Clinical and molecular characterization of a novel INS mutation identified in patients with MODY phenotype

Focusing on Rare Variants Related to Maturity-Onset Diabetes of the Young in Children

Background: In this study, we analysed the clinical and genetic characteristics and follow-up data of patients with maturity-onset diabetes of the young (MODY). Methods: From January 2015 to December 2022, patients with persistent hyperglycaemia suspected of having monogenic diabetes or diabetes syndrome were recruited, and next-generation sequencing (NGS) was performed at the Shanghai Children's Medical Center. Patients' clinical and laboratory findings were recorded preceding follow-ups. Candidate variants were verified using Sanger sequencing. Variant pathogenicity was evaluated according to the American College of Medical Genetics and Genomics (ACMG) guidelines. Results: Genetic testing was performed in 175 children. MODY-related pathogenic or likely pathogenic gene variants were identified in 30 patients from different families. Of these, 11 were diagnosed with GCK-MODY (36.7%), six with INS-MODY (20%), five with HNF1A-MODY (16.7%), five with ABCC8-MODY (16.7%), two with HNF1B-MODY (6.7%) and one with HNF4A-MODY (3.3%). There was one shift variant and seven splice-site variants, and the rest were missense variants. We discovered six novel variants. Of the 30 patients, 63.3% had a family history of diabetes, 13.3% had diabetic ketoacidosis (DKA), and 16.7% had positive diabetes-associated autoantibodies. The diabetes phenotype of patients with the INS variant was similar to that of patients with type 1 diabetes. All patients, including those having positive autoantibodies, required long-term insulin therapy during follow-ups. Four patients with the ABCC8 variant were unable to switch to oral sulfonylurea therapy and continued insulin therapy. Conclusion: Genetic testing is helpful for the precise diagnosis and treatment of patients with MODY, including those with DKA history and positive diabetes autoantibody. GCK-MODY is the most common type of MODY, and patients with INS variant account for a relatively large proportion of MODY cases in our cohort.

A Unique Phenotype of Maturity-Onset Diabetes of the Young With a Novel Disease-Causing Insulin Gene Variant

Maturity-onset diabetes of the young (MODY) represents 1% to 5% of patients with diabetes mellitus (DM), and numerous genes associated with MODY have been identified. While mutations of the insulin gene (INS) are known to cause permanent neonatal DM, rare disease-causing variants have also been found in MODY. These patients demonstrate variable clinical phenotypes-from milder forms requiring lifestyle or oral agent interventions to severe forms requiring lifelong insulin. We present a case of MODY arising from a novel disease-causing INS variant, in an adolescent with atypical features. He was obese with clinical evidence of insulin resistance, diagnosed with DM through opportunistic oral glucose tolerance testing. He developed symptomatic hyperglycemia with worsening glycemic trend, requiring treatment with high-dose insulin and metformin. After 2.5 years, his glycemic profile normalized following weight loss, and pharmacotherapy was discontinued. Targeted gene testing revealed a de novo novel missense variant in exon 2 of the INS gene (p.His29Tyr), confirmed using bidirectional Sanger sequencing. Insulin resistance in patients with MODY can worsen their clinical course and increase risks of long-term complications. Management of these patients should be individualized. This case highlights the utility of genetic testing in diagnosing uncommon and variable forms of MODY, particularly those with atypical features.

Hierarchical Negative Sampling Based Graph Contrastive Learning Approach for Drug-Disease Association Prediction

Predicting potential drug-disease associations (RDAs) plays a pivotal role in elucidating therapeutic strategies for diseases and facilitating drug repositioning, making it of paramount importance. However, existing methods are constrained and rely heavily on limited domain-specific knowledge, impeding their ability to effectively predict candidate associations between drugs and diseases. Moreover, the simplistic definition of unknown information pertaining to drug-disease relationships as negative samples presents inherent limitations. To overcome these challenges, we introduce a novel hierarchical negative sampling-based graph contrastive model, termed HSGCLRDA, which aims to forecast latent associations between drugs and diseases. In this study, HSGCLRDA integrates the association information as well as similarity between drugs, diseases and proteins. Meanwhile, the model constructs a drug-disease-protein heterogeneous network. Subsequently, employing a hierarchical structural sampling technique, we establish reliable negative drug-disease samples utilizing PageRank algorithms. Utilizing meta-path aggregation within the heterogeneous network, we derive low-dimensional representations for drugs and diseases, thereby constructing global and local feature graphs that capture their interactions comprehensively. To obtain representation information, we adopt a self-supervised graph contrastive approach that leverages graph convolutional networks (GCNs) and second-order GCNs to extract feature graph information. Furthermore, we integrate a contrastive cost function derived from the cross-entropy cost function, facilitating holistic model optimization. Experimental results obtained from benchmark datasets not only showcase the superior performance of HSGCLRDA compared to various baseline methods in predicting RDAs but also emphasize its practical utility in identifying novel potential diseases associated with existing drugs through meticulous case studies.

