Wolfram syndrome: new mutations, different phenotype

Insights from a Wolfram syndrome cohort: clinical and molecular findings from a specialized diabetes reference center

Objective

Considering the rarity and clinical and molecular diversity of Wolfram syndrome (WS), the objective of this study was to identify patients with a clinical presentation suggestive of WS following up at a single Brazilian diabetes service and analyze their clinical and molecular characteristics.

Subjects and methods

The study included all patients with a clinical presentation of WS following up between 1991 and 2022 with early-onset diabetes mellitus and other WS signs and symptoms. A retrospective analysis was conducted, including patients' age, sex, consanguinity, age at symptom onset, diagnosis of diabetes mellitus, optic atrophy, diabetes insipidus, neurological and psychiatric disorders, hearing loss, urinary disorders, hypogonadism, and WFS1 molecular analysis.

Results

Eight patients were identified, all of whom were diagnosed with diabetes mellitus at an average age of 3.7 years. Optic atrophy, diabetes insipidus, and hearing loss were common, while psychiatric and neurological alterations were observed in some cases. Genetic analysis revealed pathogenic variants in homozygosity or compound heterozygosity. The most frequent variant was p. Val412Serfs29, present in five of the seven families.

Conclusions

This study represents the second-largest Brazilian sample of WS and is the first cohort from a single center in Southeast Brazil. The patients had an early, severe, and complete clinical presentation. The genetic variants identified were consistent with previous literature descriptions. The variant p. Val412Serfs29 was particularly common in this cohort, highlighting its relevance in the region.

Wolfram Syndrome 1: A Neuropsychiatric Perspective on a Rare Disease

Wolfram syndrome 1 (WS1) is an uncommon autosomal recessive neurological disorder that is characterized by diabetes insipidus, early-onset non-autoimmune diabetes mellitus, optic atrophy, and deafness (DIDMOAD). Other clinical manifestations are neuropsychiatric symptoms, urinary tract alterations, and endocrinological disorders. The rapid clinical course of WS1 results in death by the age of 30. Severe brain atrophy leads to central respiratory failure, which is the main cause of death in WS1 patients. Mutations in the WFS1 gene, located on chromosome 4p16, account for approximately 90% of WS1 cases. The gene produces wolframin, a transmembrane glycoprotein widely distributed and highly expressed in retinal, neural, and muscular tissues. Wolframin plays a crucial role in the regulation of apoptosis, insulin signaling, and ER calcium homeostasis, as well as the ER stress response. WS1 has been designated as a neurodegenerative and neurodevelopmental disorder due to the numerous abnormalities in the ER stress-mediated system. WS1 is a devastating neurodegenerative disease that affects patients and their families. Early diagnosis and recognition of the initial clinical signs may slow the disease's progression and improve symptomatology. Moreover, genetic counseling should be provided to the patient's relatives to extend multidisciplinary care to their first-degree family members. Regrettably, there are currently no specific drugs for the therapy of this fatal disease. A better understanding of the etiology of WS1 will make possible the development of new therapeutic approaches that may enhance the life expectancy of patients. This review will examine the pathogenetic mechanisms, development, and progression of neuropsychiatric symptoms commonly associated with WS1. A thorough understanding of WS1's neurophysiopathology is critical for achieving the goal of improving patients' quality of life and life expectancy.

Identification of causative gene variants for patients with known monogenic diabetes using a targeted next-generation sequencing panel in a single-center study

Aims

We aimed to verify the usefulness of targeted next-generation sequencing (NGS) technology for diagnosing monogenic diabetes in a single center.

Methods

We designed an amplicon-based NGS panel targeting 34 genes associated with known monogenic diabetes and performed resequencing in 56 patients with autoantibody-negative diabetes mellitus diagnosed at < 50 years who had not been highly obese. By bioinformatic analysis, we filtered significant variants based on allele frequency (< 0.005 in East Asians) and functional prediction. We estimated the pathogenicity of each variant upon considering the family history.

Results

Overall, 16 candidate causative variants were identified in 16 patients. Among them, two previously known heterozygous nonsynonymous single-nucleotide variants associated with monogenic diabetes were confirmed as causative variants: one each in the GCK and WFS1 genes. The former was found in two independent diabetes-affected families. Two novel putatively deleterious heterozygous variants were also assumed to be causative from the family history: one frameshift and one nonsynonymous single-nucleotide variant in the HNF4A gene. Twelve variants remained as candidates associated with the development of diabetes.

Conclusion

Targeted NGS panel testing was useful to diagnose various forms of monogenic diabetes in combination with familial analysis, but additional ingenuity would be needed for practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00669-3.

Next generation sequencing identifies a pathogenic mutation of WFS1 gene in a Moroccan family with Wolfram syndrome: a case report

BACKGROUND

Wolfram syndrome is a rare autosomal recessive neurodegenerative disorder that affects 1/200,000 to 1/1,000,000 children. It is characterized by juvenile onset diabetes, optic nerve atrophy and other systemic manifestations. Symptoms of the disease arise mostly in early childhood with a high mortality rate due to severe neurological complications. Two causative genes have been identifed in this syndrome; the classical form is caused by autosomal recessive mutations of the WFS1 gene, and a smaller portion of patients has mutations in the CIDS2 gene, which are responsible for autosomal recessive Wolfram syndrome 2.

CASE PRESENTATION

We report the case of a 28-year-old Moroccan boy born from consanguineous parents referred to the department of medical genetics at the National Institute of Health in Rabat. The diagnosis of Wolfram syndrome was made based on insulin-dependent diabetes, optic nerve atrophy, sensorineural deafness, urological abnormalities and psychiatric illness. To establish the diagnosis at a molecular level, we performed next-generation sequencing in the index patient, which revealed compound heterozygous WFS1 mutations: c.1113G > A (p.Trp371Ter) and c.1223_1224insGGAACCACCTGGAGCCCTATGCCCATTT (p.Phe408fs). This second variant has never been described in patients with Wolfram syndrome.

CONCLUSION

The identification of the genetic substrate in our patient confirmed the clinical diagnosis of Wolfram syndrome and allowed us to provide him an appropriate management and genetic counseling to his family.

