Towards a systematic nationwide screening strategy for MODY

De novo HNF1A mutation of young maturity-onset diabetes 3 of a young girl-Case report

Young maturity-onset diabetes of the young type3(MODY3) as a special type of diabetes, the probability of diagnosis is low. This article reports on a case and reviews the relevant knowledge of the disease. We report an 11-year-and-11-month-old girl whose grandmother died from diabetic complications while the rest of the families were non-diabetes. The proband was initially treated with insulin and metformin but the threatment proved inefficient. After an exome-targeted capture sequencing test, she was diagnosed with mature-onset diabetes of young type 3 (MODY3), and sulfonylureas make sense. The key to mody treatment is a correct and timely diagnosis, which contributes to helping patients overcome the problems of MODY3, especially for blood sugar control.

Monogenic diabetes in New Zealand - An audit based revision of the monogenic diabetes genetic testing pathway in New Zealand

AIMS

To evaluate (a) the diagnostic yield of genetic testing for monogenic diabetes when using single gene and gene panel-based testing approaches in the New Zealand (NZ) population, (b) whether the MODY (Maturity Onset Diabetes of the Young) pre-test probability calculator can be used to guide referrals for testing in NZ, (c) the number of referrals for testing for Māori/Pacific ethnicities compared to NZ European, and (d) the volume of proband vs cascade tests being requested.

METHODS

A retrospective audit of 495 referrals, from NZ, for testing of monogenic diabetes genes was performed. Referrals sent to LabPlus (Auckland) laboratory for single gene testing or small multi-gene panel testing, or to the Exeter Genomics Laboratory, UK, for a large gene panel, received from January 2014 - December 2021 were included. Detection rates of single gene, small multi-gene and large gene panels (neonatal and non-neonatal), and cascade testing were analysed. Pre-test probability was calculated using the Exeter MODY probability calculator and ethnicity data was also collected.

RESULTS

The diagnostic detection rate varied across genes, from 32% in GCK, to 2% in HNF4A, with single gene or small gene panel testing averaging a 12% detection rate. Detection rate by type of panel was 9% for small gene panel, 23% for non-neonatal monogenic diabetes large gene panel and 40% for neonatal monogenic diabetes large gene panel. 45% (67/147) of patients aged 1-35 years at diabetes diagnosis scored <20% on MODY pre-test probability, of whom 3 had class 4/5 variants in HNF1A, HNF4A or HNF1B. Ethnicity data of those selected for genetic testing correlated with population diabetes prevalence for Māori (15% vs 16%), but Pacific People appeared under-represented (8% vs 14%). Only 1 in 6 probands generated a cascade test.

CONCLUSIONS

A new monogenic diabetes testing algorithm for NZ is proposed, which directs clinicians to choose a large gene panel in patients without syndromic features who score a pre-test MODY probability of above 20%.

A multigenerational study on phenotypic consequences of the most common causal variant of HNF1A-MODY

AIMS/HYPOTHESIS

Systematic studies on the phenotypic consequences of variants causal of HNF1A-MODY are rare. Our aim was to assess the phenotype of carriers of a single HNF1A variant and genetic and clinical factors affecting the clinical spectrum.

METHODS

We conducted a family-based multigenerational study by comparing heterozygous carriers of the HNF1A p.(Gly292fs) variant with the non-carrier relatives irrespective of diabetes status. During more than two decades, 145 carriers and 131 non-carriers from 12 families participated in the study, and 208 underwent an OGTT at least once. We assessed the polygenic risk score for type 2 diabetes, age at onset of diabetes and measures of body composition, as well as plasma glucose, serum insulin, proinsulin, C-peptide, glucagon and NEFA response during the OGTT.

RESULTS

Half of the carriers remained free of diabetes at 23 years, one-third at 33 years and 13% even at 50 years. The median age at diagnosis was 21 years (IQR 17-35). We could not identify clinical factors affecting the age at conversion; sex, BMI, insulin sensitivity or parental carrier status had no significant effect. However, for 1 SD unit increase of a polygenic risk score for type 2 diabetes, the predicted age at diagnosis decreased by 3.2 years. During the OGTT, the carriers had higher levels of plasma glucose and lower levels of serum insulin and C-peptide than the non-carriers. The carriers were also leaner than the non-carriers (by 5.0 kg, p=0.012, and by 2.1 kg/m² units of BMI, p=2.2 × 10^-4, using the first adult measurements) and, possibly as a result of insulin deficiency, demonstrated higher lipolytic activity (with medians of NEFA at fasting 621 vs 441 μmol/l, p=0.0039; at 120 min during an OGTT 117 vs 64 μmol/l, p=3.1 × 10^-5).

