinine level (15.4 mg/dL) and normal liver enzyme levels. MYH9 genetic analysis identified a heterozygous mutation, c.101T>A, p.Val34Glu at exon 2 in both patients. These clinical and laboratory findings were consistent with a diagnosis of an MYH9-related disorder with different phenotypes observed in the same family. MYH9-related disorders were recognised in 2003, but were often misdiagnosed as immune thrombocytopenia, and hence, they have rarely been reported in Taiwan.

circ-NRIP1 Promotes Glycolysis and Tumor Progression by Regulating miR-186-5p/MYH9 Axis in Gastric Cancer

Background

Gastric cancer (GC) is a severe threat to human life, with high incidence and mortality. Circular RNAs (circRNAs) play crucial roles in the progression of GC. This study attempted to investigate the potential role of circ-NRIP1 and associated action mechanisms in GC cells.

Methods

The expression of circ-NRIP1 and miR-186-5p was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, apoptosis, and migration were assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, flow cytometry assay, and transwell assay, respectively. Cellular glycolysis, including cellular glucose uptake, lactate, and ATP/ADP ratios, was also detected by commercial assay kits. The protein levels of hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2) were quantified by Western blot. The relationship between miR-186-5p and circ-NRIP1 or myosin heavy chain 9 (MYH9) was predicted by the online bioinformatics tool, starBase, and verified by dual-luciferase reporter assay. Xenograft tumor model was used to evaluate biological function in vivo.

Results

The expression of circ-NRIP1 was up-regulated in tissues of GC patients and cells, as well as negatively associated with that of miR-186-5p in tissues. circ-NRIP1 knockdown inhibited cell proliferation, migration, and glycolysis, but induced apoptosis in HGC-27 and AGS cells. circ-NRIP1 competitively targeted miR-186-5p, and MYH9 was a target of miR-186-5p. miR-186-5p knockdown inverted the bio-function effects and glycolytic activation from circ-NRIP1 silencing in HGC-27 and AGS cells. Meanwhile, MYH9 overexpression could rescue the effects of miR-186-5p. Besides, miR-186-5p knockdown inverted the expression pattern of si-circ-NRIP1 transfection in GC cells. Additionally, in vivo experiments confirmed that sh-circ-NRIP1 inhibited tumor growth.

Conclusion

circ-NRIP1 accelerated the glycolysis and GC progression by modulating MYH9 via miR-186-5p, suggesting that circ-NRIP1 was a promising biomarker for the treatment of GC.

Muscle myosins form folded monomers, dimers, and tetramers during filament polymerization in vitro

Muscle contraction depends on the cyclical interaction of myosin and actin filaments. Therefore, it is important to understand the mechanisms of polymerization and depolymerization of muscle myosins. Muscle myosin 2 monomers exist in two states: one with a folded tail that interacts with the heads (10S) and one with an unfolded tail (6S). It has been thought that only unfolded monomers assemble into bipolar and side-polar (smooth muscle myosin) filaments. We now show by electron microscopy that, after 4 s of polymerization in vitro in both the presence (smooth muscle myosin) and absence of ATP, skeletal, cardiac, and smooth muscle myosins form tail-folded monomers without tail-head interaction, tail-folded antiparallel dimers, tail-folded antiparallel tetramers, unfolded bipolar tetramers, and small filaments. After 4 h, the myosins form thick bipolar and, for smooth muscle myosin, side-polar filaments. Nonphosphorylated smooth muscle myosin polymerizes in the presence of ATP but with a higher critical concentration than in the absence of ATP and forms only bipolar filaments with bare zones. Partial depolymerization in vitro of nonphosphorylated smooth muscle myosin filaments by the addition of MgATP is the reverse of polymerization.