Genetic Etiology of Nonsyndromic Hearing Loss in Hungarian Patients

Hearing loss is the most prevalent sensory disorder worldwide. The majority of congenital nonsyndromic hearing loss (NSHL) cases are caused by hereditary factors. Previously, the majority of NSHL studies focused on the GJB2 gene; however, with the availability of next-generation sequencing (NGS) methods, the number of novel variants associated with NSHL has increased. The purpose of this study was to design effective genetic screening for a Hungarian population based on a pilot study with 139 NSHL patients. A stepwise, comprehensive genetic approach was developed, including bidirectional capillary sequencing, multiplex ligation-dependent probe amplification (MLPA), and an NGS panel of 108 hearing loss genes. With our results, a genetic diagnosis was possible for 92 patients. Sanger sequencing and MLPA identified the genetic background of 50% of these diagnosed cases, and the NGS panel identified another 16%. The vast majority (92%) of the diagnosed cases showed autosomal recessive inheritance and 76% were attributed to GJB2. The implementation of this stepwise analysis markedly increased our diagnostic yield and proved to be cost-effective as well.

Delineating Wolfram-like syndrome: A systematic review and discussion of the WFS1-associated disease spectrum

Wolfram-like syndrome (WFLS) is a recently described autosomal dominant disorder with phenotypic similarities to autosomal recessive Wolfram syndrome (WS), including optic atrophy, hearing impairment, and diabetes mellitus. We summarize current literature, define the clinical characteristics, and investigate potential genotype phenotype correlations. A systematic literature search was conducted in electronic databases Pubmed/MEDLINE, EMBACE, and Cochrane Library. We included studies reporting patients with a clinical picture consisting at least 2 typical clinical manifestations of WSF1 disorders and heterozygous mutations in WFS1. In total, 86 patients from 35 studies were included. The most common phenotype consisted of the combination of optic atrophy (87%) and hearing impairment (94%). Diabetes mellitus was seen in 44% of the patients. Nineteen percent developed cataract. Patients with missense mutations in WFS1 had a lower number of clinical manifestations, less chance of developing diabetes insipidus, but a younger age at onset of hearing impairment compared to patients with nonsense mutations or deletions causing frameshift. There were no studies reporting decreased life expectancy. This review shows that, within the spectrum of WFS1-associated disorders or "wolframinopathies," autosomal dominantly inherited WFLS has a relatively mild phenotype compared to autosomal recessive WS. The clinical manifestations and their age at onset are associated with the specific underlying mutations in the WFS1 gene.

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.

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.

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

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.

Altered islet prohormone processing: A cause or consequence of diabetes?

Peptide hormones are first produced as larger precursor prohormones that require endoproteolytic cleavage to liberate the mature hormones. A structurally conserved but functionally distinct family of nine prohormone convertase enzymes (PCs) are responsible for cleavage of protein precursors of which PC1/3 and PC2 are known to be exclusive to neuroendocrine cells and responsible for prohormone cleavage. Differential expression of PCs within tissues define prohormone processing; whereas glucagon is the major product liberated from proglucagon via PC2 in pancreatic α-cells, proglucagon is preferentially processed by PC1/3 in intestinal L cells to produce glucagon-like peptides 1 and 2 (GLP-1, GLP-2). Beyond our understanding of processing of islet prohormones in healthy islets, there is convincing evidence that proinsulin, proIAPP, and proglucagon processing is altered during prediabetes and diabetes. There is predictive value of elevated circulating proinsulin or proinsulin : C-peptide ratio for progression to type 2 diabetes and elevated proinsulin or proinsulin : C-peptide is predictive for development of type 1 diabetes in at risk groups. After onset of diabetes, patients have elevated circulating proinsulin and proIAPP and proinsulin may be an autoantigen in type 1 diabetes. Further, preclinical studies reveal that α-cells have altered proglucagon processing during diabetes leading to increased GLP-1 production. We conclude that despite strong associative data, current evidence is inconclusive on the potential causal role of impaired prohormone processing in diabetes, and suggest that future work should focus on resolving the question of whether altered prohormone processing is a causal driver or merely a consequence of diabetes pathology.

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.

Monogenic diabetes: A single center experience from South India

Monogenic forms of diabetes in children are frequently misclassified as either type 1 diabetes or young-onset type 2 diabetes. There is a paucity of literature regarding pediatric monogenic diabetes in the Indian population. A retrospective analysis of case records of 37 children with monogenic diabetes who were diagnosed between 2008 and 2019 in a South Indian tertiary care center was performed. The write-up describes the clinical, biochemical, and genetic characterization of these patients with the diagnoses of neonatal diabetes mellitus (15 patients), MODY (five patients), and various forms of syndromic diabetes (13 with Wolfram syndrome, two with H syndrome, one with mitochondrial diabetes, and one with thiamine responsive megaloblastic anemia).

Wolfram syndrome: new pathophysiological insights and therapeutic strategies

Wolfram Syndrome (WS) is an ultra-rare, progressive neurodegenerative disease characterized by early-onset diabetes mellitus and irreversible loss of vision, secondary to optic nerve degeneration. Visual loss in WS is an important cause of registrable blindness in children and young adults and the pathological hallmark is the preferential loss of retinal ganglion cells within the inner retina. In addition to optic atrophy, affected individuals frequently develop variable combinations of neurological, endocrinological, and psychiatric complications. The majority of patients carry recessive mutations in the WFS1 (4p16.1) gene that encodes for a multimeric transmembrane protein, wolframin, embedded within the endoplasmic reticulum (ER). An increasingly recognised subgroup of patients harbor dominant WFS1 mutations that usually cause a milder phenotype, which can be limited to optic atrophy. Wolframin is a ubiquitous protein with high levels of expression in retinal, neuronal, and muscle tissues. It is a multifunctional protein that regulates a host of cellular functions, in particular the dynamic interaction with mitochondria at mitochondria-associated membranes. Wolframin has been implicated in several crucial cellular signaling pathways, including insulin signaling, calcium homeostasis, and the regulation of apoptosis and the ER stress response. There is currently no cure for WS; management remains largely supportive. This review will cover the clinical, genetic, and pathophysiological features of WS, with a specific focus on disease models and the molecular pathways that could serve as potential therapeutic targets. The current landscape of therapeutic options will also be discussed in the context of the latest evidence, including the pipeline for repurposed drugs and gene therapy.

