Wolfram syndrome, a rare neurodegenerative disease: from pathogenesis to future treatment perspectives

Variable Expressivity of Wolfram Syndrome in a Family with Multiple Affected Subjects

Purpose

To study the genetic basis and clinical manifestations of Wolfram syndrome in a multi-affected family.

Methods

Complete clinical examinations including urological, ophthalmic, neurological, and endocrinologic assessment were performed for three affected family members. Genomic DNA was extracted from peripheral blood leukocytes with salting out method and all WFS1 exons and their flanking regions were sequenced. Candidate variation was screened for segregation in the pedigree by Sanger sequencing.

Results

A known pathogenic missense mutation in WFS1 gene (c.1885C>T which leads to p.Arg629Trp in the encoded protein) was identified in all affected individuals. Both clinical and genetic investigations confirmed Wolfram syndrome diagnosis with variable phenotypic features

Conclusion

Identical mutations in the Wolfram syndrome causative gene can lead to variable manifestations of the syndrome even in the same family. Although the medical findings and clinical examination are imperative for the diagnosis of Wolfram syndrome, genetic testing is useful to confirm the diagnosis, especially in cases with possible reduced penetrance of the characteristic signs.

Multiomic analysis on human cell model of wolfram syndrome reveals changes in mitochondrial morphology and function

BACKGROUND

Wolfram syndrome (WFS) is a rare autosomal recessive syndrome in which diabetes mellitus and neurodegenerative disorders occur as a result of Wolframin deficiency and increased ER stress. In addition, WFS1 deficiency leads to calcium homeostasis disturbances and can change mitochondrial dynamics. The aim of this study was to evaluate protein levels and changes in gene transcription on human WFS cell model under experimental ER stress.

METHODS

We performed transcriptomic and proteomic analysis on WFS human cell model-skin fibroblasts reprogrammed into induced pluripotent stem (iPS) cells and then into neural stem cells (NSC) with subsequent ER stress induction using tunicamycin (TM). Results were cross-referenced with publicly available RNA sequencing data in hippocampi and hypothalami of mice with WFS1 deficiency.

RESULTS

Proteomic analysis identified specific signal pathways that differ in NSC WFS cells from healthy ones. Next, detailed analysis of the proteins involved in the mitochondrial function showed the down-regulation of subunits of the respiratory chain complexes in NSC WFS cells, as well as the up-regulation of proteins involved in Krebs cycle and glycolysis when compared to the control cells. Based on pathway enrichment analysis we concluded that in samples from mice hippocampi the mitochondrial protein import machinery and OXPHOS were significantly down-regulated.

CONCLUSIONS

Our results show the functional and morphological secondary mitochondrial damage in patients with WFS. Video Abstract.

Urinary Tract Involvement in Wolfram Syndrome: A Narrative Review

Wolfram Syndrome (WS) is a rare neurodegenerative disease with autosomal recessive inheritance and characterized by juvenile onset, non-autoimmune diabetes mellitus and later followed by optic atrophy leading to blindness, diabetes insipidus, hearing loss, and other neurological and endocrine dysfunctions. A wide spectrum of neurodegenerative abnormalities affecting the central nervous system has been described. Among these complications, neurogenic bladder and urodynamic abnormalities also deserve attention. Urinary tract dysfunctions (UTD) up to end stage renal disease are a life-threatening complication of WS patients. Notably, end stage renal disease is reported as one of the most common causes of death among WS patients. UTD have been also reported in affected adolescents. Involvement of the urinary tract occurs in about 90% of affected patients, at a median age of 20 years and with peaks at 13, 21 and 33 years. The aim of our narrative review was to provide an overview of the most important papers regarding urological impairment in Wolfram Syndrome. A comprehensive search on PubMed including Wolfram Syndrome and one or more of the following terms: chronic renal failure, bladder dysfunction, urological aspects, and urinary tract dysfunction, was done. The exclusion criteria were studies not written in English and not including urinary tract dysfunction deep evaluation and description. Studies mentioning general urologic abnormalities without deep description and/or follow-up were not considered. Due to the rarity of the condition, we considered not only papers including pediatric patients, but also papers with pediatric and adult case reports

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.

