Ion Channel Defects Research Articles

XMEN-associated Systemic EBV-positive T-cell Lymphoma of Childhood: Report of Two Cases and Literature Review.

X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia (XMEN) is an extremely rare inborn error of immunity (IEI) caused by X-linked recessive inheritance and loss-of-function mutations in the MAGT1 gene, resulting in magnesium ion channel defects. This article reports 2 cases of systemic EBV-positive T-cell Lymphoma of childhood (SETLC) associated with XMEN, which have not been reported before. Whole exome sequencing (WES) in their family revealed previously unreported MAGT1 gene mutations (c.77T>C, p.I26T; c.956-957del: p.Ser319Tyrfs) inherited from their mothers. These mutations expand the spectrum of gene mutations in XMEN disease. The importance of genetic testing for MAGT1 mutations in the initial diagnosis of SETLC was emphasized. We also review the literature on this uncommon IEI.

TRPV4 Channel Modulators as Potential Drug Candidates for Cystic Fibrosis.

Cystic fibrosis (CF) is a genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, resulting in defective chloride ion channels. This leads to thick, dehydrated mucus that severely disrupts mucociliary clearance in the respiratory system and triggers infection that eventually is the cause of death of CF patients. Current therapeutic strategies primarily focus on restoring CFTR function, blocking epithelial sodium channels to prevent mucus dehydration, or directly targeting mucus to reduce its viscosity. Among the ion channels expressed in ciliated bronchial epithelial cells, the transient receptor potential vanilloid 4 (TRPV4) channel emerges as a significant channel in CF pathogenesis. Activation of TRPV4 channels affects the regulation of airway surface liquid by modulating sodium absorption and intracellular calcium levels, which indirectly influences CFTR activity. TRPV4 is also involved in the regulatory volume decrease (RVD) process and enhances inflammatory responses in CF patients. Here, we combine current findings on TRPV4 channel modulation as a promising therapeutic approach for CF. Although limited studies have directly explored TRPV4 in CF, emerging evidence indicates that TRPV4 activation can significantly impact key pathological processes in the disease. Further investigation into TRPV4 modulators could lead to innovative treatments that alleviate severe respiratory complications and improve outcomes for CF patients.

Predicting Mutational Effects on Ca2+-Activated Chloride Conduction of TMEM16A Based on a Simulation Study.

The dysfunction and defects of ion channels are associated with many human diseases, especially for loss-of-function mutations in ion channels such as cystic fibrosis transmembrane conductance regulator mutations in cystic fibrosis. Understanding ion channels is of great current importance for both medical and fundamental purposes. Such an understanding should include the ability to predict mutational effects and describe functional and mechanistic effects. In this work, we introduce an approach to predict mutational effects based on kinetic information (including reaction barriers and transition state locations) obtained by studying the working mechanism of target proteins. Specifically, we take the Ca2+-activated chloride channel TMEM16A as an example and utilize the computational biology model to predict the mutational effects of key residues. Encouragingly, we verified our predictions through electrophysiological experiments, demonstrating a 94% prediction accuracy regarding mutational directions. The mutational strength assessed by Pearson's correlation coefficient is -0.80 between our calculations and the experimental results. These findings suggest that the proposed methodology is reliable and can provide valuable guidance for revealing functional mechanisms and identifying key residues of the TMEM16A channel. The proposed approach can be extended to a broad scope of biophysical systems.

Next Generation Sequencing and Electromyography Reveal the Involvement of the P2RX6 Gene in Myopathy.

