ISR inhibition reverses pancreatic ß-cell failure in Wolfram syndrome models.

Pancreatic ß-cell failure by WFS1 deficiency is manifested in individuals with wolfram syndrome (WS). The lack of a suitable human model in WS has impeded progress in the development of new treatments. Here, human pluripotent stem cell derived pancreatic islets (SC-islets) harboring WFS1 deficiency and mouse model of ß cell specific Wfs1 knockout were applied to model ß-cell failure in WS. We charted a high-resolution roadmap with single-cell RNA-seq (scRNA-seq) to investigate pathogenesis for WS ß-cell failure, revealing two distinct cellular fates along pseudotime trajectory: maturation and stress branches. WFS1 deficiency disrupted ß-cell fate trajectory toward maturation and directed it towards stress trajectory, ultimately leading to ß-cell failure. Notably, further investigation of the stress trajectory identified activated integrated stress response (ISR) as a crucial mechanism underlying WS ß-cell failure, characterized by aberrant eIF2 signaling in WFS1-deficient SC-islets, along with elevated expression of genes in regulating stress granule formation. Significantly, we demonstrated that ISRIB, an ISR inhibitor, efficiently reversed ß-cell failure in WFS1-deficient SC-islets. We further validated therapeutic efficacy in vivo with ß-cell specific Wfs1 knockout mice. Altogether, our study provides novel insights into WS pathogenesis and offers a strategy targeting ISR to treat WS diabetes.

The genetic and clinical characteristics of WFS1 related diabetes in Chinese early onset type 2 diabetes.

Diabetes is one of the most common phenotypes of Wolfram syndrome owing to the presence of the variants of the WFS1 gene and is often misdiagnosed as other types of diabetes. We aimed to explore the prevalence of WFS1-related diabetes (WFS1-DM) and its clinical characteristics in a Chinese population with early-onset type 2 diabetes (EOD). We sequenced all exons of the WFS1 gene in 690 patients with EOD (age at diagnosis ≤ 40 years) for rare variants. Pathogenicity was defined according to the standards and guidelines of the American College of Medical Genetics and Genomics. We identified 33 rare variants predicted to be deleterious in 39 patients. The fasting [1.57(1.06-2.22) ng/ml] and postprandial C-peptide levels [2.8(1.75-4.46) ng/ml] of the patients with such WFS1 variations were lower than those of the patients without WFS1 variation [2.09(1.43-3.05) and 4.29(2.76-6.07) respectively, ng/ml]. Six (0.9%) patients carried pathogenic or likely pathogenic variants; they met the diagnostic criteria for WFS1-DM according to the latest guidelines, but typical phenotypes of Wolfram syndrome were seldom observed. They were diagnosed at an earlier age and usually presented with an absence of obesity, impaired beta cell function, and the need for insulin treatment. WFS1-DM is usually mistakenly diagnosed as type 2 diabetes, and genetic testing is helpful for individualized treatment.

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.

Generation of induced pluripotent stem cells (IBMSi027-A) from a patient with hearing loss carrying WFS1 c.2051C > T (p.Ala684Val) variant.

Pathogenic variants of the WFS1 gene can cause recessive-inherited Wolfram syndrome or dominant-inherited Wolfram-like syndrome with optic atrophy and hearing impairment. Using the Sendai virus delivery system, we generated induced pluripotent stem cells from the peripheral blood mononuclear cells of a female patient with the WFS1 pathogenic variant c.2051C > T (p.Ala684Val). The resulting induced pluripotent stem cells exhibited a normal karyotype and pluripotency, as confirmed using immunofluorescence staining, and differentiated into three germ layers in vivo. This cellular model provides a useful platform for investigating the pathogenic mechanisms of both blindness and deafness related to WFS1 variants.

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.

Comprehensive Genetic Analysis Unraveled the Missing Heritability in a Chinese Cohort With Wolfram Syndrome 1: Clinical and Genetic Findings.

