Presenilins, Notch dose control the fate of pancreatic endocrine progenitors during a narrow developmental window.

Canonical Notch signaling is thought to control the endocrine/exocrine decision in early pancreatic progenitors. Later, RBP-Jkappa interacts with Ptf1a and E12 to promote acinar differentiation. To examine the involvement of Notch signaling in selecting specific endocrine lineages, we deregulated this pathway by targeted deletion of presenilin1 and presenilin2, the catalytic core of gamma-secretase, in Ngn3- or Pax6-expressing endocrine progenitors. Surprisingly, whereas Pax6(+) progenitors were irreversibly committed to the endocrine fate, we discovered that Ngn3(+) progenitors were bipotential in vivo and in vitro. When presenilin amounts are limiting, Ngn3(+) progenitors default to an acinar fate; subsequently, they expand rapidly to form the bulk of the exocrine pancreas. gamma-Secretase inhibitors confirmed that enzymatic activity was required to block acinar fate selection by Ngn3 progenitors. Genetic interactions identified Notch2 as the substrate, and suggest that gamma-secretase and Notch2 act in a noncanonical titration mechanism to sequester RBP-Jkappa away from Ptf1a, thus securing selection of the endocrine fate by Ngn3 progenitors. These results revise the current view of pancreatic cell fate hierarchy, establish that Ngn3 is not in itself sufficient to commit cells to the endocrine fate in the presence of Ptf1a, reveal a noncanonical action for Notch2 protein in endocrine cell fate selection, and demonstrate that acquisition of an endocrine fate by Ngn3(+) progenitors is gamma-secretase-dependent until Pax6 expression begins.

Common variants in WFS1 confer risk of type 2 diabetes.

We studied genes involved in pancreatic beta cell function and survival, identifying associations between SNPs in WFS1 and diabetes risk in UK populations that we replicated in an Ashkenazi population and in additional UK studies. In a pooled analysis comprising 9,533 cases and 11,389 controls, SNPs in WFS1 were strongly associated with diabetes risk. Rare mutations in WFS1 cause Wolfram syndrome; using a gene-centric approach, we show that variation in WFS1 also predisposes to common type 2 diabetes.

Genetic deficiency of glycogen synthase kinase-3beta corrects diabetes in mouse models of insulin resistance.

Despite treatment with agents that enhance beta-cell function and insulin action, reduction in beta-cell mass is relentless in patients with insulin resistance and type 2 diabetes mellitus. Insulin resistance is characterized by impaired signaling through the insulin/insulin receptor/insulin receptor substrate/PI-3K/Akt pathway, leading to elevation of negatively regulated substrates such as glycogen synthase kinase-3beta (Gsk-3beta). When elevated, this enzyme has antiproliferative and proapoptotic properties. In these studies, we designed experiments to determine the contribution of Gsk-3beta to regulation of beta-cell mass in two mouse models of insulin resistance. Mice lacking one allele of the insulin receptor (Ir+/-) exhibit insulin resistance and a doubling of beta-cell mass. Crossing these mice with those having haploinsufficiency for Gsk-3beta (Gsk-3beta+/-) reduced insulin resistance by augmenting whole-body glucose disposal, and significantly reduced beta-cell mass. In the second model, mice missing two alleles of the insulin receptor substrate 2 (Irs2-/-), like the Ir+/- mice, are insulin resistant, but develop profound beta-cell loss, resulting in early diabetes. We found that islets from these mice had a 4-fold elevation of Gsk-3beta activity associated with a marked reduction of beta-cell proliferation and increased apoptosis. Irs2-/- mice crossed with Gsk-3beta+/- mice preserved beta-cell mass by reversing the negative effects on proliferation and apoptosis, preventing onset of diabetes. Previous studies had shown that islets of Irs2-/- mice had increased cyclin-dependent kinase inhibitor p27(kip1) that was limiting for beta-cell replication, and reduced Pdx1 levels associated with increased cell death. Preservation of beta-cell mass in Gsk-3beta+/- Irs2-/- mice was accompanied by suppressed p27(kip1) levels and increased Pdx1 levels. To separate peripheral versus beta-cell-specific effects of reduction of Gsk3beta activity on preservation of beta-cell mass, mice homozygous for a floxed Gsk-3beta allele (Gsk-3(F/F)) were then crossed with rat insulin promoter-Cre (RIP-Cre) mice to produce beta-cell-specific knockout of Gsk-3beta (betaGsk-3beta-/-). Like Gsk-3beta+/- mice, betaGsk-3beta-/- mice also prevented the diabetes of the Irs2-/- mice. The results of these studies now define a new, negatively regulated substrate of the insulin signaling pathway specifically within beta-cells that when elevated, can impair replication and increase apoptosis, resulting in loss of beta-cells and diabetes. These results thus form the rationale for developing agents to inhibit this enzyme in obese insulin-resistant individuals to preserve beta-cells and prevent diabetes onset.