Plain language summary

Wolfram syndrome - disease mechanisms and treatment options Wolfram syndrome (WS) is an ultra-rare genetic disease that causes diabetes mellitus and progressive loss of vision from early childhood. Vision is affected in WS because of damage to a specialized type of cells in the retina, known as retinal ganglion cells (RGCs), which converge at the back of the eye to form the optic nerve. The optic nerve is the fast-conducting cable that transmits visual information from the eye to the vision processing centers within the brain. As RGCs are lost, the optic nerve degenerates and it becomes pale in appearance (optic atrophy). Although diabetes mellitus and optic atrophy are the main features of WS, some patients can develop more severe problems because the brain and other organs, such as the kidneys and the bladder, are also affected. The majority of patients with WS carry spelling mistakes (mutations) in the WFS1 gene, which is located on the short arm of chromosome 4 (4p16.1). This gene is highly expressed in the eye and in the brain, and it encodes for a protein located within a compartment of the cell known as the endoplasmic reticulum. For reasons that still remain unclear, WFS1 mutations preferentially affect RGCs, accounting for the prominent visual loss in this genetic disorder. There is currently no effective treatment to halt or slow disease progression and management remains supportive, including the provision of visual aids and occupational rehabilitation. Research into WS has been limited by its relative rarity and the inability to get access to eye and brain tissues from affected patients. However, major advances in our understanding of this disease have been made recently by making use of more accessible cells from patients, such as skin cells (fibroblasts), or animal models, such as mice and zebrafish. This review summarizes the mechanisms by which WFS1 mutations affect cells, impairing their function and eventually leading to their premature loss. The possible treatment strategies to block these pathways are also discussed, with a particular focus on drug repurposing (i.e., using drugs that are already approved for other diseases) and gene therapy (i.e., replacing or repairing the defective WFS1 gene).

Functional Innovation in the Evolution of the Calcium-Dependent System of the Eukaryotic Endoplasmic Reticulum

The origin of eukaryotes was marked by the emergence of several novel subcellular systems. One such is the calcium (Ca²⁺)-stores system of the endoplasmic reticulum, which profoundly influences diverse aspects of cellular function including signal transduction, motility, division, and biomineralization. We use comparative genomics and sensitive sequence and structure analyses to investigate the evolution of this system. Our findings reconstruct the core form of the Ca²⁺-stores system in the last eukaryotic common ancestor as having at least 15 proteins that constituted a basic system for facilitating both Ca²⁺ flux across endomembranes and Ca²⁺-dependent signaling. We present evidence that the key EF-hand Ca²⁺-binding components had their origins in a likely bacterial symbiont other than the mitochondrial progenitor, whereas the protein phosphatase subunit of the ancestral calcineurin complex was likely inherited from the asgard archaeal progenitor of the stem eukaryote. This further points to the potential origin of the eukaryotes in a Ca²⁺-rich biomineralized environment such as stromatolites. We further show that throughout eukaryotic evolution there were several acquisitions from bacteria of key components of the Ca²⁺-stores system, even though no prokaryotic lineage possesses a comparable system. Further, using quantitative measures derived from comparative genomics we show that there were several rounds of lineage-specific gene expansions, innovations of novel gene families, and gene losses correlated with biological innovation such as the biomineralized molluscan shells, coccolithophores, and animal motility. The burst of innovation of new genes in animals included the wolframin protein associated with Wolfram syndrome in humans. We show for the first time that it contains previously unidentified Sel1, EF-hand, and OB-fold domains, which might have key roles in its biochemistry.

Wolfram syndrome 1 in the Italian population: genotype-phenotype correlations

OBJECTIVES

We studied 45 patients with Wolfram syndrome 1 (WS1) to describe their clinical history and to search for possible genotype-phenotype correlations.

METHODS

Clinical criteria contributing to WS1 diagnosis were analyzed. The patients were classified into three genotypic classes according to type of detected mutations.

RESULTS

WS1 prevalence in Italy is 0.74/1,000,000. All four manifestations of DIDMOAD were found in 46.7% of patients. Differently combined WS1 clinical features were detected in 53.3% of patients. We found 35 WFS1 different mutations and a novel missense mutation, c.1523A>G. WS1 patients were homozygotes or compound heterozygotes for WFS1 mutations except for 2 heterozygote patients (4.5%). Each genotypic group exhibited a different age onset of DM, D, and DI but not of OA. Genotypic Group 2 patients manifested a lower number of clinical manifestations compared to Groups 1 and 3. Moreover, genotypic Group 1 patients tended to have a shorter survival time than the other groups. No differences were found regarding type of clinical pictures.

CONCLUSIONS

Our study suggested that molecular WFS1 typing is a useful tool for early assessment of clinical history, follow-up, and prognosis of WS1.

The Precise Diagnosis of Wolfram Syndrome Type 1 Based on Next-Generation Sequencing

Purpose: To explore a method for the early, rapid and accurate diagnosis of Wolfram syndrome 1 (WS1) and further enrich the spectrum of WFS1 mutations in the Chinese population. Methods: We analyzed 279 patients with unexplained optic atrophy using next-generation sequencing. All patients underwent detailed clinical evaluations. Furthermore, Sanger sequencing and cosegregation analyses were performed within families. Results: Five patients with WS1 were identified in four unrelated families, and their clinical features were reviewed in detail. Seven variants of WFS1 were detected, including three reported variants (p.G674R, p.Tyr508Cysfs*34, and p.G702D) and four novel variants (p.W540G, p.K634*, p.F770C, and p.Q584P). Furthermore, the variant p.G674R was recurrent. Conclusion: Considering that WS1 is a rare progressive neurodegenerative disease, early diagnosis is beneficial to the systematic evaluation, monitoring and management of complications to improve patient quality of life and delay the progression of the disease. In the future, precise diagnosis on the basis of clinical manifestation and genetic testing will become the gold standard for the diagnosis of hereditary eye diseases and syndromes. Finally, our results further increase the spectrum of WFS1 mutations by adding four novel variants to the limited data available in the Chinese population.