Efficacy of GLP-1 Agonist Therapy in Autosomal Dominant WFS1-Related Disorder: A Case Report

BACKGROUND

Wolfram syndrome is a rare neurodegenerative disorder, characterized by the presence of diabetes insipidus, diabetes mellitus, optic atrophy, and sensorineural deafness. The majority of cases are due to autosomal recessive biallelic variants in the WFS1 gene; however, pathogenic autosomal dominant (AD) mutations have also been described. Glucagon-like peptide (GLP-1) agonists have been studied in both animal models and humans with classic Wolfram syndrome.

CASE

We present a 15-year-old female with a personal and family history of congenital strabismus, bilateral cataracts, low-frequency sensorineural hearing loss, and diabetes mellitus. Trio whole exome sequencing revealed a previously unknown maternally inherited heterozygous variant in exon 8 of the WFS1 gene c.2605_2616del12 p.Ser869_His872del, leading to the diagnosis of AD WFS1-related disorder. Treatment with a GLP-1 agonist resulted in marked improvement in glycemic control and discontinuation of insulin therapy. This patient's response to a GLP-1 agonist provides suggestive indirect evidence for a role of WFS1 on β-cell endoplasmic reticulum stress and suggests that treatment with a GLP-1 agonist should be considered in patients with dominant forms of WS.

Intracellular targeting of Cisd2/Miner1 to the endoplasmic reticulum

Background

Cisd1 and Cisd2 proteins share very similar structures with an N-terminal membrane-anchoring domain and a C-terminal cytosolic domain containing an iron-cluster binding domain and ending with a C-terminal KKxx sequence. Despite sharing a similar structure, Cisd1 and Cisd2 are anchored to different compartments: mitochondria for Cisd1 and endoplasmic reticulum for Cisd2. The aim of this study was to identify the protein motifs targeting Cisd2 to the ER and ensuring its retention in this compartment.

Results

We used new recombinant antibodies to localize Cisd1 and Cisd2 proteins, as well as various protein chimeras. Cisd2 is targeted to the ER by its N-terminal sequence. It is then retained in the ER by the combined action of a C-terminal COPI-binding KKxx ER retrieval motif, and of an ER-targeting transmembrane domain. As previously reported for Cisd1, Cisd2 can alter the morphology of the compartment in which it accumulates.

Conclusion

Although they share a very similar structure, Cisd1 and Cisd2 use largely different intracellular targeting motifs to reach their target compartment (mitochondria and endoplasmic reticulum, respectively).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00387-1.

Uniting the divergent Wolfram syndrome-linked proteins WFS1 and CISD2 as modulators of Ca2+ signaling

[Figure: see text].

Monogenic diabetes in Pakistani infants and children: challenges in a resource poor country

OBJECTIVES

To review the data of infants and children with suspected monogenic diabetes who underwent genetic testing.

METHODS

Monogenic diabetes is a rare form of diabetes resulting from mutations in a single gene. It can be caused by dominant as well as recessive modes of inheritance. In a country like Pakistan where interfamily marriages are common the incidence of genetic disorders is increased. As Pakistan a resource-poor country, the diagnosis of insulin-dependent diabetes is often delayed and a genetic diagnosis of monogenic diabetes is extremely difficult. Children with clinical diagnosis of monogenic and syndromic diabates were recruited and blood samples were sent for genetic analysis.

RESULTS

One thousand sixty four new cases diagnosed with type 1 diabetes were registered at the National Institute of Child Health, Karachi, in the last 10 years. Of these 39 patients were selected for genetic testing who were diagnosed with diabetes/had a sibling diagnosed with diabetes before the age of nine months (n = 27) or had extra pancreatic features ( n= 12). We identified mutations in 18/27 cases diagnosed with diabetes before nine months of age. The most common genetic subtype was WolcottRallison syndrome caused by EIF2AK3 mutations (seven cases). KCNJ11 mutations were identified in two cases, ABCC8mutations were identified in four cases from three families, GCK and INS mutations were each identified in two cases, and one SLC2A2 mutation was identified in one case. A genetic diagnosis was made in 12/12 children from six families with diabetes diagnosed after the age of nine months who had extrapancreatic features. Six patients had genetically confirmed Wolfram syndrome (WFS1), three had thiamine-responsive megaloblastic anemia (SLC19A2) and three were diagnosed with histocytosis lymphadenopathy plus syndrome (SLC29A3).

