Genetic Dissection and Clinical Features of MODY6 (NEUROD1-MODY)

Monogenic diabetes: An evidence-based clinical approach

Monogenic diabetes is a heterogeneous disorder characterized by hyperglycemia arising from defects in a single gene. Maturity-onset diabetes of the young (MODY) is the most common type with 14 subtypes, each linked to specific mutations affecting insulin synthesis, secretion and glucose regulation. Common traits across MODY subtypes include early-onset diabetes, a family history of autosomal dominant diabetes, lack of features of insulin resistance, and absent islet cell autoimmunity. Many cases are misdiagnosed as type 1 and type 2 diabetes mellitus. Biomarkers and scoring systems can help identify candidates for genetic testing. GCK-MODY, a common subtype, manifests as mild hyperglycemia and doesn’t require treatment except during pregnancy. In contrast, mutations in HNF4A, HNF1A, and HNF1B genes lead to progressive beta-cell failure and similar risks of complications as type 2 diabetes mellitus. Neonatal diabetes mellitus (NDM) is a rare form of monogenic diabetes that usually presents within the first six months. Half of the cases are lifelong, while others experience transient remission. Permanent NDM is most commonly due to activating mutations in genes encoding the adenosine triphosphate-sensitive potassium channel (KCNJ11 or ABCC8) and can be transitioned to sulfonylurea after confirmation of diagnosis. Thus, in many cases, monogenic diabetes offers an opportunity to provide precision treatment. The scope has broadened with next-generation sequencing (NGS) technologies, replacing older methods like Sanger sequencing. NGS can be for targeted gene panels, whole-exome sequencing (WES), or whole-genome sequencing. Targeted gene panels offer specific information efficiently, while WES provides comprehensive data but comes with bioinformatic challenges. The surge in testing has also led to an increase in variants of unknown significance (VUS). Deciding whether VUS is disease-causing or benign can be challenging. Computational models, functional studies, and clinical knowledge help to determine pathogenicity. Advances in genetic testing technologies offer hope for improved diagnosis and personalized treatment but also raise concerns about interpretation and ethics.

A perfect islet: reviewing recent protocol developments and proposing strategies for stem cell derived functional pancreatic islets

The search for an effective cell replacement therapy for diabetes has driven the development of "perfect" pancreatic islets from human pluripotent stem cells (hPSCs). These hPSC-derived pancreatic islet-like β cells can overcome the limitations for disease modelling, drug development and transplantation therapies in diabetes. Nevertheless, challenges remain in generating fully functional and mature β cells from hPSCs. This review underscores the significant efforts made by researchers to optimize various differentiation protocols aimed at enhancing the efficiency and quality of hPSC-derived pancreatic islets and proposes methods for their improvement. By emulating the natural developmental processes of pancreatic embryogenesis, specific growth factors, signaling molecules and culture conditions are employed to guide hPSCs towards the formation of mature β cells capable of secreting insulin in response to glucose. However, the efficiency of these protocols varies greatly among different human embryonic stem cell (hESC) and induced pluripotent stem cell (hiPSC) lines. This variability poses a particular challenge for generating patient-specific β cells. Despite recent advancements, the ultimate goal remains to develop a highly efficient directed differentiation protocol that is applicable across all genetic backgrounds of hPSCs. Although progress has been made, further research is required to optimize the protocols and characterization methods that could ensure the safety and efficacy of hPSC-derived pancreatic islets before they can be utilized in clinical settings.

A case report of a MODY6 patient coexistence with Charcot-Marie-Toothe 1A syndrome

Monogenic diabetes, which encompasses neonatal diabetes (NDM), maturity onset diabetes of the young (MODY), and several diabetes-associated syndromes, primarily arises from impaired function or abnormal development of the islets of Langerhans, particularly pancreatic β-cells responsible for insulin secretion. This condition is typically associated with a single pathogenic genetic mutation. Charcot-Marie-Tooth disease type 1A (CMT1A) is a hereditary demyelinating neuropathy that is caused by a duplication of the PMP22 gene located on chromosome 17. Herein, we report a case of a young Chinese patient with MODY6 harboring a novel mutation (c. 317C>T, p. Ala106Val) in the NEUROD1 gene. Additionally, this patient concurrently presents with CMT1A, which is characterized by a large segmental duplication within the exon of the PMP22 gene and its adjacent regions. Considering the patient's compromised islet function, we treat him with insulin and oral hypoglycemic agents (metformin, acarbose). This represents the first reported instance of a patient with NEUROD1-MODY coexisting with CMT1A.