Maturity-onset diabetes of the young type 10 caused by an Ala2Thr mutation of INS: A case report

BACKGROUND

Maturity-onset diabetes of the young 10 caused by the c.4G>A (p.Ala2Thr) mutation is extremely rare, with only two reported studies to date. Herein, we report another case that differs from previous cases in phenotype.

CASE SUMMARY

The proband developed diabetes at the age of 27 years, despite having a normal body mass index (BMI). She exhibited partial impairment of islet function, tested positive for islet antibodies, and required high doses of insulin. Her sister also carried the c.4G>A (p.Ala2Thr) mutation, and their mother was strongly suspected to carry the mutated gene. Her sister developed diabetes around 40 years of age and required high doses of insulin, while the mother was diagnosed in her 20s and was managed with oral hypoglycemic agents; neither of them were obese.

CONCLUSION

p.Ala2Thr mutation carriers often experience relatively later onset and normal BMI. Treatment regimens vary between individuals.

Early-onset diabetes in Africa: A mini-review of the current genetic profile

Early-onset diabetes is poorly diagnosed partly due to its heterogeneity and variable presentations. Although several genes have been associated with the disease, these genes are not well studied in Africa. We sought to identify the major neonatal, early childhood, juvenile, or early-onset diabetes genes in Africa; and evaluate the available molecular methods used for investigating these gene variants. A literature search was conducted on PubMed, Scopus, Africa-Wide Information, and Web of Science databases. The retrieved records were screened and analyzed to identify genetic variants associated with early-onset diabetes. Although 319 records were retrieved, 32 were considered for the current review. Most of these records (22/32) were from North Africa. The disease condition was genetically heterogenous with most cases possessing unique gene variants. We identified 22 genes associated with early-onset diabetes, 9 of which had variants (n = 19) classified as pathogenic or likely pathogenic (PLP). Among the PLP variants, IER3IP1: p.(Leu78Pro) was the variant with the highest number of cases. There was limited data from West Africa, hence the contribution of genetic variability to early-onset diabetes in Africa could not be comprehensively evaluated. It is worth mentioning that most studies were focused on natural products as antidiabetics and only a few studies reported on the genetics of the disease. ABCC8 and KCNJ11 were implicated as major contributors to early-onset diabetes gene networks. Gene ontology analysis of the network associated ion channels, impaired glucose tolerance, and decreased insulin secretions to the disease. Our review highlights 9 genes from which PLP variants have been identified and can be considered for the development of an African diagnostic panel. There is a gap in early-onset diabetes genetic research from sub-Saharan Africa which is much needed to develop a comprehensive, efficient, and cost-effective genetic panel that will be useful in clinical practice on the continent and among the African diasporas.

A Review of the Biosynthesis and Structural Implications of Insulin Gene Mutations Linked to Human Disease

The discovery of the insulin hormone over 100 years ago, and its subsequent therapeutic application, marked a key landmark in the history of medicine and medical research. The many roles insulin plays in cell metabolism and growth have been revealed by extensive investigations into the structure and function of insulin, the insulin tyrosine kinase receptor (IR), as well as the signalling cascades, which occur upon insulin binding to the IR. In this review, the insulin gene mutations identified as causing disease and the structural implications of these mutations will be discussed. Over 100 studies were evaluated by one reviewing author, and over 70 insulin gene mutations were identified. Mutations may impair insulin gene transcription and translation, preproinsulin trafficking and proinsulin sorting, or insulin-IR interactions. A better understanding of insulin gene mutations and the resultant pathophysiology can give essential insight into the molecular mechanisms underlying impaired insulin biosynthesis and insulin-IR interaction.

Next Generation Sequencing Analysis of MODY-X Patients: A Case Report Series

BACKGROUND

Classic criteria for a maturity-onset diabetes of the young (MODY) diagnosis are often unable to identify all subjects, and traditional Sanger sequencing, using a candidate gene approach, leads to a high prevalence of missed genetic diagnosis, classified as MODY-X. Next generation sequencing (NGS) panels provide a highly sensitive method even for rare forms.

METHODS

We investigated 28 pediatric subjects suspected for MODY-X, utilizing a 15-gene NGS panel for monogenic diabetes (MD).