Clinical and molecular assessment of 13 Iranian families with Wolfram syndrome

PURPOSE

Wolfram syndrome (WS) is a rare genetic disorder described by a pattern of clinical manifestations such as diabetes mellitus, diabetes insipidus, optic nerve atrophy, sensorineural hearing loss, urinary tract abnormalities, and psychiatric disorders. WFS1 and WFS2 loci are the main genetic loci associated with this disorder.

METHODS

In the current study, we investigated associations between these loci and WS via STR markers and homozygosity mapping in 13 Iranian families with WS. All families were linked to WFS1 locus.

RESULTS

Mutation analysis revealed four novel mutations (Q215X, E89X, S168Del, and E391Sfs*51) in the assessed families. Bioinformatics tools confirmed the pathogenicity of the novel mutations. Other identified mutations were previously reported in other populations for their pathogenicity.

CONCLUSIONS

The current study adds to the mutation repository of WS and shows a panel of mutations in Iranian population. Such panel would facilitate genetic counseling and prenatal diagnosis in families with WS cases.

Novel mutations and the ophthalmologic characters in Chinese patients with Wolfram Syndrome

BACKGROUND

Wolfram Syndrome (WFS) is a rare autosomal recessive neurodegenerative disease which has a wide spectrum of manifestations including diabetes insipidus, diabetes mellitus, optic atrophy and deafness. WFS1 and CISD2 are two main causing genes of WFS. The aim of this study was to illustrate the ophthalmologic manifestations and determine the genotype of Chinese WFS patients.

RESULTS

Completed ophthalmic examinations and family investigations were performed on 4 clinically diagnosed WFS patients from 4 unrelated families. Genetic testing was done by the next generation sequencing of candidate genes. One patient carried a homozygous mutation (c.272_273del) in CISD2, two patients carried compound heterozygous mutations (c.1618 T > G + c.2020G > A and c.1048 T > A + c.2020G > A) in WFS1, and one patient carried a heterozygous mutation (c.937C > T) in WFS1. Three of them were novel mutations.

CONCLUSIONS

Our study indicated WFS in Chinese is a neurodegenerative disease with both wide spectrum of clinical features and genetic heterogeneity. We found three novel mutations in WFS patients, and to our best knowledge, this is the first report of Chinese WFS patient with mutation in CISD2.

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

Background

Wolfram syndrome (WS), a rare genetic disorder, is considered the best prototype of endoplasmic reticulum (ER) diseases. Classical WS features are childhood-onset diabetes mellitus, optic atrophy, deafness, diabetes insipidus, neurological signs, and other abnormalities. Two causative genes (WFS1 and WFS2) have been identified. The transmission of the disease takes place in an autosomal recessive mode but autosomal dominant mutations responsible for WS-related disorders have been described. Prognosis is poor, death occurs at the median age of 39 years with a major cause represented by respiratory failure as a consequence of brain stem atrophy and neurodegeneration. The aim of this narrative review is to focus on etiology, pathogenesis and natural history of WS for an adequate patient management and for the discussion of future therapeutic interventions.

Main body

WS requires a multidisciplinary approach in order to be successfully treated. A prompt diagnosis decreases morbidity and mortality through prevention and treatment of complications. Being a monogenic pathology, WS represents a perfect model to study the mechanisms of ER stress and how this condition leads to cell death, in comparison with other prevalent diseases in which multiple factors interact to produce the disease manifestations. WS is also an important disease prototype to identify drugs and molecules associated with ER homeostasis. Evidence indicates that specific metabolic diseases (type 1 and type 2 diabetes), neurodegenerative diseases, atherosclerosis, inflammatory pathologies and also cancer are closely related to ER dysfunction.

Conclusions

Therapeutic strategies in WS are based on drug repurposing (i.e., investigation of approved drugs for novel therapeutic indications) with the aim to stop the progression of the disease by reducing the endoplasmic reticulum stress. An extensive understanding of WS from pathophysiology to therapy is fundamental and more studies are necessary to better manage this devastating disease and guarantee the patients a better quality of life and longer life expectancy.

Longitudinal hearing loss in Wolfram syndrome

BACKGROUND

Wolfram syndrome (WFS) is a rare autosomal recessive disease with clinical manifestations of diabetes mellitus (DM), diabetes insipidus (DI), optic nerve atrophy (OA) and sensorineural hearing loss (SNHL). Although SNHL is a key symptom of WFS, there is limited information on its natural history using standardized measures. Such information is important for clinical care and determining its use as an outcome measure in clinical trials.

METHODS

Standardized audiologic measures, including pure-tone testing, tympanometry, speech perception, and the unaided Speech Intelligibility Index (SII) were assessed in patients with confirmed WFS annually. Mixed model analyses were used to examine main effects of age, time or interactions for pure tone average (PTA), high frequency average (HFA) and SII.

RESULTS

Forty WFS patients were evaluated between 1 and 6 times. Mean age at initial enrollment was 13.5 years (SD = 5.6). Patients were classified as having normal hearing (n = 10), mild-to-severe (n = 24) or profound SNHL (n = 6). Mean age of diagnosis for SNHL was 8.3 years (SD = 5.1) with 75% prevalence. HFA worsened over time for both ears, and SII worsened over time in the worse ear, with greater decline in both measures in younger patients. Average estimated change over 1 year for all measures was in the subclinical range and power analyses suggest that 100 patients would be needed per group (treatment vs. placebo) to detect a 60% reduction in annual change of HFA over 3 years. If trials focused on just those patients with SNHL, power estimates suggest 55 patients per group would be sufficient.

CONCLUSIONS

Most patients had a slow progressive SNHL emerging in late childhood. Change over time with standard audiologic tests (HFA, SII) was small and would not be detectable for at least 2 years in an individual. Relatively large sample sizes would be necessary to detect significant impact on hearing progression in a clinical trial. Hearing function should be monitored clinically in WFS to provide appropriate intervention. Because SNHL can occur very early in WFS, audiologists and otolaryngologists should be aware of and refer for later emerging symptoms.

