Wolfram syndrome-associated mutations lead to instability and proteasomal degradation of wolframin

Wolfram Syndrome Type I Case Report and Review-Focus on Early Diagnosis and Genetic Variants

Background and Objectives: Wolfram syndrome type 1 (OMIM# 222300; ORPHAcode 3463) is an extremely rare autosomal recessive syndrome with a 25% recurrence risk in children. It is characterized by the presence of juvenile-onset diabetes mellitus (DM), progressive optic atrophy (OA), diabetes insipidus (DI), and sensorineural deafness (D), often referred to by the acronym DIDMOAD. It is a severe neurodegenerative disease with a life expectancy of 39 years, with death occurring due to cerebral atrophy. For a positive diagnosis, the presence of diabetes mellitus and optic nerve atrophy is sufficient. The disease occurs because of pathogenic variants in the WFS1 gene. The aim of this article is to present a case report of Wolfram Syndrome Type I, alongside a review of genetic variants, clinical manifestations, diagnosis, therapy, and long-term management. Emphasizing the importance of early diagnosis and a multidisciplinary approach, the study aims to enhance understanding and improve outcomes for patients with this complex syndrome. Materials and Methods: A case of a 28-year-old patient diagnosed with DM at the age of 6 and with progressive optic atrophy at 26 years old is presented. Molecular diagnosis revealed the presence of a heterozygous nonsense variant WFS1 c.1943G>A (p.Trp648*), and a heterozygous missense variant WFS1 c.1675G>C (p.Ala559Pro). Results: The molecular diagnosis of the patient confirmed the presence of a heterozygous nonsense variant and a heterozygous missense variant in the WFS1 gene, correlating with the clinical presentation of Wolfram syndrome type 1. Both allelic variants found in our patient have been previously described in other patients, whilst this combination has not been described before. Conclusions: This case report and review underscores the critical role of early recognition and diagnosis in Wolfram syndrome, facilitated by genetic testing. By identifying pathogenic variants in the WFS1 gene, genetic testing not only confirms diagnosis but also guides clinical management and informs genetic counseling for affected families. Timely intervention based on genetic insights can potentially reduce the progressive multisystem manifestations of the syndrome, thereby improving the quality of life and outcomes for patients.

Genomics of Wolfram Syndrome 1 (WFS1)

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

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Gene-edited human stem cell-derived β cells from a patient with monogenic diabetes reverse preexisting diabetes in mice

Differentiation of insulin-producing pancreatic β cells from induced pluripotent stem cells (iPSCs) derived from patients with diabetes promises to provide autologous cells for diabetes cell replacement therapy. However, current approaches produce patient iPSC-derived β (SC-β) cells with poor function in vitro and in vivo. Here, we used CRISPR-Cas9 to correct a diabetes-causing pathogenic variant in Wolfram syndrome 1 (WFS1) in iPSCs derived from a patient with Wolfram syndrome (WS). After differentiation to β cells with our recent six-stage differentiation strategy, corrected WS SC-β cells performed robust dynamic insulin secretion in vitro in response to glucose and reversed preexisting streptozocin-induced diabetes after transplantation into mice. Single-cell transcriptomics showed that corrected SC-β cells displayed increased insulin and decreased expression of genes associated with endoplasmic reticulum stress. CRISPR-Cas9 correction of a diabetes-inducing gene variant thus allows for robust differentiation of autologous SC-β cells that can reverse severe diabetes in an animal model.

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.

Functional assessment of variants associated with Wolfram syndrome

Wolfram syndrome (WS) is a heterogeneous multisystem neurodegenerative disorder with two allelic variations in addition to a separate subtype known as WS type 2. The wide phenotypic spectrum of WS includes diabetes mellitus and optic atrophy which is often accompanied by diabetes insipidus, deafness, urological and neurological complications in combination or in isolation. To date, the understanding of the genotype-phenotype relationship in this complex syndrome remains poorly understood. In this study, we identified and explored the functionality of rare and novel variants in the two causative WS genes WFS1 and CISD2 by assessing the effects of the mutations on the encoded proteins Wolframin and ERIS, in a cohort of 12 patients with autosomal recessive WS, dominant WS and WS type 2. The identified pathogenic variants included missense changes, frameshift deletions and insertions in WFS1 and an exonic deletion in CISD2 which all altered the respective encoded protein in a manner that did not correlate to the phenome previously described. These observations suggest the lack of genotype-phenotype correlation in this complex syndrome and the need to explore other molecular genetic mechanisms. Additionally, our findings highlight the importance of functionally assessing variants for their pathogenicity to tackle the problem of increasing variants of unknown significance in the public genetic databases.