RESULTS

NGS detected variants of uncertain significance (VUS), likely pathogenic or pathogenic for rarer subtypes of MODY, in six patients. We found variants in the wolframin gene (WFS1), traditionally not considered in MD genetic screening panels, in three patients; KCNJ11 gene mutation, typically responsible for neonatal diabetes and rarely causing isolated diabetes in adolescents; INS gene mutation; a variant in the HNF1B gene in a young male with diabetes on sulfonylurea treatment.

CONCLUSION

In our cohort, the availability of an NGS panel for MD was determined for the correct identification of MD subtypes in six patients with MODY-X. Our study underlines how a precise diagnosis utilizing NGS may have an impact on the management of different forms of MODY and, thus, lead to a tailored treatment and enable genetic counselling of other family members.

Precision Diagnosis of Maturity-Onset Diabetes of the Young with Next-Generation Sequencing: Findings from the MODY-IST Study in Adult Patients

Maturity-onset diabetes of the young (MODY) is a highly heterogeneous group of monogenic and nonautoimmune diseases. Misdiagnosis of MODY is a widespread problem and about 5% of patients with type 2 diabetes mellitus and nearly 10% with type 1 diabetes mellitus may actually have MODY. Using next-generation DNA sequencing (NGS) to facilitate accurate diagnosis of MODY, this study investigated mutations in 13 MODY genes (HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, and KCNJ11). In addition, we comprehensively investigated the clinical phenotypic effects of the genetic variations identified. Fifty-one adult patients with suspected MODY and 64 healthy controls participated in the study. We identified 7 novel and 10 known missense mutations localized in PDX1, HNF1B, KLF11, CEL, BLK, and ABCC8 genes in 29.4% of the patient sample. Importantly, we report several mutations that were classified as "deleterious" as well as those predicted as "benign." Notably, the ABCC8 p.R1103Q, ABCC8 p.V421I, CEL I336T, CEL p.N493H, BLK p.L503P, HNF1B p.S362P, and PDX1 p.E69A mutations were identified for the first time as causative variants for MODY. More aggressive clinical features were observed in three patients with double- and triple-heterozygosity of PDX1-KLF11 (p.E69A/p.S182R), CEL-ABCC8-KCNJ11 (p.I336, p.G157R/p.R1103Q/p.A157A), and HNF1B-KLF11 (p.S362P/p.P261L). Interestingly, the clinical effects of the BLK mutations appear to be exacerbated in the presence of obesity. In conclusion, NGS analyses of the adult patients with suspected MODY appear to be informative in a clinical context. These findings warrant further clinical diagnostic research and development in different world populations suffering from diabetes with genetic underpinnings.

Genetic Etiology of Neonatal Diabetes Mellitus in Vietnamese Infants and Characteristics of Those With INS Gene Mutations

BACKGROUND

Neonatal diabetes mellitus (NDM) is a rare (1:90,000 newborns) but potentially devastating metabolic disorder characterized by hyperglycemia combined with low levels of insulin. Dominantly-acting insulin (INS) gene mutations cause permanent NDM through single amino acid changes in the protein sequence leading to protein misfolding, which is retained within the endoplasmic reticulum (ER), causing ER stress and β-cell apoptosis. Over 90 dominantly-acting INS gene mutations have been identified in individuals with permanent NDM.

PATIENTS AND METHODS

The study included 70 infants diagnosed with NDM in the first year of life between May 2008 and May 2021 at the Vietnam National Children's Hospital. Sequencing analysis of all the genes known to cause NDM was performed at the Exeter Genomic Laboratory, UK. Clinical characteristics, molecular genetics, and annual data relating to glycemic control (HbA1c) and severe hypoglycemia of those with INS mutations were collected. The main outcomes of interest were HbA1c, daily insulin dose, growth, and cognitive/motor development.

RESULTS

Fifty-five of 70 infants (78.5%) with NDM harbored a mutation in a known disease-causing gene and of these, 10 had six different de novo heterozygous INS mutations. Mean gestational age was 38.1 ± 2.5 weeks and mean birth weight was 2.8 ± 0.5 g. They presented with NDM at 20 ± 17 weeks of age; 6/10 had diabetic ketoacidosis with pH 7.13 ± 0.26; plasma glucose level 32.6 ± 14.3 mmol/l and HbA1C 81 ± 15% mmol/mol. After 5.5 ± 4.8 years of insulin treatment, 9/10 have normal development with a developmental quotient of 80-100% and HbA1C 64 ± 7.3 mmol/mol, 9/10 have normal height, weight, and BMI on follow-up.