CONCLUSIONS

Genetic testing is essential to confirm a diagnosis of monogenic diabetes which guides clinical management and future counselling. Our study highlights the importance of diagnosing monogenic diabetes in the largely consanguineously-married population of Pakistan.

High-fat diet associated sensitization to metabolic stress in Wfs1 heterozygous mice

Wolfram syndrome is a rare autosomal recessive disorder caused by mutations in the wolframin ER transmembrane glycoprotein (WFS1) gene and characterized by diabetes mellitus, diabetes insipidus, optic atrophy and deafness. In experimental models the homozygous Wfs1 mutant mice have a full penetrance and clearly expressed phenotype, whereas heterozygous mutants have a less-pronounced phenotype between the wild-type and homozygous mutant mice. Heterozygous WFS1 mutations have been shown to be significant risk factors for diabetes and metabolic disorders in humans. In the present study we analyzed the response of heterozygous Wfs1 mice to high fat diet (HFD) by exploring potential outcomes and molecular changes induced by this challenge. The HFD treatment increased the body weight (BW) similarly both in Wfs1 wild-type (WT) and heterozygous (HZ) mice, and therefore HFD also prevented the impaired BW gain found in Wfs1 mutant mice. In Wfs1HZ mutant mice, HFD impaired the normalized insulin secretion and the expression of ER stress genes in isolated pancreatic islets. These results suggest that Wfs1HZ mice have a decreased insulin response and pronounced cellular stress response due to a higher sensitivity to HFD as hypothesized. In Wfs1HZ mice, HFD increased the expression of Ire1α and Chop in pancreas and decreased that of Ire1α and Atf4 in liver. The present study shows that HFD can disturb insulin function with an increased ER stress in Wfs1HZ mice and only one functional Wfs1 gene copy is not sufficient to compensate this challenge. In conclusion, our study indicates that quantitative Wfs1 gene deficiency is sufficient to predispose the carriers of single functional Wfs1 copy to diabetes and metabolic syndrome and makes them susceptible to the environmental challenges such as HFD.

Genetic syndromes with diabetes: A systematic review

Previous reviews and clinical guidelines have identified 10-20 genetic syndromes associated with diabetes, but no systematic review has been conducted to date. We provide the first comprehensive catalog for syndromes with diabetes mellitus. We conducted a systematic review of MEDLINE, Embase, CENTRAL, PubMed, OMIM, and Orphanet databases for case reports, case series, and observational studies published between 1946 and January 15, 2020, that described diabetes mellitus in adults and children with monogenic or chromosomal syndromes. Our literature search identified 7,122 studies, of which 160 fulfilled inclusion criteria. Our analysis of these studies found 69 distinct diabetes syndromes. Thirty (43.5%) syndromes included diabetes mellitus as a cardinal clinical feature, and 56 (81.2%) were fully genetically elucidated. Sixty-three syndromes (91.3%) were described more than once in independent case reports, of which 59 (93.7%) demonstrated clinical heterogeneity. Syndromes associated with diabetes mellitus are more numerous and diverse than previously anticipated. While knowledge of the syndromes is limited by their low prevalence, future reviews will be needed as more cases are identified. The genetic etiologies of these syndromes are well elucidated and provide potential avenues for future gene identification efforts, aid in diagnosis and management, gene therapy research, and developing personalized medicine treatments.

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.

Lessons from Wolfram Syndrome: Initiation of DDAVP Therapy Causes Renal Salt Wasting Due to Elevated ANP/BNP Levels, Rescued by Fludrocortisone Treatment

Initiation of desmopressin acetate (DDAVP) for untreated diabetes insipidus (DI) in Wolfram syndrome (WS) causes abrupt volume expansion resulting in particularly high secretion of Atrial Natriuretic Peptide (ANP) and/or Brain Natriuretic Peptide (BNP), which in turn blocks all stimulators of zona glomerulosa steroidogenesis, resulting in secondary mineralocorticoid deficiency and acute hyponatremia, causing renal salt wasting (RSW). Two sisters, a 19-y-old girl (A) and a 7-y-old girl (B) with WS, presented with severe polyuria-polydipsia due to never treated DI. Both had neurogenic bladder and "B" had severe hydronephrosis secondary to untreated grade III bilateral vesicoureteral reflux. They initiated therapy with oral melt DDAVP which resulted in RSW. ANP was found ×50 and BNP ×2-4 fold elevated. Fludrocortisone 100-200 × 2 μg/d controlled natriuresis and restored electrolytes to normal within 48 h. Fludrocortisone treatment rescues otherwise potentially life-threatening hyponatremia due to RSW and the secondary mineralocorticoid deficiency driven by elevated ANP and/or BNP, caused by sudden volume expansion following DDAVP initiation.

