ER-mitochondria cross-talk is regulated by the Ca2+ sensor NCS1 and is impaired in Wolfram syndrome

Optic disc drusen: Dystrophic calcification, a potential target for treatment

Optic disc drusen (ODD) are calcified, acellular bodies, seen in the optic nerve head of up to 2% of the population. Although seldomly affecting visual acuity, visual field defects are common, and severe, ischemic complications causing irreversible vision loss are known to occur. Different treatment strategies for ODD have been explored, but so far without success. This review focuses on the unique, calcified property of ODD, describing what we know about ODD pathogenesis and previously tried treatment strategies. In this context, we discuss current knowledge about calcium and pathological calcifications, including intracranial and ocular calcifications. We also explore some of the obstacles that must be addressed to develop a therapy centred on the concept of calcification, should calcification be identified as a pathogenic factor contributing to vision loss.

Molecular recording of calcium signals via calcium-dependent proximity labeling

Calcium ions serve as key intracellular signals. Local, transient increases in calcium concentrations can activate calcium sensor proteins that in turn trigger downstream effectors. In neurons, calcium transients play a central role in regulating neurotransmitter release and synaptic plasticity. However, it is challenging to capture the molecular events associated with these localized and ephemeral calcium signals. Here we present an engineered biotin ligase that generates permanent molecular traces in a calcium-dependent manner. The enzyme, calcium-dependent BioID (Cal-ID), biotinylates nearby proteins within minutes in response to elevated local calcium levels. The biotinylated proteins can be identified via mass spectrometry and visualized using microscopy. In neurons, Cal-ID labeling is triggered by neuronal activity, leading to prominent protein biotinylation that enables transcription-independent activity labeling in the brain. In summary, Cal-ID produces a biochemical record of calcium signals and neuronal activity with high spatial resolution and molecular specificity.

The Wolfram-like variant WFS1E864K destabilizes MAM and compromises autophagy and mitophagy in human and mice

Dominant variants in WFS1 (wolframin ER transmembrane glycoprotein), the gene coding for a mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) resident protein, have been associated with Wolfram-like syndrome (WLS). In vitro and in vivo, WFS1 loss results in reduced ER to mitochondria calcium (Ca2+) transfer, mitochondrial dysfunction, and enhanced macroautophagy/autophagy and mitophagy. However, in the WLS pathological context, whether the mutant protein triggers the same cellular processes is unknown. Here, we show that in human fibroblasts and murine neuronal cultures the WLS protein WFS1E864K leads to decreases in mitochondria bioenergetics and Ca2+ uptake, deregulation of the mitochondrial quality system mechanisms, and alteration of the autophagic flux. Moreover, in the Wfs1E864K mouse, these alterations are concomitant with a decrease of MAM number. These findings reveal pathophysiological similarities between WS and WLS, highlighting the importance of WFS1 for MAM's integrity and functionality. It may open new treatment perspectives for patients with WLS.Abbreviations: BafA1: bafilomycin A1; ER: endoplasmic reticulum; HSPA9/GRP75: heat shock protein family A (Hsp70) member 9; ITPR/IP3R: inositol 1,4,5-trisphosphate receptor; MAM: mitochondria-associated endoplasmic reticulum membrane; MCU: mitochondrial calcium uniporter; MFN2: mitofusin 2; OCR: oxygen consumption rate; ROS: reactive oxygen species; ROT/AA: rotenone+antimycin A; VDAC1: voltage dependent anion channel 1; WLS: Wolfram-like syndrome; WS: Wolfram syndrome; WT: wild-type.

The Janus-faced functions of Apolipoproteins L in membrane dynamics

The functions of human Apolipoproteins L (APOLs) are poorly understood, but involve diverse activities like lysis of bloodstream trypanosomes and intracellular bacteria, modulation of viral infection and induction of apoptosis, autophagy, and chronic kidney disease. Based on recent work, I propose that the basic function of APOLs is the control of membrane dynamics, at least in the Golgi and mitochondrion. Together with neuronal calcium sensor-1 (NCS1) and calneuron-1 (CALN1), APOL3 controls the activity of phosphatidylinositol-4-kinase-IIIB (PI4KB), involved in both Golgi and mitochondrion membrane fission. Whereas secreted APOL1 induces African trypanosome lysis through membrane permeabilization of the parasite mitochondrion, intracellular APOL1 conditions non-muscular myosin-2A (NM2A)-mediated transfer of PI4KB and APOL3 from the Golgi to the mitochondrion under conditions interfering with PI4KB-APOL3 interaction, such as APOL1 C-terminal variant expression or virus-induced inflammatory signalling. APOL3 controls mitophagy through complementary interactions with the membrane fission factor PI4KB and the membrane fusion factor vesicle-associated membrane protein-8 (VAMP8). In mice, the basic APOL1 and APOL3 activities could be exerted by mAPOL9 and mAPOL8, respectively. Perspectives regarding the mechanism and treatment of APOL1-related kidney disease are discussed, as well as speculations on additional APOLs functions, such as APOL6 involvement in adipocyte membrane dynamics through interaction with myosin-10 (MYH10).

Comprehensive overview of disease models for Wolfram syndrome: toward effective treatments

Wolfram syndrome (OMIM 222300) is a rare autosomal recessive disease with a devastating array of symptoms, including diabetes mellitus, optic nerve atrophy, diabetes insipidus, hearing loss, and neurological dysfunction. The discovery of the causative gene, WFS1, has propelled research on this disease. However, a comprehensive understanding of the function of WFS1 remains unknown, making the development of effective treatment a pressing challenge. To bridge these knowledge gaps, disease models for Wolfram syndrome are indispensable, and understanding the characteristics of each model is critical. This review will provide a summary of the current knowledge regarding WFS1 function and offer a comprehensive overview of established disease models for Wolfram syndrome, covering animal models such as mice, rats, flies, and zebrafish, along with induced pluripotent stem cell (iPSC)-derived human cellular models. These models replicate key aspects of Wolfram syndrome, contributing to a deeper understanding of its pathogenesis and providing a platform for discovering potential therapeutic approaches.

Methane-Rich Saline Suppresses ER-Mitochondria Contact and Activation of the NLRP3 Inflammasome by Regulating the PERK Signaling Pathway to Ameliorate Intestinal Ischemia‒Reperfusion Injury

Intestinal ischemia‒reperfusion (I/R) injury is a common pathological process in patients undergoing gastrointestinal surgery, leading to local intestinal damage and increased microvascular permeability, eventually causing extraintestinal multiple organ dysfunction or sepsis. The NLRP3-mediated inflammatory response is associated with I/R injury. Methane saline (MS) has anti-pyroptosis properties. This study aims to explore the protective effect of MS on intestinal I/R injury and its potential mechanisms. After MS pretreatment, the in vivo model was established by temporarily clipping the mouse superior mesentery artery with a noninvasive vascular clamp, and the in vitro model was established by OGD/R on Caco-2 cells. The results of HE and TUNEL staining showed intestinal barrier damage after I/R injury, which was consistent with the IHC staining results of tight junction proteins. Moreover, the expression of the NLRP3 signaling pathway was increased after I/R injury, and inhibition of NLRP3 activation reduced Caco-2 cell injury, indicating that NLRP3-mediated pyroptosis was one of the main forms of cell death after I/R injury. Subsequently, we found that MS treatment ameliorated intestinal barrier function after I/R injury by suppressing NLRP3-mediated pyroptosis. MS treatment also reduced mitochondria-associated membrane (MAM) formation, which was considered to be a platform for activation of the NLRP3 inflammasome. Importantly, MS reduced ER stress, which was related to the PERK signaling pathway. Knocking down PERK, a key protein involved in ER stress and MAM formation, reversed the protective effect of MS, indicating that MS suppressed NLRP3 by reducing ER stress and MAM formation. In conclusion, we believe that MS suppresses MAMs and activation of the NLRP3 inflammasome by regulating the PERK signaling pathway to ameliorate intestinal I/R injury.

Convolamine, a tropane alkaloid extracted from Convolvulus plauricalis, is a potent sigma-1 receptor-positive modulator with cognitive and neuroprotective properties

BACKGROUND AND AIM

By using an in vivo phenotypic screening assay in zebrafish, we identified Convolamine, a tropane alkaloid from Convulvus plauricalis, as a positive modulator of the sigma-1 receptor (S1R). The wfs1abKO zebrafish larva, a model of Wolfram syndrome, exhibits an increased visual-motor response due to a mutation in Wolframin, a protein involved in endoplasmic reticulum-mitochondria communication. We previously reported that ligand activating S1R, restored the cellular and behavioral deficits in patient fibroblasts and zebrafish and mouse models.

EXPERIMENTAL PROCEDURES

We screened a library of 108 repurposing and natural compounds on zebrafish motor response.