CONCLUSIONS

We report a series of Vietnamese NDM cases with dominant INS mutations. INS mutations are the third commonest cause of permanent NDM. We recommend screening of the INS gene in all children diagnosed with diabetes in the first year of life.

Diabetes Mellitus Diagnosed in Childhood and Adolescence With Negative Autoimmunity: Results of Genetic Investigation

Monogenic diabetes is a rare form of diabetes, accounting for approximately 1% to 6% of pediatric diabetes patients. Some types of monogenic diabetes can be misdiagnosed as type 1 diabetes in children or adolescents because of similar clinical features. Identification of the correct etiology of diabetes is crucial for clinical, therapeutic, and prognostic issues. Our main objective was to determine the prevalence of monogenic diabetes in patients with diabetes mellitus, diagnosed in childhood or in adolescence, and negative autoimmunity. We retrospectively analyzed clinical data of 275 patients diagnosed with insulin-dependent diabetes at age <18yr in the last 10 years. 8.4% of subjects has negative autoimmunity. Their DNA was sequenced by NGS custom panel composed by 45 candidate genes involved in glucose metabolism disorder. Two novel heterozygous pathogenic or likely pathogenic variants (10,5% of autoantibody negative subjects) were detected: the frameshift variant c.617_618insA in NEUROD1 exon 2 and the missense change c.116T>C in INS exon 2. Our study corroborates previous results of other reports in literature. NGS assays are useful methods for a correct diagnosis of monogenic diabetes, even of rarest forms, highlighting mechanisms of pediatric diabetes pathogenesis.

Causal variants in Maturity Onset Diabetes of the Young (MODY) - A systematic review

BACKGROUND

Maturity Onset Diabetes of the Young (MODY) is an autosomal dominant type of diabetes. Pathogenic variants in fourteen genes are reported as causes of MODY. Its symptoms overlap with type 1 and type 2 diabetes. Reviews for clinical characteristics, diagnosis and treatments are available but a comprehensive list of genetic variants, is lacking. Therefore this study was designed to collect all the causal variants involved in MODY, reported to date.

METHODS

We searched PubMed from its date of inception to December 2019. The search terms we used included disease names and name of all the known genes involved. The ClinVar database was also searched for causal variants in the known 14 MODY genes.

RESULTS

The record revealed 1647 studies and among them, 326 studies were accessed for full-text. Finally, 239 studies were included, as per our inclusion criteria. A total of 1017 variants were identified through literature review and 74 unpublished variants from Clinvar database. The gene most commonly affected was GCK, followed by HNF1a. The traditional Sanger sequencing was used in 76 % of the cases and 65 % of the studies were conducted in last 10 years. Variants from countries like Jordan, Oman and Tunisia reported that the MODY types prevalent worldwide were not common in their countries.

CONCLUSIONS

We expect that this paper will help clinicians interpret MODY genetics results with greater confidence. Discrepancies in certain middle-eastern countries need to be investigated as other genes or factors, like consanguinity may be involved in developing diabetes.

Distinct states of proinsulin misfolding in MIDY

A precondition for efficient proinsulin export from the endoplasmic reticulum (ER) is that proinsulin meets ER quality control folding requirements, including formation of the Cys(B19)–Cys(A20) “interchain” disulfide bond, facilitating formation of the Cys(B7)–Cys(A7) bridge. The third proinsulin disulfide, Cys(A6)–Cys(A11), is not required for anterograde trafficking, i.e., a “lose-A6/A11” mutant [Cys(A6), Cys(A11) both converted to Ser] is well secreted. Nevertheless, an unpaired Cys(A11) can participate in disulfide mispairings, causing ER retention of proinsulin. Among the many missense mutations causing the syndrome of Mutant INS gene-induced Diabetes of Youth (MIDY), all seem to exhibit perturbed proinsulin disulfide bond formation. Here, we have examined a series of seven MIDY mutants [including G(B8)V, Y(B26)C, L(A16)P, H(B5)D, V(B18)A, R(Cpep + 2)C, E(A4)K], six of which are essentially completely blocked in export from the ER in pancreatic β-cells. Three of these mutants, however, must disrupt the Cys(A6)–Cys(A11) pairing to expose a critical unpaired cysteine thiol perturbation of proinsulin folding and ER export, because when introduced into the proinsulin lose-A6/A11 background, these mutants exhibit native-like disulfide bonding and improved trafficking. This maneuver also ameliorates dominant-negative blockade of export of co-expressed wild-type proinsulin. A growing molecular understanding of proinsulin misfolding may permit allele-specific pharmacological targeting for some MIDY mutants.