Increased dosage of mammalian Sir2 in pancreatic beta cells enhances glucose-stimulated insulin secretion in mice.

Sir2 NAD-dependent deacetylases connect transcription, metabolism, and aging. Increasing the dosage or activity of Sir2 extends life span in yeast, worms, and flies and promotes fat mobilization and glucose production in mammalian cells. Here we show that increased dosage of Sirt1, the mammalian Sir2 ortholog, in pancreatic beta cells improves glucose tolerance and enhances insulin secretion in response to glucose in beta cell-specific Sirt1-overexpressing (BESTO) transgenic mice. This phenotype is maintained as BESTO mice age. Pancreatic perfusion experiments further demonstrate that Sirt1 enhances insulin secretion in response to glucose and KCl. Microarray analyses of beta cell lines reveal that Sirt1 regulates genes involved in insulin secretion, including uncoupling protein 2 (Ucp2). Isolated BESTO islets also have reduced Ucp2, increased ATP production, and enhanced insulin secretion during glucose and KCl stimulation. These findings establish the importance of Sirt1 in beta cell function in vivo and suggest therapeutic interventions for type 2 diabetes.

Variants in the CD36 gene associate with the metabolic syndrome and high-density lipoprotein cholesterol.

A region along chromosome 7q was recently linked to components of the metabolic syndrome (MetS) in several genome-wide linkage studies. Within this region, the CD36 gene, which encodes a membrane receptor for long-chain fatty acids and lipoproteins, is a potentially important candidate. CD36 has been documented to play an important role in fatty acid metabolism in vivo and subsequently may be involved in the etiology of the MetS. The protein also impacts survival to malaria and the influence of natural selection has resulted in high CD36 genetic variability in populations of African descent. We evaluated 36 tag SNPs across CD36 in the HyperGen population sample of 2020 African-Americans for impact on the MetS and its quantitative traits. Five SNPs associated with increased odds for the MetS [P = 0.0027-0.03, odds ratio (OR) = 1.3-1.4]. Coding SNP, rs3211938, previously shown to influence malaria susceptibility, is documented to result in CD36 deficiency in a homozygous subject. This SNP conferred protection against the MetS (P = 0.0012, OR = 0.61, 95%CI: 0.46-0.82), increased high-density lipoprotein cholesterol, HDL-C (P = 0.00018) and decreased triglycerides (P = 0.0059). Fifteen additional SNPs associated with HDL-C (P = 0.0028-0.044). We conclude that CD36 variants may impact MetS pathophysiology and HDL metabolism, both predictors of the risk of heart disease and type 2 diabetes.

Genetic epidemiology of diabetes.

Conventional genetic analysis focuses on the genes that account for specific phenotypes, while traditional epidemiology is more concerned with the environmental causes and risk factors related to traits. Genetic epidemiology is an alliance of the 2 fields that focuses on both genetics, including allelic variants in different populations, and environment, in order to explain exactly how genes convey effects in different environmental contexts and to arrive at a more complete comprehension of the etiology of complex traits. In this review, we discuss the epidemiology of diabetes and the current understanding of the genetic bases of obesity and diabetes and provide suggestions for accelerated accumulation of clinically useful genetic information.