KEY RESULTS

One hit, the tropane alkaloid Convolamine, restored normal mobility in wfs1abKO larvae without affecting wfs1abWT controls. They did not bind to the S1R agonist/antagonist binding site nor dissociated S1R from BiP, an S1R activity assay in vitro, but behaved as a positive modulator by shifting the IC50 value of the reference agonist PRE-084 to lower values. Convolamine restored learning in Wfs1∆Exon8 , Dizocilpine-treated, and Aβ25-35 -treated mice. These effects were observed at low ~1 mg/kg doses, not shared by Convolvine, the desmethyl metabolite, and blocked by an S1R antagonist.

CONCLUSION AND IMPLICATIONS

Convolamine therefore acts as an S1R positive modulator and this pharmacological action is relevant to the traditional use of Shankhpushpi in memory and cognitive protection.

Disruption of MAM integrity in mutant FUS oligodendroglial progenitors from hiPSCs

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disorder, characterized by selective loss of motor neurons (MNs). A number of causative genetic mutations underlie the disease, including mutations in the fused in sarcoma (FUS) gene, which can lead to both juvenile and late-onset ALS. Although ALS results from MN death, there is evidence that dysfunctional glial cells, including oligodendroglia, contribute to neurodegeneration. Here, we used human induced pluripotent stem cells (hiPSCs) with a R521H or a P525L mutation in FUS and their isogenic controls to generate oligodendrocyte progenitor cells (OPCs) by inducing SOX10 expression from a TET-On SOX10 cassette. Mutant and control iPSCs differentiated efficiently into OPCs. RNA sequencing identified a myelin sheath-related phenotype in mutant OPCs. Lipidomic studies demonstrated defects in myelin-related lipids, with a reduction of glycerophospholipids in mutant OPCs. Interestingly, FUSR521H OPCs displayed a decrease in the phosphatidylcholine/phosphatidylethanolamine ratio, known to be associated with maintaining membrane integrity. A proximity ligation assay further indicated that mitochondria-associated endoplasmic reticulum membranes (MAM) were diminished in both mutant FUS OPCs. Moreover, both mutant FUS OPCs displayed increased susceptibility to ER stress when exposed to thapsigargin, and exhibited impaired mitochondrial respiration and reduced Ca2+ signaling from ER Ca2+ stores. Taken together, these results demonstrate a pathological role of mutant FUS in OPCs, causing defects in lipid metabolism associated with MAM disruption manifested by impaired mitochondrial metabolism with increased susceptibility to ER stress and with suppressed physiological Ca2+ signaling. As such, further exploration of the role of oligodendrocyte dysfunction in the demise of MNs is crucial and will provide new insights into the complex cellular mechanisms underlying ALS.

Apolipoproteins L1 and L3 control mitochondrial membrane dynamics

Apolipoproteins L1 and L3 (APOLs) are associated at the Golgi with the membrane fission factors phosphatidylinositol 4-kinase-IIIB (PI4KB) and non-muscular myosin 2A. Either APOL1 C-terminal truncation (APOL1Δ) or APOL3 deletion (APOL3-KO [knockout]) reduces PI4KB activity and triggers actomyosin reorganization. We report that APOL3, but not APOL1, controls PI4KB activity through interaction with PI4KB and neuronal calcium sensor-1 or calneuron-1. Both APOLs are present in Golgi-derived autophagy-related protein 9A vesicles, which are involved in PI4KB trafficking. Like APOL3-KO, APOL1Δ induces PI4KB dissociation from APOL3, linked to reduction of mitophagy flux and production of mitochondrial reactive oxygen species. APOL1 and APOL3, respectively, can interact with the mitophagy receptor prohibitin-2 and the mitophagosome membrane fusion factor vesicle-associated membrane protein-8 (VAMP8). While APOL1 conditions PI4KB and APOL3 involvement in mitochondrion fission and mitophagy, APOL3-VAMP8 interaction promotes fusion between mitophagosomal and endolysosomal membranes. We propose that APOL3 controls mitochondrial membrane dynamics through interactions with the fission factor PI4KB and the fusion factor VAMP8.

Loss of INPP5K attenuates IP3-induced Ca2+ responses in the glioblastoma cell line U-251 MG cells

INPP5K (inositol polyphosphate 5-phosphatase K) is an endoplasmic reticulum (ER)-resident enzyme that acts as a phosphoinositide (PI) 5-phosphatase, capable of dephosphorylating various PIs including PI 4,5-bisphosphate (PI(4,5)P2), a key phosphoinositide found in the plasma membrane. Given its ER localization and substrate specificity, INPP5K may play a role in ER-plasma membrane contact sites. Furthermore, PI(4,5)P2 serves as a substrate for phospholipase C, an enzyme activated downstream of extracellular agonists acting on Gq-coupled receptors or tyrosine-kinase receptors, leading to IP3 production and subsequent release of Ca2+ from the ER, the primary intracellular Ca2+ storage organelle. In this study, we investigated the impact of INPP5K on ER Ca2+ dynamics using a previously established INPP5K-knockdown U-251 MG glioblastoma cell model. We here describe that loss of INPP5K impairs agonist-induced, IP3 receptor (IP3R)-mediated Ca2+ mobilization in intact cells, while the ER Ca2+ content and store-operated Ca2+ influx remain unaffected. To further elucidate the underlying mechanisms, we examined Ca2+ release in permeabilized cells stimulated with exogenous IP3. Interestingly, the absence of INPP5K also disrupted IP3-induced Ca2+ release events. These results suggest that INPP5K may directly influence IP3R activity through mechanisms yet to be resolved. The findings from this study point towards role of INPP5K in modulating ER calcium dynamics, particularly in relation to IP3-mediated signaling pathways. However, further work is needed to establish the general nature of our findings and to unravel the exact molecular mechanisms underlying the interplay between INNP5K function and Ca2+ signaling.

Genomics of Wolfram Syndrome 1 (WFS1)

Wolfram Syndrome (WFS) is a rare, autosomal, recessive neurogenetic disorder that affects many organ systems. It is characterised by diabetes insipidus, diabetes mellites, optic atrophy, and deafness and, therefore, is also known as DIDMOAD. Nearly 15,000-30,000 people are affected by WFS worldwide, and, on average, patients suffering from WFS die at 30 years of age, usually from central respiratory failure caused by massive brain atrophy. The more prevalent of the two kinds of WFS is WFS1, which is a monogenic disease and caused by the loss of the WFS1 gene, whereas WFS2, which is more uncommon, is caused by mutations in the CISD2 gene. Currently, there is no treatment for WFS1 to increase the life expectancy of patients, and the treatments available do not significantly improve their quality of life. Understanding the genetics and the molecular mechanisms of WFS1 is essential to finding a cure. The inability of conventional medications to treat WFS1 points to the need for innovative strategies that must address the fundamental cause: the deletion of the WFS1 gene that leads to the profound ER stress and disturbances in proteostasis. An important approach here is to understand the mechanism of the cell degeneration after the deletion of the WFS1 gene and to describe the differences in these mechanisms for the different tissues. The studies so far have indicated that remarkable clinical heterogeneity is caused by the variable vulnerability caused by WFS1 mutations, and these differences cannot be attributed solely to the positions of mutations in the WFS1 gene. The present review gives a broader overview of the results from genomic studies on the WFS1 mouse model.

Mitochondrial Dynamics in Neurodegenerative Diseases: Unraveling the Role of Fusion and Fission Processes

Neurodegenerative diseases (NDs) are a diverse group of disorders characterized by the progressive degeneration and death of neurons, leading to a range of neurological symptoms. Despite the heterogeneity of these conditions, a common denominator is the implication of mitochondrial dysfunction in their pathogenesis. Mitochondria play a crucial role in creating biomolecules, providing energy through adenosine triphosphate (ATP) generated by oxidative phosphorylation (OXPHOS), and producing reactive oxygen species (ROS). When they're not functioning correctly, becoming fragmented and losing their membrane potential, they contribute to these diseases. In this review, we explore how mitochondria fuse and undergo fission, especially in the context of NDs. We discuss the genetic and protein mutations linked to these diseases and how they impact mitochondrial dynamics. We also look at the key regulatory proteins in fusion (MFN1, MFN2, and OPA1) and fission (DRP1 and FIS1), including their post-translational modifications. Furthermore, we highlight potential drugs that can influence mitochondrial dynamics. By unpacking these complex processes, we aim to direct research towards treatments that can improve life quality for people with these challenging conditions.

A proximity labeling strategy enables proteomic analysis of inter-organelle membrane contacts

Inter-organelle membrane contacts are highly dynamic and act as central hubs for many biological processes, but the protein compositions remain largely unknown due to the lack of efficient tools. Here, we developed BiFCPL to analyze the contact proteome in living cells by a bimolecular fluorescence complementation (BiFC)-based proximity labeling (PL) strategy. BiFCPL was applied to study mitochondria-endoplasmic reticulum contacts (MERCs) and mitochondria-lipid droplet (LD) contacts. We identified 403 highly confident MERC proteins, including many transiently resident proteins and potential tethers. Moreover, we demonstrated that mitochondria-LD contacts are sensitive to nutrient status. A comparative proteomic analysis revealed that 60 proteins are up- or downregulated at contact sites under metabolic challenge. We verified that SQLE, an enzyme for cholesterol synthesis, accumulates at mitochondria-LD contact sites probably to utilize local ATP for cholesterol synthesis. This work provides an efficient method to identify key proteins at inter-organelle membrane contacts in living cells.