Clinical Spectrum Associated with Wolfram Syndrome Type 1 and Type 2: A Review on Genotype-Phenotype Correlations

Wolfram syndrome is a rare neurodegenerative disorder that is typically characterized by diabetes mellitus and optic atrophy. Other common features are diabetes insipidus and hearing loss, but additional less-frequent findings may also be present. The phenotype spectrum is quite wide, and penetrance may be incomplete. The syndrome is progressive, and thus, the clinical picture may change during follow-up. Currently, two different subtypes of this syndrome have been described, and they are associated with two different disease-genes, wolframin (WFS1) and CISD2. These genes encode a transmembrane protein and an endoplasmic reticulum intermembrane protein, respectively. These genes are detected in different organs and account for the pleiotropic features of this syndrome. In this review, we describe the phenotypes of both syndromes and discuss the most pertinent literature about the genotype–phenotype correlation. The clinical presentation of Wolfram syndrome type 1 suggests that the pathogenic variant does not predict the phenotype. There are few papers on Wolfram syndrome type 2 and, thus, predicting the phenotype on the basis of genotype is not yet supported. We also discuss the most pertinent approach to gene analysis.

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.

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.

Mild Phenotype of Wolfram Syndrome Associated With a Common Pathogenic Variant Is Predicted by a Structural Model of Wolframin

Objective

To describe the WFS1 c.1672C>T; p.R558C missense variant, found in 1.34% of Ashkenazi Jews, that has a relatively mild phenotype and to use computational normal mode analysis (NMA) to explain the genotype-phenotype relationship.

Methods

The clinical, laboratory, and genetic features of 8 homozygotes were collected. A model of the wolframin protein was constructed, and NMA was used to simulate the effect of the variant on protein thermodynamics.

Results

Mean age at Wolfram syndrome (WS) diagnosis among homozygotes was 30 years; diabetes (7/8) was diagnosed at mean age 19 years (15–21 years), and bilateral optic atrophy (with MRI evidence of optic/chiasm atrophy) (6/8) at mean age 29 years (15–48 years). The oldest patient (62 years) also had gait difficulties, memory problems, parietal and cerebellar atrophy, and white matter hyperintense lesions. All retained functional vision with independent ambulation and self-care; none had diabetes insipidus or hearing loss. The p.R558C variant caused less impairment of protein entropy than WFS1 variants associated with a more severe phenotype.

Conclusions

The p.R558C variant causes a milder, late-onset phenotype of WS. We report a structural model of wolframin protein based on empirical functional studies and use NMA modeling to show a genotype-phenotype correlation across all homozygotes. Clinicians should be alert to this condition in patients with juvenile diabetes and patients of any age with a combination of diabetes and optic atrophy. Computational NMA has potential benefit for prediction of the genotype-phenotype relationship.

Novel mutations in the WFS1 gene are associated with Wolfram syndrome and systemic inflammation

Mutations in the WFS1 gene, encoding wolframin (WFS1), cause endoplasmic reticulum (ER) stress and are associated with a rare autosomal-recessive disorder known as Wolfram syndrome (WS). WS is clinically characterized by childhood-onset diabetes mellitus, optic atrophy, deafness, diabetes insipidus and neurological signs. We identified two novel WFS1 mutations in a patient with WS, namely, c.316-1G > A (in intron 3) and c.757A > T (in exon 7). Both mutations, located in the N-terminal region of the protein, were predicted to generate a truncated and inactive form of WFS1. We found that although the WFS1 protein was not expressed in peripheral blood mononuclear cells (PBMCs) of the proband, no constitutive ER stress activation could be detected in those cells. In contrast, WS proband’s PBMCs produced very high levels of proinflammatory cytokines (i.e. TNF-α, IL-1β, and IL-6) in the absence of any stimulus. WFS1 silencing in PBMCs from control subjects by means of small RNA interference also induced a pronounced proinflammatory cytokine profile. The same cytokines were also significantly higher in sera from the WS patient as compared to matched healthy controls. Moreover, the chronic inflammatory state was associated with a dominance of proinflammatory T helper 17 (Th17)-type cells over regulatory T (Treg) lymphocytes in the WS PBMCs. The identification of a state of systemic chronic inflammation associated with WFS1 deficiency may pave the way to innovative and personalized therapeutic interventions in WS.