A global approach to identify differentially expressed genes in cDNA (two-color) microarray experiments.

MOTIVATION: Currently most of the methods for identifying differentially expressed genes fall into the category of so called single-gene-analysis, performing hypothesis testing on a gene-by-gene basis. In a single-gene-analysis approach, estimating the variability of each gene is required to determine whether a gene is differentially expressed or not. Poor accuracy of variability estimation makes it difficult to identify genes with small fold-changes unless a very large number of replicate experiments are performed. RESULTS: We propose a method that can avoid the difficult task of estimating variability for each gene, while reliably identifying a group of differentially expressed genes with low false discovery rates, even when the fold-changes are very small. In this article, a new characterization of differentially expressed genes is established based on a theorem about the distribution of ranks of genes sorted by (log) ratios within each array. This characterization of differentially expressed genes based on rank is an example of all-gene-analysis instead of single gene analysis. We apply the method to a cDNA microarray dataset and many low fold-changed genes (as low as 1.3 fold-changes) are reliably identified without carrying out hypothesis testing on a gene-by-gene basis. The false discovery rate is estimated in two different ways reflecting the variability from all the genes without the complications related to multiple hypothesis testing. We also provide some comparisons between our approach and single-gene-analysis based methods. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Glucose regulates Foxo1 through insulin receptor signaling in the pancreatic islet beta-cell.

Glucose controls islet beta-cell mass and function at least in part through the phosphatidylinositol 3-kinase (PI3K)/Akt pathway downstream of insulin signaling. The Foxo proteins, transcription factors known in other tissues to be negatively regulated by Akt activation, affect proliferation and metabolism. In this study, we tested the hypothesis that glucose regulates Foxo1 activity in the beta-cell via an autocrine/paracrine effect of released insulin on its receptor. Mouse insulinoma cells (MIN6) were starved overnight for glucose (5 mmol/l) then refed with glucose (25 mmol/l), resulting in rapid Foxo1 phosphorylation (30 min, P < 0.05 vs. untreated). This glucose response was demonstrated to be time (0.5-2 h) and dose (5-30 mmol/l) dependent. The use of inhibitors demonstrated that glucose-induced Foxo1 phosphorylation was dependent upon depolarization, calcium influx, and PI3K signaling. Additionally, increases in glucose concentration over a physiological range (2.5-20 mmol/l) resulted in nuclear to cytoplasmic translocation of Foxo1. Phosphorylation and translocation of Foxo1 following glucose refeeding were eliminated in an insulin receptor knockdown cell line, indicating that the glucose effects are mediated primarily through the insulin receptor. Activity of Foxo1 was observed to increase with decreased glucose concentrations, assessed by an IGF binding protein-1 promoter luciferase assay. Starvation of MIN6 cells identified a putative Foxo1 target, Chop, and a Chop-promoter luciferase assay in the presence of cotransfected Foxo1 supported this hypothesis. The importance of these observations was that nutritional alterations in the beta-cell are associated with changes in Foxo1 transcriptional activity and that these changes are predominantly mediated through glucose-stimulated insulin secretion acting through its own receptor.

Defective insulin secretion and increased susceptibility to experimental diabetes are induced by reduced Akt activity in pancreatic islet beta cells.