Wolfram syndrome 1 regulates sleep in dopamine receptor neurons by modulating calcium homeostasis

Sleep disruptions are quite common in psychological disorders, but the underlying mechanism remains obscure. Wolfram syndrome 1 (WS1) is an autosomal recessive disease mainly characterized by diabetes insipidus/mellitus, neurodegeneration and psychological disorders. It is caused by loss-of function mutations of the WOLFRAM SYNDROME 1 (WFS1) gene, which encodes an endoplasmic reticulum (ER)-resident transmembrane protein. Heterozygous mutation carriers do not develop WS1 but exhibit 26-fold higher risk of having psychological disorders. Since WS1 patients display sleep abnormalities, we aimed to explore the role of WFS1 in sleep regulation so as to help elucidate the cause of sleep disruptions in psychological disorders. We found in Drosophila that knocking down wfs1 in all neurons and wfs1 mutation lead to reduced sleep and dampened circadian rhythm. These phenotypes are mainly caused by lack of wfs1 in dopamine 2-like receptor (Dop2R) neurons which act to promote wake. Consistently, the influence of wfs1 on sleep is blocked or partially rescued by inhibiting or knocking down the rate-limiting enzyme of dopamine synthesis, suggesting that wfs1 modulates sleep via dopaminergic signaling. Knocking down wfs1 alters the excitability of Dop2R neurons, while genetic interactions reveal that lack of wfs1 reduces sleep via perturbation of ER-mediated calcium homeostasis. Taken together, we propose a role for wfs1 in modulating the activities of Dop2R neurons by impinging on intracellular calcium homeostasis, and this in turn influences sleep. These findings provide a potential mechanistic insight for pathogenesis of diseases associated with WFS1 mutations.

GLP-1R agonists demonstrate potential to treat Wolfram syndrome in human preclinical models

AIMS/HYPOTHESIS

Wolfram syndrome is a rare autosomal recessive disorder caused by pathogenic variants in the WFS1 gene. It is characterised by insulin-dependent diabetes mellitus, optic nerve atrophy, diabetes insipidus, hearing loss and neurodegeneration. Considering the unmet treatment need for this orphan disease, this study aimed to evaluate the therapeutic potential of glucagon-like peptide 1 receptor (GLP-1R) agonists under wolframin (WFS1) deficiency with a particular focus on human beta cells and neurons.

METHODS

The effect of the GLP-1R agonists dulaglutide and exenatide was examined in Wfs1 knockout mice and in an array of human preclinical models of Wolfram syndrome, including WFS1-deficient human beta cells, human induced pluripotent stem cell (iPSC)-derived beta-like cells and neurons from control individuals and individuals affected by Wolfram syndrome, and humanised mice.

RESULTS

Our study shows that the long-lasting GLP-1R agonist dulaglutide reverses impaired glucose tolerance in WFS1-deficient mice, and that exenatide and dulaglutide improve beta cell function and prevent apoptosis in different human WFS1-deficient models including iPSC-derived beta cells from people with Wolfram syndrome. Exenatide improved mitochondrial function, reduced oxidative stress and prevented apoptosis in Wolfram syndrome iPSC-derived neural precursors and cerebellar neurons.

CONCLUSIONS/INTERPRETATION

Our study provides novel evidence for the beneficial effect of GLP-1R agonists on WFS1-deficient human pancreatic beta cells and neurons, suggesting that these drugs may be considered as a treatment for individuals with Wolfram syndrome.

Wfs1E864K knock-in mice illuminate the fundamental role of Wfs1 in endocochlear potential production

Wolfram syndrome (WS) is a rare neurodegenerative disorder encompassing diabetes mellitus, diabetes insipidus, optic atrophy, hearing loss (HL) as well as neurological disorders. None of the animal models of the pathology are presenting with an early onset HL, impeding the understanding of the role of Wolframin (WFS1), the protein responsible for WS, in the auditory pathway. We generated a knock-in mouse, the Wfs1E864K line, presenting a human mutation leading to severe deafness in affected individuals. The homozygous mice showed a profound post-natal HL and vestibular syndrome, a collapse of the endocochlear potential (EP) and a devastating alteration of the stria vascularis and neurosensory epithelium. The mutant protein prevented the localization to the cell surface of the Na+/K+ATPase β1 subunit, a key protein for the maintenance of the EP. Overall, our data support a key role of WFS1 in the maintenance of the EP and the stria vascularis, via its binding partner, the Na+/K+ATPase β1 subunit.

Genotype and clinical characteristics of patients with Wolfram syndrome and WFS1-related disorders

Objective: Wolfram syndrome (WFS) is an autosomal recessive disorder associated with juvenile-onset diabetes mellitus, optic atrophy, diabetes insipidus, and sensorineural hearing loss. We sought to elucidate the relationship between genotypic and phenotypic presentations of Wolfram syndrome which would assist clinicians in classifying the severity and prognosis of Wolfram syndrome more accurately. Approach: Patient data from the Washington University International Registry and Clinical Study for Wolfram Syndrome and patient case reports were analyzed to select for patients with two recessive mutations in the WFS1 gene. Mutations were classified as being either nonsense/frameshift variants or missense/in-frame insertion/deletion variants. Missense/in-frame variants were further classified as transmembrane or non-transmembrane based on whether they affected amino acid residues predicted to be in transmembrane domains of WFS1. Statistical analysis was performed using Wilcoxon rank-sum tests with multiple test adjustment applied via the Bonferonni correction. Results: A greater number of genotype variants correlated with earlier onset and a more severe presentation of Wolfram syndrome. Secondly, non-sense and frameshift variants had more severe phenotypic presentations than missense variants, as evidenced by diabetes mellitus and optic atrophy emerging significantly earlier in patients with two nonsense/frameshift variants compared with zero or one nonsense/frameshift variants. In addition, the number of transmembrane in-frame variants demonstrated a statistically significant dose-effect on age of onset of diabetes mellitus and optic atrophy among patients with either one or two in-frame variants. Summary/Conclusion: The results contribute to our current understanding of the genotype-phenotype relationship of Wolfram syndrome, suggesting that alterations in coding sequences result in significant changes in the presentation and severity of Wolfram. The impact of these findings is significant, as the results will aid clinicians in predicting more accurate prognoses and pave the way for personalized treatments for Wolfram syndrome.

GLP-1 receptor agonists as promising disease-modifying agents in WFS1 spectrum disorder

WFS1 spectrum disorder (WFS1-SD) is a rare monogenic neurodegenerative disorder whose cardinal symptoms are childhood-onset diabetes mellitus, optic atrophy, deafness, diabetes insipidus, and neurological signs ranging from mild to severe. The prognosis is poor as most patients die prematurely with severe neurological disabilities such as bulbar dysfunction and organic brain syndrome. Mutation of the WFS1 gene is recognized as the prime mover of the disease and responsible for a dysregulated ER stress signaling, which leads to neuron and pancreatic β-cell death. There is no currently cure and no treatment that definitively arrests the progression of the disease. GLP-1 receptor agonists appear to be an efficient way to reduce elevated ER stress in vitro and in vivo, and increasing findings suggest they could be effective in delaying the progression of WFS1-SD. Here, we summarize the characteristics of GLP-1 receptor agonists and preclinical and clinical data obtained by testing them in WFS1-SD as a feasible strategy for managing this disease.

Calcium signaling in chemotherapy-induced neuropathy

Alterations in calcium (Ca²⁺) signaling is a major mechanism in the development of chemotherapy-induced peripheral neuropathy (CIPN), a side effect caused by multiple chemotherapy regimens. CIPN is associated with numbness and incessant tingling in hands and feet which diminishes quality of life during treatment. In up to 50% of survivors, CIPN is essentially irreversible. There are no approved, disease-modifying treatments for CIPN. The only recourse for oncologists is to modify the chemotherapy dose, a situation that can compromise optimal chemotherapy and impact patient outcomes. Here we focus on taxanes and other chemotherapeutic agents that work by altering microtubule assemblies to kill cancer cells, but also have off-target toxicities. There have been many molecular mechanisms proposed to explain the effects of microtubule-disrupting drugs. In neurons, an initiating step in the off-target effects of treatment by taxane is binding to neuronal calcium sensor 1 (NCS1), a sensitive Ca²⁺ sensor protein that maintains the resting Ca²⁺ concentration and dynamically enhances responses to cellular stimuli. The taxane/NCS1 interaction causes a Ca²⁺ surge that starts a pathophysiological cascade of consequences. This same mechanism contributes to other conditions including chemotherapy-induced cognitive impairment. Strategies to prevent the Ca²⁺ surge are the foundation of current work.