Monogenic Diabetes: A Comprehensive Overview and Therapeutic Management of Subtypes of Mody

BACKGROUND

Monogenic diabetes often occurs as a result of single-gene mutations. The illness is minimally affected by environmental and behavioral factors, and it constitutes around one to five percent of all cases of diabetes.

METHODS

Newborn diabetes mellitus (NDM) and maturity-onset diabetes of the young (MODY) are the predominant causes of monogenic diabetes, accounting for a larger proportion of cases, while syndromic diabetes represents a smaller percentage. MODY, a group of inherited non-autoimmune diabetes mellitus disorders, is quite common. However, it remains frequently misdiagnosed despite increasing public awareness. The condition is characterized by insulin resistance, the development of diabetes at a young age (before 25 years), mild high blood sugar levels, inheritance in an autosomal dominant pattern, and the preservation of natural insulin production.

RESULTS

Currently, there are 14 distinct subtypes of MODY that have been identified. Each subtype possesses distinct characteristics in terms of their frequency, clinical symptoms, severity of diabetes, related complications, and response to medicinal interventions. Due to the clinical similarities, lack of awareness, and high expense of genetic testing, distinguishing between type I (T1D) and type II diabetes mellitus (T2D) can be challenging, resulting in misdiagnosis of this type of diabetes. As a consequence, a significant number of individuals are being deprived of adequate medical attention. Accurate diagnosis enables the utilization of novel therapeutic strategies and enhances the management of therapy in comparison to type II and type I diabetes.

CONCLUSION

This article offers a concise overview of the clinical subtypes and characteristics of monogenic diabetes. Furthermore, this article discusses the various subtypes of MODY, as well as the process of diagnosing, managing, and treating the condition. It also addresses the difficulties encountered in detecting and treating MODY.

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.

[Research advances in maturity-onset diabetes of the young]

Maturity-onset diabetes of the young (MODY) is a special type of diabetes characterized by clinical features including early onset of diabetes (before 30 years of age), autosomal dominant inheritance, impaired glucose-induced insulin secretion, and hyperglycemia. So far, 14 types of MODY have been reported, accounting for about 1%-5% of the patients with diabetes. MODY often presents with an insidious onset, and although 14 subtypes have been identified for MODY, it is frequently misdiagnosed as type 1 or type 2 diabetes due to overlapping clinical features and high costs and limitations of genetic testing. This article reviews the clinical features of MODY subtypes in order to improve the accuracy of the diagnosis and treatment of MODY.

NEUROD1: transcriptional and epigenetic regulator of human and mouse neuronal and endocrine cell lineage programs

Transcription factors belonging to the basic helix-loop-helix (bHLH) family are key regulators of cell fate specification and differentiation during development. Their dysregulation is implicated not only in developmental abnormalities but also in various adult diseases and cancers. Recently, the abilities of bHLH factors have been exploited in reprogramming strategies for cell replacement therapy. One such factor is NEUROD1, which has been associated with the reprogramming of the epigenetic landscape and potentially possessing pioneer factor abilities, initiating neuronal developmental programs, and enforcing pancreatic endocrine differentiation. The review aims to consolidate current knowledge on NEUROD1's multifaceted roles and mechanistic pathways in human and mouse cell differentiation and reprogramming, exploring NEUROD1 roles in guiding the development and reprogramming of neuroendocrine cell lineages. The review focuses on NEUROD1's molecular mechanisms, its interactions with other transcription factors, its role as a pioneer factor in chromatin remodeling, and its potential in cell reprogramming. We also show a differential potential of NEUROD1 in differentiation of neurons and pancreatic endocrine cells, highlighting its therapeutic potential and the necessity for further research to fully understand and utilize its capabilities.