The insulin and IGF signaling pathways are critical for development and maintenance of pancreatic beta cell mass and function. The serine-threonine kinase Akt is one of several mediators regulated by these pathways. We have studied the role of Akt in pancreatic beta cell physiology by generating transgenic mice expressing a kinase-dead mutant of this enzyme in beta cells. Reduction of Akt activity in transgenic animals resulted in impaired glucose tolerance due to defective insulin secretion. The mechanisms involved in dysregulation of secretion in these mice lie at the level of insulin exocytosis and are not the result of abnormalities in glucose signaling or function of voltage-gated Ca2+ channels. Therefore, transgenic mice showed increased susceptibility to developing glucose intolerance and diabetes following fat feeding. These observations suggest that Akt plays a novel and important role in the regulation of distal components of the secretory pathway and that this enzyme represents a therapeutic target for improvement of beta cell function in diabetes.

Diabetes and insulin secretion: the ATP-sensitive K+ channel (K ATP) connection.

The ATP-sensitive K+ channel (K ATP channel) senses metabolic changes in the pancreatic beta-cell, thereby coupling metabolism to electrical activity and ultimately to insulin secretion. When K ATP channels open, beta-cells hyperpolarize and insulin secretion is suppressed. The prediction that K ATP channel "overactivity" should cause a diabetic state due to undersecretion of insulin has been dramatically borne out by recent genetic studies implicating "activating" mutations in the Kir6.2 subunit of K ATP channel as causal in human diabetes. This article summarizes the emerging picture of K ATP channel as a major cause of neonatal diabetes and of a polymorphism in K ATP channel (E23K) as a type 2 diabetes risk factor. The degree of K ATP channel "overactivity" correlates with the severity of the diabetic phenotype. At one end of the spectrum, polymorphisms that result in a modest increase in K ATP channel activity represent a risk factor for development of late-onset diabetes. At the other end, severe "activating" mutations underlie syndromic neonatal diabetes, with multiple organ involvement and complete failure of glucose-dependent insulin secretion, reflecting K ATP channel "overactivity" in both pancreatic and extrapancreatic tissues.

Endoplasmic reticulum stress-induced apoptosis is partly mediated by reduced insulin signaling through phosphatidylinositol 3-kinase/Akt and increased glycogen synthase kinase-3beta in mouse insulinoma cells.

An imbalance between the rate of protein synthesis and folding capacity of the endoplasmic reticulum (ER) results in stress that has been increasingly implicated in pancreatic islet beta-cell apoptosis and diabetes. Because insulin/IGF/Akt signaling has been implicated in beta-cell survival, we sought to determine whether this pathway is involved in ER stress-induced apoptosis. Mouse insulinoma cells treated with pharmacological agents commonly used to induce ER stress exhibited apoptosis within 48 h. ER stress-induced apoptosis was inhibited by cotreatment of the cells with IGF-1. Stable cell lines were created by small-interfering RNA (siRNA) with graded reduction of insulin receptor expression, and these cells had enhanced susceptibility to ER stress-induced apoptosis and reduced levels of phospho-glycogen synthase kinase 3beta (GSK3beta). In control cells, ER stress-induced apoptosis was associated with a reduction in phospho-Akt and phospho-GSK3beta. To further assess the role of GSK3beta in ER stress-induced apoptosis, stable cell lines were created by siRNA with up to 80% reduction in GSK3beta expression. These cells were found to resist ER stress-induced apoptosis. These results illustrate that ER stress-induced apoptosis is mediated at least in part by signaling through the phosphatidylinositol 3-kinase/Akt/GSK3beta pathway and that GSK3beta represents a novel target for agents to promote beta-cell survival.

Activation of nuclear factor-kappaB by depolarization and Ca(2+) influx in MIN6 insulinoma cells.