Depletion of WFS1 compromises mitochondrial function in hiPSC-derived neuronal models of Wolfram syndrome

Mitochondrial dysfunction involving mitochondria-associated ER membrane (MAM) dysregulation is implicated in the pathogenesis of late-onset neurodegenerative diseases, but understanding is limited for rare early-onset conditions. Loss of the MAM-resident protein WFS1 causes Wolfram syndrome (WS), a rare early-onset neurodegenerative disease that has been linked to mitochondrial abnormalities. Here we demonstrate mitochondrial dysfunction in human induced pluripotent stem cell-derived neuronal cells of WS patients. VDAC1 is identified to interact with WFS1, whereas loss of this interaction in WS cells could compromise mitochondrial function. Restoring WFS1 levels in WS cells reinstates WFS1-VDAC1 interaction, which correlates with an increase in MAMs and mitochondrial network that could positively affect mitochondrial function. Genetic rescue by WFS1 overexpression or pharmacological agents modulating mitochondrial function improves the viability and bioenergetics of WS neurons. Our data implicate a role of WFS1 in regulating mitochondrial functionality and highlight a therapeutic intervention for WS and related rare diseases with mitochondrial defects.

The ER-mitochondria interface, where Ca2+ and cell death meet

Endoplasmic reticulum (ER)-mitochondria contact sites are crucial to allow Ca²⁺ flux between them and a plethora of proteins participate in tethering both organelles together. Inositol 1,4,5-trisphosphate receptors (IP₃Rs) play a pivotal role at such contact sites, participating in both ER-mitochondria tethering and as Ca²⁺-transport system that delivers Ca²⁺ from the ER towards mitochondria. At the ER-mitochondria contact sites, the IP₃Rs function as a multi-protein complex linked to the voltage-dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane, via the chaperone glucose-regulated protein 75 (GRP75). This IP₃R-GRP75-VDAC1 complex supports the efficient transfer of Ca²⁺ from the ER into the mitochondrial intermembrane space, from which the Ca²⁺ ions can reach the mitochondrial matrix through the mitochondrial calcium uniporter. Under physiological conditions, basal Ca²⁺ oscillations deliver Ca²⁺ to the mitochondrial matrix, thereby stimulating mitochondrial oxidative metabolism. However, when mitochondrial Ca²⁺ overload occurs, the increase in [Ca²⁺] will induce the opening of the mitochondrial permeability transition pore, thereby provoking cell death. The IP₃R-GRP75-VDAC1 complex forms a hub for several other proteins that stabilize the complex and/or regulate the complex's ability to channel Ca²⁺ into the mitochondria. These proteins and their mechanisms of action are discussed in the present review with special attention for their role in pathological conditions and potential implication for therapeutic strategies.

WFS1 autosomal dominant variants linked with hearing loss: update on structural analysis and cochlear implant outcome

BACKGROUND

Wolfram syndrome type 1 gene (WFS1), which encodes a transmembrane structural protein (wolframin), is essential for several biological processes, including proper inner ear function. Unlike the recessively inherited Wolfram syndrome, WFS1 heterozygous variants cause DFNA6/14/38 and wolfram-like syndrome, characterized by autosomal dominant nonsyndromic hearing loss, optic atrophy, and diabetes mellitus. Here, we identified two WFS1 heterozygous variants in three DFNA6/14/38 families using exome sequencing. We reveal the pathogenicity of the WFS1 variants based on three-dimensional (3D) modeling and structural analysis. Furthermore, we present cochlear implantation (CI) outcomes in WFS1-associated DFNA6/14/38 and suggest a genotype-phenotype correlation based on our results and a systematic review.

METHODS

We performed molecular genetic test and evaluated clinical phenotypes of three WFS1-associated DFNA6/14/38 families. A putative WFS1-NCS1 interaction model was generated, and the impacts of WFS1 variants on stability were predicted by comparing intramolecular interactions. A total of 62 WFS1 variants associated with DFNA6/14/38 were included in a systematic review.

RESULTS

One variant is a known mutational hotspot variant in the endoplasmic reticulum (ER)-luminal domain WFS1(NM_006005.3) (c.2051 C > T:p.Ala684Val), and the other is a novel frameshift variant in transmembrane domain 6 (c.1544_1545insA:p.Phe515LeufsTer28). The two variants were pathogenic, based on the ACMG/AMP guidelines. Three-dimensional modeling and structural analysis show that non-polar, hydrophobic substitution of Ala684 (p.Ala684Val) destabilizes the alpha helix and contributes to the loss of WFS1-NCS1 interaction. Also, the p.Phe515LeufsTer28 variant truncates transmembrane domain 7-9 and the ER-luminal domain, possibly impairing membrane localization and C-terminal signal transduction. The systematic review demonstrates favorable outcomes of CI. Remarkably, p.Ala684Val in WFS1 is associated with early-onset severe-to-profound deafness, revealing a strong candidate variant for CI.

CONCLUSIONS

We expanded the genotypic spectrum of WFS1 heterozygous variants underlying DFNA6/14/38 and revealed the pathogenicity of mutant WFS1, providing a theoretical basis for WFS1-NCS1 interactions. We presented a range of phenotypic traits for WFS1 heterozygous variants and demonstrated favorable functional CI outcomes, proposing p.Ala684Val a strong potential marker for CI candidates.

Chronic Stress Alters Hippocampal Renin-Angiotensin-Aldosterone System Component Expression in an Aged Rat Model of Wolfram Syndrome

Biallelic mutations in the gene encoding WFS1 underlie the development of Wolfram syndrome (WS), a rare neurodegenerative disorder with no available cure. We have previously shown that Wfs1 deficiency can impair the functioning of the renin-angiotensin-aldosterone system (RAAS). The expression of two key receptors, angiotensin II receptor type 2 (Agtr2) and bradykinin receptor B1 (Bdkrb1), was downregulated both in vitro and in vivo across multiple organs in a rat model of WS. Here, we show that the expression of key RAAS components is also dysregulated in neural tissue from aged WS rats and that these alterations are not normalized by pharmacological treatments (liraglutide (LIR), 7,8-dihydroxyflavone (7,8-DHF) or their combination). We found that the expression of angiotensin II receptor type 1a (Agtr1a), angiotensin II receptor type 1b (Agtr1b), Agtr2 and Bdkrb1 was significantly downregulated in the hippocampus of WS animals that experienced chronic experimental stress. Treatment-naïve WS rats displayed different gene expression patterns, underscoring the effect of prolonged experiment-induced stress. Altogether, we posit that Wfs1 deficiency disturbs RAAS functioning under chronic stressful conditions, thereby exacerbating neurodegeneration in WS.

Cannabinoids modulate the microbiota-gut-brain axis in HIV/SIV infection by reducing neuroinflammation and dysbiosis while concurrently elevating endocannabinoid and indole-3-propionate levels

BACKGROUND

Although the advent of combination anti-retroviral therapy (cART) has transformed HIV into a manageable chronic disease, an estimated 30-50% of people living with HIV (PLWH) exhibit cognitive and motor deficits collectively known as HIV-associated neurocognitive disorders (HAND). A key driver of HAND neuropathology is chronic neuroinflammation, where proinflammatory mediators produced by activated microglia and macrophages are thought to inflict neuronal injury and loss. Moreover, the dysregulation of the microbiota-gut-brain axis (MGBA) in PLWH, consequent to gastrointestinal dysfunction and dysbiosis, can lead to neuroinflammation and persistent cognitive impairment, which underscores the need for new interventions.

METHODS

We performed RNA-seq and microRNA profiling in basal ganglia (BG), metabolomics (plasma) and shotgun metagenomic sequencing (colon contents) in uninfected and SIV-infected rhesus macaques (RMs) administered vehicle (VEH/SIV) or delta-9-tetrahydrocannabinol (THC) (THC/SIV).

RESULTS

Long-term, low-dose THC reduced neuroinflammation and dysbiosis and significantly increased plasma endocannabinoid, endocannabinoid-like, glycerophospholipid and indole-3-propionate levels in chronically SIV-infected RMs. Chronic THC potently blocked the upregulation of genes associated with type-I interferon responses (NLRC5, CCL2, CXCL10, IRF1, IRF7, STAT2, BST2), excitotoxicity (SLC7A11), and enhanced protein expression of WFS1 (endoplasmic reticulum stress) and CRYM (oxidative stress) in BG. Additionally, THC successfully countered miR-142-3p-mediated suppression of WFS1 protein expression via a cannabinoid receptor-1-mediated mechanism in HCN2 neuronal cells. Most importantly, THC significantly increased the relative abundance of Firmicutes and Clostridia including indole-3-propionate (C. botulinum, C. paraputrificum, and C. cadaveris) and butyrate (C. butyricum, Faecalibacterium prausnitzii and Butyricicoccus pullicaecorum) producers in colonic contents.