Ion channelopathies result from impaired ion channel protein function, due to mutations affecting ion transport across cell membranes. Over 40 diseases, including neuropathy, pain, migraine, epilepsy, and ataxia, are associated with ion channelopathies, impacting electrically excitable tissues and significantly affecting skeletal muscle. Gene mutations affecting transmembrane ionic flow are strongly linked to skeletal muscle disorders, particularly myopathies, disrupting muscle excitability and contraction. Electromyography (EMG) analysis performed on a patient who complained of weakness and fatigue revealed the presence of primary muscular damage, suggesting an early-stage myopathy. Whole exome sequencing (WES) did not detect potentially causative variants in known myopathy-associated genes but revealed a novel homozygous deletion of the P2RX6 gene likely disrupting protein function. The P2RX6 gene, predominantly expressed in skeletal muscle, is an ATP-gated ion channel receptor belonging to the purinergic receptors (P2RX) family. In addition, STRING pathways suggested a correlation with more proteins having a plausible role in myopathy. No previous studies have reported the implication of this gene in myopathy. Further studies are needed on patients with a defective ion channel pathway, and the use of in vitro functional assays in suppressing P2RX6 gene expression will be required to validate its functional role.

Channelopathies in Epilepsy: from Precision Medicine to Gene Therapy

Epilepsy is a common and debilitating neurological disease with a significant genetic component. Inherited or de novo mutations in ion channels resulting in periodic network hyperexcitability is a major cause of epileptogenesis. Understanding of the genetic etiology of epilepsy opens up the avenue of personalized treatment. A range of precision medications are designed to target the defective ion channels, with varied effects. In addition, the underlying mechanisms of channelopathies can also be addressed by gene therapy. Expression of mutated ion channel genes can be regulated via gene replacement or gene silencing approaches, including viral vector-mediated gene replacement and antisense oligonucleotides. Aside from directly compensating of ion channel dysfunction, another strategy of gene therapy involves the overexpression of certain ion channels to modulate neuronal excitability, which particularly targets focal epilepsies. In line with the paroxysmal nature of epileptic seizures, optogenetic and chemogenetic approaches, which permits conditional activation of gene products can be particularly beneficial. The ideal gene therapy to treat genetic epilepsies and channelopathies would be in vivo gene editing, making precise gene modifications to correct mutations harbored by each individual. Advances in CRISPR- Cas technology has brought the idea closer to reality, yet technical and ethical concerns surround its therapeutic application.

Steroid-induced hypokalemic periodic paralysis: a case report and literature review

BackgroundHypokalemic periodic paralysis (HPP) is a rare channelopathy characterized by episodic attacks of acute muscle weakness concomitant with hypokalemia. The etiology of hypokalemia is the shift of potassium into the cells, and the clinical symptoms resolve when potassium starts to leak back to the serum. Most of the time, the underlying ion channel defects are well compensated, and an additional trigger is often required to initiate an attack. Well-known trigger factors include carbohydrate-rich meals, exercise followed by rest, stress, cold weather, and alcohol consumption.Case presentationHere, we present the case of a 26-year-old Asian man who suffered from an acute onset of bilateral lower limb weakness with hypokalemia following dexamethasone injection. He was diagnosed with HPP.ConclusionsWe would like to remind physicians to think of steroids as an unusual precipitating factor while managing patients with HPP, per results of this case study.

Nontoxic Artificial Chloride Channel Formation in Epithelial Cells by Isophthalic Acid-Based Small Molecules.

Artificial channels capable of facilitating the transport of Cl- ions across cell membranes while being nontoxic to the cells are rare. Such synthetic ion channels can mimic the functions of membrane transport proteins and, therefore, have the potential to treat channelopathies by replacing defective ion channels. Here we report isophthalic acid-based structurally simple molecules 1 a and 2 a, which self-assemble to render supramolecular nanochannels that allow selective transport of Cl- ions. As evident from the single-crystal X-ray diffraction analysis, the self-assembly is governed by intermolecular hydrogen bonding and π-π stacking interactions. The MD simulation studies for both 1 a and 2 a confirmed the formation of stable Cl- channel assembly in the lipid membrane and Cl- transport through them. The MQAE assay showed the efficacy of the compounds in delivering Cl- ions into cells, and the MTT assays proved that the compounds are nontoxic to cells even at a concentration of 100 μM.

Common Supraventricular and Ventricular Arrhythmias in Children.