Genetic and clinical aspects of Wolfram syndrome 1, a severe neurodegenerative disease

Wolfram syndrome 1 (WS1) is a rare autosomal recessive neurodegenerative disease characterized by diabetes insipidus, diabetes mellitus, optic atrophy, deafness, and other abnormalities. WS1 usually results in death before the age of 50 years. The pathogenesis of WS1 is ascribed to mutations of human WFS1 gene on chromosome 4p encoding a transmembrane protein called wolframin, which has physiological functions in membrane trafficking, secretion, processing, and/or regulation of ER calcium homeostasis. Different types of WFS1 mutations have been identified, and some of these have been associated with a dominant, severe type of WS. Mutations of CISD2 gene cause autosomal recessive Wolfram syndrome 2 (WS2) characterized by the absence of diabetes insipidus and psychiatric disorders, and by bleeding upper intestinal ulcer and defective platelet aggregation. Other WFS1-related disorders such as DFNA6/14/38 nonsyndromic low-frequency sensorineural hearing loss and Wolfram syndrome-like disease with autosomal dominant transmission have been described. WS1 is a devastating disease for the patients and their families. Thus, early diagnosis is imperative to enable proper prognostication, prevent complications, and reduce the transmission to further progeny. Although there is currently no effective therapy, potential new drugs have been introduced, attempting to improve the progression of this fatal disease.

TMTC2 variant associated with sensorineural hearing loss and auditory neuropathy spectrum disorder in a family dyad

BACKGROUND

Sensorineural hearing loss (SNHL) is a common form of hearing loss that can be inherited or triggered by environmental insults; auditory neuropathy spectrum disorder (ANSD) is a SNHL subtype with unique diagnostic criteria. The genetic factors associated with these impairments are vast and diverse, but causal genetic factors are rarely characterized.

METHODS

A family dyad, both cochlear implant recipients, presented with a hearing history of bilateral, progressive SNHL, and ANSD. Whole-exome sequencing was performed to identify coding sequence variants shared by both family members, and screened against genes relevant to hearing loss and variants known to be associated with SNHL and ANSD.

RESULTS

Both family members are successful cochlear implant users, demonstrating effective auditory nerve stimulation with their devices. Genetic analyses revealed a mutation (rs35725509) in the TMTC2 gene, which has been reported previously as a likely genetic cause of SNHL in another family of Northern European descent.

CONCLUSION

This study represents the first confirmation of the rs35725509 variant in an independent family as a likely cause for the complex hearing loss phenotype (SNHL and ANSD) observed in this family dyad.

Hippocampus and Hypothalamus RNA-sequencing of WFS1-deficient Mice

Wolfram syndrome is caused by mutations in the WFS1 gene. WFS1 protein dysfunction results in a range of neuroendocrine syndromes and is mostly characterized by juvenile-onset diabetes mellitus and optic atrophy. WFS1 has been shown to participate in membrane trafficking, protein processing and Ca²⁺ homeostasis in the endoplasmic reticulum. Aim of the present study was to find the transcriptomic changes influenced by WFS1 in the hypothalamus and hippocampus using RNA-sequencing. The WFS1-deficient mice were used as a model system to analyze the changes in transcriptional networks. The number of differentially expressed genes between hypothalami of WFS1-deficient (Wfs1KO) and wild-type (WT) mice was 43 and between hippocampi 311 with False Discovery Rate (FDR) <0.05. Avpr1a and Avpr1b were significantly upregulated in the hypothalamus and hippocampus of Wfs1KO mice respectively. Trpm8 was the most upregulated gene in the hippocampus of Wfs1KO mice. The functional analysis revealed significant enrichment of networks and pathways associated with protein synthesis, cell-to-cell signaling and interaction, molecular transport, metabolic disease and nervous system development and function. In conclusion, the transcriptomic profiles of WFS1-deficient hypothalamus and hippocampus do indicate the activation of degenerative molecular pathways causing the clinical occurrences typical to Wolfram syndrome.

Cochlear Proteins Associated with Noise-induced Hearing Loss: An Update

Noise-induced hearing loss (NIHL) is one of the major occupational disease that has influence on the quality of life of mining workers. Several reports suggest NIHL is attributed to noise exposure at workplace and approximately 16% of hearing loss is due to it. NIHL occurs as a result of exposure to high-level noise (>85 dB) in the workplace. Noise disrupts proteins present in the micromachinery of the ear that is required for mechano-electric transduction of sound waves. High-level noise exposure can lead to hearing impairment owing to mechanical and metabolic exhaustion in cochlea, the major organ responsible for resilience of sound. Several key proteins of cochlea include tectorial membrane, inner hair cells, outer hair cells, and stereocilia are damaged due to high-level noise exposure. Numerous studies conducted in animals have shown cochlear proteins involvement in NIHL, but the pertinent literature remains limited in humans. Detection of proteins and pathways perturbed within the micromachinery of the ear after excessive sound induction leads toward the early identification of hearing loss. The situation insisted to present this review as an update on cochlear proteins associated with NIHL after an extensive literature search using several electronic databases which help to understand the pathophysiology of NIHL.

Multiple fractures and impaired bone metabolism in Wolfram syndrome: a case report

Wolfram Syndrome (WS) is a rare and lethal disease characterized by optic atrophy, diabetes mellitus, diabetes insipidus, and hearing loss. To date, osteoporotic related fractures have not been reported in affected patients. Here, we describe the case of a man affected by WS complicated by several bone fragility fractures. A 50-year-old Caucasian man was hospitalized because of tibia and fibula fractures. His clinical features included diabetes mellitus, diabetes insipidus, optic atrophy and deafness that were consistent with an unrecognized WS diagnosis, which was confirmed by the identification of a specific mutation in gene WFS1 encoding wolframin. Bone mineral density by phalangeal quantitative ultrasound demonstrated severe osteoporosis, with high serum levels of surrogate markers of bone turn-over. Previously unidentified rib fractures were also detected. To the best of our knowledge, this is the first report of osteoporotic related fractures in a patient affected by WS. Although no effective treatments are currently available to delay the progression of the disease, this case report suggests to evaluate fracture risk in the diagnostic work-up of WS.