Maturity-onset diabetes of the young (MODY) - in search of ideal diagnostic criteria and precise treatment

Maturity-onset diabetes of the young (MODY) is a spectrum of clinically heterogenous forms of monogenic diabetes mellitus characterized by autosomal dominant inheritance, onset at a young age, and absence of pancreatic islets autoimmunity. This rare form of hyperglycemia, with clinical features overlapping with type 1 and type 2 diabetes mellitus, has 14 subtypes with differences in prevalence and complications occurrence which tailor therapeutic approach. MODY phenotypes differ based on the gene involved, gene penetrance and expressivity. While MODY 2 rarely leads to diabetic complications and is easily managed with lifestyle interventions alone, more severe subtypes, such as MODY 1, 3, and 6, require an individualized treatment approach to maintain a patient's quality of life and prevention of complications. This review summarizes current evidence on the presentation, diagnosis, and management of MODY, an example of a genetic cause of hyperglycemia that calls for a precision medicine approach.

Identification of gene mutations associated with type 1 diabetes by next-generation sequencing in affected Palestinian families

Introduction: Diabetes Mellitus is a group of metabolic disorders characterized by hyperglycemia secondary to insulin resistance or deficiency. It is considered a major health problem worldwide. T1DM is a result of a combination of genetics, epigenetics, and environmental factors. Several genes have been associated with T1DM, including HLA, INS, CTLA4, and PTPN22. However, none of these findings have been based on linkage analysis because it is rare to find families with several diabetic individuals. Two Palestinian families with several afflicted members with variations in the mode of inheritance were identified and selected for this study. This study aimed to identify the putative causative gene(s) responsible for T1DM development in these families to improve our understanding of the molecular genetics of the disease. Methods: One afflicted member from each family was selected for Whole-Exome Sequencing. Data were mapped to the reference of the human genome, and the resulting VCF file data were filtered. The variants with the highest phenotype correlation score were checked by Sanger sequencing for all family members. The confirmed variants were analyzed in silico by bioinformatics tools. Results: In one family, the IGF1R p.V579F variant, which follows autosomal dominant inheritance, was confirmed and segregated in the family. In another family, the NEUROD1 p.P197H variant, which follows autosomal recessive inheritance, was positively confirmed and segregated. Conclusion: IGF1R p.V579F and NEUROD1 p.P197H variants were associated with T1DM development in the two inflicted families. Further analysis and functional assays will be performed, including the generation of mutant model cell systems, to unravel their specific molecular mechanism in the disease development.

Molecular diagnosis in patients with monogenic diabetes mellitus, and detection of a novel candidate gene

AIM

We aimed to investigate molecular genetic basis of monogenic diabetes (DM) and novel responsible candidate genes with targeted Next Generation Sequencing (NGS) and Whole Exome Sequencing (WES).

METHODS

A hundred cases presenting with clinical findings and a family history of monogenic DM were included in the study. Molecular analysis was performed using an NGS panel including 14 genes. Following targeted NGS, WES was planned in cases in whom no variant was detected.

RESULTS

Thirty different disease-causing variants in seven different genes were detected in thirty-five (35 %) cases with targeted NGS approach. Most common pathogenic variant was found in GCK gene in 25 (25 %) cases. Four different variants were detected in 4 (4 %) patients in ABCC8 gene. In 45 of 65 cases; WES analyses were done. A heterozygous c.2635C > T(p.Gln879Ter) variant was detected in IFIH1 gene in a patient with incidental hyperglycemia. In the segregation analysis affected mother was shown to be heterozygous for the same variant.

CONCLUSION

Molecular etiology was determined in 35 % cases with the NGS targeted panel. Seventeen novel variants in monogenic DM genes have been identified. A candidate gene determined by WES analysis in a case that could not be diagnosed with NGS panel in this study.

NEUROD1 reinforces endocrine cell fate acquisition in pancreatic development

NEUROD1 is a transcription factor that helps maintain a mature phenotype of pancreatic β cells. Disruption of Neurod1 during pancreatic development causes severe neonatal diabetes; however, the exact role of NEUROD1 in the differentiation programs of endocrine cells is unknown. Here, we report a crucial role of the NEUROD1 regulatory network in endocrine lineage commitment and differentiation. Mechanistically, transcriptome and chromatin landscape analyses demonstrate that Neurod1 inactivation triggers a downregulation of endocrine differentiation transcription factors and upregulation of non-endocrine genes within the Neurod1-deficient endocrine cell population, disturbing endocrine identity acquisition. Neurod1 deficiency altered the H3K27me3 histone modification pattern in promoter regions of differentially expressed genes, which resulted in gene regulatory network changes in the differentiation pathway of endocrine cells, compromising endocrine cell potential, differentiation, and functional properties.