The most common pediatric arrhythmias are tachycardias, and the most common type is supraventricular tachycardia, originating from or above the atrioventricular node and HIS bundle. Ventricular tachycardias are less common but more dangerous. Supraventricular tachycardias usually cause a narrow complex tachycardia unless there is a basal bundle branch block or rate-dependent aberration. A wide QRS tachycardia should be treated as ventricular tachycardias unless proven to be an supraventricular tachycardia with aberration. Diagnosis of both tachyarrhythmia types depends mainly on 12-lead electrocardiography. The most common supraventricular tachycardia type in newborns and infants is atrioventricular reentry tachycardia, related to manifest or concealed accessory pathways and in adolescent atrioventricular nodal reentry tachycardia, whereas focal atrial tachycardias consist of 10%-15% of supraventricular tachycardias during all ages. Supraventricular tachycardias have a low risk of morbidity, and ablation therapy is successful in most types with success rates over 90%. Ventricular tachycardias can be monomorphic or polymorphic, nonsustained or sustained, and can cause more hemodynamic instability than supraventricular tachycardias, requiring more close monitoring and urgent therapies. If hemodynamically unstable, synchronized cardioversion must be performed. Polymorphic ventricular tachycardias are very dangerous and often associated with primary ion channel defects (channelopathies), which can cause sudden cardiac death.

Towards Innovative Antibacterial Correctors for Cystic Fibrosis Targeting the Lung Microbiome with a Multifunctional Effect.

Cystic fibrosis (CF) is a genetic disease caused by loss-of-function mutations in the CFTR gene, which codes for a defective ion channel. This causes an electrolyte imbalance and results in a spiral of negative effects on multiple organs, most notably the accumulation of thick mucus in the lungs, chronic respiratory tract infections and inflammation leading to pulmonary exacerbation and premature death. Progressive decline of lung function is mainly linked to persistent or recurring infections, mostly caused by bacteria, which require treatments with antibiotics and represent one of the major life-limiting factors in subjects with CF. Treatment of such a complex disease require multiple drugs with a consequent therapeutic burden and complications caused by drug-drug interactions and rapid emergence of bacterial drug resistance. We report herein our recent efforts in developing innovative multifunctional antibiotics specifically tailored to CF by a direct action on bacterial topoisomerases and a potential indirect effect on the pulmonary mucociliary clearance mediated by ΔF508-CFTR correction. The obtained results may pave the way for the development of a simplified therapeutic approach with a single agent acting as multifunctional Antibacterial-Corrector.

Chloride Transport across Liposomes and Cells by Nontoxic 3-(1H-1,2,3-Triazol-1-yl)benzamides.

Synthetic anion transmembrane transporters are adding new aspirations for treating channelopathies by replacing defective ion channels. The availability of such suitable candidates is still infrequent due to the associated toxicity. Here, we report 3-(1H-1,2,3-triazol-1-yl)benzamides as transmembrane anion carriers, nontoxic to cells. The selective and electrogenic chloride transport activity was established by fluorescence and ion selective electrode-based assays. MQAE assay confirmed the chloride uptake into the cells by the nontoxic compounds.