The purpose of the current study was to determine whether nuclear factor-kappaB (NF-kappaB) activation is a component of the depolarization/Ca(2+)-dependent signaling in beta-cells. MIN6 cells were transfected with a plasmid containing five tandem repeats of NF-kappaB binding sites linked to a luciferase reporter. The results of these experiments showed that KCl induced depolarization-activated NF-kappaB-dependent transcription (3.8-fold at 45 mmol/l, P < 0.01) in a concentration-dependent manner. Tumor necrosis factor-alpha (TNF-alpha), a known inducer of NF-kappaB signaling, activated this construct by 3.4-fold (P < 0.01). The response of NF-kappaB to depolarization was inhibited by the Ca(2+)-channel blocker verapamil and by the mitogen-activated protein kinase kinase (MEK) inhibitor PD98059 (70 and 62%, respectively). TNF-alpha, glucose, and KCl treatment resulted in inhibitory kappaBalpha degradation by Western blot analysis. TNF-alpha treatment and depolarization activation of NF-kappaB differed significantly in that TNF-alpha activation was not blocked by PD98059. Transfection with PKA, MEK, and MEK kinase induced NF-kappaB-dependent transcription by 20-, 90-, and 300-fold, respectively, suggesting that these pathways contribute to the activation in the depolarization response. These findings demonstrate that depolarization/Ca(2+) influx, as well as TNF-alpha treatment, can activate NF-kappaB-dependent transcription in pancreatic beta-cells, but by different signaling pathways. The current studies show that Ca(2+) signals in pancreatic beta-cells can activate transcription factors involved in the regulation of cell cycle and apoptosis. These findings now add NF-kappaB to the list of depolarization-induced transcription factors in pancreatic beta-cells.

Glucose and insulin treatment of insulinoma cells results in transcriptional regulation of a common set of genes.

Glucose and insulin are important regulators of islet beta-cell growth and function by activating signaling pathways resulting in transcriptional changes that lead to adaptive responses. Several immediate early genes have been shown to be rapidly induced by glucose-activated depolarization in islet beta-cells. The current studies address aspects of glucose-regulated transcription: 1) the number and characteristics of these genes, 2) if depolarization is the major mechanism, and 3) if glucose-stimulated insulin secretion is responsible, because insulin per se can activate transcription. Here, the expression profiles of glucose-responsive insulinoma cells 45 min after the addition of glucose, KCl to induce depolarization, or insulin were assessed by endocrine pancreas cDNA microarrays. Glucose activated more than 90 genes, representing diverse gene ontology functions, and most were not previously known to be glucose responsive. KCl activated 80% of these same glucose-regulated genes and, along with the effects of pretreatment with diazoxide, suggested that glucose signaling is mediated primarily via depolarization. There were >150 genes activated by insulin, and remarkably 71% were also regulated by glucose. Preincubation with a phosphatidylinositol (PI) 3-kinase inhibitor resulted in almost total inhibition of depolarization and insulin-activated transcriptional responses. Thus, through gene expression profiling, these data demonstrate that glucose and insulin rapidly activate a PI 3-kinase pathway, resulting in transcription of a common set of genes. This is consistent with glucose activation of gene transcription either directly or indirectly through a paracrine/autocrine effect via insulin release. These results illustrate that expression gene profiling can contribute to the elucidation of important beta-cell biological functions.

A common polymorphism in the upstream promoter region of the hepatocyte nuclear factor-4 alpha gene on chromosome 20q is associated with type 2 diabetes and appears to contribute to the evidence for linkage in an ashkenazi jewish population.

Variants in hepatocyte nuclear factor-4 alpha (HNF4 alpha), a transcription factor that influences the expression of glucose metabolic genes, have been correlated with maturity-onset diabetes of the young, a monogenic form of diabetes. Previously, in a genome scan of Ashkenazi Jewish type 2 diabetic families, we observed linkage to the chromosome 20q region encompassing HNF4 alpha. Here, haplotype-tag single nucleotide polymorphisms (htSNPs) were identified across a 78-kb region around HNF4 alpha and evaluated in an association analysis of Ashkenazi Jewish type 2 diabetic (n = 275) and control (n = 342) subjects. We found that two of nine htSNPs were associated with type 2 diabetes: a 3' intronic SNP, rs3818247 (29.2% case subjects vs. 21.7% control subjects; P = 0.0028, odds ratio [OR] 1.49) and a 5' htSNP located approximately 3.9 kb upstream of P2, rs1884614 (26.9% case subjects vs. 20.3% control subjects; P = 0.0078, OR 1.45). Testing of additional SNPs 5' of rs1884614 revealed a >10-kb haplotype block that was associated with type 2 diabetes. Conditioning on the probands' rs1884614 genotype suggested that the chromosomal region identified by the htSNP accounted for the linkage signal on chromosome 20q in families in which the proband carried at least one risk allele. Notably, the associations and the partitioned linkage profiles near P2 were independently observed in a Finnish sample, suggesting the presence of potential regulatory element(s) that may contribute to the risk for type 2 diabetes.

