Mitochondrial mutation commonly associated with Leber's hereditary optic neuropathy observed in a patient with Wolfram syndrome (DIDMOAD)

A novel WFS1 variant associated with severe diabetic retinopathy in Wolfram syndrome type 1

BACKGROUND

Wolfram syndrome type 1 is a rare neurodegenerative disorder including diabetes insipidus, diabetes mellitus, optic atrophy, and deafness, with variable additional findings. The phenotypic spectrum is very heterogeneous, with non-autoimmune juvenile-onset diabetes and optic atrophy as minimal criteria for the diagnosis. Biallelic mutations in the WFS1 gene are the causative genetic anomaly for the syndrome, with, however, no evident genotype-phenotype correlation. Among the clinical features of the disease, diabetic retinopathy depicts a rarely reported microvascular complication. In this report, we describe the clinical and genetic findings in a 26-year-old patient presenting with Wolfram syndrome and severe diabetic retinopathy.

METHODS

The mutation screening was performed by polymerase chain reaction followed by Sanger sequencing of the entire coding sequence of the WFS1 gene.

RESULTS

A novel homozygous missense variant c.1901A>T (p.Lys634Met) was found in the proband and classified as probably pathogenic according to the American College of Medical Genetics and Genomics.

CONCLUSIONS

The molecular study of the WFS1 gene is essential for the diagnostic confirmation, to provide appropriate genetic counseling and a mutational screening in the at-risk relatives. The c.1901A>T (p.Lys634 Met) is a novel variant that could be responsible for a severe form of Wolfram syndrome with early and proliferative diabetic retinopathy.

Wolframin deficiency is accompanied with metabolic inflexibility in rat striated muscles

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

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

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

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Metabolic inflexibility in early-stage WS rat muscle mitochondria.

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

BACKGROUND

Wolfram syndrome (WS), caused by mutations in WFS1 gene, is a multi-targeting disease affecting multiple organ systems. Wolframin is localized in the membrane of the endoplasmic reticulum (ER), influencing Ca²⁺ metabolism and ER interaction with mitochondria, but the exact role of the protein remains unclear. In this study we aimed to characterize alterations in energy metabolism in the cardiac and in the oxidative and glycolytic skeletal muscles in Wfs1-deficiency.

METHODS

Alterations in the bioenergetic profiles in the cardiac and skeletal muscles of Wfs1-knock-out (KO) male mice and their wild type male littermates were determined using high resolution respirometry, quantitative RT-PCR, NMR spectroscopy, and immunofluorescence confocal microscopy.

RESULTS

Oxygen consumption without ATP synthase activation (leak) was significantly higher in the glycolytic muscles of Wfs1 KO mice compared to wild types. ADP-stimulated respiration with glutamate and malate was reduced in the Wfs1-deficient cardiac as well as oxidative and glycolytic skeletal muscles.

CONCLUSIONS

Wfs1-deficiency in both cardiac and skeletal muscles results in functional alterations of energy transport from mitochondria to ATP-ases. There was a substrate-dependent decrease in the maximal Complex I -linked respiratory capacity of the electron transport system in muscles of Wfs1 KO mice. Moreover, in cardiac and gastrocnemius white muscles a decrease in the function of one pathway were balanced by the increase in the activity of the parallel pathway.

GENERAL SIGNIFICANCE

This work provides new insights to the muscle involvement at early stages of metabolic syndrome like WS as well as developing glucose intolerance.

Knockdown of wfs1, a fly homolog of Wolfram syndrome 1, in the nervous system increases susceptibility to age- and stress-induced neuronal dysfunction and degeneration in Drosophila

Wolfram syndrome (WS), caused by loss-of-function mutations in the Wolfram syndrome 1 gene (WFS1), is characterized by juvenile-onset diabetes mellitus, bilateral optic atrophy, and a wide spectrum of neurological and psychiatric manifestations. WFS1 encodes an endoplasmic reticulum (ER)-resident transmembrane protein, and mutations in this gene lead to pancreatic β-cell death induced by high levels of ER stress. However, the mechanisms underlying neurodegeneration caused by WFS1 deficiency remain elusive. Here, we investigated the role of WFS1 in the maintenance of neuronal integrity in vivo by knocking down the expression of wfs1, the Drosophila homolog of WFS1, in the central nervous system. Neuronal knockdown of wfs1 caused age-dependent behavioral deficits and neurodegeneration in the fly brain. Knockdown of wfs1 in neurons and glial cells resulted in premature death and significantly exacerbated behavioral deficits in flies, suggesting that wfs1 has important functions in both cell types. Although wfs1 knockdown alone did not promote ER stress, it increased the susceptibility to oxidative stress-, excitotoxicity- or tauopathy-induced behavioral deficits, and neurodegeneration. The glutamate release inhibitor riluzole significantly suppressed premature death phenotypes induced by neuronal and glial knockdown of wfs1. This study highlights the protective role of wfs1 against age-associated neurodegeneration and furthers our understanding of potential disease-modifying factors that determine susceptibility and resilience to age-associated neurodegenerative diseases.