CONCLUSION

This study demonstrates the potential of long-term, low-dose THC to positively modulate the MGBA by reducing neuroinflammation, enhancing endocannabinoid levels and promoting the growth of gut bacterial species that produce neuroprotective metabolites, like indole-3-propionate. The findings from this study may benefit not only PLWH on cART, but also those with no access to cART and more importantly, those who fail to suppress the virus under cART.

Calcium signaling and genetic rare diseases: An auditory perspective

Deafness is a highly heterogeneous disorder which stems, for 50%, from genetic origins. Sensory transduction relies mainly on sensory hair cells of the cochlea, in the inner ear. Calcium is key for the function of these cells and acts as a fundamental signal transduction. Its homeostasis depends on three factors: the calcium influx, through the mechanotransduction channel at the apical pole of the hair cell as well as the voltage-gated calcium channel at the base of the cells; the calcium buffering via Ca²⁺-binding proteins in the cytoplasm, but also in organelles such as mitochondria and the reticulum endoplasmic mitochondria-associated membranes with specialized proteins; and the calcium extrusion through the Ca-ATPase pump, located all over the plasma membrane. In addition, the synaptic transmission to the central nervous system is also controlled by calcium. Genetic studies of inherited deafness have tremendously helped understand the underlying molecular pathways of calcium signaling. In this review, we discuss these different factors in light of the associated genetic diseases (syndromic and non-syndromic deafness) and the causative genes.

Genotype and Phenotype Analyses of a Novel WFS1 Variant (c.2512C>T p.(Pro838Ser)) Associated with DFNA6/14/38

The aim of this study is to contribute to a better description of the genotypic and phenotypic spectrum of DFNA6/14/38 and aid in counseling future patients identified with this variant. Therefore, we describe the genotype and phenotype in a large Dutch-German family (W21-1472) with autosomal dominant non-syndromic, low-frequency sensorineural hearing loss (LFSNHL). Exome sequencing and targeted analysis of a hearing impairment gene panel were used to genetically screen the proband. Co-segregation of the identified variant with hearing loss was assessed by Sanger sequencing. The phenotypic evaluation consisted of anamnesis, clinical questionnaires, physical examination and examination of audiovestibular function. A novel likely pathogenic WFS1 variant (NM_006005.3:c.2512C>T p.(Pro838Ser)) was identified in the proband and found to co-segregate with LFSNHL, characteristic of DFNA6/14/38, in this family. The self-reported age of onset of hearing loss (HL) ranged from congenital to 50 years of age. In the young subjects, HL was demonstrated in early childhood. At all ages, an LFSNHL (0.25-2 kHz) of about 50-60 decibel hearing level (dB HL) was observed. HL in the higher frequencies showed inter-individual variability. The dizziness handicap inventory (DHI) was completed by eight affected subjects and indicated a moderate handicap in two of them (aged 77 and 70). Vestibular examinations (n = 4) showed abnormalities, particularly in otolith function. In conclusion, we identified a novel WFS1 variant that co-segregates with DFNA6/14/38 in this family. We found indications of mild vestibular dysfunction, although it is uncertain whether this is related to the identified WFS1 variant or is an incidental finding. We would like to emphasize that conventional neonatal hearing screening programs are not sensitive to HL in DFNA6/14/38 patients, because high-frequency hearing thresholds are initially preserved. Therefore, we suggest screening newborns in DFNA6/14/38 families with more frequency-specific methods.

Case Report: A novel mutation in WFS1 gene (c.1756G>A p.A586T) is responsible for early clinical features of cognitive impairment and recurrent ischemic stroke

Wolfram syndrome 1 (WFS1) gene mutations can be dominantly or recessively inherited, and the onset of the clinical picture is highly heterogeneity in both appearance and degree of severity. Different types of WFS1 mutations have been identified. Autosomal recessive mutations in the WFS1 gene will underlie Wolfram syndrome 1 (WS1), a rare and severe neurodegenerative disease characterized by diabetes insipidus, diabetes mellitus, optic atrophy, deafness, and other neurological, urological and psychiatric abnormalities. Other WFS1-related disorders such as low-frequency sensorineural hearing impairment (LFSNHI) and Wolfram syndrome-like disease with autosomal dominant transmission have been described. It is difficult to establish genotype-phenotype correlations because of the molecular complexity of wolframin protein. In this report, we presented a case of WSF1 gene mutation-related disease with cognitive impairment as the initial symptom and recurrent cerebral infarction in the course of the disease. Brain structural imaging results suggested decreased intracranial volume, dramatically reduced in cerebral cortex and cerebellum regions. Multimodal molecular imaging results suggested Tau protein deposition in the corresponding brain regions without Aβ pathology changes. These pathological changes may indicate a role of WFS1 in neuronal vulnerability to tau pathology associated with neurodegeneration and ischemia-induced damage.

Understanding the molecular basis and pathogenesis of hereditary optic neuropathies: towards improved diagnosis and management

Hereditary optic neuropathies result from defects in the human genome, both nuclear and mitochondrial. The two main and most recognised phenotypes are dominant optic atrophy and Leber hereditary optic neuropathy. Advances in modern molecular diagnosis have expanded our knowledge of genotypes and phenotypes of inherited disorders that affect the optic nerve, either alone or in combination, with various forms of neurological and systemic degeneration. A unifying feature in the pathophysiology of these disorders appears to involve mitochondrial dysfunction, suggesting that the retinal ganglion cells and their axons are especially susceptible to perturbations in mitochondrial homoeostasis. As we better understand the pathogenesis behind these genetic diseases, aetiologically targeted therapies are emerging and entering into clinical trials, including treatments aimed at halting the cascade of neurodegeneration, replacing or editing the defective genes or their protein products, and potentially regenerating damaged optic nerves, as well as preventing generational disease transmission.

MCT1-dependent energetic failure and neuroinflammation underlie optic nerve degeneration in Wolfram syndrome mice

Wolfram syndrome 1 (WS1) is a rare genetic disorder caused by mutations in the WFS1 gene leading to a wide spectrum of clinical dysfunctions, among which blindness, diabetes, and neurological deficits are the most prominent. WFS1 encodes for the endoplasmic reticulum (ER) resident transmembrane protein wolframin with multiple functions in ER processes. However, the WFS1-dependent etiopathology in retinal cells is unknown. Herein, we showed that Wfs1 mutant mice developed early retinal electrophysiological impairments followed by marked visual loss. Interestingly, axons and myelin disruption in the optic nerve preceded the degeneration of the retinal ganglion cell bodies in the retina. Transcriptomics at pre-degenerative stage revealed the STAT3-dependent activation of proinflammatory glial markers with reduction of the homeostatic and pro-survival factors glutamine synthetase and BDNF. Furthermore, label-free comparative proteomics identified a significant reduction of the monocarboxylate transport isoform 1 (MCT1) and its partner basigin that are highly enriched on retinal glia and myelin-forming oligodendrocytes in optic nerve together with wolframin. Loss of MCT1 caused a failure in lactate transfer from glial to neuronal cell bodies and axons leading to a chronic hypometabolic state. Thus, this bioenergetic impairment is occurring concurrently both within the axonal regions and cell bodies of the retinal ganglion cells, selectively endangering their survival while impacting less on other retinal cells. This metabolic dysfunction occurs months before the frank RGC degeneration suggesting an extended time-window for intervening with new therapeutic strategies focused on boosting retinal and optic nerve bioenergetics in WS1.

Mitochondrial optic neuropathies

Mitochondrial optic neuropathies have a leading role in the field of mitochondrial medicine ever since 1988, when the first mutation in mitochondrial DNA was associated with Leber's hereditary optic neuropathy (LHON). Autosomal dominant optic atrophy (DOA) was subsequently associated in 2000 with mutations in the nuclear DNA affecting the OPA1 gene. LHON and DOA are both characterized by selective neurodegeneration of retinal ganglion cells (RGCs) triggered by mitochondrial dysfunction. This is centered on respiratory complex I impairment in LHON and defective mitochondrial dynamics in OPA1-related DOA, leading to distinct clinical phenotypes. LHON is a subacute, rapid, severe loss of central vision involving both eyes within weeks or months, with age of onset between 15 and 35 years old. DOA is a more slowly progressive optic neuropathy, usually apparent in early childhood. LHON is characterized by marked incomplete penetrance and a clear male predilection. The introduction of next-generation sequencing has greatly expanded the genetic causes for other rare forms of mitochondrial optic neuropathies, including recessive and X-linked, further emphasizing the exquisite sensitivity of RGCs to compromised mitochondrial function. All forms of mitochondrial optic neuropathies, including LHON and DOA, can manifest either as pure optic atrophy or as a more severe multisystemic syndrome. Mitochondrial optic neuropathies are currently at the forefront of a number of therapeutic programs, including gene therapy, with idebenone being the only approved drug for a mitochondrial disorder.