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

Communication between the endoplasmic reticulum (ER) and mitochondria plays a pivotal role in Ca²⁺ signaling, energy metabolism, and cell survival. Dysfunction in this cross-talk leads to metabolic and neurodegenerative diseases. Wolfram syndrome is a fatal neurodegenerative disease caused by mutations in the ER-resident protein WFS1. Here, we showed that WFS1 formed a complex with neuronal calcium sensor 1 (NCS1) and inositol 1,4,5-trisphosphate receptor (IP₃R) to promote Ca²⁺ transfer between the ER and mitochondria. In addition, we found that NCS1 abundance was reduced in WFS1-null patient fibroblasts, which showed reduced ER-mitochondria interactions and Ca²⁺ exchange. Moreover, in WFS1-deficient cells, NCS1 overexpression not only restored ER-mitochondria interactions and Ca²⁺ transfer but also rescued mitochondrial dysfunction. Our results describe a key role of NCS1 in ER-mitochondria cross-talk, uncover a pathogenic mechanism for Wolfram syndrome, and potentially reveal insights into the pathogenesis of other neurodegenerative diseases.

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.

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.

Laminin β2 gene missense mutation produces endoplasmic reticulum stress in podocytes

Mutations in the laminin β2 gene (LAMB2) cause Pierson syndrome, a severe congenital nephrotic syndrome with ocular and neurologic defects. LAMB2 is a component of the laminin-521 (α5β2γ1) trimer, an important constituent of the glomerular basement membrane (GBM). The C321R-LAMB2 missense mutation leads to congenital nephrotic syndrome but only mild extrarenal symptoms; the mechanisms underlying the development of proteinuria with this mutation are unclear. We generated three transgenic mouse lines, in which rat C321R-LAMB2 replaced mouse LAMB2 in the GBM. During the first postnatal month, expression of C321R-LAMB2 attenuated the severe proteinuria exhibited by Lamb2(-/-) mice in a dose-dependent fashion; proteinuria eventually increased, however, leading to renal failure. The C321R mutation caused defective secretion of laminin-521 from podocytes to the GBM accompanied by podocyte endoplasmic reticulum (ER) stress, likely resulting from protein misfolding. Moreover, ER stress preceded the onset of significant proteinuria and was manifested by induction of the ER-initiated apoptotic signal C/EBP homologous protein (CHOP), ER distention, and podocyte injury. Treatment of cells expressing C321R-LAMB2 with the chemical chaperone taurodeoxycholic acid (TUDCA), which can facilitate protein folding and trafficking, greatly increased the secretion of the mutant LAMB2. Taken together, these results suggest that the mild variant of Pierson syndrome caused by the C321R-LAMB2 mutation may be a prototypical ER storage disease, which may benefit from treatment approaches that target the handling of misfolded proteins.

WFS1 variants in Finnish patients with diabetes mellitus, sensorineural hearing impairment or optic atrophy, and in suicide victims