Wolfram syndrome (WS), a neurodegenerative disorder with an autosomal recessive inheritance pattern, has a variable clinical presentation that includes diabetes mellitus, optic atrophy, and a wide spectrum of neurological and psychiatric manifestations. Homozygous mutations in WFS1 are causative for WS. The prognosis of WS is poor, and most patients die prematurely with respiratory failure due to brain stem atrophy. However, the mechanisms underlying the neurological manifestations of WS remain elusive. In this study, we used the fruit fly Drosophila to examine the neurological features of WS by generating genetically modified flies harboring knockdown of wfs1, the fly homolog of WFS1, in the central nervous system. These flies developed age-dependent behavioral deficits, neurodegeneration and premature death. wfs1-deficient flies were vulnerable to various age-related stressors such as oxidative stress and excitotoxicity, and to neurodegeneration caused by Alzheimer’s disease-related toxic proteins. The premature death phenotype in wfs1-deficient flies was ameliorated by administration of riluzole, which inhibits glutamate-induced excitotoxicity. This study provides insight into the mechanisms underlying neurodegeneration not only in WS, but also in age-associated neurodegenerative diseases such as Alzheimer’s disease.

Endocrine disorders in mitochondrial disease

Endocrine dysfunction in mitochondrial disease is commonplace, but predominantly restricted to disease of the endocrine pancreas resulting in diabetes mellitus. Other endocrine manifestations occur, but are relatively rare by comparison. In mitochondrial disease, neuromuscular symptoms often dominate the clinical phenotype, but it is of paramount importance to appreciate the multi-system nature of the disease, of which endocrine dysfunction may be a part. The numerous phenotypes attributable to pathogenic mutations in both the mitochondrial (mtDNA) and nuclear DNA creates a complex and heterogeneous catalogue of disease which can be difficult to navigate for novices and experts alike. In this article we provide an overview of the endocrine disorders associated with mitochondrial disease, the way in which the underlying mitochondrial disorder influences the clinical presentation, and how these factors influence subsequent management.

Recent advancement of understanding pathogenesis of type 1 diabetes and potential relevance to diabetic nephropathy

Type 1 diabetes mellitus is an autoimmune disease characterized by progressive destruction of pancreatic beta cells by genetic and environmental factors which leads to an absolute dependence of insulin for survival and maintenance of health. Although the majority of mechanisms of beta cell destruction remain unclear, many molecules, including proinflammatory cytokines and chemokines such as tumor necrosis factor alpha and monocyte chemoattractant protein-1, are implicated in the development of beta cell damage. Furthermore, beta cell destruction is enhanced by the Th1 and Th17 subsets of CD4+ T cells. In contrast, there are mechanisms involved in the maintenance of peripheral tolerance by regulatory T cells, the function of which depends on the pleiotropic cytokine transforming growth factor beta. Development and progression of renal injuries in patients with diabetic nephropathy are also associated with several growth factors and proinflammatory cytokines, including tumor necrosis factor alpha, insulin-like growth factor-1, monocyte chemoattractant protein-1, vascular endothelial growth factor, and transforming growth factor beta. Although the pathogenic mechanisms underlying type 1 diabetes and diabetic nephropathy are principally different, i.e., autoimmunity and inflammation, some common factors, including susceptibility genes and proinflammatory cytokines, are involved in both mechanisms, including infiltrating cell recruitment, upregulation of other cytokines and chemokines, or apoptosis.

Ataxie cérébelleuse révélant un syndrome de Wolfram

INTRODUCTION

Wolfram syndrome is a genetic disease with recessive autosomic transmission, associating early-onset diabetes mellitus and bilateral optical atrophy.

CASE REPORT

We report the case of a 47-year-old patient for whom we diagnosed a Wolfram syndrome in view of a late neurological syndrome in association with ataxia and bilateral horizontal nystagmus. The brain resonance magnetic imaging revealed a major atrophy of the brainstem and cerebellum.