Wolfram syndrome 1b mutation suppresses Mauthner-cell axon regeneration via ER stress signal pathway

Wolfram Syndrome (WS) is a fatal human inherited disease with symptoms of diabetes, vision decreasing, and neurodegeneration caused by mutations in the endoplasmic reticulum (ER)-resident protein WFS1. WFS1 has been reported to play an important role in glucose metabolism. However, the role of WFS1 in axonal regeneration in the central nervous system has so far remained elusive. Herein, we established a model of the wfs1b globally deficient zebrafish line. wfs1b deficiency severely impeded the Mauthner-cell (M-cell) axon regeneration, which was partly dependent on the ER stress response. The administration of ER stress inhibitor 4-Phenylbutyric acid (4-PBA) promoted M-cell axon regeneration in wfs1b^-/- zebrafish larvae, while the ER stress activator Tunicamycin (TM) inhibited M-cell axon regeneration in wfs1b^+/+ zebrafish larvae. Moreover, complementation of wfs1b at the single-cell level stimulated M-cell axon regeneration in the wfs1b^-/- zebrafish larvae. Altogether, our results revealed that wfs1b promotes M-cell axon regeneration through the ER stress signal pathway and provide new evidence for a therapeutic target for WS and axon degeneration.

Sidestream Smoke Extracts from Harm-Reduction and Conventional Camel Cigarettes Inhibit Osteogenic Differentiation via Oxidative Stress and Differential Activation of intrinsic Apoptotic Pathways

Epidemiological studies suggest cigarette smoking as a probable environmental factor for a variety of congenital anomalies, including low bone mass, increased fracture risk and poor skeletal health. Human and animal in vitro models have confirmed hypomineralization of differentiating cell lines with sidestream smoke being more harmful to developing cells than mainstream smoke. Furthermore, first reports are emerging to suggest a differential impact of conventional versus harm-reduction tobacco products on bone tissue as it develops in the embryo or in vitro. To gather first insight into the molecular mechanism of such differences, we assessed the effect of sidestream smoke solutions from Camel (conventional) and Camel Blue (harm-reduction) cigarettes using a human embryonic stem cell osteogenic differentiation model. Sidestream smoke from the conventional Camel cigarettes concentration-dependently inhibited in vitro calcification triggered by high levels of mitochondrially generated oxidative stress, loss of mitochondrial membrane potential, and reduced ATP production. Camel sidestream smoke also induced DNA damage and caspase 9-dependent apoptosis. Camel Blue-exposed cells, in contrast, invoked only intermediate levels of reactive oxygen species insufficient to activate caspase 3/7. Despite the absence of apoptotic gene activation, damage to the mitochondrial phenotype was still noted concomitant with activation of an anti-inflammatory gene signature and inhibited mineralization. Collectively, the presented findings in differentiating pluripotent stem cells imply that embryos may exhibit low bone mineral density if exposed to environmental smoke during development.

Inhibition of Pyruvate Dehydrogenase Kinase 4 in CD4+ T Cells Ameliorates Intestinal Inflammation

BACKGROUND & AIMS

Despite recent evidence supporting the metabolic plasticity of CD4⁺ T cells, it is uncertain whether the metabolic checkpoint pyruvate dehydrogenase kinase (PDK) in T cells plays a role in the pathogenesis of colitis.

METHODS

To investigate the role of PDK4 in colitis, we used dextran sulfate sodium (DSS)-induced colitis and T-cell transfer colitis models based on mice with constitutive knockout (KO) or CD4⁺ T-cell-specific KO of PDK4 (Pdk4^fl/flCD4^Cre). The effect of PDK4 deletion on T-cell activation was also studied in vitro. Furthermore, we examined the effects of a pharmacologic inhibitor of PDK4 on colitis.

RESULTS

Expression of PDK4 increased during colitis development in a DSS-induced colitis model. Phosphorylated PDHE1α, a substrate of PDK4, accumulated in CD4⁺ T cells in the lamina propria of patients with inflammatory bowel disease. Both constitutive KO and CD4⁺ T-cell-specific deletion of PDK4 delayed DSS-induced colitis. Adoptive transfer of PDK4-deficient CD4⁺ T cells attenuated murine colitis, and PDK4 deficiency resulted in decreased activation of CD4⁺ T cells and attenuated aerobic glycolysis. Mechanistically, there were fewer endoplasmic reticulum-mitochondria contact sites, which are responsible for interorganelle calcium transfer, in PDK4-deficient CD4⁺ T cells. Consistent with this, GM-10395, a novel inhibitor of PDK4, suppressed T-cell activation by reducing endoplasmic reticulum-mitochondria calcium transfer, thereby ameliorating murine colitis.

CONCLUSIONS

PDK4 deletion from CD4⁺ T cells mitigates colitis by metabolic and calcium signaling modulation, suggesting PDK4 as a potential therapeutic target for IBD.

A preliminary, prospective study of peripheral neuropathy and cognitive function in patients with breast cancer during taxane therapy

Dramatic improvements in cancer survival have occurred in the last decade, but the quality of life for many survivors is compromised due to severe, long-lasting, and often irreversible side effects of chemotherapy. The neurological side effects, chemotherapy induced peripheral neuropathy (CIPN) and cancer related/induced cognitive impairment (CRCI/CICI), are under-recognized and can occur after chemotherapy, immunotherapy, or radiation. The cellular mechanisms underlying these neurological side effects are poorly understood and there are no effective treatments or preventions, other than reduction or termination of cancer therapy. In our preliminary prospective, non-interventional study to examine the side effects of chemotherapy in patients with breast cancer (NCT03872141), patients with breast cancer who received standard of care single agent weekly taxane-based chemotherapy were assessed at baseline, midpoint, and end of treatment for neurological and cognitive changes and for blood levels of potential protein biomarkers (n = 13). CIPN and CRCI both showed an increase in severity with accumulating taxane and these changes were compared to protein alternations over the course of treatment. Using peripheral blood collected from patients (n = 10) during chemotherapy and tested with an antibody array curated by the MD Anderson RPPA Core), we found that 19 proteins were increased, and 12 proteins decreased over 12 weeks of treatment. Among those downregulate were proteins known to be critical for neuronal viability and function including GRB2 (growth factor receptor-bound protein 2) and NCS1 (neuronal calcium sensor 1). Concurrently, proteins associated with apoptosis, including BAK1 (Bcl-1 homologous antagonist/killer), were upregulated. These results support the proposal that CIPN and CRCI increase with increasing taxane exposure, and identified several proteins that are altered with taxane exposure that could be implicated in their pathogenesis. In conclusion, our study provides evidence for progressive neurological changes and the rationale to investigate the molecular basis for these changes with the goal of target identification for mitigation of these neurological side effects.

NCS1 overexpression restored mitochondrial activity and behavioral alterations in a zebrafish model of Wolfram syndrome

Wolfram syndrome (WS) is a rare neurodegenerative disease resulting in deafness, optic atrophy, diabetes, and neurological disorders. Currently, no treatment is available for patients. The mutated gene, WFS1, encodes an endoplasmic reticulum (ER) protein, Wolframin. We previously reported that Wolframin regulated the ER-mitochondria Ca²⁺ transfer and mitochondrial activity by protecting NCS1 from degradation in patients' fibroblasts. We relied on a zebrafish model of WS, the wfs1ab ^KO line, to analyze the functional and behavioral impact of NCS1 overexpression as a novel therapeutic strategy. The wfs1ab ^KO line showed an increased locomotion in the visual motor and touch-escape responses. The absence of wfs1 did not impair the cellular unfolded protein response, in basal or tunicamycin-induced ER stress conditions. In contrast, metabolic analysis showed an increase in mitochondrial respiration in wfs1ab ^KO larvae. Interestingly, overexpression of NCS1 using mRNA injection restored the alteration of mitochondrial respiration and hyperlocomotion. Taken together, these data validated the wfs1ab ^KO zebrafish line as a pertinent experimental model of WS and confirmed the therapeutic potential of NCS1. The wfs1ab ^KO line therefore appeared as an efficient model to identify novel therapeutic strategies, such as gene or pharmacological therapies targeting NCS1 that will correct or block WS symptoms.

Multidimensional analysis and therapeutic development using patient iPSC-derived disease models of Wolfram syndrome

Wolfram syndrome is a rare genetic disorder largely caused by pathogenic variants in the WFS1 gene and manifested by diabetes mellitus, optic nerve atrophy, and progressive neurodegeneration. Recent genetic and clinical findings have revealed Wolfram syndrome as a spectrum disorder. Therefore, a genotype-phenotype correlation analysis is needed for diagnosis and therapeutic development. Here, we focus on the WFS1 c.1672C>T, p.R558C variant, which is highly prevalent in the Ashkenazi Jewish population. Clinical investigation indicated that patients carrying the homozygous WFS1 c.1672C>T, p.R558C variant showed mild forms of Wolfram syndrome phenotypes. Expression of WFS1 p.R558C was more stable compared with the other known recessive pathogenic variants associated with Wolfram syndrome. Human induced pluripotent stem cell-derived (iPSC-derived) islets (SC-islets) homozygous for WFS1 c.1672C>T variant recapitulated genotype-related Wolfram syndrome phenotypes. Enhancing residual WFS1 function through a combination treatment of chemical chaperones mitigated detrimental effects caused by the WFS1 c.1672C>T, p.R558C variant and increased insulin secretion in SC-islets. Thus, the WFS1 c.1672C>T, p.R558C variant causes a mild form of Wolfram syndrome phenotypes, which can be remitted with a combination treatment of chemical chaperones. We demonstrate that our patient iPSC-derived disease model provides a valuable platform for further genotype-phenotype analysis and therapeutic development for Wolfram syndrome.

