Genetic variations in the WFS1 gene in Japanese with type 2 diabetes and bipolar disorder

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.

Psychiatric Diagnoses and Medications in Wolfram Syndrome

Background

Wolfram Syndrome is a rare genetic disorder usually resulting from pathogenic variation in the WFS1 gene, which leads to an exaggerated endoplasmic reticulum (ER) stress response. The disorder is typically characterized by diabetes insipidus, diabetes mellitus, optic nerve atrophy, hearing loss, and neurodegenerative features. Existing literature suggests it may also have psychiatric manifestations.

Objective

To examine lifetime psychiatric diagnoses and medication history in Wolfram Syndrome.

Method

Child, adolescent, and young adult Wolfram Syndrome participants (n=39) were assessed by a child & adolescent psychiatrist to determine best estimate DSM-5 lifetime psychiatric diagnoses as well as psychoactive medication history. In addition, the Child & Adolescent Symptom Inventory-5 (CASI-5) Parent Checklist was used to determine likely psychiatric diagnoses based on symptom counts in Wolfram Syndrome patients (n=33), type 1 diabetes (n=15), and healthy comparison (n=18) groups.

Results

Study participants with Wolfram Syndrome had high lifetime rates of anxiety disorders (77%). Also, 31% had an obsessive-compulsive spectrum disorder, 33% had a mood disorder, 31% had a neurodevelopmental or disruptive behavior disorder, and 31% had a sleep-wake disorder. More than half of Wolfram Syndrome participants had taken at least one psychoactive medication, and one third had taken at least one selective serotonin reuptake inhibitor (SSRI). Some individuals reported poor response to sertraline but better response after switching to another SSRI (fluoxetine or citalopram). In general, people with Wolfram Syndrome often reported benefit from psychotherapy and/or commonly used psychoactive medications appropriate for their psychiatric diagnoses.

Conclusions

Wolfram Syndrome may be associated with elevated risk for anxiety and obsessive-compulsive spectrum disorders, which seem generally responsive to usual treatments for these disorders.

Identification of a missense variant in the WFS1 gene that causes a mild form of Wolfram syndrome and is associated with risk for type 2 diabetes in Ashkenazi Jewish individuals

AIMS/HYPOTHESIS

Wolfram syndrome is a rare, autosomal recessive syndrome characterised by juvenile-onset diabetes and optic atrophy and is caused by bi-allelic mutations in the WFS1 gene. In a recent sequencing study, an individual with juvenile-onset diabetes was observed to be homozygous for a rare missense variant (c.1672C>T, p.R558C) in the WFS1 gene. The aim of this study was to perform the genetic characterisation of this variant and to determine whether it is causal for young-onset diabetes and Wolfram syndrome.

METHODS

We analysed the allele frequency of the missense variant in multiple variant databases. We genotyped the variant in 475 individuals with type 1 diabetes and 2237 control individuals of Ashkenazi Jewish ancestry and analysed the phenotypes of homozygotes. We also investigated the association of this variant with risk for type 2 diabetes using genotype and sequence data for type 2 diabetes cases and controls.

RESULTS

The missense variant demonstrated an allele frequency of 1.4% in individuals of Ashkenazi Jewish ancestry, 60-fold higher than in other populations. Genotyping of this variant in 475 individuals diagnosed with type 1 diabetes identified eight homozygotes compared with none in 2237 control individuals (genotype relative risk 135.3, p = 3.4 × 10^-15). The age at diagnosis of diabetes for these eight individuals (17.8 ± 8.3 years) was several times greater than for typical Wolfram syndrome (5 ± 4 years). Further, optic atrophy was observed in only one of the eight individuals, while another individual had the Wolfram syndrome-relevant phenotype of neurogenic bladder. Analysis of sequence and genotype data in two case-control cohorts of Ashkenazi ancestry demonstrated that this variant is also associated with an increased risk of type 2 diabetes in heterozygotes (OR 1.81, p = 0.004).

CONCLUSIONS/INTERPRETATION

We have identified a low-frequency coding variant in the WFS1 gene that is enriched in Ashkenazi Jewish individuals and causes a mild form of Wolfram syndrome characterised by young-onset diabetes and reduced penetrance for optic atrophy. This variant should be considered for genetic testing in individuals of Ashkenazi ancestry diagnosed with young-onset non-autoimmune diabetes and should be included in Ashkenazi carrier screening panels.

No association between wolframin gene H611R polymorphism and mood disorders: evidence from 2,570 subjects

BACKGROUND

In the past few decades, a number of studies have investigated the association of the wolframin (WFS1) gene H611R polymorphism with mood disorders, but the findings are not always consistent.

AIMS

The objective of the present study is to assess the association between WFS1 gene H611R polymorphism and mood disorders by using a meta-analysis.