Identification of Three Novel and One Known Mutation in the WFS1 Gene in Four Unrelated Turkish Families: The Role of Homozygosity Mapping in the Early Diagnosis

OBJECTIVE

Bi-allelic mutations in the wolframin gene (WFS1) cause Wolfram syndrome 1 (WS1 or DIDMOAD) characterized by nonautoimmune diabetes mellitus, optic atrophy, diabetes insipidus, sensorineural deafness, urinary tract abnormalities, and neuropsychiatric disorders. Patients presenting with an incomplete phenotype of WS1 were evaluated using homozygosity mapping and subsequent whole-exome sequencing.

METHODS

Four unrelated consanguineous Turkish families, including seven affected children, and their unaffected parents and siblings were evaluated. Homozygosity mapping was performed, followed by whole-exome sequencing of WFS1. Mutations were classified according to results of “in silico” analyses, protein prediction, and functional consequences.

RESULTS

Homozygosity mapping confirmed shared homozygous regions on chromosome 4 (chr4p16.1) between the affected individuals, that was absent in their unaffected siblings. Exome sequencing identified three novel (c.1215T>A, c.554G>A, c.1525_1540dup) and one known (c.1522_1523delTA) mutations in WFS1. All mutations were predicted to cause stop codon leading to early termination of protein synthesis and complete loss-of-function. All patients were found to be homozygous for the change, with parents and other unaffected siblings being carriers.

CONCLUSION

Our study expands the mutation spectrum of WSF1 mutations with three novel mutations. Homozygosity mapping may provide enrichment for molecular genetic analysis and early diagnosis of WS1 patients with incomplete phenotype, particularly in consanguineous pedigrees.

Sweet and Salty: Diabetic Ketoacidosis in a Patient With Nephrogenic Diabetes Insipidus

The co-existence of nephrogenic diabetes insipidus (NDI) with diabetes mellitus (DM) in a patient that presents in diabetic ketoacidosis (DKA) is rare and, to our knowledge, has not been described even in case reports. We report the case of a 16-year-old male with known NDI who presented to the pediatric emergency department (ED) for one day with generalized weakness and decreased appetite, found to be in moderate DKA from new-onset DM. The initial management of his dehydration and hyperosmolar state presented a unique challenge. Fluid resuscitation with isotonic fluids in a patient with NDI poses a risk of worsening hypernatremia, which can lead to seizures and death. However, the use of hypotonic fluids has the potential to lower serum osmolality too quickly, which can result in cerebral edema. Nephrology, endocrinology, and the pediatric intensive care unit (PICU) consultants were notified of this patient, and a discussion was coordinated between sub-specialists to determine the appropriate fluid resuscitation. The patient was allowed to drink free water in addition to receiving intravenous fluids (IVF) of dextrose 5% with 0.2% sodium chloride at a rate of one-and-a-half maintenance (150 mL/hr) in the ED prior to transfer to the PICU where insulin infusion was initiated. This case report provides guidance to inpatient providers on the management of patients with co-existent NDI and DM in DKA, a rare combination that requires thoughtful and urgent management.