β-cyclodextrin based nano gene delivery using pharmaceutical applications to treat Wolfram syndrome

Wolfram syndrome is a rare multisystem autosomal recessive neurodegenerative disorder that affects the brain and central nervous system. Currently, there is no cure or treatment for Wolfram syndrome. Therefore, new techniques are needed to target the loss of the WFS1 gene. Gene therapy approach to introduce a functional gene using a viral or a non-viral vector could be a treatment strategy for Wolfram syndrome 1 (WS1). Viral vectors have therapeutic benefits and greater efficiency; however, they pose a high health risk. Recently pharmaceutical therapeutic research has developed cell-penetrating non-viral nano molecules that could be used as vectors for gene delivery. Among nonviral vectors, the unique properties of β-cyclodextrin suggest that it can be a promising safe vector for gene delivery.

Wolframin deficiency is accompanied with metabolic inflexibility in rat striated muscles

The protein wolframin is localized in the membrane of the endoplasmic reticulum (ER), influencing Ca2+ metabolism and ER interaction with mitochondria, but the exact role of the protein remains unclear. Mutations in Wfs1 gene cause autosomal recessive disorder Wolfram syndrome (WS). The first symptom of the WS is diabetes mellitus, so accurate diagnosis of the disease as WS is often delayed. In this study we aimed to characterize the role of the Wfs1 deficiency on bioenergetics of muscles. Alterations in the bioenergetic profiles of Wfs1-exon-5-knock-out (Wfs1KO) male rats in comparison with their wild-type male littermates were investigated using high-resolution respirometry, and enzyme activity measurements. The changes were followed in oxidative (cardiac and soleus) and glycolytic (rectus femoris and gastrocnemius) muscles. There were substrate-dependent alterations in the oxygen consumption rate in Wfs1KO rat muscles. In soleus muscle, decrease in respiration rate was significant in all the followed pathways. The relatively small alterations in muscle during development of WS, such as increased mitochondrial content and/or increase in the OxPhos-related enzymatic activity could be an adaptive response to changes in the metabolic environment. The significant decrease in the OxPhos capacity is substrate dependent indicating metabolic inflexibility when multiple substrates are available.

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Wolfram syndrome (WS) model rats have muscle type-dependent metabolic changes.

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Substrate-dependent modulation of OxPhos in WS model rat muscles.

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Metabolic inflexibility in early-stage WS rat muscle mitochondria.

Dysregulated Ca2+ Homeostasis as a Central Theme in Neurodegeneration: Lessons from Alzheimer's Disease and Wolfram Syndrome

Calcium ions (Ca²⁺) operate as important messengers in the cell, indispensable for signaling the underlying numerous cellular processes in all of the cell types in the human body. In neurons, Ca²⁺ signaling is crucial for regulating synaptic transmission and for the processes of learning and memory formation. Hence, the dysregulation of intracellular Ca²⁺ homeostasis results in a broad range of disorders, including cancer and neurodegeneration. A major source for intracellular Ca²⁺ is the endoplasmic reticulum (ER), which has close contacts with other organelles, including mitochondria. In this review, we focus on the emerging role of Ca²⁺ signaling at the ER–mitochondrial interface in two different neurodegenerative diseases, namely Alzheimer’s disease and Wolfram syndrome. Both of these diseases share some common hallmarks in the early stages, including alterations in the ER and mitochondrial Ca²⁺ handling, mitochondrial dysfunction and increased Reactive oxygen species (ROS) production. This indicates that similar mechanisms may underly these two disease pathologies and suggests that both research topics might benefit from complementary research.

The pattern of retinal ganglion cell loss in Wolfram syndrome is distinct from mitochondrial optic neuropathies

PURPOSE

To describe the clinical phenotype of a cohort of Wolfram syndrome (WS) patients, focusing on the pattern of optic atrophy correlated with brain MRI measurements, as compared to OPA1-associated mitochondrial optic neuropathy.

DESIGN

Retrospective, comparative cohort study METHODS: 25 WS patients and 33 age-matched patients affected by OPA1-related Dominant Optic Atrophy (DOA). Ophthalmological, neurological, endocrinological and MRI data from WS patients were retrospectively retrieved. Ophthalmological data were compared to OPA1-related DOA and further analyzed for age dependency dividing patients in age quartiles. In a subgroup of WS patients, we correlated the structural damage assessed by optical coherence tomography (OCT) with brain MRI morphological measurements. Visual acuity (VA), visual field mean defect (MD), retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness assessed by OCT, MRI morphological measurements of anterior and posterior visual pathways.

RESULTS

In our cohort optic atrophy was present in 100% of WS patients. VA, MD and RNFL thickness loss were worse in WS patients with a faster decline since early age as compared to DOA patients, who displayed a more stable visual function over the years. Conversely, GCL sectors were overall thinner in DOA patients since early age compared to WS, in which GCL thickness started to decline later in life. The neuroradiological sub-analysis on 11 WS patients exhibited bilateral thinning of the anterior optic pathway, especially prechiasmatic optic nerves and optic tracts. Optic tract thinning was significantly correlated with the GCL thickness but not with RNFL parameters.

CONCLUSIONS

Our results showed a generally more severe and diffuse degeneration of both anterior and posterior visual pathways in WS, with fast deterioration of visual function and structural OCT parameters since early age. The pattern observed at OCT suggests that retinal ganglion cells axonal degeneration (i.e. RNFL) precedes of about a decade the cellular body atrophy (i.e. GCL). This differs substantially from DOA, in which a more stable visual function is evident with predominant early loss of GCL, indirectly supporting the lack of a primary mitochondrial dysfunction in WS.

Wolfram Syndrome 1: From Genetics to Therapy

Wolfram syndrome 1 (WS1) is a rare neurodegenerative disease transmitted in an autosomal recessive mode. It is characterized by diabetes insipidus (DI), diabetes mellitus (DM), optic atrophy (OA), and sensorineural hearing loss (D) (DIDMOAD). The clinical picture may be complicated by other symptoms, such as urinary tract, endocrinological, psychiatric, and neurological abnormalities. WS1 is caused by mutations in the WFS1 gene located on chromosome 4p16 that encodes a transmembrane protein named wolframin. Many studies have shown that wolframin regulates some mechanisms of ER calcium homeostasis and therefore plays a role in cellular apoptosis. More than 200 mutations are responsible for WS1. However, abnormal phenotypes of WS with or without DM, inherited in an autosomal dominant mode and associated with one or more WFS1 mutations, have been found. Furthermore, recessive Wolfram-like disease without DM has been described. The prognosis of WS1 is poor, and the death occurs prematurely. Although there are no therapies that can slow or stop WS1, a careful clinical monitoring can help patients during the rapid progression of the disease, thus improving their quality of life. In this review, we describe natural history and etiology of WS1 and suggest criteria for a most pertinent approach to the diagnosis and clinical follow up. We also describe the hallmarks of new therapies for WS1.

Activation of the sigma-1 receptor chaperone alleviates symptoms of Wolfram syndrome in preclinical models

The Wolfram syndrome is a rare autosomal recessive disease affecting many organs with life-threatening consequences; currently, no treatment is available. The disease is caused by mutations in the WSF1 gene, coding for the protein wolframin, an endoplasmic reticulum (ER) transmembrane protein involved in contacts between ER and mitochondria termed as mitochondria-associated ER membranes (MAMs). Inherited mutations usually reduce the protein's stability, altering its homeostasis and ultimately reducing ER to mitochondria calcium ion transfer, leading to mitochondrial dysfunction and cell death. In this study, we found that activation of the sigma-1 receptor (S1R), an ER-resident protein involved in calcium ion transfer, could counteract the functional alterations of MAMs due to wolframin deficiency. The S1R agonist PRE-084 restored calcium ion transfer and mitochondrial respiration in vitro, corrected the associated increased autophagy and mitophagy, and was able to alleviate the behavioral symptoms observed in zebrafish and mouse models of the disease. Our findings provide a potential therapeutic strategy for treating Wolfram syndrome by efficiently boosting MAM function using the ligand-operated S1R chaperone. Moreover, such strategy might also be relevant for other degenerative and mitochondrial diseases involving MAM dysfunction.