Purpose: To identify the missing heritability of patients with Wolfram syndrome 1 (WFS1) in a Chinese cohort and to report their clinical and genetic features. Methods: We recruited 24 unrelated patients with suspected WFS1 who carried at least one variant in WFS1. All patients underwent ophthalmic examinations and comprehensive molecular genetic analyses, including Sanger-DNA sequencing of WFS1 and next-generation sequencing of the whole WFS1 sequence. Results: We identified 38 distinct pathogenic variants of WFS1 in the 24 probands, comprising 23 patients with biallelic variants and one patient with a monoallelic variant. Sanger-DNA sequencing of WFS1 initially detected 35 variants, and subsequent whole genome sequencing revealed three missing variants: one novel deep intronic variant (DIV), one copy number variant (CNV), and one variant in the promoter region. Minigene assays showed that the DIV activated cryptic splice sites, leading to the insertion of pseudoexons. Optic atrophy was observed in all patients, and diabetes mellitus (DM) was revealed in 21 patients (91.3%), hearing loss in nine patients (39.1%), renal tract abnormalities in nine patients (39.1%), and diabetes insipidus in five patients (21.7%). The mean onset age for DM was significantly younger in the patients with biallelic null variants than in the patients with biallelic missense variants. Conclusions: Our results extend the pathogenic variant spectrum of WFS1. DIVs and CNVs explained rare unresolved Chinese cases with WFS1. The patients showed a wide and variable clinical spectrum, supporting the importance of genetic analysis for patients with atypical WFS1.

Loss of Function of WFS1 Causes ER Stress-Mediated Inflammation in Pancreatic Beta-Cells.

Wolfram syndrome is a rare genetic disorder characterized by juvenile-onset diabetes mellitus, optic nerve atrophy, hearing loss, diabetes insipidus, and progressive neurodegeneration. Pathogenic variants in the WFS1 gene are the main causes of Wolfram syndrome. WFS1 encodes a transmembrane protein localized to the endoplasmic reticulum (ER) and regulates the unfolded protein response (UPR). Loss of function of WFS1 leads to dysregulation of insulin production and secretion, ER calcium depletion, and cytosolic calpains activation, resulting in activation of apoptotic cascades. Although the terminal UPR has been shown to induce inflammation that accelerates pancreatic ß-cell dysfunction and death in diabetes, the contribution of pancreatic ß-cell inflammation to the development of diabetes in Wolfram syndrome has not been fully understood. Here we show that WFS1-deficiency enhances the gene expression of pro-inflammatory cytokines and chemokines, leading to cytokine-induced ER-stress and cell death in pancreatic ß-cells. PERK and IRE1α pathways mediate high glucose-induced inflammation in a ß-cell model of Wolfram syndrome. M1-macrophage infiltration and hypervascularization are seen in the pancreatic islets of Wfs1 whole-body knockout mice, demonstrating that WFS1 regulates anti-inflammatory responses in pancreatic ß-cells. Our results indicate that inflammation plays an essential role in the progression of ß-cell death and diabetes in Wolfram syndrome. The pathways involved in ER stress-mediated inflammation provide potential therapeutic targets for the treatment of Wolfram syndrome.

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.

WFS1 Gene-associated Diabetes Phenotypes and Identification of a Founder Mutation in Southern India.

CONTEXT: Wolfram syndrome (WFS) is a rare autosomal recessive disorder characterized by juvenile-onset diabetes, diabetes insipidus, optic atrophy, deafness, and progressive neurodegeneration. However, due to the progressive nature of the disease and a lack of complete clinical manifestations, a confirmed diagnosis of WFS at the time of onset of diabetes is a challenge. OBJECTIVE: With WFS1 rare heterozygous variants reported in diabetes, there is a need for comprehensive genetic screening strategies for the early diagnosis of WFS and delineating the phenotypic spectrum associated with the WFS1 gene variants in young-onset diabetes. METHODS: This case series of 11 patients who were positive for WFS1 variants were identified with next-generation sequencing (NGS)-based screening of 17 genemonogenic diabetes panel. These results were further confirmed with Sanger sequencing. RESULTS: 9 out of 11 patients were homozygous for pathogenic/likely pathogenic variants in the WFS1 gene. Interestingly, 3 of these probands were positive for the novel WFS1 (NM_006005.3): c.1107_1108insA (p.Ala370Serfs*173) variant, and haplotype analysis suggested a founder effect in 3 families from Southern India. Additionally, we identified 2 patients with young-onset diabetes who were heterozygous for a likely pathogenic variant or a variant of uncertain significance in the WFS1 gene. CONCLUSION: These results project the need for NGS-based parallel multigene testing as a tool for early diagnosis of WFS and identify heterozygous WFS1 variants implicated in young-onset diabetes.

Human iPSC-derived neurons reveal early developmental alteration of neurite outgrowth in the late-occurring neurodegenerative Wolfram syndrome.