A nonsynonymous mutation in the WFS1 gene in a Finnish family with age-related hearing impairment

Wolfram syndrome (WS) is caused by recessive mutations in the Wolfram syndrome 1 (WFS1) gene. Sensorineural hearing impairment (HI) is a frequent feature in WS and, furthermore, certain mutations in WFS1 cause nonsyndromic dominantly inherited low-frequency sensorineural HI. These two phenotypes are clinically distinct indicating that WFS1 is a reasonable candidate for genetic studies in patients with other phenotypes of HI. Here we have investigated, whether the variation in WFS1 has a pathogenic role in age-related hearing impairment (ARHI). WFS1 gene was investigated in a population sample of 518 Finnish adults born in 1938-1949 and representing variable hearing phenotypes. Identified variants were evaluated with respect to pathogenic potential. A rare mutation predicted to be pathogenic was found in a family with many members with impaired hearing. Twenty members were recruited to a segregation study and a detailed clinical examination. Heterozygous p.Tyr528His variant segregated completely with late-onset HI in which hearing deteriorated first at high frequencies and progressed to mid and low frequencies later in life. We report the first mutation in the WFS1 gene causing late-onset HI with audiogram configurations typical for ARHI. Monogenic forms of ARHI are rare and our results add WFS1 to the short list of such genes.

Clinical and Molecular Genetic Analysis in Three Children with Wolfram Syndrome: A Novel WFS1 Mutation (c.2534T>A)

Wolfram syndrome (WS) is an autosomal recessive disorder caused by mutations in WFS1 gene. The clinical features include diabetes insipidus, diabetes mellitus (DM), optic atrophy, deafness, and other variable clinical manifestations. In this paper, we present the clinical and genetic characteristics of 3 WS patients from 3 unrelated Turkish families. Clinical characteristics of the patients and the age of onset of symptoms were quite different in each pedigree. The first two cases developed all symptoms of the disease in their first decade of life. The heterozygous father of case 2 was symptomatic with bilateral deafness. The first ocular finding of one patient (patient 3) was bilateral cataract which was accompanying DM as a first feature of the syndrome. In this patient's family, there were two members with features suggestive of WS. Previously known homozygous mutations, c.460+1G>A in intron 4 and c.1885C>T in exon 8, were identified in these cases. A novel homozygous c.2534T>A mutation was also detected in the exon 8 of WFS1 gene. Because of the rarity and heterogeneity of WS, detection of specific and nonspecific clinical signs including ocular findings and family history in non-autoimmune, insulinopenic diabetes cases should lead to a tentative diagnosis of WS. Genetic testing is required to confirm the diagnosis.

Identification of four novel mutations of the WFS1 gene in Iranian Wolfram syndrome pedigrees

AIMS

Wolfram syndrome is a rare neurodegenerative disorder with an autosomal recessive pattern of inheritance characterized by various clinical manifestations. The related gene, WFS1, encodes a transmembrane glycoprotein, named wolframin. Genetic analyses demonstrated that mutations in this gene are associated with WS type 1. Our aim in this study was to sequence WFS1 coding region in Iranian Wolfram syndrome pedigrees.

METHODS

Genomic DNA was extracted from peripheral blood of 12 WS patients and their healthy parents. Exons 2-8 and the exon-intron junctions of WFS1 were sequenced. DNA sequences were compared to the reference using Sequencher software.

RESULTS

Molecular analysis of WFS1 revealed six different mutations. Four novel and two previously reported mutations were identified. One novel mutation, c.1379_1381del, is predicted to produce an aberrant protein. A second novel mutation, c.1384G > T, encodes a truncated protein. Novel mutation, c.1097-1107dup (11 bp), causes a frameshift which results in a premature stop codon. We screened for the novel missense mutation, c.1010C > T, in 100 control alleles. This mutation was not found in any of the healthy controls.

CONCLUSION

Our study increased the spectrum of WFS1 mutations and supported the role of WFS1 in susceptibility to WS. We hope that these findings open new horizons to future molecular investigations which may help to prevent and treat this devastating disease.

A novel compound heterozygous mutation in an adolescent with insulin-dependent diabetes: The challenge of characterizing Wolfram syndrome

WS diagnosis is often delayed since misdiagnosed as autoimmune diabetes. The rarity of the condition and the absence of other diseases at diabetes diagnosis might make extremely challenging the recognition of WS. However the novel compound heterozygosity for the here reported mutations, seems to confer a mild phenotype among the spectrum of WS manifestations.

Identification of a novel WFS1 homozygous nonsense mutation in Jordanian children with Wolfram syndrome

Wolfram syndrome (WS) is a rare autosomal recessive neurodegenerative disorder characterized by the presentation of early onset type I diabetes mellitus and optic atrophy with later onset diabetes insipidus and deafness. WFS1 gene was identified on chromosome 4p16.1 as the gene responsible for WS disease given that most of the WS patients were found to carry mutations in this gene. This study was carried out to investigate the molecular spectrum of WFS1 gene in Jordanian families. Molecular and clinical characterization was performed on five WS patients from two unrelated Jordanian families. Our data indicated that WS patients of the first family harbored two deletion mutations (V415del and F247fs) located in exon 8 and exon 7 respectively, with a compound heterozygous pattern of inheritance; while in the second family, we identified a novel nonsense mutation (W185X) located in exon 5 in the N-terminal cytoplasmic domain with a homozygous pattern of inheritance. This mutation can be considered as loss of function mutation since the resulting truncated protein lost both the transmembrane domain and the C-terminal domain. Additionally, the W185X mutation lies within the CaM binding domain in wolframin protein which is thought to have a role in the regulation of wolframin function in response to calcium levels.

Management of diabetes insipidus and adipsia in the child

Central diabetes insipidus (CDI) is a complex and heterogeneous clinical syndrome affecting the hypothalamic-neurohypophyseal network and water balance. A recent national surveillance in Denmark showed a prevalence rate of twenty-three CDI patients per 100,000 inhabitants in five years. The differential diagnosis between several presenting conditions with polyuria and polydipsia is puzzling, and the etiological diagnosis of CDI remains a challenge before the identification of an underlying cause. For clinical practice, a timely diagnosis for initiating specific treatment in order to avoid central nervous system damage, additional pituitary defects and the risk of dissemination of germ cell tumor is advisable. Proper etiological diagnosis can be achieved via a series of steps that start with careful clinical observation of several signs and endocrine symptoms and then progress to more sophisticated imaging tools. This review summarizes the best practice and approach for the diagnosis and treatment of patients with CDI.

