Neonatal Diabetes Research Articles

Widening the phenotypic spectrum caused by pathogenic PDX1 variants in individuals with neonatal diabetes

IntroductionBiallelic PDX1 variants are a rare cause of isolated pancreatic agenesis and neonatal diabetes (NDM) without exocrine pancreatic insufficiency, with 17 cases reported in the literature.Research design and methodsTo determine...

Type 1 diabetes genetic risk contributes to phenotypic presentation in monogenic autoimmune diabetes.

Disease-causing variants in key immune homeostasis genes can lead to monogenic autoimmune diabetes. Some individuals carrying disease-causing variants do not develop autoimmune diabetes, even though they develop other autoimmune disease. We aimed to determine whether type 1 diabetes polygenic risk contributes to phenotypic presentation in monogenic autoimmune diabetes. We used a 67 SNP type 1 diabetes genetic risk score (T1D-GRS) to determine polygenic risk in 62 individuals with monogenic autoimmune diabetes and 180 non-autoimmune neonatal diabetes (NDM) controls. We used population-based controls (n=10,405) and individuals with type 1 diabetes (n=285) as a comparator. Individuals with monogenic autoimmune diabetes had higher T1D-GRSs compared to non-autoimmune NDM (mean 11.3 vs. 9.8; P=1.7×10-5) and controls (mean 10.3; P=7.5×10-6) but were markedly lower than type 1 diabetes (14.9; P= 3.3 × 10-21). These differences were explained by monogenic autoimmune diabetes cases having higher Class II HLA genetic risk, specifically from the DRB1*03:01-DQA1*05:01-DQB1*02:01 haplotype (DR3-DQ2) (P<0.01). In the presence of monogenic autoimmunity, the polygenic class II HLA susceptibility contributes to development of autoimmune diabetes. This suggests a role of class II HLA in targeting the dysregulated immune response towards the beta-cell.

The Identification of a Novel Pathogenic Variant in the GATA6 Gene in a Child with Neonatal Diabetes

GATA6 syndrome is a rare monogenic disorder caused by heterozygous variants in the gene GATA6, which controls the early embryonic differentiation of germ layers and the development of different organs. We present the results of the 7-year follow-up of a child with this syndrome as well as the following conditions: diabetes mellitus, exocrine pancreatic insufficiency, gallbladder atresia, and congenital heart disease (CHD). At birth, the patient was diagnosed with neonatal diabetes mellitus (NDM) associated with heart (mitral valve prolapse) and gastrointestinal abnormalities (gallbladder atresia). Diabetes remitted within weeks and relapsed at the age of 2. We identified a de novo variant of a 4-nucleotide deletion (c.1302+4_1302+7del), previously unreported in the literature, in the donor splicing site of exon 3 of the GATA6 gene in a heterozygous state. Screening for other possible components of GATA6 syndrome revealed exocrine pancreatic insufficiency, and pancreatic enzyme replacement therapy resulted in improved dyspeptic symptoms, and growth rates increased. In addition, the patient was diagnosed with autoimmune thyroiditis and progressive myopia.

A homozygous TARS2 variant is a novel cause of syndromic neonatal diabetes.

Neonatal diabetes is a monogenic condition which can be the presenting feature of complex syndromes. The aim of this study was to identify novel genetic causes of neonatal diabetes with neurological features including developmental delay and epilepsy. We performed genome sequencing in 27 individuals with neonatal diabetes plus epilepsy and/or developmental delay of unknown genetic cause. Replication studies were performed in 123 individuals with diabetes diagnosed aged ≤1 year without a known genetic cause using targeted next-generation sequencing. Three individuals, all diagnosed with diabetes in the first week of life, shared a rare homozygous missense variant, p.(Arg327Gln), in TARS2. Replication studies identified the same homozygous variant in a fourth individual diagnosed with diabetes at 1 year. One proband had epilepsy, one had development delay and two had both. Biallelic TARS2 variants cause a mitochondrial encephalopathy (COXPD-21) characterised by severe hypotonia, epilepsy and developmental delay. Diabetes is not a known feature of COXPD-21. Current evidence suggests that the p.(Arg327Gln) variant disrupts TARS2's regulation of the mTORC1 pathway which is essential for β-cells. Our findings establish the homozygous p.(Arg327Gln) TARS2 variant as a novel cause of syndromic neonatal diabetes and uncover a role for TARS2 in pancreatic β-cells.

Molecular and clinical profiles of pediatric monogenic diabetes subtypes: comprehensive genetic analysis of 138 patients.