CONCLUSION

Wolfram syndrome is a rare pathology, with fatal consequences before the age of 50. The association of diabetes mellitus and optical atrophy, especially when there are other symptoms (ataxia, deafness, diabetes insipidus, neuropsychiatric manifestations or urinary tract disorders) should lead to this diagnosis and to carry out a genetic confirmation.

Cranial magnetic resonance imaging of Wolfram (DIDMOAD) syndrome

Wolfram syndrome is a rare neurodegenerative disorder characterized by diabetes insipidus, diabetes mellitus, optic atrophy and deafness (DIDMOAD). A wide spectrum of abnormalities of the central nervous system, urinary tract and endocrine glands is also observed. We report cranial MRI findings in a 32-year-old female patient with Wolfram syndrome. In addition to the classical features, including absence of the normal high signal of the neurohypophysis, atrophy of visual pathways, the brainstem, cerebellum and cerebral cortex, we observed bilateral hyperintensity on proton density- and T2- weighted images related to the optic radiations in the periventricular white matter of the temporal and parieto-occipital lobes, which may reflect gliosis pathologically.

Clinical spectrum and diagnosis of mitochondrial disorders

Respiratory chain deficiencies have long been regarded as neuromuscular diseases mostly originating from mutations in the mitochondrial DNA. Actually, oxidative phosphorylation, i.e., adenosine triphosphate (ATP) synthesis-coupled electron transfer from substrate to oxygen through the respiratory chain, does not only occur in the neuromuscular system. For this reason, a respiratory chain deficiency can theoretically give rise to any symptom, in any organ or tissue, at any age and with any mode of inheritance, owing to the dual genetic origin of respiratory chain enzymes (nuclear DNA and mitochondrial DNA). In recent years, it has become increasingly clear that genetic defects of oxidative phosphorylation account for a large variety of clinical symptoms in both childhood and adulthood. Diagnosis of a respiratory chain deficiency is difficult initially when only one symptom is present, and easier when additional, seemingly unrelated, symptoms are observed. The clinical heterogeneity is echoed by the genetic heterogeneity illustrated by the increasing number of nuclear genes that have been shown to be involved in these diseases. In the absence of clear-cut genotype-phenotype correlations and in front of the large number of possibly involved genes, biochemical analyses are still the cornerstone of the diagnosis of this condition.

Presence of a major WFS1 mutation in Spanish Wolfram syndrome pedigrees

Wolfram syndrome (WS) is an autosomal recessive neurodegenerative disease mainly characterized by familial diabetes mellitus and optic atrophy. WS patients frequently present with other clinical features such as diabetes insipidus, renal abnormalities, psychiatric disorders, and a variety of neurologic symptoms: deafness, ataxia, peripheral neuropathy. A gene responsible for Wolfram Syndrome (WFS1) has been recently identified on chromosome 4p16.1. Twenty-two Wolfram patients from 16 Spanish families were screened for mutations in the WFS1 coding region by SSCP analysis and direct sequencing. Since WS has been considered a mitochondrial disorder for some time, mitochondrial DNA (mtDNA) in these families was also examined. WFS1 mutations were detected in 75% of families (12 of 16). One of these mutations, an insertion of 16 base pairs in exon 4, turned out to be notably frequent in Spanish pedigrees. As many as 50% of pedigrees with WFS1 mutations harbored this insertion, either in one (33% of cases) or in two chromosomes (67%). Ten other mutations were identified: 7 missense changes, 2 deletions, and 1 nonsense mutation. Only 3 of these changes had been previously described in non-Spanish pedigrees. Large mtDNA rearrangements and LHON point mutations were detected in four and six families, respectively. No correlation could be established between WFS1 gene mutations and specific point mutations or rearrangements in mtDNA. We would suggest first screening for the 16-bp insertion in exon 4 when a new Spanish WS case is reported.

[Wolfram syndrome. Urologic implications]

OBJECTIVES

We report on four new cases of Wolfram's Syndrome. We emphasize in urological aspects of this disease.

PATIENTS AND METHODS

Three male siblings. The other patient is also a male, without familiar relation with the other ones. All four patients presents different levels of urological alterations, mainly urinary collecting system dilation and decrease in detrusor muscle contractility.

CONCLUSIONS

Urological findings are cardinal aspects in Wolfram syndrome. Due to its high frequency and prognostic value in natural history of disease. Urological disease seems to be within a systemic neurological tissues affectation of etiology that remains unknown.