Identification of unsuspected Wolfram syndrome cases through clinical assessment and WFS1 gene screening in type 1 diabetes mellitus patients

OBJECTIVE

Wolfram syndrome (WS) is a severe autosomal recessive pleiotropic disease primarily characterized by the association of juvenile-onset diabetes mellitus and optic atrophy. Earlier reports have shown that a proportion of WS cases may remain unrecognized due to misdiagnosis as type 1 diabetes mellitus (T1DM). The objectives of this work were to estimate the prevalence of patients fulfilling clinical criteria for WS in a cohort of subjects diagnosed as T1DM and to identify causal WFS1 gene mutations in those individuals meeting clinical criteria for the disease.

METHODS

A cohort of 131 unrelated Mexican T1DM patients was collected, including 77 females and 54 males. Additional clinical anomalies suggesting WS were identified through review of medical files, detailed physical examination and/or specialized tests. WFS1 gene analysis was performed using exon-by-exon PCR amplification and direct Sanger sequencing on genomic DNA from patients reaching WS clinical criteria.

RESULTS

Clinical criteria for a WS diagnosis were reached in 6 probands, corresponding to a 4.58% frequency of the disease. WFS1 mutations were identified in 4 out of 5 (80%) individuals fulfilling WS clinical criteria, including two homozygous, one compound heterozygous, and one patient with a single allele mutation. No WFS1 mutations were identified in the remaining subject.

CONCLUSIONS

In our cohort, approximately 6% of cases diagnosed as T1DM were in fact patients with Wolfram syndrome. WFS1 mutations were identified in 4 out of 5 individuals (80%) fulfilling clinical criteria for WS. Clinical and genetic analyses of large cohorts of T1DM patients from different ethnic origins would help to better estimate the occurrence of WS and will lead to a better management of such patients.

Early-onset central diabetes insipidus is associated with de novo arginine vasopressin-neurophysin II or Wolfram syndrome 1 gene mutations

OBJECTIVE

Idiopathic early-onset central diabetes insipidus (CDI) might be due to mutations of arginine vasopressin-neurophysin II (AVP-NPII (AVP)) or wolframin (WFS1) genes.

DESIGN AND METHODS

Sequencing of AVP and WFS1 genes was performed in nine children with CDI, aged between 9 and 68 months, and negative family history for polyuria and polydipsia.

RESULTS

Two patients carried a mutation in the AVP gene: a heterozygous G-to-T transition at nucleotide position 322 of exon 2 (c.322G>T) resulting in a stop codon at position 108 (p.Glu108X), and a novel deletion from nucleotide 52 to 54 (c.52_54delTCC) producing a deletion of a serine at position 18 (p.Ser18del) of the AVP pre-prohormone signal peptide. A third patient carried two heterozygous mutations in the WFS1 gene localized on different alleles. The first change was A-to-G transition at nucleotide 997 in exon 8 (c.997A>G), resulting in a valine residue at position 333 in place of isoleucine (p.Ile333Val). The second novel mutation was a 3 bp insertion in exon 8, c.2392_2393insACG causing the addition of an aspartate residue at position 797 and the maintenance of the correct open reading frame (p. Asp797_Val798insAsp). While similar WFS1 protein levels were detected in fibroblasts from healthy subjects and from the patient and his parents, a major sensitivity to staurosporine-induced apoptosis was observed in the patient fibroblasts as well as in patients with Wolfram syndrome.

CONCLUSIONS

Early-onset CDI is associated with de novo mutations of the AVP gene and with hereditary WFS1 gene changes. These findings have valuable implications for management and genetic counseling.

Identification of a novel missense mutation in the WFS1 gene as a cause of autosomal dominant nonsyndromic sensorineural hearing loss in all-frequencies

Hearing loss is the most common sensory disorder affecting 278 million people in the world, and more than 60% of hearing loss patients can be attributed to genetic causes. Although many loci have been linked to hereditary hearing impairment, most of the causative genes have not been identified as yet. The goal of this study was to investigate the cause of dominantly inherited sensorineural all-frequency hearing loss in a six-generation Chinese family. We performed exome sequencing to screen responsible candidate genes in three family members with all-frequency hearing loss and one member with normal hearing. Sanger sequencing was employed to examine the variant mutations in the members of this family and 200 healthy persons. PCR-RFLP was performed to further confirm the nucleotide mutation. A novel missense mutation c.2389G > A (GAC → AAC) in WFS1 gene was identified, which was co-segregated with the hearing loss phenotype. No mutation was found in 200 controls and the family members with normal hearing in this site. The present study identifies, for the first time, a novel mutation in WFS1 gene that causes non-syndromic hearing loss in all, rather than in low or high, frequencies.

Significant expressivity of Wolfram syndrome: phenotypic assessment of two known and one novel mutation in the WFS1 gene in three Iranian families

Wolfram syndrome also known as DIDMOAD (Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy, and Deafness) is a rare neurodegenerative autosomal recessive disorder. There is evidence of variable expressivity both in patients and heterozygous carriers. In this study, we describe three Persian Wolfram syndrome families with differences in the age of onset, signs and symptoms of the disease. We clinically evaluated affected families for verifying WS clinical diagnosis. After linkage analysis via 5 STR markers, molecular analysis for WFS1 was performed by direct sequencing for patients and available family members. Three homozygous mutations were identified including c.1885 C>T, c.2205C>A both in exon 8 and c.460+1G>A in intron 4. The mutation c.2205C>A was found to be novel. We report interesting phenotype-genotype correlations: homozygous c.1885C>T and c.2205C>A variants were correlated with quite different disease severity and onset in the siblings. We report a rare case of WS with homozygous c.1885C>T who is married and has a healthy child. c.460+1G>A showed a possible partial dominant inheritance put forth by a heterozygous parent showing partial WS symptoms while her daughter displayed typical WS symptoms. Due to variable expressivity, detailed clinical examination and molecular diagnostics should be used to confirm WS and a more exact recurrence risk data.