Single gene variants that give rise to neonatal diabetes mellitus (NDM), maturity onset diabetes of the young (MODY) and syndromic forms of diabetes mellitus (SDM) are responsible for 3.1-4.2% of all diabetes cases. This single-center study with a relatively larger sample size aimed to evaluate the clinical and genetic characteristics of Chinese children with suspected monogenic diabetes (MD) using next generation sequencing (NGS) methods. Data were collected from 1550 consecutive children diagnosed with diabetes/hyperglycemia at the Endocrinology Department of Children's Hospital of Nanjing Medical University from 2012 to 2023. The genotype and phenotype of 138 children with suspected MD were retrospectively analyzed. Among 138 children, 16, 97, and 25 patients with NDM, suspected MODY and SDM were assessed by NGS, with a pick-up rate of 87.5%, 57.8%, and 56%, respectively. In total, there was a high pick-up rate of MD, with 58% (80 of 138) among antibody-negative pediatric patients. Pathogenic variants were found in GCK, HNF1A, INS, KCNJ11, INSR, HNF4A, ABCC8, WFS1, ALMS1, HNF1B, BLK and ZFP57 genes with 13 novel variants in addition to 4 patients with CNVs. In this cohort, GCK-MODY was the leading cause and the mildest type of MODY. GCK-MODY displayed favorable lipid profile when compared to non-GCK-MODY and MODYX, which might be cardioprotective. Following an accurate genetic diagnosis of diabetes, 19 patients switched from insulin therapy to oral agents or lifestyle interventions. NGS tests helped to identify the precise etiology of monogenic diabetic patients which has implications for better individualized management.

Zebrafish as a model to study PERK function in developmental diseases: implications for Wolcott-Rallison syndrome.

Developmental diseases are challenging to investigate due to their clinical heterogeneity and relatively low prevalence. The Wolcott-Rallison Syndrome (WRS) is a rare developmental disease characterized by skeletal dysplasia and permanent neonatal diabetes due to loss-of-function mutations in the endoplasmic reticulum stress kinase PERK (EIF2AK3). The lack of efficient and less invasive therapies for WRS highlights the need for new animal models that replicate the complex pathological phenotypes, while preserving scalability for drug screening. Zebrafish exhibits high fecundity and rapid development that facilitate efficient and scalable in vivo drug testing. Here, we aimed to assess the potential of zebrafish to study PERK function and its pharmacological modulation, and as model organism of developmental diseases such as the WRS. Using bioinformatic analyses, we showed high similarity between human and zebrafish PERK. We used the pharmacological PERK inhibitor GSK2606414, which was bioactive in zebrafish, to modulate PERK function. Using transgenic zebrafish expressing fluorescent pancreatic markers and a fluorescent glucose probe, we observed that PERK inhibition decreased β cell mass and disrupted glucose homeostasis. By combining behavioural and functional assays, we show that PERK-inhibited zebrafish present marked skeletal defects and defective growth, as well as neuromuscular and cardiac deficiencies, which are clinically relevant in WRS patients, while sparing parameters like otolith area and eye/body ratio which are not associated with WRS. These results show that zebrafish holds potential to study PERK function and its pharmacological modulation in developmental disorders like WRS, assisting research on their pathophysiology and experimental treatments.

Dysregulation of FicD AMPylation causes diabetes by disrupting pancreatic endocrine homeostasis.

Bi-functional enzyme FicD regulates the endoplasmic reticulum chaperone BiP using AMPylation and deAMPylation during ER homeostasis and stress, respectively. Human FicD with an arginine-to-serine mutation disrupts FicD deAMPylation activity resulting in severe neonatal diabetes. We generated the FicD R371S mutation in mice to create a pre-clinical murine model for neonatal diabetes. We observed elevated BiP AMPylation levels across multiple tissues and signature markers for diabetes including glucose intolerance and reduced serum insulin levels. While the pancreas of FicD R371S mice appeared normal at birth, adult FicD R371S mice displayed disturbed pancreatic islet organization that progressed with age. FicD R371S mice provide a preclinical mouse model for the study of UPR associated diabetes and demonstrate the essentiality of FicD for tissue resilience.

IER3IP1 mutations cause neonatal diabetes due to impaired proinsulin trafficking.