Early onset of diabetes mellitus associated with the mitochondrial DNA T14709C point mutation: patient report and literature review

We report a family in which a mother and son were affected with diabetes mellitus and myopathy characterized by ragged red fibers and suggestive of mitochondrial disease. Mitochondrial DNA (mtDNA) analysis of DNA isolated from peripheral blood showed a T-->C point mutation at nucleotide position 14709, in the transfer RNA gene for glutamic acid. We review the association of diabetes and mtDNA mutations. This child's case is unusual because of the early onset of diabetes, which is more typical of mtDNA deletions.

Optic atrophy in Wolfram (DIDMOAD) syndrome

Wolfram syndrome is the association of diabetes mellitus and optic atrophy, also called DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy and deafness). Incomplete characterisation has caused diagnostic confusion; we therefore undertook a nation-wide cross-sectional case finding study. We identified 45 patients with Wolfram syndrome, median age 29 years. All patients fulfilled the ascertainment criteria (juvenile onset diabetes mellitus and optic atrophy). Optic atrophy presented in 38 patients with reduced visual acuity and colour vision defect (median age 11 years), progressing to visual acuity of 6/60 or less in 35 patients (median time 8 years, range 1-25 years). Visual field examinations recorded before acuity deteriorated showed central scotomas with peripheral constriction. Blind patients had absent pupillary reflexes. Horizontal nystagmus was seen in patients with other signs of cerebellar degeneration. There was no pigmentary retinal dystrophy; only 3 patients had background diabetic retinopathy, despite a median duration of diabetes of 24 years. Electroretinography was normal in 3 patients and showed reduced amplitude in 3 patients; visual evoked responses were abnormal (10/10 patients: reduced amplitude to both flash and pattern stimulation). Magnetic resonance imaging showed generalised brain atrophy with reduced signal from the optic nerves and chiasm. A postmortem brain specimen from one patient revealed atrophy of the optic nerves, chiasm, cerebellum and brainstem. We found no evidence of mitochondrial genome defects or rearrangements. This primary neurogenerative disorder presents with diabetes mellitus and progressive optic atrophy, probably due to pathology in the optic nerve.

Analysis of the mitochondrial DNA from patients with Wolfram (DIDMOAD) syndrome

Wolfram or DIDMOAD (Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness) syndrome, which has long been known as an autosomal-recessive disorder, has recently been proposed to be a mitochondrial-mediated disease with either a nuclear or a mitochondrial genetic background. The phenotypic characteristics of the syndrome resemble those found in other mitochondrial (mt)DNA mediated disorders such as Leber's hereditary optic neuropathy (LHON) or maternally inherited diabetes and deafness (MIDD). Therefore, we looked for respective mtDNA alterations in blood samples from 7 patients with DIDMOAD syndrome using SSCP-analysis of PCR-amplified fragments, encompassing all mitochondrial ND and tRNA genes, followed by direct sequencing. Subsequently, we compared mtDNA variants identified in this disease group with those detected in a group of LHON patients (n = 17) and in a group of 69 healthy controls. We found that 4/7 (57%) DIDMOAD patients harbored a specific set of point mutations in tRNA and ND genes including the so-called class II or secondary LHON mutations at nucleotide positions (nps) 4216 and 4917 (haplogroup B). In contrast, LHON-patients were frequently (10/17, 59%) found in association with another cluster of mtDNA variants including the secondary LHON mutations at nps 4216 and 13708 and further mtDNA polymorphisms in ND genes (haplogroup A), overlapping with haplogroup B only by variants at nps 4216 and 11251. The frequencies of both haplogroups were significantly lower in the control group versus the respective disease groups. We propose that haplogroup B represents a susceptibility factor for DIDMOAD which, by interaction with further exogeneous or genetic factors, might increase the risk for disease.

Non-insulin-dependent diabetes mellitus in childhood and adolescence

NIDDM in children and adolescents represents a heterogeneous group of disorders with different underlying pathophysiologic mechanisms. Most subtypes of NIDDM that occur in childhood are uncommon, but some, such as early onset of "classic" NIDDM, seem to be increasing in prevalence. This observed increase is thought to be caused by societal factors that lead to sedentary lifestyles and an increased prevalence of obesity. In adults, hyperglycemia frequently exists for years before a diagnosis of NIDDM is made and treatment is begun. Microvascular complications, such as retinopathy, are often already present at the time of diagnosis. Children are frequently asymptomatic at the time of diagnosis, so screening for this disorder in high-risk populations is important. Screening should be considered for children of high-risk ethnic populations with a strong family history of NIDDM with obesity or signs of hyperinsulinism, such as acanthosis nigricans. Even for children in these high-risk groups who do not yet manifest hyperglycemia, primary care providers can have an important role in encouraging lifestyle modifications that might delay or prevent onset of NIDDM.