CONCLUSIONS/INTERPRETATION

The most common causal variant of HNF1A-MODY, p.(Gly292fs), presents not only with hyperglycaemia and insulin deficiency, but also with increased lipolysis and markedly lower adult BMI. Serum insulin was more discriminative than C-peptide between carriers and non-carriers. A considerable proportion of carriers develop diabetes after young adulthood. Even among individuals with a monogenic form of diabetes, polygenic risk of diabetes modifies the age at onset of diabetes.

Syndromic Monogenic Diabetes Genes Should Be Tested in Patients With a Clinical Suspicion of Maturity-Onset Diabetes of the Young

At present, outside of infancy, genetic testing for monogenic diabetes is typically for mutations in maturity-onset diabetes of the young (MODY) genes that predominantly result in isolated diabetes. Monogenic diabetes syndromes are usually only tested for when supported by specific syndromic clinical features. How frequently patients with suspected MODY have a mutation in a monogenic syndromic diabetes gene is unknown and thus missed by present testing regimes. We performed genetic testing of 27 monogenic diabetes genes (including 18 associated with syndromic diabetes) for 1,280 patients with a clinical suspicion of MODY who were not suspected of having monogenic syndromic diabetes. We confirmed monogenic diabetes in 297 (23%) patients. Mutations in seven different syndromic diabetes genes accounted for 19% (95% CI 15-24%) of all monogenic diabetes. The mitochondrial m.3243A>G and mutations in HNF1B were responsible for the majority of mutations in syndromic diabetes genes. They were also the 4th and 5th most common causes of monogenic diabetes overall. These patients lacked typical features, and their diabetes phenotypes overlapped with patients with nonsyndromic monogenic diabetes. Syndromic monogenic diabetes genes (particularly m.3243A>G and HNF1B) should be routinely tested in patients with suspected MODY who do not have typical features of a genetic syndrome.

REPRINT OF: CLASSIFICATION OF DIABETES MELLITUS

Executive Summary This document updates the 1999 World Health Organization (WHO) classification of diabetes. It prioritizes clinical care and guides health professionals in choosing appropriate treatments at the time of diabetes diagnosis, and provides practical guidance to clinicians in assigning a type of diabetes to individuals at the time of diagnosis. It is a compromise between clinical and aetiological classification because there remain gaps in knowledge of the aetiology and pathophysiology of diabetes. While acknowledging the progress that is being made towards a more precise categorization of diabetes subtypes, the aim of this document is to recommend a classification that is feasible to implement in different settings throughout the world. The revised classification is presented in Table 1. Unlike the previous classification, this classification does not recognize subtypes of type 1 diabetes and type 2 diabetes and includes new types of diabetes ("hybrid types of diabetes" and "unclassified diabetes").

A new screening strategy and whole-exome sequencing for the early diagnosis of maturity-onset diabetes of the young

AIMS

This study aimed to establish a systematic screening strategy to select candidates for genetic testing among patients with maturity-onset diabetes of the young (MODY) and to accomplish early diagnosis of MODY.

MATERIALS AND METHODS

We enrolled 1478 sporadic patients from the outpatient department of endocrinology. Out of the1478 patients, 1279 participants were successfully screened according to the "AACM" strategy, which includes the age of onset, autoantibody to islet antigen, C-peptide and metabolic syndrome. Another six probands and their families who fulfilled the common clinical criteria for MODY were also examined for causative gene mutations. Whole-exome sequencing (WES) was performed to examine the mutations.

RESULTS

A total of 24 out of 1279 sporadic patients with newly diagnosed diabetes were eligible for genetic testing. Mutations were found in 4/24 participants in the cohort, as well as in 2/6 pedigrees. A likely pathogenic alteration, a likely benign alteration and three alterations with uncertain significance were identified with WES. Most of the mutant genes recognised in our trial were not the most common causative genes of MODY, and all of the mutations were specifically reported in Asian patients only, suggesting a unique genetic background of MODY in different ethnicities.