Mutations in the wolframin gene, WFS1, cause Wolfram syndrome, a rare recessive neurodegenerative disorder. The clinical features include early-onset bilateral optic atrophy (OA), diabetes mellitus (DM), diabetes insipidus, hearing impairment, urinary tract abnormalities and psychiatric illness, and, furthermore, WFS1 variants appear to be associated with non-syndromic DM and hearing impairment. Variation of WFS1 was investigated in Finnish subjects consisting 182 patients with DM, 117 patients with sensorineural hearing impairment (SNHI) and 44 patients with OA, and in 95 suicide victims. Twenty-two variants were found in the coding region of WFS1, including three novel nonsynonymous variants. The frequency of the p.[His456] allele was significantly higher in the patients with SNHI (11.5%; corrected P=0.00008), DM (6.6%; corrected P=0.036) or OA (9.1%; corrected P=0.043) than that in the 285 controls (3.3%). The frequency of the p.[His611] allele was 55.8% in the patients with DM being higher than that in the controls (47%; corrected P=0.039). The frequencies of p.[His456] and p.[His611] were similarly increased in an independent group of patients with DM (N=299). The results support previous findings that genetic variation of WFS1 contributes to the risk of DM and SNHI.

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 homozygous WFS1 mutations (p.Asp211Asn, p.Gln486*) causing severe Wolfram syndrome and first report of male fertility

Wolfram syndrome (WFS) is a neurodegenerative genetic condition characterized by juvenile-onset of diabetes mellitus and optic atrophy. We studied clinical features and the molecular basis of severe WFS (neurodegenerative complications) in two consanguineous families from Iran. A clinical and molecular genetic investigation was performed in the affected and healthy members of two families. The clinical diagnosis of WFS was confirmed by the existence of diabetes mellitus and optic atrophy in the affected patients, who in addition had severe neurodegenerative complications. Sequencing of WFS1 was undertaken in one affected member from each family. Targeted mutations were tested in all members of relevant families. Patients had most of the reported features of WFS. Two affected males in the first family had fathered unaffected children. We identified two homozygous mutations previously reported with apparently milder phenotypes: family 1: c.631G>A (p.Asp211Asn) in exon 5, and family 2: c.1456C>T (p.Gln486*) in exon 8. Heterozygous carriers were unaffected. This is the first report of male Wolfram patients who have successfully fathered children. Surprisingly, they also had almost all the complications associated with WFS. Our report has implications for genetic counseling and family planning advice for other affected families.

A new structural rearrangement associated to Wolfram syndrome in a child with a partial phenotype

Wolfram syndrome (WS) is a rare autosomal recessive disorder characterized by diabetes insipidus (DI), insulin-dependent diabetes mellitus (DM), optic atrophy (OA) and deafness caused by mutations in WFS1 gene (4p16.1), which encodes an endoplasmic reticulum protein, called Wolframin. We describe the case of an infant who presented hypernatremia and severe hypoplasia of the left eyeball with alteration of visual evoked potentials. Persistent hypernatremia, iposmolar polyuria and high plasma osmolality suggested DI, confirmed by a normal urine concentration after vasopressin test. Treatment with vasopressin allowed a normalization of sodium levels and urine output. Brain magnetic resonance imaging showed absence of the neurohypophysis hyperintense signal, normal adenohypophysis and optic tracts hypoplasia. The concomitant presence of DI and OA, even in the absence of DM and deafness, prompted the suspicion of WS and complete genetic analysis was performed. Genomic DNA sequencing of WFS1 showed no inactivating mutations described to date, but suggested a structural mutation as markers genotyping revealed a segmental paternal heterodisomy involving the upstream regulatory region (promoter and 5'UTR). cDNA sequencing revealed the coexistence of the wild-type transcript and two splice variants; one variant, probably benign, is known in literature and the other one causes the loss of exon 2, containing the translation initiation site. Western blot confirmed a marked protein reduction. During the clinical follow-up child's condition remained stable and glucose metabolism is still in the standard. In conclusion, the phenotype associated with this structural rearrangement, which substantially reduces the synthesis of Wolframin, confirms a tissue-specific pattern of expression of WFS1, suggests the presence of a different protein dosage sensitivity in different tissues and could be causative of DI and OA in our patient. The "incomplete" phenotype here described, usually absent in typical WS cases, is explained by the residual Wolframin expression that would preserve other organs, i.e. pancreatic islets. A careful longitudinal clinical follow-up will assess any changes in the phenotypic penetrance in our patient.