Common variants of the hepatocyte nuclear factor-4alpha P2 promoter are associated with type 2 diabetes in the U.K. population.

Hepatocyte nuclear factor (HNF)-4alpha is part of a transcription factor network that is key for the development and function of the beta-cell. Rare mutations in the HNF4alpha gene cause maturity-onset diabetes of the young. A number of type 2 diabetes linkage studies have found evidence of linkage to 20q12-13.1 where the HNF4alpha gene is located. Two recent studies have found an association between four common variants of the alternative P2 promoter region and type 2 diabetes. These variants are in strong linkage disequilibrium, and the minor alleles define one common risk haplotype. In both studies, the risk haplotype explained a large proportion of the evidence of linkage to 20q12-13.1. We aimed to assess this haplotype in a U.K. Caucasian study of 5,256 subjects. We typed two single nucleotide polymorphisms tagging the risk haplotype (rs4810424 and rs2144908) and found evidence of association in both case-control and family-based studies; rs4810424 marginally demonstrated the stronger association with an overall estimated odds ratio of 1.15 (95% CI 1.02-1.33) (P = 0.02). The effect of the P2 haplotype on type 2 diabetes risk is less than in the initial studies, probably reflecting that these studies used 20q12-13.1-linked cases. In conclusion, we have replicated the association of the HNF4alpha P2 promoter haplotype with type 2 diabetes in a U.K. Caucasian population where there is no evidence of linkage to 20q.

Functional genomics of the endocrine pancreas: the pancreas clone set and PancChip, new resources for diabetes research.

Over the past 5 years, microarrays have greatly facilitated large-scale analysis of gene expression levels. Although these arrays were not specifically geared to represent tissues and pathways known to be affected by diabetes, they have been used in both type 1 and type 2 diabetes research. To prepare a tool that is particularly useful in the study of type 1 diabetes, we have assembled a nonredundant set of 3,400 clones representing genes expressed in the mouse pancreas or pathways known to be affected by diabetes. We have demonstrated the usefulness of this clone set by preparing a cDNA glass microarray, the PancChip, and using it to analyze pancreatic gene expression from embryonic day 14.5 through adulthood in mice. The clone set and corresponding array are useful resources for diabetes research.

Transcriptional program of the endocrine pancreas in mice and humans.

The Endocrine Pancreas Consortium was formed in late 1999 to derive and sequence cDNA libraries enriched for rare transcripts expressed in the mammalian endocrine pancreas. Over the past 3 years, the Consortium has generated 20 cDNA libraries from mouse and human pancreatic tissues and deposited >150,000 sequences into the public expressed sequence tag databases. A special effort was made to enrich for cDNAs from the endocrine pancreas by constructing libraries from isolated islets. In addition, we constructed a library in which fetal pancreas from Neurogenin 3 null mice, which consists of only exocrine and duct cells, was subtracted from fetal wild-type pancreas to enrich for the transcripts from the endocrine compartment. Sequence analysis showed that these clones cluster into 9,464 assembly groups (approximating unique transcripts) for the mouse and 13,910 for the human sequences. Of these, >4,300 were unique to Consortium libraries. We have assembled a core clone set containing one cDNA for each assembly group for the mouse and have constructed the corresponding microarray, termed "PancChip 4.0," which contains >9,000 nonredundant elements. We show that this PancChip is highly enriched for genes expressed in the endocrine pancreas. The mouse and human clone sets and corresponding arrays will be important resources for diabetes research.