Abstract #1165127: A Case Presentation of Thyrotoxic Periodic Paralysis

Periodic Paralysis (PP) is a rare inherited neuromuscular disorder caused by a sodium-potassium ion channel defect leading to hypo- or hyperkalemia. Thyrotoxic periodic paralysis (TPP) is a sporadic form of hypokalemic PP associated with a hyperthyroid state, most commonly Graves’ disease. It clinically presents as painless proximal muscle weakness often precipitated by exercise, stress, or a high carbohydrate diet. Here we present a case of hypokalemic TPP. A 63-year-old female from Thailand with a history of meningioma treated with gross total resection (without radiation) three years ago presented to the Emergency Department (ED) with two weeks of neck pain, subjective weight loss, and tremors after receiving the influenza vaccine. Due to elevated thyroid function tests, she was discharged on steroids for presumed subacute thyroiditis with plan for Endocrinology follow up. One week later, she returned to the ED for a potassium of 2.5 mmol/L (3.5-5.1 mmol/L) on outpatient labs. On physical exam, vitals were notable for a heart rate of 99 and palpable goiter. Her neurologic exam demonstrated mildly decreased strength with hip flexion (4/5), shoulder abduction (4-/5), and elbow flexion and extension (4/5). Labs were notable for a potassium of 2.4 mmol/L with undetectable TSH, elevated T4 4.80 mcg/dl (0.60-1.12 mcg/dl), and T3 315 ng/dL (80-210 ng/dL). The TSI was 4.7 IU/L (< 1.3 IU/L) and TSH receptor antibody 4.46 IU/L (< 1.75 IU/L). EKG demonstrated U-waves. The patient was admitted to telemetry and repleted with intravenous and oral potassium. Repeat potassium was 3.8 mmol/L without rebound hyperkalemia. She was also started on propranolol 20 mg twice daily and methimazole 20 mg three times daily for treatment of Graves’ disease. Periodic paralysis (PP) is an autosomal dominant hereditary form of channelopathy that is classified as either hypo- or hyperkalemic. Acquired cases of PP present at an older age and mostly in the context of hyperthyroidism—in these cases the diagnosis is termed thyrotoxic periodic paralysis (TPP). The condition is more common in Asian men, unlike most cases of hyperthyroidism which have a female predominance. Diagnostic lab findings include hypokalemia with hyperthyroidism. Treatment in the acute setting is directed at correcting hypokalemia with cardiac monitoring during the first 24 hours as rebound hyperkalemia occurs in 40-60% of cases. Recommended potassium repletion is 30 mEq every 2 hours, with a maximum dose of 90 mEq in 24 hours. Oral supplementation is preferred. Propranolol and potassium supplementation can be used to prevent attacks until euthyroid state is achieved.

Современные нейрохимические и молекулярно-генетические аспекты патогенеза неонатальных судорог

The article is devoted to the modern aspects of the pathogenesis of neonatal seizures (NS). The main mechanisms of the development of perinatal brain injuries, which are fundamental in the genesis of NS, are considered, the prospects for research devoted to the study of the possibilities of molecular genetic prediction of the individual risk of ischemia and the development of NS are outlined. The mechanisms of ischemic brain damage during the neonatal period and the role of glutamate, the main excitatory neurotransmitter acting on NMDA receptors that regulate the electrical activity of neurons, are described in detail. The review focuses on the involvement of metalloproteinases, primarily MMP-9, which destroys type IV collagen, which is the main component of the basement membrane of the cerebral endothelium, and creates conditions for cell migration across the BBB, thereby causing a cytokine storm and the development of inflammation, leading to NS. The possible role of calcium-dependent proteinases — calpains in the development of NS is analyzed, since in some forms of CNS pathology, uncontrolled hyperactivation of calpains is observed, leading to a disruption of the regulation of neurotransmitter transmission, which can, in turn, become an additional factor for the development of the neurodegenerative process in the brain and the development of seizures. Also are presented the results of studies devoted to the role of ion channels, providing synaptic transmission of excitation from an excited neuron to other cells. It has been shown that molecular defects in ion channels can be one of the factors that create prerequisites for the development of NS. The article shows the prospects for studying the genetic polymorphism of enzymes involved in the pathogenesis of ischemic brain damage, based on ideas about the pathogenesis of cerebral disorders in newborns, which are based on oxidative damage. The concluding part of the article outlines the modern principles of NS therapy, their main goal is to relieve the symptoms of the underlying disease, to ensure the normalization of blood circulation and brain metabolism, to optimize the conditions for the functioning of the preserved brain structures to prevent the formation of severe neurological complications, as well as to maintain optimal parameters of respiration, glucose-electrolyte composition of blood and thermal regime. Based on the data presented, it is concluded that early diagnosis of NS is necessary, which is determined by the fact that seizures in newborns are usually caused by serious damage to the child's brain, and in some cases — by life-threatening conditions, the timely diagnosis of which contributes to the early onset of specific treatment. No conflict of interest was declared by the author. Key words: newborn, cerebral ischemia, neonatal seizures.