Incomplete penetrance and variable expressivity in monogenic diabetes; a challenge but also an opportunity

Monogenic Forms of Diabetes (MFD) account for about 3% of all diabetes, and their accurate diagnosis often results in life-changing therapeutic reassignment for the patients. Like other Mendelian diseases, reduced penetrance and variable expressivity are often seen in several different types of MFD, where symptoms develop only in a portion of the persons who carry the pathogenic variant or vary widely in symptom severity and age of onset. This complicates diagnosis and disease management in MFD. In addition to its clinical importance, knowledge of genetic modifiers that confer penetrance and expressivity variability opens possibilities to identify protective genetic variants which may help probe the mechanisms of more common forms of diabetes and shed light in new therapeutic strategies. In this review, we will mainly address penetrance and expressivity variation in different types of MFD, factors that confer such variations and opportunities that come with such knowledge. Related literature was searched in PubMed, Medline and Embase. Papers with publication year from 1974 to 2023 are included. Data are either sourced from literatures or from OMIM, Clinvar and 1000 genome browser.

From glucose sensing to exocytosis: takes from maturity onset diabetes of the young

Monogenic diabetes gave us simplified models of complex molecular processes occurring within β-cells, which allowed to explore the roles of numerous proteins from single protein perspective. Constellation of characteristic phenotypic features and wide application of genetic sequencing techniques to clinical practice, made the major form of monogenic diabetes - the Maturity Onset Diabetes of the Young to be distinguishable from type 1, type 2 as well as neonatal diabetes mellitus and understanding underlying molecular events for each type of MODY contributed to the advancements of antidiabetic therapy and stem cell research tremendously. The functional analysis of MODY-causing proteins in diabetes development, not only provided better care for patients suffering from diabetes, but also enriched our comprehension regarding the universal cellular processes including transcriptional and translational regulation, behavior of ion channels and transporters, cargo trafficking, exocytosis. In this review, we will overview structure and function of MODY-causing proteins, alterations in a particular protein arising from the deleterious mutations to the corresponding gene and their consequences, and translation of this knowledge into new treatment strategies.

Atypical familial diabetes associated with a novel NEUROD1 nonsense variant

OBJECTIVES

We aimed to identify the origin of atypical diabetes in a family with four generations of diabetes from South Asia. The family members showed different clinical phenotypes. Members of generation one to three were presumed to have type 2 diabetes and generation four to have type 1 diabetes.

CASE PRESENTATION

We performed a genetic analysis of the family using targeted high throughput sequencing.

CONCLUSIONS

We identified a novel nonsense variant in the neurogenic differentiation 1 (NEUROD1) gene, co-segregating with diabetes. The variant was located in the DNA-binding domain, altering a protein residue that was very well conserved among different species.

Disease-causing mutations in genes encoding transcription factors critical for photoreceptor development

Photoreceptor development of the vertebrate visual system is controlled by a complex transcription regulatory network. OTX2 is expressed in the mitotic retinal progenitor cells (RPCs) and controls photoreceptor genesis. CRX that is activated by OTX2 is expressed in photoreceptor precursors after cell cycle exit. NEUROD1 is also present in photoreceptor precursors that are ready to specify into rod and cone photoreceptor subtypes. NRL is required for the rod fate and regulates downstream rod-specific genes including the orphan nuclear receptor NR2E3 which further activates rod-specific genes and simultaneously represses cone-specific genes. Cone subtype specification is also regulated by the interplay of several transcription factors such as THRB and RXRG. Mutations in these key transcription factors are responsible for ocular defects at birth such as microphthalmia and inherited photoreceptor diseases such as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP) and allied dystrophies. In particular, many mutations are inherited in an autosomal dominant fashion, including the majority of missense mutations in CRX and NRL. In this review, we describe the spectrum of photoreceptor defects that are associated with mutations in the above-mentioned transcription factors, and summarize the current knowledge of molecular mechanisms underlying the pathogenic mutations. At last, we deliberate the outstanding gaps in our understanding of the genotype-phenotype correlations and outline avenues for future research of the treatment strategies.