In celebration of a century with insulin - Update of insulin gene mutations in diabetes

Background

While insulin has been central to the pathophysiology and treatment of patients with diabetes for the last 100 years, it has only been since 2007 that genetic variation in the INS gene has been recognised as a major cause of monogenic diabetes. Both dominant and recessive mutations in the INS gene are now recognised as important causes of neonatal diabetes and offer important insights into both the structure and function of insulin. It is also recognised that in rare cases, mutations in the INS gene can be found in patients with diabetes diagnosed outside the first year of life.

Scope of Review

This review examines the genetics and clinical features of monogenic diabetes resulting from INS gene mutations from the first description in 2007 and includes information from 389 patients from 292 families diagnosed in Exeter with INS gene mutations. We discuss the implications for diagnosing and treating this subtype of monogenic diabetes.

Major Conclusions

The dominant mutations in the INS gene typically affect the secondary structure of the insulin protein, usually by disrupting the 3 disulfide bonds in mature insulin. The resulting misfolded protein results in ER stress and beta-cell destruction. In contrast, recessive INS gene mutations typically result in no functional protein being produced due to reduced insulin biosynthesis or loss-of-function mutations in the insulin protein. There are clinical differences between the two genetic aetiologies, between the specific mutations, and within patients with identical mutations.

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Dominant and recessive mutations in the insulin (INS) gene are important causes of neonatal diabetes.

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Associated phenotypes are variable in terms of age at diabetes onset, birth weight and treatment requirements.

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Dominant mutations affect the secondary structure of the insulin protein, resulting in beta-cell ER stress and destruction.

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Recessive mutations result in reduced insulin biosynthesis or loss-of-function mutations of the insulin protein.

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The studies of these forms of diabetes offer important insights into the structure, biosynthesis and secretion of insulin.

Clinical features, complications and treatment of rarer forms of maturity-onset diabetes of the young (MODY) - A review

Maturity onset diabetes of the young (MODY) is the most common form of monogenic diabetes and is currently believed to have 14 subtypes. While much is known about the common subtypes of MODY (MODY-1, 2, 3 and 5) little is known about its rare subtypes (MODY4, 6-14). With the advent of next-generation sequencing (NGS) there are several reports of the rarer subtypes of MODY emerging from across the world. Therefore, a greater understanding on these rarer subtypes is needed. A search strategy was created, and common databases were searched, and 51 articles finally selected. INS-(MODY10) and ABCC8-(MODY12) mutations were reported in relatively large numbers compared to the other rare subtypes. The clinical characteristics of the rare MODY subtypes exhibited heterogeneity between families reported with the same mutation. Obesity and diabetic ketoacidosis (DKA) were also reported among rarer MODY subtypes which presents as a challenge as these are not part of the original description of MODY by Tattersal and Fajans. The treatment modalities of the rarer subtypes included oral drugs, predominantly sulfonylureas, insulin but also diet alone. Newer drugs like DPP-4 and SGLT2 inhibitors have also been tried as new modes of treatment. The microvascular and macrovascular complications among the patients with various MODY subtypes are less commonly reported. Recently, there is a view that not all the 14 forms of 'MODY' are true MODY and the very existence of some of these rarer subtypes as MODY has been questioned. This scoping review aims to report on the clinical characteristics, treatment and complications of the rarer MODY subtypes published in the literature.

An Exploratory Association Analysis of the Insulin Gene Region With Diabetes Mellitus in Two Dog Breeds

Samoyeds and Australian Terriers are the 2 dog breeds at highest risk (>10-fold) for diabetes mellitus in the United States. It is unknown if the insulin (INS) gene is involved in the pathophysiology of diabetes in Samoyeds and Australian Terriers. It was hypothesized that the INS gene region provides a common genetic causality for diabetes in Samoyeds and Australian Terriers. We conducted a 2-stage genetic association study involving both breeds. In the discovery stage (Stage 1), Samoyeds with and without diabetes were compared in the frequencies of 447 tagging single-nucleotide polymorphisms (SNPs) within 2.5 megabases (Mb) up- and downstream of the INS gene on the Illumina CanineHD BeadChip. SNPs yielding a P-value < 0.005 were selected for further follow-up. In the validation stage (Stage 2), Australian Terriers with and without diabetes were compared in the SNPs genotyped by the Affymetrix GeneChip Canine Genome 2.0 Array and within 1 Mb up- and downstream of the selected SNPs from Stage 1. Two SNPs that were in high linkage disequilibrium (LD, r2 = 0.7) were selected from Stage 1. In Stage 2, among the 76 SNPs examined, 5 were significantly associated with diabetes after Bonferroni's correction for multiple comparisons. Three of these 5 SNPs were in complete LD (r2 = 1 for all associations) and the 2 remaining SNPs were in moderate LD (r2 = 0.4). In conclusion, an association between the INS gene region and diabetes was suggested in 2 dog breeds of different clades. This region could have importance in diabetes in other breeds or in canine diabetes at large.