Defective Ion Channel in Cystic Fibrosis: Current Development in Treatment of Cystic Fibrosis

Cystic fibrosis is an inherited disorder that causes severe damage to the lungs, digestive system and other organs in the body. Cystic fibrosis transmembrane conductance regulator (CFTR) is involved in the production of mucus, sweat and digestive juices. These secreted fluids are normally thin and slippery. But in people with cystic fibrosis, a defective gene in CFTR causes the secretions to become sticky and thick. Instead of acting as a lubricant, the secretions plug up tubes, ducts and passage ways, especially in the lungs and pancreas. This mucus leads to the formation of bacterial microenvironments known as biofilms (a niche that harbors bacteria; Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa ) that are difficult for immune cells and antibiotics to penetrate. Viscous secretions and persistent respiratory infections repeatedly damage the lung by gradually remodeling the airways, which makes infection even more difficult to eradicate. CFTR, a Cl– selective ion channel, is a prototypic member of the ATP-binding cassette transporter super family that is expressed in several organs. Understanding how these complexes regulate the intracellular trafficking and activity of CFTR provides a unique insight into the aetiology of cystic fibrosis and other diseases associated to it. Cystic fibrosis patients exhibit lung disease consistent with a failure of innate airway defense mechanisms. The link between abnormal ion transport, disease initiation and progression is not fully understood, but airway mucus dehydration seems paramount in the initiation of CF lung disease. New therapies are currently in development that target the ion transport defects in CF with the intention of rehydrating airway surfaces.

Mechanisms of altered skeletal muscle action potentials in the R6/2 mouse model of Huntington's disease.

Huntington's disease (HD) patients suffer from progressive and debilitating motor dysfunction for which only palliative treatment is currently available. Previously, we discovered reduced skeletal muscle Cl- channel (ClC-1) and inwardly rectifying K+ channel (Kir) currents in R6/2 HD transgenic mice. To further investigate the role of ClC-1 and Kir currents in HD skeletal muscle pathology, we measured the effect of reduced ClC-1 and Kir currents on action potential (AP) repetitive firing in R6/2 mice using a two-electrode current clamp. We found that R6/2 APs had a significantly lower peak amplitude, depolarized maximum repolarization, and prolonged decay time compared with wild type (WT). Of these differences, only the maximum repolarization was accounted for by the reduction in ClC-1 and Kir currents, indicating the presence of additional ion channel defects. We found that both KV1.5 and KV3.4 mRNA levels were significantly reduced in R6/2 skeletal muscle compared with WT, which explains the prolonged decay time of R6/2 APs. Overall, we found that APs in WT and R6/2 muscle significantly and progressively change during activity to maintain peak amplitude despite buildup of Na+ channel inactivation. Even with this resilience, the persistently reduced peak amplitude of R6/2 APs is expected to result in earlier fatigue and may help explain the motor impersistence experienced by HD patients. This work lays the foundation to link electrical changes to force generation defects in R6/2 HD mice and to examine the regulatory events controlling APs in WT muscle.

From Genetic Testing to Precision Medicine in Epilepsy.

Epilepsy includes a number of medical conditions with recurrent seizures as common denominator. The large number of different syndromes and seizure types as well as the highly variable inter-individual response to the therapies makes management of this condition often challenging. In the last two decades, a genetic etiology has been revealed in more than half of all epilepsies and single gene defects in ion channels or neurotransmitter receptors have been associated with most inherited forms of epilepsy, including some focal and lesional forms as well as specific epileptic developmental encephalopathies. Several genetic tests are now available, including targeted assays up to revolutionary tools that have made sequencing of all coding (whole exome) and non-coding (whole genome) regions of the human genome possible. These recent technological advances have also driven genetic discovery in epilepsy and increased our understanding of the molecular mechanisms of many epileptic disorders, eventually providing targets for precision medicine in some syndromes, such as Dravet syndrome, pyroxidine-dependent epilepsy, and glucose transporter 1 deficiency. However, these examples represent a relatively small subset of all types of epilepsy, and to date, precision medicine in epilepsy has primarily focused on seizure control, and other clinical aspects, such as neurodevelopmental and neuropsychiatric comorbidities, have yet been possible to address. We herein summarize the most recent advances in genetic testing and provide up-to-date approaches for the choice of the correct test for some epileptic disorders and tailored treatments that are already applicable in some monogenic epilepsies. In the next years, the most probably scenario is that epilepsy treatment will be very different from the currently almost empirical approach, eventually with a "precision medicine" approach applicable on a large scale.