Maturity-Onset Diabetes of the Young: Mutations, Physiological Consequences, and Treatment Options

Maturity-Onset Diabetes of the Young (MODY) is a rare form of diabetes which affects between 1% and 5% of diagnosed diabetes cases. Clinical characterizations of MODY include onset of diabetes at an early age (before the age of 30), autosomal dominant inheritance pattern, impaired glucose-induced secretion of insulin, and hyperglycemia. Presently, 14 MODY subtypes have been identified. Within these subtypes are several mutations which contribute to the different MODY phenotypes. Despite the identification of these 14 subtypes, MODY is often misdiagnosed as type 1 or type 2 diabetes mellitus due to an overlap in clinical features, high cost and limited availability of genetic testing, and unfamiliarity with MODY outside of the medical profession. The primary aim of this review is to investigate the genetic characterization of the MODY subtypes. Additionally, this review will elucidate the link between the genetics, function, and clinical manifestations of MODY in each of the 14 subtypes. In providing this knowledge, we hope to assist in the accurate diagnosis of MODY patients and, subsequently, in ensuring they receive appropriate treatment.

Diabetes Out-of-the-Box: Diabetes Mellitus and Impairment in Hearing and Vision

PURPOSEOF REVIEW

This review aims to provide an update on the etiologies of diabetes that are due to genetic disorders and that co-occur with impaired hearing or vision and to compare them. The potential mechanisms, including novel treatments, will be detailed.

RECENT FINDINGS

Wolfram syndrome, Kearns-Sayre syndrome, thiamine-responsive megaloblastic anemia, and maternally inherited diabetes and deafness are genetic disorders characterized by diabetes, impaired hearing, and vision. They differ in mode of inheritance, age at presentation, and the involvement of other organs; they are often misdiagnosed as type 1 or type 2 diabetes. Suspicion of a genetic diabetes syndrome should be raised when pancreatic autoantibodies are negative, other organs are involved, and family history includes diabetes. Correct diagnosis of the various syndromes is important for tailoring the most advanced treatment, preventing disease progression, and enabling proper genetic counseling.

The application of precision medicine in monogenic diabetes

INTRODUCTION

Monogenic diabetes, a form of diabetes mellitus, is caused by a mutation in a single gene and may account for 1-2% of all clinical forms of diabetes. To date, more than 40 loci have been associated with either isolated or syndromic monogenic diabetes.

AREAS COVERED

While the request of a genetic test is mandatory for cases with diabetes onset in the first 6 months of life, a decision may be difficult for childhood or adolescent diabetes. In an effort to assist the clinician in this task, we have grouped monogenic diabetes genes according to the age of onset (or incidental discovery) of hyperglycemia and described the additional clinical features found in syndromic diabetes. The therapeutic options available are reviewed.

EXPERT OPINION

Technical improvements in DNA sequencing allow for rapid, simultaneous analysis of all genes involved in monogenic diabetes, progressively shrinking the area of unsolved cases. However, the complexity of the analysis of genetic data requires close cooperation between the geneticist and the diabetologist, who should play a proactive role by providing a detailed clinical phenotype that might match a specific disease gene.

First Japanese Family With PDX1-MODY (MODY4): A Novel PDX1 Frameshift Mutation, Clinical Characteristics, and Implications

CONTEXT

The PDX1 gene encodes pancreatic and duodenal homeobox, a critical transcription factor for pancreatic β-cell differentiation and maintenance of mature β-cells. Heterozygous loss-of-function mutations cause PDX1-MODY (MODY4).

CASE DESCRIPTION

Our patient is an 18-year-old lean man who developed diabetes at 16 years of age. Given his early-onset age and leanness, we performed genetic testing. Targeted next-generation sequencing and subsequent Sanger sequencing detected a novel heterozygous frameshift mutation (NM_00209.4:c.218delT. NP_000200.1: p.Leu73Profs*50) in the PDX1 transactivation domain that resulted in loss-of-function and was validated by an in vitro functional study. The proband and his 56-year-old father, who had the same mutation, both showed markedly reduced insulin and gastric inhibitory polypeptide (GIP) secretion compared with the dizygotic twin sister, who was negative for the mutation and had normal glucose tolerance. The proband responded well to sitagliptin, suggesting its utility as a treatment option. Notably, the proband and his father showed intriguing phenotypic differences: the proband had been lean for his entire life but developed early-onset diabetes requiring an antihyperglycemic agent. In contrast, his father was overweight, developed diabetes much later in life, and did not require medication, suggesting the oligogenic nature of PDX1-MODY. A review of all reported cases of PDX1-MODY also showed heterogeneous phenotypes regarding onset age, obesity, and treatment, even in the presence of the same mutation.