The Impact of Mutations in Wolframin on Psychiatric Disorders

Wolfram Syndrome is a rare autosomal recessive disease characterized by early-onset diabetes mellitus, neurodegeneration, and psychological disorders. Mutations in the gene WFS1, coding for the protein wolframin, cause Wolfram Syndrome and are associated with bipolar disorder and schizophrenia. This report aims to connect WFS1 mutations to their impact on protein expression and structure, which ultimately translates to altered cell function and behavioral alterations of an individual. Methods: Published data were used to compile WFS1 mutations associated with psychiatric symptoms, both in homozygous patients and heterozygous carriers of WFS1 mutations. These mutations were evaluated in silico using SNAP2, PolyPhen-2, and PROVEAN to predict the effects of sequence variants. Statistical analysis was performed to assess the correlation between the locations of the mutations and the damage prediction scores. Results: Several mutations, clustering in the center and C-terminus of the WFS1 polypeptide, such as A559T and R558C, are found in individuals with psychiatric diseases and appear particularly impactful on protein structure. Our analysis showed that mutations in all regions of wolframin were present in patients with schizophrenia whereas only cytoplasmic and ER luminal mutations were reported in patients with manic episodes and bipolar disorders. According to Poly-Phen-2 predictions, 82.4% of the ER lumen mutations and 85.7% of the membrane mutations are damaging. Conclusion: We propose mood disorders in Wolfram Syndrome and heterozygous carriers of WFS1 mutations are the consequence of specific mutations in WFS1 that alter the structure of wolframin, resulting in intracellular calcium dysregulations and impaired cell signaling, Understanding the effect of WFS1 mutations on bipolar disorder and schizoprenia is integral to designing clinically targeted treatments for both diseases, which need more specialized treatments.

Therapeutic challenge: Unusual coexistence of idiopathic central diabetes insipidus and diabetes mellitus in a male with vitiligo

BACKGROUND

Idiopathic central diabetes insipidus (DI) is a rare endocrine disorder that results from total or partial deficiency of vasopressin secretion. It is idiopathic when the cause is unknown, but in many cases, is associated with autoimmune disorders.

CASE PRESENTATION

We present the case of a 44-year-old male with vitiligo and a family history of diabetes mellitus and thyroid disease. The patient presented with polydipsia and polyuria greater than 8 L/day. After water deprivation test, the patient was diagnosed with partial central diabetes insipidus. Contrast-enhanced pituitary magnetic resonance imaging showed decreased brightness of the neurohypophysis and normal thickness of the pituitary stalk. Because desmopressin was not initially available, the patient was managed with chlorpropamide, carbamazepine, and hydrochlorothiazide, and afterwards substituted. During his outpatient checkups, he presented many episodes of polyuria, the last after 13 years, with polyuria of up to 15 L associated with weight loss, and abnormal blood glucose levels; anti-GAD 65 and IA-2 antibodies were negative. He was subsequently diagnosed with diabetes mellitus and received metformin and insulin; this latter was suspended in subsequent check-ups due to hypoglycemic episodes.

CONCLUSION

We highlight the importance of treatment and adequate control of these pathologies, since they share similar clinical manifestations, can easily have electrolyte imbalance and represent a challenge for endocrinologists and internists.

Idebenone: When an antioxidant is not an antioxidant

Idebenone is a well described drug that was initially developed against dementia. The current literature widely portrays this molecule as a potent antioxidant and CoQ₁₀ analogue. While numerous papers seem to support this view, a closer look indicates that the pharmacokinetics of idebenone do not support these claims. A major discrepancy between achievable tissue levels, especially in target tissues such as the brain, and doses required to show the proposed effects, significantly questions our current understanding. This review explains how this has happened and highlights the discrepancies in the current literature. More importantly, based on some recent discoveries, a new framework is presented that can explain the mode of action of this molecule and can align formerly contradictory results. Finally, this new appreciation of the molecular activities of idebenone provides a rational approach to test idebenone in novel indications that might have not been considered previously for this drug.

Chemical targeting of NEET proteins reveals their function in mitochondrial morphodynamics

Several human pathologies including neurological, cardiac, infectious, cancerous, and metabolic diseases have been associated with altered mitochondria morphodynamics. Here, we identify a small organic molecule, which we named Mito-C. Mito-C is targeted to mitochondria and rapidly provokes mitochondrial network fragmentation. Biochemical analyses reveal that Mito-C is a member of a new class of heterocyclic compounds that target the NEET protein family, previously reported to regulate mitochondrial iron and ROS homeostasis. One of the NEET proteins, NAF-1, is identified as an important regulator of mitochondria morphodynamics that facilitates recruitment of DRP1 to the ER-mitochondria interface. Consistent with the observation that certain viruses modulate mitochondrial morphogenesis as a necessary part of their replication cycle, Mito-C counteracts dengue virus-induced mitochondrial network hyperfusion and represses viral replication. The newly identified chemical class including Mito-C is of therapeutic relevance for pathologies where altered mitochondria dynamics is part of disease etiology and NEET proteins are highlighted as important therapeutic targets in anti-viral research.

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.