Molecular diagnosis of maturity-onset diabetes of the young in a cohort of Chinese children

OBJECTIVE

The purpose of this study was to investigate the molecular basis of maturity-onset diabetes of the young (MODY) by whole-exome sequencing (WES) and estimate the frequency and describe the clinical characteristics of MODY in southern China.

METHODS

Genetic analysis was performed in 42 patients with MODY aged 1 month to 18 years among a cohort of 759 patients with diabetes, identified with the following four clinical criteria: age of diagnosis ≤18 years; negative pancreatic autoantibodies; family history of diabetes; or persistently detectable C-peptide; or diabetes associated with extrapancreatic features. GCK gene mutations were first screened by Sanger sequencing. GCK mutation-negative patients were further analyzed by WES.

RESULTS

Mutations were identified in 24 patients: 20 mutations in GCK, 1 in HNF4A, 1 in INS, 1 in ABCC8, and a 17q12 microdeletion. Four previously unpublished novel GCK mutations: c.1108G>C in exon 9, and c.1339C>T, c.1288_1290delCTG, and c.1340_1343delGGGGinsCTGGTCT in exon 10 were detected. WES identified a novel missense mutation c.311A>G in exon 3 in the INS gene, and copy number variation analysis detected a 1.4 Mb microdeletion in the long arm of the chromosome 17q12 region. Compared with mutation-negative subjects, the mutation-positive subjects had lower hemoglobin A1c and initial blood glucose levels.

CONCLUSIONS

Most MODY cases in this study were due to GCK mutations, which is in contrast to previous reports in Chinese patients. Diabetes associated with extrapancreatic features should be a clinical criterion for MODY genetic analysis. Mutational analysis by WES provided a precise diagnosis of MODY subtypes. Moreover, WES can be useful for detecting large deletions in coding regions in addition to point mutations.

A homozygous mutation in the insulin gene (INS) causing autosomal recessive neonatal diabetes in Saudi families

PURPOSE

Insulin gene (INS) mutations are a rare cause of permanent neonatal diabetes and mature-onset diabetes of the young (MODY10). Homozygous mutations have been reported to cause diabetes by decreasing insulin biosynthesis through distinct mechanisms. In this study, we report a homozygous mutation c.-331C>G in the INS gene causing autosomal recessive neonatal diabetes in Saudi families and share our experience with diagnosis and management.

METHODS

We retrospectively reviewed all cases diagnosed with diabetes during the first week of life. We identified 18 cases, and all underwent genetic testing to identify the cause. Most had mutations in common genes (9 in KCNJ11 and 5 in ABCC8). The inclusion criterion for this study was a mutation in the INS gene.

RESULTS

Four patients from 3 Saudi families had mutations in the INS gene. All patients were born with low birth weight and were diagnosed with neonatal diabetes at the age of 2 days. Sanger sequencing analysis identified a homozygous INS pathogenic promoter variant, c.-331C>G. All patients were managed by insulin therapy. Two patients had persistent diabetes and in 2 cases diabetes resolved.

CONCLUSION

This report indicates that a homozygous mutation in the INS gene is a probable and important cause of neonatal diabetes in Saudi Arabia. The c.-331C>G variant in the INS gene identified in our study showed variability both within and between families and different outcomes ranging from early resolution of diabetes after 2 months of life to permanent diabetes.

Monogenic Forms of Diabetes Mellitus

In addition to the common types of diabetes mellitus, two major monogenic diabetes forms exist. Maturity-onset diabetes of the young (MODY) represents a heterogenous group of monogenic, autosomal dominant diseases. MODY accounts for 1-2% of all diabetes cases, and it is not just underdiagnosed but often misdiagnosed to type 1 or type 2 diabetes. More than a dozen MODY genes have been identified to date, and their molecular classification is of great importance in the correct treatment decision and in the judgment of the prognosis. The most prevalent subtypes are HNF1A, GCK, and HNF4A. Genetic testing for MODY has changed recently due to the technological advancements, as contrary to the sequential testing performed in the past, nowadays all MODY genes can be tested simultaneously by next-generation sequencing. The other major group of monogenic diabetes is neonatal diabetes mellitus which can be transient or permanent, and often the diabetes is a part of a syndrome. It is a severe monogenic disease appearing in the first 6 months of life. The hyperglycemia usually requires insulin. There are two forms, permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). In TNDM, the diabetes usually reverts within several months but might relapse later in life. The incidence of NDM is 1:100,000-1:400,000 live births, and PNDM accounts for half of the cases. Most commonly, neonatal diabetes is caused by mutations in KCNJ11 and ABCC8 genes encoding the ATP-dependent potassium channel of the β cell. Neonatal diabetes has experienced a quick and successful transition into the clinical practice since the discovery of the molecular background. In case of both genetic diabetes groups, recent guidelines recommend genetic testing.