CONCLUSIONS

We identified the first Japanese family with PDX1-MODY. The similarities and differences found among the cases highlight the wide phenotypic spectrum of PDX1-MODY.

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.

Exosomal miR-19a decreases insulin production by targeting Neurod1 in pancreatic cancer associated diabetes

BACKGROUND

New onset diabetes mellitus demonstrates a roughly correlation with pancreatic cancer (PaC), which is unique in PaC and was named as PaC-induced DM, but the inner mechanism remains unclear. Exosomes mediate intercellular communication and bearing microRNAs might be direct constituent of effect in target cells.

METHODS AND RESULTS

The isolated exosomes from PaC cells were used to treat pancreatic β cells or the primary mice islets, and the glucose stimulated insulin secretions were measured. We validated the exosomal miR-19a from PaC cells to be an important mediator in the down regulation of insulin secretion by targeting Neurod1, the validated gene involved in insulin secretion, by using the quantitative real-time PCR, western blot, and promoter luciferase activity. The relative insulin, cAMP and Ca²⁺ expressions were also assayed to verify the inverse correlation between cancerous miR-19a and pancreatic islets Neurod1.

CONCLUSIONS

Our study indicated that signal changes between cancer cells and β cells via exosomes might be important in the pathogenesis of PaC-induced DM and supplemented the pathogenesis of PaC-induced DM and provide a possible access of PaC screening strategy.

Monogenic Childhood Diabetes: Dissecting Clinical Heterogeneity by Next-Generation Sequencing in Maturity-Onset Diabetes of the Young

Diabetes is a common disorder with a heterogeneous clinical presentation and an enormous burden on health care worldwide. About 1-6% of patients with diabetes suffer from maturity-onset diabetes of the young (MODY), the most common form of monogenic diabetes with autosomal dominant inheritance. MODY is genetically and clinically heterogeneous and caused by genetic variations in pancreatic β-cell development and insulin secretion. We report here new findings from targeted next-generation sequencing (NGS) of 13 MODY-related genes. A sample of 22 unrelated pediatric patients with MODY and 13 unrelated healthy controls were recruited from a Turkish population. Targeted NGS was performed with Miseq 4000 (Illumina) to identify genetic variations in 13 MODY-related genes: HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, and KCNJ11. The NGS data were analyzed adhering to the Genome Analysis ToolKit (GATK) best practices pipeline, and variant filtering and annotation were performed. In the patient sample, we identified 43 MODY-specific genetic variations that were not present in the control group, including 11 missense mutations and 4 synonymous mutations. Importantly, and to the best of our knowledge, the missense mutations NEUROD1 p.D202E, KFL11 p.R461Q, BLK p.G248R, and KCNJ11 p.S385F were first associated with MODY in the present study. These findings contribute to the worldwide knowledge base on MODY and molecular correlates of clinical heterogeneity in monogenic childhood diabetes. Further comparative population genetics and functional genomics studies are called for, with an eye to discovery of novel diagnostics and personalized medicine in MODY. Because MODY is often misdiagnosed as type 1 or type 2 diabetes mellitus, advances in MODY diagnostics with NGS stand to benefit diabetes overall clinical care as well.

Neuronal Differentiation 1 gene Ala45Thr polymorphism and type 2 diabetes mellitus: A meta-analysis of 7,940 subjects

BACKGROUND AND AIMS

Previous studies have shown that there was a possible relationship between human Neuronal Differentiation 1 (NEUROD1) gene Ala45Thr polymorphism and type 2 diabetes mellitus (T2DM) susceptibility. Nevertheless, no public opinion has been formed because of the conflicting results in the past studies. In order to illuminate the potential association of human NEUROD1 gene Ala45Thr polymorphism and T2DM, the present meta-analysis was conducted.

METHODS AND RESULTS

In the current meta-analysis, 7940 subjects from 14 individual studies were included. The fixed or random effects models were used to evaluate the pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs). The current meta-analysis found a significant association between NEUROD1 gene Ala45Thr polymorphism and T2DM under allelic (OR: 1.21, 95% CI: 1.04-1.41, P = 0.01), dominant (OR: 0.819, 95% CI: 0.734-0.913, P = 3.31 × 10^-4), heterozygous (OR:1.199, 95% CI: 1.068-1.346, P = 0.002), and additive (OR: 1.33, 95% CI: 1.09-1.62, P = 0.004) genetic models.