Assessing allele frequencies of single nucleotide polymorphisms in DNA pools by pyrosequencing technology.

Single nucleotide polymorphism (SNP) association studies searching for differences in allele frequencies between cases and controls have been widely used for genetic analysis. Individual genotyping is prohibitively expensive in large sample sizes. Pooling of samples provides the obvious advantage of higher throughput and lower cost. Here we report our results with the analysis of SNP allele frequencies in DNA pools using Pyrosequencing technology. For seven different SNPs, we observed a mean difference of 1.1 +/- 0.6% between allele frequencies determined in two different DNA pools (n = 150 cases and 150 controls) compared to individually genotyped samples.

Phenotypic characteristics of early Wolfram syndrome.

BACKGROUND: Wolfram Syndrome (WFS:OMIM 222300) is an autosomal recessive, progressive, neurologic and endocrinologic degenerative disorder caused by mutations in the WFS1 gene, encoding the endoplasmic reticulum (ER) protein wolframin, thought to be involved in the regulation of ER stress. This paper reports a cross section of data from the Washington University WFS Research Clinic, a longitudinal study to collect detailed phenotypic data on a group of young subjects in preparation for studies of therapeutic interventions. METHODS: Eighteen subjects (ages 5.9-25.8, mean 14.2 years) with genetically confirmed WFS were identified through the Washington University International Wolfram Registry. Examinations included: general medical, neurologic, ophthalmologic, audiologic, vestibular, and urologic exams, cognitive testing and neuroimaging. RESULTS: Seventeen (94%) had diabetes mellitus with the average age of diabetes onset of 6.3 ± 3.5 years. Diabetes insipidus was diagnosed in 13 (72%) at an average age of 10.6 ± 3.3 years. Seventeen (94%) had optic disc pallor and defects in color vision, 14 (78%) had hearing loss and 13 (72%) had olfactory defects, eight (44%) had impaired vibration sensation. Enuresis was reported by four (22%) and nocturia by three (17%). Of the 11 tested for bladder emptying, five (45%) had elevated post-void residual bladder volume. CONCLUSIONS: WFS causes multiple endocrine and neurologic deficits detectable on exam, even early in the course of the disease. Defects in olfaction have been underappreciated. The proposed mechanism of these deficits in WFS is ER stress-induced damage to neuronal and hormone-producing cells. This group of subjects with detailed clinical phenotyping provides a pool for testing proposed treatments for ER stress. Longitudinal follow-up is necessary for establishing the natural history and identifying potential biomarkers of progression.

Balance impairment in individuals with Wolfram syndrome.

AIM: Wolfram syndrome (WFS), a rare neurodegenerative disorder, is characterized by early onset insulin-dependent diabetes mellitus, optic atrophy, deafness, diabetes insipidus, and neurological abnormalities. Although previously unreported, we hypothesized that neurological complications may be detectable in relatively early stages of the disease. As the cerebellum and brainstem seem particularly vulnerable in WFS, we focused on balance functions critically dependent on these regions. The primary goal of this investigation was to compare balance in young individuals with WFS, in relatively early stages of the disease, to an age-matched cohort using a clinically applicable test. METHOD: Balance was assessed via the mini-BESTest in 13 children, adolescents and young adults with WFS and 30 typically developing age-matched individuals. RESULTS: A significant difference was observed between groups in balance as well as in three of four subcomponents of the mini-BESTest and in two timed tasks related to balance. Mini-BESTest scores were correlated with age among typically developing individuals. In the WFS group, mini-BESTest scores were related to overall motor dysfunction, but not age. INTERPRETATION: Impairments in balance in WFS may occur earlier in the disease process than previously recognized and appear to be related to overall neurological progression rather than chronological age. Recognizing balance impairments and understanding which balance systems contribute to balance deficits in those with WFS may allow for development of effective patient-centered treatment paradigms.