[Alström syndrome--a rare disease of diabetic association]

BACKGROUND

Alström's disease is a rare hereditary multiple-system illness, whereas a second-messenger defect can be assumed.

CASE REPORT

We describe a case-the first in Germany of 15 known cases in the world literature-, who suffers from all clinical features, such as non-insulin-dependent diabetes mellitus, retinitis pigmentosa, pancochlear damage of the ears, hypogonadism, obesity and chronic nephropathy, with the exception of acanthosis nigricans.

CONCLUSION

Because of the multiplicity of affected organs the diagnosis of Alström's disease is difficult.

Wolfram syndrome: hereditary diabetes mellitus with brainstem and optic atrophy

Wolfram syndrome was originally described as a combination of familial juvenile-onset diabetes mellitus and optic atrophy. Other neurological features subsequently emerged, and "DIDMOAD" (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness) became a commonly accepted acronym. Here, we describe 4 further cases from 2 families, in whom there occurred previously unrecognized neurological features, central apnea and neurogenic upper airway collapse, together precipitating primary respiratory failure (fatal in 1 case), startle myoclonus (in 2 unrelated cases), axial rigidity, and Parinaud's syndrome. Magnetic resonance images revealed striking brainstem atrophy affecting, in particular, the pons and midbrain. The mitochondrial DNA from 3 cases (and relatives) showed no evidence of any of the previously reported abnormalities. These neurological and neuroradiological features, in conjunction with (1) analyses showing the neurodegenerative origin of optic atrophy, deafness, diabetes insipidus, and incontinence, (2) other previously reported neurological complications (including anosmia, ataxia, epilepsy, and neuropsychiatric and cognitive abnormalities), and (3) the very small number of published postmortem studies, indicate that Wolfram syndrome should be reemphasized as a unique hereditary neurodegenerative disorder with prominent optic atrophy and diabetes mellitus.

Neurodegeneration and diabetes: UK nationwide study of Wolfram (DIDMOAD) syndrome

Wolfram syndrome is the association of diabetes mellitus and optic atrophy, and is sometimes called DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness). Incomplete characterisation of this autosomal recessive syndrome has relied on case-reports, and there is confusion with mitochondrial genome disorders. We therefore undertook a UK nationwide cross-sectional case-finding study to describe the natural history, complications, prevalence, and inheritance of the syndrome. We identified 45 patients with Wolfram syndrome--a prevalence of one per 770,000. Non-autoimmune, insulin-deficient diabetes mellitus presented at a median age of 6 years, followed by optic atrophy (11 years). Cranial diabetes insipidus occurred in 33 patients (73%) with sensorineural deafness (28, 62%) in the second decade; renal-tract abnormalities (26, 58%) presented in the third decade followed by neurological complications (cerebellar ataxia, myoclonus [28, 62%]) in the fourth decade. Other abnormalities included gastrointestinal dysmotility in 11 (24%), and primary gonadal atrophy in seven of ten males investigated. Median age at death (commonly central respiratory failure with brain-stem atrophy) was 30 years (range 25-49). The natural history of Wolfram syndrome suggests that most patients will eventually develop most complications of this progressive, neurodegenerative disorder. Family studies indicate autosomal recessive inheritance with a carrier frequency of one in 354, an absence of a maternal history of diabetes or deafness, and an absence of the mitochondrial tRNA Leu (3243) mutation. Juvenile-onset diabetes mellitus and optic atrophy are the best available diagnostic criteria for Wolfram syndrome, the differential diagnosis of which includes other causes of neurodegeneration.

Mitochondrial diabetes mellitus: a review

We review the relationship between various types of mitochondrial DNA mutations and the prevalence as well as the pathobiochemical and clinical features of mitochondrial diabetes mellitus. An A to G transversion mutation in the tRNA(Leu(UUR)) gene is associated with diabetes in about 1.5% of the diabetic population in different countries and races. Phenotypically this type of mitochondrial diabetes is combined with deafness in more than 60% and is clinically distinguishable with respect to several characteristics from the two idiopathic forms of diabetes. The underlying pathomechanism is probably a delayed insulin secretion due to an impaired mitochondrial ATP production in consequence of the mtDNA defect.

Wolfram syndrome. A report of four cases and review of the literature

This is a report of four new cases of Wolfram syndrome in three families and a review of the literature. The ophthalmologic, urologic, otologic, psychiatric and endocrine findings of the syndrome are discussed as well as their pathophysiology. Two recent reports with features atypical of the Wolfram syndrome are discussed. The genetics of this syndrome are also discussed.