The E3 ligase Smurf1 regulates Wolfram syndrome protein stability at the endoplasmic reticulum

The HECT-type ubiquitin ligase (E3) Smad ubiquitination regulatory factor 1 (Smurf1) targets various substrates, including Smad1/5, RhoA, Prickle 1, MEKK2, and JunB for degradation and thereby regulates adult bone formation and embryonic development. Here, we identify the endoplasmic reticulum (ER)-localized Wolfram syndrome protein (WFS1) as a specific degradation substrate of Smurf1. Mutations in the WFS1 gene cause Wolfram syndrome, an autosomal recessive disorder characterized by diabetes mellitus and optic atrophy. WFS1 negatively regulates the ER stress response, and WFS1 deficiency in mice increases ER stress and triggers apoptosis. We show that Smurf1 interacts with WFS1 at the ER and promotes the ubiquitination and proteasomal degradation of WFS1. A C-terminal luminal region in WFS1, including residues 667-700, is involved in this degradation. Wild-type WFS1 as well as a subset of WFS1 mutants that include this degron region are susceptible to Smurf1-mediated degradation. By contrast, pathophysiological deletion mutants of WFS1 lacking the degron, such as W648X, Y660X, and Q667X, are resistant to degradation by Smurf1. Depletion of Smurf1 by RNA interference results in increased WFS1 and decreased ATF6α levels. Furthermore, we show that ER stress induces Smurf1 degradation and WFS1 up-regulation. These findings reveal for the first time that Smurf1 targets an ER-localized protein for degradation and that Smurf1 is regulated by ER stress.

Wolfram syndrome and WFS1 gene

Wolfram syndrome (WS) (MIM 222300) is a rare multisystem neurodegenerative disorder of autosomal recessive inheritance, also known as DIDMOAD (diabetes insipidus, insulin-deficient diabetes mellitus, optic atrophy and deafness). A Wolfram gene (WFS1) has been mapped to chromosome 4p16.1 which encodes an endoplasmic reticulum (ER) membrane-embedded protein. ER localization suggests that WFS1 protein has physiological functions in membrane trafficking, secretion, processing and/or regulation of ER calcium omeostasis. Disturbances or overloading of these functions induce ER stress responses, including apoptosis. Most WS patients carry mutations in this gene, but some studies provided evidence for genetic heterogeneity, and the genotype-phenotype relationships are not clear. Here we review the data regarding the mechanisms and the mutations of WFS1 gene that relate to WS.

Wolfram syndrome - clinical and diagnostic details

Wolfram syndrome, a rare genetic disorder is characterized by juvenile onset diabetes mellitus and optic atrophy. We describe two cases of wolfram syndrome belonging to same family; 25 year old female and her only 15 year old brother. In female, diabetes mellitus and optic atrophy were manifested in 1(st) decade, diabetes insipidus in 2(nd) decade and hypoacusis at the age of 25 years. Her ophthalmic evaluation revealed bilateral optic atrophy, decreased vision and peripheral constriction of visual field. However she didn't have any renal dysfunction which is also considered to be one of the features of the syndrome. Though associated psychiatric features are later manifestations of the syndrome she was admitted with alleged suicidal consumption at the age of 25 years. The brother was asymptomatic except for the diabetes mellitus and insipidus.