Recent studies indicate that neurodegenerative processes that appear during childhood and adolescence in individuals with Wolfram syndrome (WS) occur in addition to early brain development alteration, which is clinically silent. Underlying pathological mechanisms are still unknown. We have used induced pluripotent stem cell-derived neural cells from individuals affected by WS in order to reveal their phenotypic and molecular correlates. We have observed that a subpopulation of Wolfram neurons displayed aberrant neurite outgrowth associated with altered expression of axon guidance genes. Selective inhibition of the ATF6α arm of the unfolded protein response prevented the altered phenotype, although acute endoplasmic reticulum stress response-which is activated in late Wolfram degenerative processes-was not detected. Among the drugs currently tried in individuals with WS, valproic acid was the one that prevented the pathological phenotypes. These results suggest that early defects in axon guidance may contribute to the loss of neurons in individuals with WS.

Unique three-site compound heterozygous mutation in the WFS1 gene in Wolfram syndrome.

BACKGROUND: Wolfram syndrome (WFS) is a rare autosomal recessive genetic disease whose main cause is mutations in the WFS1 and CISD2 genes. Its characteristic clinical manifestations are diabetes insipidus, diabetes mellitus, optic atrophy and deafness. METHODS: In this study, two patients from this particular family underwent complete routine biochemical and ophthalmic tests. Blood, urine, routine stool test, visual acuity (VA) examination, visual field assessment, funduscope, optical coherence tomography and periorbital magnetic resonance imaging (MRI) scans were performed for each patient to evaluate whether the nerve fiber layer around the optic nerve head was atrophied and next-generation sequencing of target genes was performed in two patients. RESULTS: When the patients were diagnosed with Wolfram syndrome, their genetic analyses suggested unique three-site compound heterozygous mutations (c.2314C > T + c.2194C > T + c.2171C > T) in exon 8 of both patients' chromosome 4. One mutation (c.2314C > T) was a novel mutation in the known reports of Wolfram syndrome. As a degenerative genetic disease, the types of gene mutations in the Chinese population are generally homozygous mutations at the unit point or compound heterozygous mutations at two nucleotide change sites. However, the two patients reported in this study are the first known cases of compound heterozygous mutations with three mutation sites coexisting on the WFS1 gene in China or even globally. CONCLUSIONS: This study expands the phenotypic spectrum of Wolfram syndrome and may reveal a novel mutation pattern of pathogenesis of Wolfram syndrome. The implications of this discovery are valuable in the clinical diagnosis, prognosis, and treatment of patients with WFS1.

Different clinical entities of the same mutation: a case report of three sisters with Wolfram syndrome and efficacy of dipeptidyl peptidase-4 inhibitor therapy.

OBJECTIVES: Wolfram syndrome (WS) is a rarely seen autosomal recessive multisystem neurodegenerative disorder caused by mutations in the WFS1 gene. CASE PRESENTATION: Three sisters with WS had diabetes mellitus (DM) at 4 years of age and optic atrophy. In addition, the first case had hearing impairment, and the second case had diabetes insipidus and urinary incontinence. Linagliptin was administered to the first case as add-on therapy to intensive insulin treatment 15 years after the onset of DM, and her insulin need showed a dramatic decrease. The third case had a remission phase one month after the onset of DM. CONCLUSIONS: Even in cases with the same mutation, symptoms and findings may widely vary in WS. Remission of diabetes has rarely been reported in WS. Also, this report describes the first trial of a dipeptidyl peptidase-4 inhibitor in a patient with WS which provided a decrease in exogenous insulin need.

Wolfram-like syndrome with bicuspid aortic valve due to a homozygous missense variant in CDK13.

BACKGROUND: Wolfram syndrome (WFS) is characterized by deafness, diabetes mellitus, and diabetes insipidus along with optic atrophy. WFS has an autosomal recessive mode of inheritance and is due to variants in WFS1 and CISD2. METHODS: We evaluated the underlying molecular etiology of three affected members of a consanguineous family with hearing impairment, bicuspid aortic valve, diabetes mellitus and insipidus, clinodactyly, and gastrointestinal tract abnormalities via exome sequencing approach. We correlated clinical and imaging data with the genetic findings and their associated phenotypes. RESULTS: We identified a homozygous missense variant p.(Asn1097Lys) in CDK13, a gene previously associated with autosomal dominant congenital heart defects, dysmorphic facial features, clinodactyly, gastrointestinal tract abnormalities, intellectual developmental disorder, and seizures with variable phenotypic features. CONCLUSION: We report a homozygous variant in CDK13 and suggest that this gene causes an autosomal recessive disorder with hearing impairment, bicuspid aortic valve, diabetes mellitus and insipidus, clinodactyly, and gastrointestinal tract abnormalities.