CONCLUSIONS

In this systematic study of MODY in a new-onset diabetes cohort, MODY cases were incorrectly diagnosed as type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM), suggesting that an observant clinician is necessary for early and correct MODY diagnosis. This systematic approach to screening is practical and specific enough to identify patients who are most appropriate for genetic testing.

Clinical and laboratory clues of maturity-onset diabetes of the young and determination of association with molecular diagnosis

BACKGROUND/AIM

Maturity-onset diabetes of the young (MODY) is often misdiagnosed as other types of diabetes because it is overlooked due to atypical clinical presentations. This study aims to reveal the clinical and laboratory clues and examine their compatibility with MODY genotypes.

METHODS

Participants consisted of 230 children with atypical presentations for type1(T1DM) and type2 diabetes mellitus (T2DM). MODY-causing mutations were screened in the following genes:GCK-HNF1A-HNF4A-HNF1B-PDX1-NEUROD1-KLF11-CEL-PAX4-INS-BLK. Clinical and laboratory features were compared between children with MODY and children without MODY.

RESULTS

The most common reasons for MODY screening were as follows (n/%):low daily dose of insulin (DDI) requirement (122/53%), absence of beta-cell antibodies(58/25.3%), coincidental hyperglycemia(26/11.3%), family history of diabetes (12/5.2%), hypoglycemia/hyperglycemia episodes(7/3%), hyperglycemia related to steroids(3/1.4%) and renal glycosuria(2/0.8%). The markers with the most likelihood to distinguish MODY from T1DM were determined as follows: measurable C-peptide in follow-up, family history of early-onset diabetes and low DDI requirement (odds ratio:12.55, 5.53 and 3.43, respectively). The distribution of the most common causative genes in children with MODY(n = 24) is as follows (n/%):GCK(15/62.5%), HNF4A(7/29.1%), HNF1A(1/9.2%) and PDX1(1/9.2%).All children(n = 12) with GCK-MODY(MODY2) were screened for low DDI requirement, while beta-cell negativity was more common in HNF4A-MODY(MODY1).

CONCLUSION

The study shows that measurable C-peptide in follow-up, family history of early-onset diabetes, and low DDI are still remarkable clues to predict MODY in children with misdiagnosed T1DM. In addition, the most common mutations were found in the GCK and HNF4A genes. Among children misdiagnosed with T1DM, a low DDI requirement was found more frequently in MODY2, whereas beta-cell antibody negativity was more common in MODY1.

Novel insights into genetics and clinics of the HNF1A-MODY

MODY (Maturity Onset Diabetes of the Young) is a type of diabetes resulting from a pathogenic effect of gene mutations. Up to date, 13 MODY genes are known. Gene HNF1A is one of the most common causes of MODY diabetes (HNF1A-MODY; MODY3). This gene is polymorphic and more than 1200 pathogenic and non-pathogenic HNF1A variants were described in its UTRs, exons and introns. For HNF1A-MODY, not just gene but also phenotype heterogeneity is typical. Although there are some clinical instructions, HNF1A-MODY patients often do not meet every diagnostic criteria or they are still misdiagnosed as type 1 and type 2 diabetics. There is a constant effort to find suitable biomarkers to help with in distinguishing of MODY3 from Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D). DNA sequencing is still necessary for unambiguous confirmation of clinical suspicion of MODY. NGS (Next Generation Sequencing) methods brought discoveries of multiple new gene variants and new instructions for their pathogenicity classification were required. The most actual problem is classification of variants with uncertain significance (VUS) which is a stumbling-block for clinical interpretation. Since MODY is a hereditary disease, DNA analysis of family members is helpful or even crucial. This review is updated summary about HNF1A-MODY genetics, pathophysiology, clinics functional studies and variant classification.

Update on clinical screening of maturity-onset diabetes of the young (MODY)

BACKGROUND

Maturity-onset diabetes of the young (MODY) is the most common type of monogenic diabetes, being characterized by beta-cell disfunction, early onset, and autosomal dominant inheritance. Despite the rapid evolution of molecular diagnosis methods, many MODY cases are misdiagnosed as type 1 or type 2 diabetes. High costs of genetic testing and limited knowledge of MODY as a relevant clinical entity are some of the obstacles that hinder correct MODY diagnosis and treatment. We present a broad review of clinical syndromes related to most common MODY subtypes, emphasizing the role of biomarkers that can help improving the accuracy of clinical selection of candidates for molecular diagnosis.