Whole-exome sequencing identifies a novel INS mutation causative of maturity-onset diabetes of the young 10

Monogenic diabetes is often misdiagnosed with type 2 diabetes due to overlapping characteristics. This study aimed to discover novel causative mutations of monogenic diabetes in patients with clinically diagnosed type 2 diabetes and to explore potential molecular mechanisms. Whole-exome sequencing was performed on 31 individuals clinically diagnosed with type 2 diabetes. One novel heterozygous mutation (p.Ala2Thr) in INS was identified. It was further genotyped in an additional case-control population (6523 cases and 4635 controls), and this variant was observed in 0.09% of cases. Intracellular trafficking of insulin proteins was assessed in INS1-E and HEK293T cells. p.Ala2Thr preproinsulin-GFP was markedly retained in the endoplasmic reticulum (ER) in INS1-E cells. Activation of the PERK-eIF2α-ATF4, IRE1α-XBP1, and ATF6 pathways as well as upregulated ER chaperones were detected in INS1-E cells transfected with the p.Ala2Thr mutant. In conclusion, we identified a causative mutation in INS responsible for maturity-onset diabetes of the young 10 (MODY10) in a Chinese population and demonstrated that this mutation affected β cell function by inducing ER stress.

Comprehensive screening for monogenic diabetes in 89 Japanese children with insulin-requiring antibody-negative type 1 diabetes

BACKGROUND

Mutations in causative genes for neonatal diabetes or maturity-onset diabetes of the young have been identified in multiple patients with autoantibody-negative type 1 diabetes (T1D).

OBJECTIVES

We aimed to clarify the prevalence and phenotypic characteristics of monogenic abnormalities among 89 children with autoantibody-negative insulin-requiring T1D.

METHODS

Mutations in 30 genes were screened using next-generation sequencing, and copy-number alterations of 4 major causative genes were examined using multiplex-ligation-dependent probe amplification. We compared the clinical characteristics between mutation carriers and non-carriers.

RESULTS

We identified 11 probable pathogenic substitutions (6 in INS , 2 in HNF1A , 2 in HNF4A , and 1 in HNF1B ) in 11 cases, but no copy-number abnormalities. Only 2 mutation carriers had affected parents. De novo occurrence was confirmed for 3 mutations. The non-carrier group, but not the carrier group, was enriched with susceptible HLA alleles. Mutation carriers exhibited comparable phenotypes to those of non-carriers, except for a relatively normal body mass index (BMI) at diagnosis.

CONCLUSIONS

This study demonstrated significant genetic overlap between autoantibody-negative T1D and monogenic diabetes. Mutations in INS and HNF genes, but not those in GCK and other monogenic diabetes genes, likely play critical roles in children with insulin-requiring T1D. This study also suggests the relatively high de novo rates of INS and HNF mutations, and the etiological link between autoimmune abnormalities and T1D in the non-carrier group. Carriers of monogenic mutations show non-specific phenotypes among all T1D cases, although they are more likely to have a normal BMI at diagnosis than non-carriers.

NGS Technologies as a Turning Point in Rare Disease Research , Diagnosis and Treatment

Approximately 25-50 million Americans, 30 million Europeans, and 8% of the Australian population have a rare disease. Rare diseases are thus a common problem for clinicians and account for enormous healthcare costs worldwide due to the difficulty of establishing a specific diagnosis. In this article, we review the milestones achieved in our understanding of rare diseases since the emergence of next-generation sequencing (NGS) technologies and analyze how these advances have influenced research and diagnosis. The first half of this review describes how NGS has changed diagnostic workflows and provided an unprecedented, simple way of discovering novel disease-associated genes. We focus particularly on metabolic and neurodevelopmental disorders. NGS has enabled cheap and rapid genetic diagnosis, highlighted the relevance of mosaic and de novo mutations, brought to light the wide phenotypic spectrum of most genes, detected digenic inheritance or the presence of more than one rare disease in the same patient, and paved the way for promising new therapies. In the second part of the review, we look at the limitations and challenges of NGS, including determination of variant causality, the loss of variants in coding and non-coding regions, and the detection of somatic mosaicism variants and epigenetic mutations, and discuss how these can be overcome in the near future.