Mutation update and uncommon phenotypes in a French cohort of 96 patients with WFS1-related disorders

WFS1 mutations are responsible for Wolfram syndrome (WS) characterized by juvenile-onset diabetes mellitus and optic atrophy, and for low-frequency sensorineural hearing loss (LFSNHL). Our aim was to analyze the French cohort of 96 patients with WFS1-related disorders in order (i) to update clinical and molecular data with 37 novel affected individuals, (ii) to describe uncommon phenotypes and, (iii) to precise the frequency of large-scale rearrangements in WFS1. We performed quantitative polymerase chain reaction (PCR) in 13 patients, carrying only one heterozygous variant, to identify large-scale rearrangements in WFS1. Among the 37 novel patients, 15 carried 15 novel deleterious putative mutations, including one large deletion of 17,444 base pairs. The analysis of the cohort revealed unexpected phenotypes including (i) late-onset symptoms in 13.8% of patients with a probable autosomal recessive transmission; (ii) two siblings with recessive optic atrophy without diabetes mellitus and, (iii) six patients from four families with dominantly-inherited deafness and optic atrophy. We highlight the expanding spectrum of WFS1-related disorders and we show that, even if large deletions are rare events, they have to be searched in patients with classical WS carrying only one WFS1 mutation after sequencing.

Molecular characterization of WFS1 in an Iranian family with Wolfram syndrome reveals a novel frameshift mutation associated with early symptoms

Wolfram syndrome (WS) is a rare autosomal recessive neurodegenerative disorder that represents a likely source of childhood diabetes especially among countries in the consanguinity belt. The main responsible gene is WFS1 for which over one hundred mutations have been reported from different ethnic groups. The aim of this study was to identify the molecular etiology of WS and to perform a possible genotype-phenotype correlation in Iranian kindred. An Iranian family with two patients was clinically studied and WS was suspected. Genetic linkage analysis via 5 STR markers was carried out. For identification of mutations, DNA sequencing of WFS1 including all the exons, exon-intron boundaries and the promoter was performed. Linkage analysis indicated linkage to the WFS1 region. After DNA sequencing of WFS1, one novel pathogenic mutation, which causes frameshift alteration c.2177_2178insTCTTC (or c.2173_2177dupTCTTC) in exon eight, was found. The genotype-phenotype correlation analysis suggests that the presence of the homozygous mutation may be associated with early onset of disease symptoms. This study stresses the necessity of considering the molecular analysis of WFS1 in childhood diabetes with some symptoms of WS.

Genotypic classification of patients with Wolfram syndrome: insights into the natural history of the disease and correlation with phenotype

PURPOSE

Wolfram syndrome is a degenerative, recessive rare disease with an onset in childhood. It is caused by mutations in WFS1 or CISD2 genes. More than 200 different variations in WFS1 have been described in patients with Wolfram syndrome, which complicates the establishment of clear genotype-phenotype correlation. The purpose of this study was to elucidate the role of WFS1 mutations and update the natural history of the disease.

METHODS

This study analyzed clinical and genetic data of 412 patients with Wolfram syndrome published in the last 15 years.

RESULTS

(i) 15% of published patients do not fulfill the current -inclusion criterion; (ii) genotypic prevalence differences may exist among countries; (iii) diabetes mellitus and optic atrophy might not be the first two clinical features in some patients; (iv) mutations are nonuniformly distributed in WFS1; (v) age at onset of diabetes mellitus, hearing defects, and diabetes insipidus may depend on the patient's genotypic class; and (vi) disease progression rate might depend on genotypic class.

CONCLUSION

New genotype-phenotype correlations were established, disease progression rate for the general population and for the genotypic classes has been calculated, and new diagnostic criteria have been proposed. The conclusions raised could be important for patient management and counseling as well as for the development of treatments for Wolfram syndrome.

Identification of one novel causative mutation in exon 4 of WFS1 gene in two Italian siblings with classical DIDMOAD syndrome phenotype

The aim of the present paper is to describe a novel missense mutation (G107R) of WFS1 gene that was unexpectedly detected, in two siblings from Southern Italy, outside exon 8; a very unusual finding which has previously been reported only twice in Italian patients with Wolfram syndrome (WS). Although in Spanish pedigrees' WFS1 mutations are frequently located in exon 4, this finding is very infrequent in other pedigrees, particularly in Italian patients.

CONCLUSIONS

a) our report of two siblings with one novel WSF1 mutation (G107R) expands the molecular spectrum of WS; b) this is the 3rd report of Italian patients harbouring one mutation outside exon 8 and the 2nd with one mutation in exon 4; c) on the basis of the present observations, and literature data we can infer that mutation locations outside exon 8 do not seem to be clearly associated with peculiar phenotype expressions of WFS1 gene.

Wolfram syndrome 1 and Wolfram syndrome 2

PURPOSE OF REVIEW

Wolfram syndrome 1 (WS1) is an autosomal recessive disorder characterized by diabetes insipidus, diabetes mellitus, optic atrophy, and deafness (DI DM OA D syndrome) associated with other variable clinical manifestations. The causative gene for WS1 (WFS1) encoding wolframin maps to chromosome 4p16.1. Wolframin has an important function in maintaining the homeostasis of the endoplasmic reticulum (ER) in pancreatic β cells. Recently, another causative gene, CISD2, has been identified in patients with a type of Wolfram syndrome (WS2) resulting in early optic atrophy, diabetes mellitus, deafness, decreased lifespan, but not diabetes insipidus. The CISD2-encoded protein ERIS (endoplasmic reticulum intermembrane small protein) also localizes to ER, but does not interact directly with wolframin. ERIS maps to chromosome 4q22.

RECENT FINDINGS

Numerous studies have shown an interesting similarity between WFS1 and CISD2 genes. Experimental studies demonstrated that the Cisd2 knockout (Cisd2) mouse shows premature aging and typical symptoms of Wolfram syndrome. These researches provide interesting insight into the relation of neurodegenerative diseases, mitochondrial disorders, and autophagy and are useful for the pathophysiological understanding of both Wolfram syndrome and mitochondrial-mediated premature aging.

SUMMARY

The knowledge of WS1 and WS2 pathogenesis, and of the interactions between WFS1 and CISD2 genes, is useful for accurate diagnostic classification and for diagnosis of presymptomatic individuals.