Proarrhythmogenic Effect of the L532P and N588K KCNH2 Mutations in the Human Heart Using a 3D Electrophysiological Model.

BackgroundAtrial arrhythmia is a cardiac disorder caused by abnormal electrical signaling and transmission, which can result in atrial fibrillation and eventual death. Genetic defects in ion channels can cause myocardial repolarization disorders. Arrhythmia-associated gene mutations, including KCNH2 gene mutations, which are one of the most common genetic disorders, have been reported. This mutation causes abnormal QT intervals by a gain of function in the rapid delayed rectifier potassium channel (IKr). In this study, we demonstrated that mutations in the KCNH2 gene cause atrial arrhythmia.MethodsThe N588K and L532P mutations were induced in the Courtemanche-Ramirez-Nattel (CRN) cell model, which was subjected to two-dimensional and three-dimensional simulations to compare the electrical conduction patterns of the wild-type and mutant-type genes.ResultsIn contrast to the early self-termination of the wild-type conduction waveforms, the conduction waveform of the mutant-type retained the reentrant wave (N588K) and caused a spiral break-up, resulting in irregular wave generation (L532P).ConclusionThe present study confirmed that the KCNH2 gene mutation increases the vulnerability of the atrial tissue for arrhythmia.

Pharmacological and Genomic Approaches in Management of Cystic Fibrosis.

Cystic fibrosis (CF) is an inherited recessive autosomal disorder that affects the lungs, the digestive system, and secretory glands. It is a lethal condition caused by a mutation in the gene cystic-fibrosis-transmembrane-conductance- regulator (CFTR), which leads to defects in ion channels and results in obstruction of mucus in airway channels. Unbalanced ion exchange causes impaired water transport and accumulation of viscous mucus in the air way leads to bacterial colonization, for example, with Staphylococcus aureus. The most common mutation is the deletion of nucleotides in epithelial membrane; hence, it is a multiple-organ-defective disease that mostly effects the lungs. Researchers are working on gene therapy that aims to introduce a normal CFTR gene copy into the epithelial cells of lungs. Several approaches have been designed to improve transepithelial ion transport in CF patients. Normal CFTR gene delivery has been performed using viral and nonviral vectors, but these approaches are not more efficient against the cell barriers. Enzymes may be used that inhibit the sphingolipid to provide proper microenvironment for the CFTR gene product. Thymosin alpha-1 has also been reported as a potential corrector in treatment of CF.

Genetic potassium channel-associated epilepsies: Clinical review of the Kv family.

Next-generation sequencing has enhanced discovery of many disease-associated genes in previously unexplained epilepsies, mainly in developmental and epileptic encephalopathies and familial epilepsies. We now classify these disorders according to the underlying molecular pathways, which encompass a diverse array of cellular and sub-cellular compartments/signalling processes including voltage-gated ion-channel defects. With the aim to develop and increase the use of precision medicine therapies, understanding the pathogenic mechanisms and consequences of disease-causing variants has gained major relevance in clinical care. The super-family of voltage-gated potassium channels is the largest and most diverse family among the ion channels, encompassing approximately 80 genes. Key potassium channelopathies include those affecting the KV, KCa and Kir families, a significant proportion of which have been implicated in neurological disease. As for other ion channel disorders, different pathogenic variants within any individual voltage-gated potassium channel gene tend to affect channel protein function differently, causing heterogeneous clinical phenotypes. The focus of this review is to summarise recent clinical developments regarding the key voltage-gated potassium (KV) family-related epilepsies, which now encompasses approximately 12 established disease-associated genes, from the KCNA-, KCNB-, KCNC-, KCND-, KCNV-, KCNQ- and KCNH-subfamilies.