CONCLUSIONS

NEUROD1 gene Ala45Thr polymorphism was significantly related to T2DM, especially in the Asian population. More particularly, the Thr45 allele carriers of the NEUROD1 gene may be more susceptible to T2DM.

Monogenic diabetes: a gateway to precision medicine in diabetes

Monogenic diabetes refers to diabetes mellitus (DM) caused by a mutation in a single gene and accounts for approximately 1%-5% of diabetes. Correct diagnosis is clinically critical for certain types of monogenic diabetes, since the appropriate treatment is determined by the etiology of the disease (e.g., oral sulfonylurea treatment of HNF1A/HNF4A-diabetes vs. insulin injections in type 1 diabetes). However, achieving a correct diagnosis requires genetic testing, and the overlapping of the clinical features of monogenic diabetes with those of type 1 and type 2 diabetes has frequently led to misdiagnosis. Improvements in sequencing technology are increasing opportunities to diagnose monogenic diabetes, but challenges remain. In this Review, we describe the types of monogenic diabetes, including common and uncommon types of maturity-onset diabetes of the young, multiple causes of neonatal DM, and syndromic diabetes such as Wolfram syndrome and lipodystrophy. We also review methods of prioritizing patients undergoing genetic testing, and highlight existing challenges facing sequence data interpretation that can be addressed by forming collaborations of expertise and by pooling cases.

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.

Tunisian Maturity-Onset Diabetes of the Young: A Short Review and a New Molecular and Clinical Investigation

INTRODUCTION/AIMS

Maturity-Onset Diabetes of the Young (MODY) is a monogenic non-autoimmune diabetes with 14 different genetic forms. MODY-related mutations are rarely found in the Tunisian population. Here, we explored MODY related genes sequences among seventeen unrelated Tunisian probands qualifying the MODY clinical criteria.

MATERIALS AND METHODS

The GCK and HNF1A genes were systematically analyzed by direct sequencing in all probands. Then, clinical exome sequencing of 4,813 genes was performed on three unrelated patients. Among them, 130 genes have been reported to be involved in the regulation of glucose metabolism, β-cell development, differentiation and function. All identified variants were analyzed according to their frequencies in the GnomAD database and validated by direct sequencing.

RESULTS

We identified the previously reported GCK mutation (rs1085307455) in one patient. The clinical features of the MODY2 proband were similar to previous reports. In this study, we revealed rare and novel alterations in GCK (rs780806456) and ABCC8 (rs201499958) genes with uncertain significance. We also found two likely benign alterations in HNF1A (rs1800574) and KLF11 (rs35927125) genes with minor allele frequencies similar to those depicted in public databases. No pathogenic variants have been identified through clinical exome analysis.

CONCLUSIONS

The most appropriate patients were selected, following a strict clinical screening approach, for genetic testing. However, the known MODY1-13 genes could not explain most of the Tunisian MODY cases, suggesting the involvement of unidentified genes in the majority of Tunisian affected families.

Functional Genomics in Pancreatic β Cells: Recent Advances in Gene Deletion and Genome Editing Technologies for Diabetes Research

The inheritance of variants that lead to coding changes in, or the mis-expression of, genes critical to pancreatic beta cell function can lead to alterations in insulin secretion and increase the risk of both type 1 and type 2 diabetes. Recently developed clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) gene editing tools provide a powerful means of understanding the impact of identified variants on cell function, growth, and survival and might ultimately provide a means, most likely after the transplantation of genetically "corrected" cells, of treating the disease. Here, we review some of the disease-associated genes and variants whose roles have been probed up to now. Next, we survey recent exciting developments in CRISPR/Cas9 technology and their possible exploitation for β cell functional genomics. Finally, we will provide a perspective as to how CRISPR/Cas9 technology may find clinical application in patients with diabetes.