METHODS

A comprehensive literature search of PubMed, Excerpta Medica Database, Elsevier Science Direct and China National Knowledge Infrastructure databases was conducted to identify relevant articles, with the last report up to April 15, 2014. Pooled odds ratio (OR) with 95% confidence interval (CI) was estimated.

RESULTS

Seven studies including 1318 cases and 1252 controls were selected from potentially relevant articles. This meta-analysis showed that there was no significant association between WFS1 gene H611R polymorphism and mood disorders (R vs. H: OR = 0.93, 95% CI = 0.82-1.05, P = 0.22; HR+ RR vs. HH: OR = 0.98, 95% CI = 0.82-1.17, P = 0.80; RR vs. HH+ HR: OR = 0.84, 95% CI = 0.67-1.04, P = 0.11; RR vs. HH: OR = 0.86, 95% CI = 0.67-1.10, P = 0.24; HR vs. HH: OR = 1.03, 95% CI = 0.78-1.36, P = 0.83). In subgroup analyses by ethnicity, we did not detect any significant association of this polymorphism with mood disorders in Caucasian and Asian populations (P > 0.05). In subgroup analyses by types of mood disorders, we also did not detect any significant association of this polymorphism with bipolar disorder or major depressive disorder (P > 0.05).

CONCLUSIONS

The results of this meta-analysis suggest that there is no association between WFS1 gene H611R polymorphism and mood disorders.

Common biological mechanisms between bipolar disorder and type 2 diabetes: Focus on inflammation

INTRODUCTION

Bipolar disorder (BD) patients present a 3-5 fold greater risk of developing type 2 diabetes (T2D) compared to general population. The underlying mechanisms for the increased prevalence of T2D in BD population are poorly understood.

OBJECTIVES

The purpose of this review is to critically review evidence suggesting that inflammation may have an important role in the development of both BD and T2D.

RESULTS

The literature covered in this review suggests that inflammatory dysregulation take place among many BD patients. Such dysregulated and low grade chronic inflammatory process may also increase the prevalence of T2D in BD population. Current evidence supports the hypothesis of dysregulated inflammatory processes as a critical upstream event in BD as well as in T2D.

CONCLUSIONS

Inflammation may be a factor for the development of T2D in BD population. The identification of inflammatory markers common to these two medical conditions will enable researchers and clinicians to better understand the etiology of BD and develop treatments that simultaneously target all aspects of this multi-system condition.

Association of aggression with a novel microRNA binding site polymorphism in the wolframin gene

Rare mutations in the WFS1 gene lead to Wolfram syndrome, a severe multisystem disorder with progressive neurodegeneration and diabetes mellitus causing life-threatening complications and premature death. Only a few association studies using small clinical samples tested the possible effects of common WFS1 gene variants on mood disorders and suicide, the non-clinical spectrum has not been studied yet. Self-report data on Aggression, Impulsiveness, Anxiety, and Depression were collected from a large (N = 801) non-psychiatric sample. Single nucleotide polymorphisms (SNPs) were selected to provide an adequate coverage of the entire WFS1 gene, as well as to include putative microRNA binding site polymorphisms. Molecular analysis of the assumed microRNA binding site variant was performed by an in vitro reporter-gene assay of the cloned 3' untranslated region with coexpression of miR-668. Among the 17 WFS1 SNPs, only the rs1046322, a putative microRNA (miR-668) binding site polymorphism showed significant association with psychological dimensions after correction for multiple testing: those with the homozygous form of the minor allele reported higher aggression on the Buss-Perry Aggression Questionnaire (P = 0.0005). Functional effect of the same SNP was also demonstrated in a luciferase reporter system: the minor A allele showed lower repression compared to the major G allele, if co-expressed with miR-668. To our knowledge, this is the first report describing a microRNA binding site polymorphism of the WFS1 gene and its association with human aggression based on a large, non-clinical sample.

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.

The genetics of bipolar disorder: genome 'hot regions,' genes, new potential candidates and future directions