Expression of the diabetes risk gene wolframin (WFS1) in the human retina

Wolfram syndrome 1 (WFS1, OMIM 222300), a rare genetic disorder characterized by optic nerve atrophy, deafness, diabetes insipidus and diabetes mellitus, is caused by mutations of WFS1, encoding WFS1/wolframin. Non-syndromic WFS1 variants are associated with the risk of diabetes mellitus due to altered function of wolframin in pancreatic islet cells, expanding the importance of wolframin. This study extends a previous report for the monkey retina, using immunohistochemistry to localize wolframin on cryostat and paraffin sections of human retina. In addition, the human retinal pigment epithelial (RPE) cell line termed ARPE-19 and retinas from both pigmented and albino mice were studied to assess wolframin localization. In the human retina, wolframin was expressed in retinal ganglion cells, optic axons and the proximal optic nerve. Wolframin expression in the human retinal pigment epithelium (RPE) was confirmed with intense cytoplasmic labeling in ARPE-19 cells. Strong labeling of the RPE was also found in the albino mouse retina. Cryostat sections of the mouse retina showed a more extended pattern of wolframin labeling, including the inner nuclear layer (INL) and photoreceptor inner segments, confirming the recent report of Kawano et al. [Kawano, J., Tanizawa, Y., Shinoda, K., 2008. Wolfram syndrome 1 (Wfs1) gene expression in the normal mouse visual system. J. Comp. Neurol. 510, 1-23]. Absence of these cells in the human specimens despite the use of human-specific antibodies to wolframin may be related to delayed fixation. Loss of wolframin function in RGCs and the unmyelinated portion of retinal axons could explain optic nerve atrophy in Wolfram Syndrome 1.

Sodium-potassium ATPase 1 subunit is a molecular partner of Wolframin, an endoplasmic reticulum protein involved in ER stress

Wolfram syndrome, an autosomal recessive disorder characterized by diabetes mellitus and optic atrophy, is caused by mutations in the WFS1 gene encoding an endoplasmic reticulum (ER) membrane protein, Wolframin. Although its precise functions are unknown, Wolframin deficiency increases ER stress, impairs cell cycle progression and affects calcium homeostasis. To gain further insight into its function and identify molecular partners, we used the WFS1-C-terminal domain as bait in a yeast two-hybrid screen with a human brain cDNA library. Na+/K+ ATPase beta1 subunit was identified as an interacting clone. We mapped the interaction to the WFS1 C-terminal and transmembrane domains, but not the N-terminal domain. Our mapping data suggest that the interaction most likely occurs in the ER. We confirmed the interaction by co-immunoprecipitation in mammalian cells and with endogenous proteins in JEG3 placental cells, neuroblastoma SKNAS and pancreatic MIN6 beta cells. Na+/K+ ATPase beta1 subunit expression was reduced in plasma membrane fractions of human WFS1 mutant fibroblasts and WFS1 knockdown MIN6 pancreatic beta-cells compared with wild-type cells; Na+/K+ ATPase alpha1 subunit expression was also reduced in WFS-depleted MIN6 beta cells. Induction of ER stress in wild-type cells only partly accounted for the reduced Na+/K+ ATPase beta1 subunit expression observed. We conclude that the interaction may be important for Na+/K+ ATPase beta1 subunit maturation; loss of this interaction may contribute to the pathology seen in Wolfram syndrome via reductions in sodium pump alpha1 and beta1 subunit expression in pancreatic beta-cells.

The diagnosis of children with central diabetes insipidus

Central diabetes insipidus is the end result of a number of different diseases that affect the hypothalamic-neurohypophyseal system. In many patients, especially children and young adults, it is caused by the destruction or degeneration of neurons that originate in the supraoptic and paraventricular nuclei of the hypothalamus. The known causes of these lesions include germinoma or craniopharyngioma; Langerhans cell histiocytosis; local inflammatory, autoimmune or vascular diseases; trauma resulting from surgery or an accident; sarcoidosis; metastases; and midline cerebral and cranial malformations. In rare cases, genetic defects in AVP synthesis that are inherited as autosomal dominant, autosomal recessive or X-linked recessive traits are the underlying cause. Accurate diagnostic differentiation is essential for both safe and effective disease management. Proper etiological diagnosis can be achieved via a series of steps that start with clinical observations and then progress, as needed, to more sophisticated methods. Indeed, magnetic resonance imaging (MRI) represents the examination method of choice for evaluating hypothalamic-pituitary-related endocrine diseases due to its ability to provide strongly-contrasted high-resolution multi-planar and spatial images. Specifically, MRI allows a detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI identification of pituitary hyperintensity in the posterior part of the sella, now considered to be a clear marker of neurohypophyseal functional integrity, together with careful analysis of pituitary stalk shape and size, have provided the most striking recent findings contributing to the diagnosis and understanding of some forms of 'idiopathic' central diabetes insipidus.