Identification of nucleotide polymorphism within the NeuroD1 candidate gene and its association with type 1 diabetes susceptibility in Iranian people by polymerase chain reaction-restriction fragment length polymorphism

Objectives Diabetes is a serious disease, and the number of affected individuals with diabetes is considerably high. The aim of this study is the identification of NeuroD1 Ala45Thr polymorphism and its association with type 1 diabetes susceptibility in Iranian people. Methods Clinical and biochemical characteristics for 146 people (76 diabetics and 70 nondiabetics) were measured, such as fasting blood sugar, triacylglycerol, total cholesterol, age, and weight in each individual. Polymerase chain reaction-restriction fragment length polymorphism technique (MwoI restriction-enzyme) was used for genotyping of the NeuroD1 Ala45Thr polymorphism. Results In this study, the frequency of the A allele in diabetic patients in comparison with the healthy control group had a significantly higher percentage (p < 0.01), whereas diabetic patients had the AA genotype, approximately four times more than the healthy control group (p < 0.01). In addition, we observed that fasting blood sugar had a higher concentration in the AA genotype than in AG + GG genotypes (p < 0.01). Conclusions The A allele may be a risk factor for the expansion of type 1 diabetes in the Iranian population. However, the NeuroD1 Ala45Thr polymorphism and its role in type 1 diabetes in different populations are controversial.

Treatment Options for MODY Patients: A Systematic Review of Literature

Maturity-onset diabetes of the young (MODY) is an unusual form of diabetes with specific features that distinguish it from type 1 and type 2 diabetes. There are 14 known subtypes of MODY, and mutations in three genes (HNF1A, HNF4A, GCK) account for about 95% of all MODY cases. Diagnosis usually occurs before the age of 25 years, although less frequent forms may occur more often-but not necessarily-later in life. The molecular diagnosis may tailor the choice of the most appropriate treatment, with the aim to optimize blood glucose control, reduce the risk of hypoglycemic events and long-term complications, and enable proper genetic counseling. Treatment is usually unnecessary for patients with mutations in the GCK gene, while oral hypoglycemic agents (generally sulphonylureas) are recommended for patients with mutations in the HNF4A and HNF1A genes. More recent data show that other glucose-lowering agents can be effective in the latter patients, and additional and alternative therapies have been proposed. Proper management guidelines during pregnancy have been developed for carriers of GCK gene mutations, but such guidelines are still a subject of debate in other cases, although some recommendations are available. The other subtypes of MODY are even more rare, and very little data are available in the literature. In this review we summarize the most pertinent findings and recommendations on the treatment of patients with the different subtypes of MODY. Our aim is to provide the reader with an easy-to-read update that can be used to drive the clinician's therapeutical approach to these patients after the molecular diagnosis.

Whole-exome sequencing identifies the first French MODY 6 family with a new mutation in the NEUROD1 gene

AIM

The aim of the present study was to identify the affected gene in a French family with maturity-onset diabetes of the young (MODY) using whole-exome sequencing (WES).

METHODS

WES was performed in one patient with MODY, and candidate variants were confirmed in members of the immediate family by Sanger sequencing.

RESULTS

In the proband, a new heterozygous missense mutation (c.340A>C) was identified in the NEUROD1 gene by WES analysis and confirmed by Sanger sequencing. Additional Sanger sequencing of the proband's sister and mother revealed the same heterozygous mutation. The proband and his sister displayed typical clinical characteristics of MODY, while their mother had the same typical MODY features except for later onset. When clinical and biological profiles were established for all three patients, the severity of diabetes-related complications varied substantially from one family member to another.

CONCLUSION

A novel missense mutation found in NEUROD1 was associated with MODY 6 features in a single French family.

The first case of NEUROD1-MODY reported in Latin America

Background

MODY‐NEUROD1 is a rare form of monogenic diabetes caused by mutations in Neuronal differentiation 1 (NEUROD1). Until now, only a few cases of MODY‐NEUROD1 have been reported worldwide and the real contribution of mutations in NEUROD1 in monogenic diabetes and its clinical impact remain unclear.

Methods

Genomic DNA was isolated from peripheral blood lymphocytes of 25 unrelated Brazilians patients with clinical characteristics suggestive of monogenic diabetes and the screening of the entire coding region of NEUROD1 was performed by Sanger sequencing.

Results

We identified one novel frameshift deletion (p.Phe256Leufs*2) in NEUROD1 segregating in an autosomal dominant inheritance fashion. Almost 20 years after the first report of NEUROD1‐MODY, only a few families in Europe and Asia had shown mutations in NEUROD1 as the cause of monogenic diabetes.

Conclusion

To our knowledge, we described the first case of NEUROD1‐MODY in a Latin American family.