Bipolar disorder (BP) is a complex disorder caused by a number of liability genes interacting with the environment. In recent years, a large number of linkage and association studies have been conducted producing an extremely large number of findings often not replicated or partially replicated. Further, results from linkage and association studies are not always easily comparable. Unfortunately, at present a comprehensive coverage of available evidence is still lacking. In the present paper, we summarized results obtained from both linkage and association studies in BP. Further, we indicated new potential interesting genes, located in genome 'hot regions' for BP and being expressed in the brain. We reviewed published studies on the subject till December 2007. We precisely localized regions where positive linkage has been found, by the NCBI Map viewer (http://www.ncbi.nlm.nih.gov/mapview/); further, we identified genes located in interesting areas and expressed in the brain, by the Entrez gene, Unigene databases (http://www.ncbi.nlm.nih.gov/entrez/) and Human Protein Reference Database (http://www.hprd.org); these genes could be of interest in future investigations. The review of association studies gave interesting results, as a number of genes seem to be definitively involved in BP, such as SLC6A4, TPH2, DRD4, SLC6A3, DAOA, DTNBP1, NRG1, DISC1 and BDNF. A number of promising genes, which received independent confirmations, and genes that have to be further investigated in BP, have been also systematically listed. In conclusion, the combination of linkage and association approaches provided a number of liability genes. Nevertheless, other approaches are required to disentangle conflicting findings, such as gene interaction analyses, interaction with psychosocial and environmental factors and, finally, endophenotype investigations.

Autosomal dominant transmission of diabetes and congenital hearing impairment secondary to a missense mutation in the WFS1 gene

AIMS

Mutations of the WFS1 gene have been implicated in autosomal dominant diseases, such as low-frequency sensorineural hearing impairment (LFSNHI) and/or diabetes mellitus and/or optic atrophy. The aim was to investigate WFS1 gene sequences in a family with diabetes mellitus and hearing impairment.

METHODS

Three members of a family with a maternally inherited combination of diabetes mellitus and hearing impairment, but no specific mutations in its mitochondrial genome, were investigated for mutations in the WFS1 gene.

RESULTS

This pedigree, in which the proband had non-insulin-dependent diabetes mellitus and congenital hearing impairment and his mother a triple combination of diabetes mellitus, hearing impairment and optic atrophy, was found to be associated with autosomal dominant transmission of the E864K mutation of the WFS1 gene.

CONCLUSIONS

In the light of this confirmatory study, we recommend the systematic analysis of WFS1 gene sequences in patients with parentally inherited diabetes mellitus and deafness (+/- optic atrophy), in particular when diabetogenic mtDNA mutations have been excluded.

A novel mutation in the WFS1 gene identified in a Taiwanese family with low-frequency hearing impairment

Background

Wolfram syndrome gene 1 (WFS1) accounts for most of the familial nonsyndromic low-frequency sensorineural hearing loss (LFSNHL) which is characterized by sensorineural hearing losses equal to and below 2000 Hz. The current study aimed to contribute to our understanding of the molecular basis of LFSNHL in an affected Taiwanese family.

Methods

The Taiwanese family with LFSNHL was phenotypically characterized using audiologic examination and pedigree analysis. Genetic characterization was performed by direct sequencing of WFS1 and mutation analysis.

Results

Pure tone audiometry confirmed that the family members affected with LFSNHL had a bilateral sensorineural hearing loss equal to or below 2000 Hz. The hearing loss threshold of the affected members showed no progression, a characteristic that was consistent with a mutation in the WFS1 gene located in the DFNA6/14/38 locus. Pedigree analysis showed a hereditarily autosomal dominant pattern characterized by a full penetrance. Among several polymorphisms, a missense mutation Y669H (2005T>C) in exon 8 of WFS1 was identified in members of a Taiwanese family diagnosed with LFSNHL but not in any of the control subjects.

Conclusion

We discovered a novel heterozygous missense mutation in exon 8 of WFS1 (i.e., Y669H) which is likely responsible for the LFSNHL phenotype in this particular Taiwanese family.

Bipolar disorder and diabetes mellitus: epidemiology, etiology, and treatment implications

INTRODUCTION

Bipolar disorder (BD) is a highly prevalent and disabling condition with significant mortality risk from suicide and other unnatural causes. This ignominious description is alongside recent observations that the majority of excess deaths in BD are secondary to medical comorbidity. The medical burden in BD is associated with a clustering of risk factors (e.g., obesity, smoking, unhealthy dietary habits) and inadequate utilization of preventative and primary healthcare. Diabetes mellitus (DM) is also a prevalent multifactorial disease which imparts substantial illness burden. Preliminary investigations indicate that patients who suffer from BD with comorbid DM have a more severe course and outcome, lower quality of life, higher prevalence of medical comorbidity and higher cost of illness.

METHODS

We conducted a MedLine search of all English-language articles 1966-2004 using the key words: bipolar disorder, major depressive disorder, diabetes mellitus, glucose metabolism, mortality, overweight, obesity, body mass index. The search was supplemented with manual review of relevant references. Priority was given to randomized controlled data, when unavailable; studies of sufficient sample size are presented.

RESULTS

Subpopulations of BD patients should be considered at high risk for DM. The prevalence of DM in BD may be three times greater than in the general population.

CONCLUSIONS

Bipolar disorder populations may be an at-risk group for glucose metabolic abnormalities. Opportunistic screening and vigilance for clinical presentations suggestive of DM is encouraged.