Liposomal delivery of functional transmembrane ion channels into the cell membranes of target cells; a potential approach for the treatment of channelopathies

Defects in transmembrane ion channels underlie many disorders, commonly known as channelopathies. Current therapies are mostly symptomatic and do not treat the underlying cause. Here, we demonstrate the delivery of functional ion channels in protein form into the membrane of target cells using fusogenic proteoliposomes. The glycine receptor (GlyR) was adopted as a model channel. HEK293 cells were transfected with GlyR and GlyR-rich cell membrane fragments (CMF) were incorporated into fusogenic liposomes. Proteoliposomes were generated using 1,2-dioleoylphosphoethanolamine (DOPE) as the fusogenic lipid, lecithin, 1,2-distearoylphosphoethanolamine (DSPE), and cholesterol (Chol). Three formulations were prepared Non-fuse (2.5:0.5 Lecithin: Chol), Fuse1 (1.25:0.25:0.25:0.25) and Fuse2 (1.25:0.5:0.5:0.25 Lecithin: DOPE: DSPE: Chol). Proteoliposomes were assessed for their ability to (1) incorporate GlyR rich CMF (2) fuse with L929 fibroblast cell membrane and (3) deliver functional GlyR to these cells. All formulations were capable of integrating CMF, with Fuse2 showing highest CMF incorporation (1.2 and 1.4 folds relative to Non-fuse and Fuse1 respectively). All liposomes showed ability to fuse with the fibroblast cell membrane, with Fuse2 showing highest fusion. Patch-clamp analysis demonstrated successful delivery of functional GlyR into the fibroblast cell membrane. Thus, proof of principle was established for the use of liposomes to deliver functional ion channels to living cells.

Human sperm ion channel (dys)function: implications for fertilization.

BACKGROUNDIntensive research on sperm ion channels has identified members of several ion channel families in both mouse and human sperm. Gene knock-out studies have unequivocally demonstrated the importance of the calcium and potassium conductances in sperm for fertility. In both species, the calcium current is carried by the highly complex cation channel of sperm (CatSper). In mouse sperm, the potassium current has been conclusively shown to be carried by a channel consisting of the pore forming subunit SLO3 and auxiliary subunit leucine-rich repeat-containing 52 (LRRC52). However, in human sperm it is controversial whether the pore forming subunit of the channel is composed of SLO3 and/or SLO1. Deciphering the role of the proton-specific Hv1 channel is more challenging as it is only expressed in human sperm. However, definitive evidence for a role in, and importance for, human fertility can only be determined through studies using clinical samples.OBJECTIVE AND RATIONALEThis review aims to provide insight into the role of sperm ion channels in human fertilization as evidenced from recent studies of sperm from infertile men. We also summarize the key discoveries from mouse ion channel knock-out models and contrast the properties of mouse and human CatSper and potassium currents. We detail the evidence for, and consequences of, defective ion channels in human sperm and discuss hypotheses to explain how defects arise and why affected sperm have impaired fertilization potential.SEARCH METHODSRelevant studies were identified using PubMed and were limited to ion channels that have been characterized in mouse and human sperm. Additional notable examples from other species are included as appropriate.OUTCOMESThere are now well-documented fundamental differences between the properties of CatSper and potassium channel currents in mouse and human sperm. However, in both species, sperm lacking either channel cannot fertilize in vivo and CatSper-null sperm also fail to fertilize at IVF. Sperm-lacking potassium currents are capable of fertilizing at IVF, albeit at a much lower rate. However, additional complex and heterogeneous ion channel dysfunction has been reported in sperm from infertile men, the causes of which are unknown. Similarly, the nature of the functional impairment of affected patient sperm remains elusive. There are no reports of studies of Hv1 in human sperm from infertile men.WIDER IMPLICATIONSRecent studies using sperm from infertile men have given new insight and critical evidence supporting the supposition that calcium and potassium conductances are essential for human fertility. However, it should be highlighted that many fundamental questions remain regarding the nature of molecular and functional defects in sperm with dysfunctional ion channels. The development and application of advanced technologies remains a necessity to progress basic and clinical research in this area, with the aim of providing effective screening methodologies to identify and develop treatments for affected men in order to help prevent failed ART cycles. Conversely, development of drugs that block calcium and/or potassium conductances in sperm is a plausible strategy for producing sperm-specific contraceptives.