MAIN BODY

To date, MODY-related mutations have been reported in at least 14 different genes. Mutations in glucokinase (GCK), hepatocyte nuclear factor-1 homeobox A (HNF1A), and hepatocyte nuclear factor-4 homeobox A (HNF4A) are the most common causes of MODY. Accurate etiological diagnosis can be challenging. Many biomarkers such as apolipoprotein-M (ApoM), aminoaciduria, complement components, and glycosuria have been tested, but have not translated into helpful diagnostic tools. High-sensitivity C-reactive protein (hs-CRP) levels are lower in HNF1A-MODY and have been tested in some studies to discriminate HNF1A-MODY from other types of diabetes, although more data are needed. Overall, presence of pancreatic residual function and absence of islet autoimmunity seem the most promising clinical instruments to select patients for further investigation.

CONCLUSIONS

The selection of diabetic patients for genetic testing is an ongoing challenge. Metabolic profiling, diabetes onset age, pancreatic antibodies, and C-peptide seem to be useful tools to better select patients for genetic testing. Further studies are needed to define cut-off values in different populations.

Identification of an HNF1A p.Gly292fs Frameshift Mutation Presenting as Diabetes During Pregnancy in a Maltese Family

The diagnosis of maturity onset diabetes of the young (MODY) is a challenging process in view of the extensive clinical and genetic heterogeneity of the disease. Mutations in the gene encoding hepatocyte nuclear factor 1α (HNF1A) are responsible for most forms of monogenic diabetes in Northern European populations. Genetic analysis through a combination of whole exome sequencing and Sanger sequencing in three Maltese siblings and their father identified a rare duplication/frameshift mutation in exon 4 of HNF1A that lies within a known mutational hotspot in this gene. In this report, we provide the first description of an HNF1A-MODY3 phenotype in a Maltese family. The findings reported are relevant and new to a regional population, where the epidemiology of atypical diabetes has never been studied before. This report is of clinical interest as it highlights how monogenic diabetes can be misdiagnosed as either type 1, type 2, or gestational diabetes. It also reinforces the need for a better characterisation of monogenic diabetes in Mediterranean countries, particularly in island populations such as Malta with a high prevalence of diabetes.

COL4A3 Gene Variants and Diabetic Kidney Disease in MODY

BACKGROUND AND OBJECTIVES

Despite advances in identifying genetic factors of diabetic kidney disease (DKD), much of the heritability remains unexplained. Nine maturity-onset diabetes in young (MODY) probands with kidney biopsy-proven DKD were selected and included in this study. The probands had more severe DKD compared with their parents with MODY, with overt proteinuria or rapid progression to ESKD. We aimed to explore the contribution of the variants in susceptibility genes of DKD to the severity of kidney phenotype between the probands and their parents.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Whole-exome sequencing was performed to identify suspected MODY probands and their families. Known DKD susceptibility genes were reviewed. Variants reported to be associated with DKD, or those with minor allele frequency <0.05 and predicted to be pathogenic, were selected and analyzed. Immunofluorescence staining of COL4α3 was performed in kidney specimens of patients with DKD with or without R408H and M1209I of COL4A3 variants.

RESULTS

HNF1B-MODY, CEL-MODY, PAX4-MODY, and WFS1-MODY were diagnosed among nine families. We identified 196 selected variants of 25 DKD susceptibility genes among the participants. Analysis of phenotype between probands and parents, gene function, and protein-protein interaction networks revealed that COL4A3 variants were involved in the progression of DKD. Weak granular staining of COL4α3 was observed in the glomerular basement membrane of patients with the R408H and M1209I variants, whereas strong consecutive staining was observed in patients without these variants. Moreover, more number of DKD variants were identified in probands than in their parents with MODY.

CONCLUSIONS

The genetic effect of more pathogenic variants in various DKD susceptibility genes, especially variants in the COL4A3 gene, partially explained the more severe kidney phenotype in probands with kidney biopsy-proven DKD.