A novel mutation of WFS1 gene leading to increase ER stress and cell apoptosis is associated an autosomal dominant form of Wolfram syndrome type 1.

BACKGROUND: Wolfram syndrome (WS) is a rare autosomal recessive disorder characterized by diabetes insipidus, diabetes mellitus, optic atrophy and deafness. Mutations in Wolfram syndrome 1 (WFS1) gene may cause dysregulated endoplasmic reticulum (ER)-stress and cell apoptosis, contributing to WS symptoms. The aim of this study was to identify the molecular etiology of a case of WS and to explore the functional consequence of the mutant WFS1 gene in vitro. METHODS: A 27 years-old Chinese man was diagnosed as wolfram syndrome type 1 based on clinical data and laboratory data. DNA sequencing of WFS1 gene and mitochondrial m.3337G > A, m.3243A > G mutations were performed in the patient and his 4 family members. Functional analysis was performed to assessed the in vitro effect of the newly identified mutant. ER stress were evaluated by ER stress response element (ERSE)-luciferase assay. Cell apoptosis were performed by CCK-8, TUNEL staining and flow cytometric analysis. RESULTS: A novel heterozygous 10-base deletion (c. 2067_2076 del10, p.W690fsX706) was identified in the patient. In vitro studies showed that mutant p.W690fsX706 increased ERSE reporter activity in the presence or absence of thapsigargin instead of wild type WFS1. Knockdown of WFS1 activated the unfolded protein response (UPR) pathway and increased the cell apoptosis, which could not be restored by transfection with WFS1 mutant (p.W690fsX706) comparable to the wild type WFS1. CONCLUSIONS: A novel heterozygous mutation of WFS1 detected in the patient resulted in loss-of-function of wolframin, thereby inducing dysregulated ER stress signaling and cell apoptosis. These findings increase the spectrum of WFS1 gene mutations and broaden our insights into the roles of mutant WFS1 in the pathogenesis of WS.

Autosomal-dominant WFS1-related disorder-Report of a novel WFS1 variant and review of the phenotypic spectrum of autosomal recessive and dominant forms.

Wolfram syndrome was initially reported as an autosomal recessive (AR), progressive neurodegenerative disorder that leads to diabetes insipidus, childhood onset diabetes mellitus (DM), optic atrophy, and deafness (D) also known as DIDMOAD. However, heterozygous dominant pathogenic variants in Wolfram syndrome type 1 (WFS1) may lead to distinct, allelic conditions, described as isolated sensorineural hearing loss (SNHL), syndromic SNHL, congenital cataracts, or early onset DM. We report a family with a novel dominant, likely pathogenic variant in WFS1 (NM_006005.3) c.2605_2616del12 (p.Ser869_His872del), resulting in cataracts, SNHL, and DM in a female and her mother. A maternal aunt had cataracts, DM, and SNHL but was not tested for the familial WFS1 mutation. Both the mother and maternal aunt had early menopause by age 43 years and infertility which may be a coincidental finding that has not been associated with autosomal dominant AD WFS1-related disorder to the best of our knowledge. Screening at risk individuals in families with the AR Wolfram syndrome, for DM, SNHL, and for cataracts is indicated.

Longitudinal Assessment of Neuroradiologic Features in Wolfram Syndrome.

BACKGROUND AND PURPOSE: Wolfram syndrome is a rare genetic disease with characteristic brain involvement. We reviewed the brain MR images of patients with Wolfram syndrome to determine the frequency and characteristics of common neuroradiologic findings. MATERIALS AND METHODS: We retrospectively reviewed the imaging data of patients with genetically-confirmed Wolfram syndrome who had been recruited to the Washington University Wolfram Syndrome Research Clinic. These patients were evaluated between 2010 and 2019 with annual MRIs, along with other measures. MR images were assessed for clinical neuroradiologic signs at each individual's first and last follow-up visits to characterize the frequency, rate of progression, and clinical correlations of these signs. RESULTS: We included 30 patients (13 males/17 females; average age at first visit, 14 years; average age at last visit, 19 years). The median duration of follow-up was 5 years (range, 2-9 years). The most common findings were an absent or diminished posterior pituitary bright spot (first, 53%; last, 70%), T1/T2 pons signal abnormalities (first, 53%; last, 67%), optic nerve atrophy (first, 30%; last, 80%), white matter T2 hyperintensities (first, 27%; last, 35%), and cerebellar atrophy (first, 23%; last, 70%). CONCLUSIONS: Patients with Wolfram syndrome present characteristic neuroradiologic findings that involve the posterior pituitary gland, optic nerves, white matter, brain stem, and cerebellum. These abnormal findings appear at an early age and tend to increase in frequency with time. However, the neurologic significance and neuropathologic mechanisms of each sign require more investigation. Neuroradiologists should be aware of the pattern of these features in Wolfram syndrome.