Involvement of stanniocalcins in the deregulation of glycaemia in obese mice and type 2 diabetic patients

Stanniocalcins are expressed in the pancreas tissue, and it was suggested a direct correlation between circulating insulin and STC2 concentrations in human. Here, we show a significant correlation between STC1 and both glycaemia and glycosylated haemoglobin among DM2 patients, while DM2 patients who present the greatest glycosylated haemoglobin values exhibited the lowest STC2 expression. However, treatment of patients with antiglycaemic drugs does not significantly modify the expression of both STCs. On the other hand, STC2-/- mice that exhibited neonatal and adult overweight further presented deregulated glycaemia when they were feed with a hypercaloric diet (breeding pellet, BP). This alteration is more evident at the early stages of the animal life. Deregulated glycaemia in these mice was confirmed using glucose oral test. In addition, STC2-/- mice present enhanced pancreas size; thus, the histological analysis reveals that WT mice respond to BP diet by increasing the size of the pancreatic islets through inducing cell division, and STC2-/- mice lack this compensatory mechanism. Contrary, BP fed STC2-/- mice show enhanced number of islets but of similar size than those fed with regular pellet. Histopathological analysis demonstrates tissue structure disruption and erythrocytes infiltrations in STC2-/- mice, possibly due to the stress evoked by the BP diet. Finally, enhanced glucagon immunostaining was observed in the islet of STC2-/- mice, and the glucagon ELISA assay confirmed the increase in the circulating glucagon. Summarizing, we present evidence of the role of STCs, mainly STC2, as a possible early marker during development of diabetes mellitus.

Familial diabetes of adulthood: A bin of ignorance that needs to be addressed

AIMS

The aim of this article was to share with a wide readership some data and related reasoning about a multigenerational form of diabetes mellitus of adulthood.

DATA SYNTHESIS

We have recently described a familial form of diabetes mellitus, which in the routine clinical setting of adult individuals is simplistically diagnosed as type 2 diabetes. Such misdiagnosis involves as much as 3% of adult unrelated diabetic patients with no evidence of autoimmune disease. More recent data, obtained by means of a next-generation sequencing, indicate that approximately 25% of such patients carry mutations in the genes involved in monogenic diabetes, thus leaving unraveled the molecular causes of the remaining 75% individuals.

CONCLUSIONS

Our proposal is to define the latter patients as being affected by familial diabetes of adulthood (FDA), a clear admission of ignorance and a limbo where adult patients with multigenerational diabetes with no genetic definition of their hyperglycemia have to wait for better times.

Monogenic Diabetes Accounts for 6.3% of Cases Referred to 15 Italian Pediatric Diabetes Centers During 2007 to 2012

CONTEXT

An etiologic diagnosis of diabetes can affect the therapeutic strategy and prognosis of chronic complications.

OBJECTIVE

The aim of the present study was to establish the relative percentage of different diabetes subtypes in patients attending Italian pediatric diabetes centers and the influence of an etiologic diagnosis on therapy.

DESIGN, SETTING, AND PATIENTS

This was a retrospective study. The clinical records of 3781 consecutive patients (age, 0 to 18 years) referred to 15 pediatric diabetes clinics with a diagnosis of diabetes or impaired fasting glucose from January 1, 2007 to December 31, 2012 were examined. The clinical characteristics of the patients at their first referral to the centers, type 1 diabetes-related autoantibodies, molecular genetics records, and C-peptide measurements, if requested for the etiologic diagnosis, were acquired.

MAIN OUTCOME MEASURES

The primary outcome was to assess the percentage of each diabetes subtype in our sample.

RESULTS

Type 1 diabetes represented the main cause (92.4%) of diabetes in this group of patients, followed by monogenic diabetes, which accounted for 6.3% of cases [maturity onset diabetes of the young (MODY), 5.5%; neonatal diabetes mellitus, 0.6%, genetic syndromes, 0.2%]. A genetic diagnosis prompted the transfer from insulin to sulphonylureas in 12 patients bearing mutations in the HNF1A or KCNJ11 genes. Type 2 diabetes was diagnosed in 1% of the patients.

CONCLUSIONS

Monogenic diabetes is highly prevalent in patients referred to Italian pediatric diabetes centers. A genetic diagnosis guided the therapeutic decisions, allowed the formulation of a prognosis regarding chronic diabetic complications for a relevant number of patients (i.e.,GCK/MODY), and helped to provide genetic counseling.