Retinal vascular impairment in Wolfram syndrome: an optical coherence tomography angiography study

To evaluate differences in macular and optic disc circulation in patients affected by Wolfram Syndrome (WS) employing optical coherence tomography-angiography (OCTA) imaging. In this retrospective study, 18 eyes from 10 WS patients, 16 eyes of 8 patients affected by type I diabetes and 17 eyes from 17 healthy controls were enrolled. All patients were imaged through OCT and OCTA and vascular parameters, as perfusion density (PD) and vessel length density (VLD) were measured. OCTA showed reduced PD in WS patients at the macular superficial capillary plexus (SCP, 27.8 ± 5.3%), deep vascular complex (DVC, 33.2 ± 1.9%) and optic nerve head (ONH, 21.2 ± 9.1%) compared to both diabetic patients (SCP 33.9 ± 1.9%, P < 0.0001; DVC 33.2 ± 0.7%, P = 1.0; ONH 33.9 ± 1.3, P < 0.0001) and healthy controls (SCP 31.6 ± 2.5, P = 0.002; DVC 34.0 ± 0.7%, P = 0.089; ONH 34.6 ± 0.8%, P < 0.0001). Similarly, VLD was lower in WS patients at the SCP (10.9 ± 2.7%) and ONH levels (7.5 ± 4.1%) compared to diabetic patients (SCP 13.8 ± 1.2%, P = 0.001; DVC 13.8 ± 0.2%, P < 0.0001; ONH 13.0 ± 0.7%, P =  < 0.0001), but higher in DVC (15.7 ± 1.2%, P < 0.0001). Furthermore, VLD was lower in WS patients in all the vascular parameters compared to controls (SCP 13.8 ± 1.5%, P < 0.0001; DVC 17.3 ± 0.6%, P < 0.0001; ONH 15.7 ± 0.5%, P < 0.0001). A significant microvasculature impairment in the macular SCP and ONH microvasculature was demonstrated in eyes affected by WS. Microvascular impairment may be considered a fundamental component of the neurodegenerative changes in WS.

OUP accepted manuscript

Wolfram syndrome (WS) is a rare genetic disease characterized by diabetes, optic atrophy and deafness. Patients die at 35 years of age, mainly from respiratory failure or dysphagia. Unfortunately, there is no treatment to block the progression of symptoms and there is an urgent need for adequate research models. Here, we report on the phenotypical characterization of two loss-of-function zebrafish mutant lines: wfs1a^C825X and wfs1b^W493X. We observed that wfs1a deficiency altered the size of the ear and the retina of the fish. We also documented a decrease in the expression level of unfolded protein response (UPR) genes in basal condition and in stress condition, i.e. after tunicamycin treatment. Interestingly, both mutants lead to a decrease in their visual function measured behaviorally. These deficits were associated with a decrease in the expression level of UPR genes in basal and stress conditions. Interestingly, basal, ATP-linked and maximal mitochondrial respirations were transiently decreased in the wfs1b mutant. Taken together, these zebrafish lines highlight the critical role of wfs1a and wfs1b in UPR, mitochondrial function and visual physiology. These models will be useful tools to better understand the cellular function of Wfs1 and to develop novel therapeutic approaches for WS.

WFS1 protein expression correlates with clinical progression of optic atrophy in patients with Wolfram syndrome

BACKGROUND

Wolfram syndrome (WFS) is a rare disorder characterised by childhood-onset diabetes mellitus and progressive optic atrophy. Most patients have variants in the WFS1 gene. We undertook functional studies of WFS1 variants and correlated these with WFS1 protein expression and phenotype.

METHODS

9 patients with a clinical diagnosis of WFS were studied with quantitative PCR for markers of endoplasmic reticulum (ER) stress and immunoblotting of fibroblast protein extracts for WFS1 protein expression. Luciferase reporter assay was used to assess ATF-6 dependent unfolded protein response (UPR) activation.

RESULTS

6 patients with compound heterozygous nonsense mutations in WFS1 had no detectable WFS1 protein expression; 3 patients with missense variants had 4%, 45% and 48% WFS1 protein expression. One of these also had an OPA1 mutation and was reclassified as autosomal dominant optic atrophy-plus syndrome. There were no correlations between ER stress marker mRNA and WFS1 protein expression. ERSE-luciferase reporter indicated activation of the ATF6 branch of UPR in two patients tested. Patients with partial WFS1 expression showed milder visual acuity impairment (asymptomatic or colour blind only), compared with those with absent expression (registered severe vision impaired) (p=0.04). These differences remained after adjusting for duration of optic atrophy.

CONCLUSIONS

Patients with WFS who have partial WFS1 protein expression present with milder visual impairment. This suggests a protective effect of partial WFS1 protein expression on the severity and perhaps progression of vision impairment and that therapies to increase residual WFS1 protein expression may be beneficial.

Use of Zebrafish Models to Boost Research in Rare Genetic Diseases

Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throughput phenotypic capacity for therapeutic screening. We briefly introduce how the generation of zebrafish transgenic lines by gene-modulating technologies can be used to model rare genetic diseases. Then, we describe how zebrafish could be phenotyped using state-of-the-art technologies. Two prototypic examples of rare diseases illustrate how zebrafish models could play a critical role in deciphering the underlying mechanisms of rare genetic diseases and their use to identify innovative therapeutic solutions.

The Role of Mitochondria in Optic Atrophy With Autosomal Inheritance

Optic atrophy (OA) with autosomal inheritance is a form of optic neuropathy characterized by the progressive and irreversible loss of vision. In some cases, this is accompanied by additional, typically neurological, extra-ocular symptoms. Underlying the loss of vision is the specific degeneration of the retinal ganglion cells (RGCs) which form the optic nerve. Whilst autosomal OA is genetically heterogenous, all currently identified causative genes appear to be associated with mitochondrial organization and function. However, it is unclear why RGCs are particularly vulnerable to mitochondrial aberration. Despite the relatively high prevalence of this disorder, there are currently no approved treatments. Combined with the lack of knowledge concerning the mechanisms through which aberrant mitochondrial function leads to RGC death, there remains a clear need for further research to identify the underlying mechanisms and develop treatments for this condition. This review summarizes the genes known to be causative of autosomal OA and the mitochondrial dysfunction caused by pathogenic mutations. Furthermore, we discuss the suitability of available in vivo models for autosomal OA with regards to both treatment development and furthering the understanding of autosomal OA pathology.

Mitochondrial Phenotypes in Parkinson's Diseases-A Focus on Human iPSC-Derived Dopaminergic Neurons

Established disease models have helped unravel the mechanistic underpinnings of pathological phenotypes in Parkinson’s disease (PD), the second most common neurodegenerative disorder. However, these discoveries have been limited to relatively simple cellular systems and animal models, which typically manifest with incomplete or imperfect recapitulation of disease phenotypes. The advent of induced pluripotent stem cells (iPSCs) has provided a powerful scientific tool for investigating the underlying molecular mechanisms of both familial and sporadic PD within disease-relevant cell types and patient-specific genetic backgrounds. Overwhelming evidence supports mitochondrial dysfunction as a central feature in PD pathophysiology, and iPSC-based neuronal models have expanded our understanding of mitochondrial dynamics in the development and progression of this devastating disorder. The present review provides a comprehensive assessment of mitochondrial phenotypes reported in iPSC-derived neurons generated from PD patients’ somatic cells, with an emphasis on the role of mitochondrial respiration, morphology, and trafficking, as well as mitophagy and calcium handling in health and disease. Furthermore, we summarize the distinguishing characteristics of vulnerable midbrain dopaminergic neurons in PD and report the unique advantages and challenges of iPSC disease modeling at present, and for future mechanistic and therapeutic applications.

Quantifying inter-organelle membrane contact sites using proximity ligation assay in fixed optic nerve sections

Membrane contact sites (MCS) play crucial roles in cell physiology with dysfunction in several MCS proteins being linked with neurological and optic nerve diseases. Although there have been significant advances in imaging these interactions over the past two decades with advanced electron microscopy techniques, super-resolution imaging and proximity-dependent fluorescent reporters, a technique to observe and quantify MCS in mammalian optic nerve tissues has not yet been reported. We demonstrate for the first time that proximity ligation assay (PLA), a technique already used in mammalian cell lines, can be used as an efficient method of quantifying inter-organelle contact sites, namely mitochondria-endoplasmic reticulum (ER) and mitochondria-late-endosomes, in mammalian optic nerve tissues treated with adeno-associated virus (AAV) gene therapy with wild-type or phosphomimetic (active) protrudin. PLA utilises complementary single-stranded DNA oligomers bound to secondary antibodies that hybridise and complete a circular piece of DNA when the primary antibodies of interest interact. These interactions can be detected by amplifying the circular DNA and adding fluorescent probes. We show that PLA is a useful method that can be used to quantify MCS in optic nerve tissues. We have found that upregulation of protrudin with gene therapy significantly increases the number of mitochondria-ER and mitochondria-Rab7-late endosomes contact sites in optic nerves.