Clinical and genetic analysis of two wolfram syndrome families with high occurrence of wolfram syndrome and diabetes type II: a case report.

BACKGROUND: Mutations of the WFS1 gene are responsible for most cases of Wolfram syndrome (WS), a rare, recessively inherited neurodegenerative disorder characterized by juvenile-onset non-autoimmune diabetes mellitus and optic atrophy. Variants of WFS1 are also associated with non-syndromic hearing loss and type-2 diabetes mellitus (T2DM). Our study adds to literature significant associations between WS and T2DM. CASE PRESENTATION: In this study, we analyzed the clinical and genetic data of two families with high prevalence of WS and T2DM. Genetic linkage analysis and DNA sequencing were exploited to identify pathogenic variants. One novel pathogenic variant (c.2243-2244insC) and one known pathogenic (c.1232_1233delCT) (frameshift) variant were identified in exon eight of WFS1 gene. CONCLUSIONS: The mutational and phenotypic spectrum of WS is broadened by our report of novel WFS1 mutation. Our results reveal the value of molecular analysis of WFS1 in the improvement of clinical diagnostics for WS. This study also confirms the role of WFS1 in T2DM.

Adaptation of striated muscles to Wolframin deficiency in mice: Alterations in cellular bioenergetics.

BACKGROUND: Wolfram syndrome (WS), caused by mutations in WFS1 gene, is a multi-targeting disease affecting multiple organ systems. 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. In this study we aimed to characterize alterations in energy metabolism in the cardiac and in the oxidative and glycolytic skeletal muscles in Wfs1-deficiency. METHODS: Alterations in the bioenergetic profiles in the cardiac and skeletal muscles of Wfs1-knock-out (KO) male mice and their wild type male littermates were determined using high resolution respirometry, quantitative RT-PCR, NMR spectroscopy, and immunofluorescence confocal microscopy. RESULTS: Oxygen consumption without ATP synthase activation (leak) was significantly higher in the glycolytic muscles of Wfs1 KO mice compared to wild types. ADP-stimulated respiration with glutamate and malate was reduced in the Wfs1-deficient cardiac as well as oxidative and glycolytic skeletal muscles. CONCLUSIONS: Wfs1-deficiency in both cardiac and skeletal muscles results in functional alterations of energy transport from mitochondria to ATP-ases. There was a substrate-dependent decrease in the maximal Complex I -linked respiratory capacity of the electron transport system in muscles of Wfs1 KO mice. Moreover, in cardiac and gastrocnemius white muscles a decrease in the function of one pathway were balanced by the increase in the activity of the parallel pathway. GENERAL SIGNIFICANCE: This work provides new insights to the muscle involvement at early stages of metabolic syndrome like WS as well as developing glucose intolerance.

Segregation of two variants suggests the presence of autosomal dominant and recessive forms of WFS1-related disease within the same family: expanding the phenotypic spectrum of Wolfram Syndrome.

BACKGROUND: WFS1 was initially described as causative agent of autosomal recessive (AR) Wolfram syndrome, a childhood-onset disorder involving diabetes, optic atrophy, hearing loss and neurodegenerative features. However, the discovery of autosomal dominant (AD) disorders caused by this gene has resulted in clinical counselling and result interpretation challenges. OBJECTIVE: We seek to report a family that appears to segregate dominant and recessive forms of WFS1-related disease. METHODS/RESULTS: A 19-year-old woman presented with progressive childhood sensorineural hearing loss and recent optic atrophy, with biallelic mutations in WFS1: c.2486T>C (likely pathogenic) and c.2470G>A (uncertain significance). Her A1C was normal. Her sister carried the same variants and had a similar phenotype. Their father carried c.2486T>C and was found to have mild-moderate hearing loss but no optic atrophy or neurological symptoms. The mother carried c.2470G>A and had a normal audiogram and ophthalmological exam. Providing anticipatory guidance for this family was difficult given the phenotypic variability of WFS1-related disorders and the uncertainty surrounding whether the inheritance pattern was AR or AD. CONCLUSION: The clinical correlation of the variants identified in this family suggests an AR Wolfram-like syndrome, without the typical diabetes mellitus or diabetes insipidus nor neurological decline. To our knowledge, this is a novel WFS1-related phenotype.