Function of WFS1 and WFS2 in the Central Nervous System: Implications for Wolfram Syndrome and Alzheimer's disease

L.P. Li, L. Venkataraman, S. Chen, and H.J. Fu. Function of WFS1 and WFS2 in the Central Nervous System: Implications for Wolfram Syndrome and Alzheimer's Disease. NEUROSCI BIOBEHAV REVXXX-XXX,2020.-Wolfram syndrome (WS) is a rare monogenetic spectrum disorder characterized by insulin-dependent juvenile-onset diabetes mellitus, diabetes insipidus, optic nerve atrophy, hearing loss, progressive neurodegeneration, and a wide spectrum of psychiatric manifestations. Most WS patients belong to Wolfram Syndrome type 1 (WS1) caused by mutations in the Wolfram Syndrome 1 (WFS1/Wolframin) gene, while a small fraction of patients belongs to Wolfram Syndrome type 2 (WS2) caused by pathogenic variants in the CDGSH Iron Sulfur Domain 2 (CISD2/WFS2) gene. Although currently there is no treatment for this life-threatening disease, the molecular mechanisms underlying the pathogenesis of WS have been proposed. Interestingly, Alzheimer's disease (AD), an age-dependent neurodegenerative disease, shares some common mechanisms with WS. In this review, we focus on the function of WFS1 and WFS2 in the central nervous system as well as their implications in WS and AD. We also propose three future directions for elucidating the role of WFS1 and WFS2 in WS and AD.

Effect of 4-phenylbutyrate and valproate on dominant mutations of WFS1 gene in Wolfram syndrome

PURPOSE

Wolfram syndrome (WS) is a rare disorder caused by mutations in WFS1 that is characterized by diabetes mellitus, optic atrophy, sensorineural deafness, diabetes insipidus, and neurodegeneration. This disease is usually inherited as an autosomal recessive trait, but an autosomal dominant form has been reported. WFS1 encodes a transmembrane protein, which is a maintenance component of endoplasmic homeostasis. These dominant mutations were thought to increase endoplasmic reticulum (ER) stress. Recent studies suggest that 4-phenylbutyrate (PBA) and valproate (VPA) reduce ER stress. The objective of this study was to analyze the effect of PBA and VPA on dominant WFS1 mutants in vitro.

METHODS

We determined whether dominant WFS1 mutants (p.His313Tyr, p.Trp314Arg, p.Asp325_Ile328del, p.Glu809Lys, and p.Glu864Lys) have the dominant negative effect using a luciferase assay of ER stress response element marker as ER stress. Moreover, the rescue of cell apoptosis induced by dominant WFS1 mutants following treatment with PBA or VPA was determined by quantitative real-time PCR of C/EBP homologous protein (CHOP) mRNA expression.

RESULTS

These mutants showed the dominant negative effect on the wild-type WFS1. In addition, the levels of ER stress and CHOP mRNA were significantly elevated by all dominant WFS1 mutants. After treatment with PBA or VPA, ER stress and cell apoptosis were reduced in each mutant.

CONCLUSIONS

PBA and VPA could reduce the ER stress and cell apoptosis caused by dominant WFS1 mutants.

A homozygous missense mutation of WFS1 gene causes Wolfram's syndrome without hearing loss in an Iranian family (a report of clinical heterogeneity)

Background

Wolfram's syndrome (WFS) is a hereditary (autosomal recessive) neurodegenerative disorder. The clinical features are related to diabetes insipidus, diabetes mellitus, optic atrophy, and deafness (DIDMOAD) with other variable clinical manifestations. Pathogenic variants in the WFS1 gene, encoding wolframin, are known to be the main cause of Wolfram's syndrome. In this study, we present the clinical and genetic characteristics of two WFS patients from an Iranian family.

Methods

The mutation screening was performed by polymerase chain reaction (PCR) followed by direct Sanger sequencing of all exons from two affected WFS.

Results

The complete Sanger sequencing of the WFS1 gene detected a homozygous missense variant, c.2207G>A (p.Gly736Asp), in the eighth exon of the WFS1 gene. Both cases developed all the major symptoms of the disease, interestingly, except hearing loss.

Conclusions

Because of the rarity and clinical heterogeneity of WFS, the molecular genetic assay is essential to confirm the diagnosis and management of the WFS patients.