Immediate early response 3 interacting-protein 1 (IER3IP1) is an endoplasmic reticulum resident protein, highly expressed in pancreatic cells and the developing brain cortex. Homozygous mutations in IER3IP1 have been found in individuals with microcephaly and neonatal diabetes, yet the underlying mechanism causing beta cell failure remains unclear. Here, we utilized differentiation of genome edited-stem cells into pancreatic islet cells to elucidate the molecular basis of IER3IP1 neonatal diabetes. Using CRISPR-Cas9, we generated two distinct IER3IP1-mutant human embryonic stem cell lines: a homozygous knock-in model of a patient mutation (IER3IP1V21G), and a knockout model (IER3IP1-/-). While these mutant stem cell lines differentiated normally into definitive endoderm and pancreatic progenitors, we observed that IER3IP1-KO stem cell derived-islets (SC-islets) presented a significant decrease in beta cell numbers and elevated ER stress. Retention Using Selective Hooks (RUSH) assay revealed three-fold reduction in ER-to-Golgi trafficking of proinsulin in IER3IP1 mutant beta cells. Additionally, IER3IP1 mutant SC-islets implanted into immunocompromised mice displayed defective human insulin secretion, indicating the deleterious impact of IER3IP1 mutations on beta cell function. Our study provides valuable insights into the role of IER3IP1 in human beta cell biology and establishes a useful model to investigate ER-to-Golgi trafficking defects within beta cells.

Novel human PDX1 Asn196Thr variant causes pancreas agenesis and reduces the generation of duodenal enteroendocrine cells

Abstract Introduction/Objective Pancreatic and duodenal homeobox 1 (PDX1) is a well-studied transcription factor required for pancreas organogenesis. PDX1 mutations are associated with the development of diabetes. An 8-month-old female patient with previously uncharacterized compound heterogeneous PDX1 missense mutations (Thr151Met and Asn196Thr) was identified in this study. The patient has permanent neonatal diabetes, pancreas hypoplasia, and a malformed gallbladder. Methods/Case Report PDX1 Thr151Met and Asn196Thr variants in the patient were identified by next-generation sequencing gene panel and confirmed by Sanger sequencing. To examine how the mutations affect PDX1 functions in vitro, we expressed mouse Pdx1 Thr152Met and Asn197Thr, homologous to human PDX1 Thr151Met and Asn196Thr, respectively, in mouse insulinoma MIN6 cells and human embryonic kidney 293T cells and examined protein localization, protein stability, DNA binding, and protein-protein interaction. We also generated embryonic day 18 mouse embryos carrying Pdx1 Asn197Thr missense mutation using CRISPR/Cas9 to examine its roles in the development of the pancreas and other digestive organs in vivo. Results (if a Case Study enter NA) We found that the Pdx1 Asn197Thr variant, but not Thr152Met, altered its nuclear localization and disrupted PDX1-Onecut 1 interaction. Neither variant significantly affected PDX1 protein stability, but both reduced PDX1 binding to the Pdx1 gene promoter. Importantly, we found that the Pdx1 Asn197Thr variant caused pancreas agenesis and a reduction in the generation of enteroendocrine cells in the proximal duodenum in mouse models. Conclusion Our data indicated that the PDX1 Asn196Thr variant impairs its DNA binding and protein-protein interaction, causing pancreas agenesis and a reduction in the generation of duodenal enteroendocrine cells.

12599 Early Remission Of Chromosome 6 Q 24-related Neonatal Diabetes Mellitus

Abstract Disclosure: R. Pratibha: None. K. Dummula: None. Introduction: Chromosome 6q24 imprinting abnormalities represent the predominant cause of transient neonatal diabetes mellitus (TNDM), accounting for over two-thirds of cases with an estimated prevalence of 1 in 400,000. While remission typically manifests by 3 months of age, herein we detail a case of Chromosome 6q24-related TNDM exhibiting remission by 1.5 months of age. We share our clinical experience in managing this case without hypoglycemia and using C-Peptide levels as a monitoring tool to track the resolution. Case: A female infant, born at 36 weeks via elective C-section due to fetal growth restriction and oligohydramnios, was closely monitored in the nursery for potential hypoglycemia. Contrary to the expectation, she displayed escalating hyperglycemia, necessitating insulin infusion within 25 hours of birth. Apgar scores were 7 and 9, and the birth weight was 2095 g (6th percentile). Maternal history included impaired glucose tolerance in a previous pregnancy with borderline glucose tolerance during this gestation. The newborn physical exam was unremarkable except for mild macroglossia. Despite initial blood glucose (BG) of 52 mg/dl, it rose to 257 mg/dL by 16 hours. Insulin drip was started at 24 hours due to BG of 304 mg/dL. The monogenic diabetes panel obtained on day of life (DOL) #2 was negative; no acidosis was observed. The C- Peptide was low at 0.2 ng/ml. Insulin infusion was continued until DOL # 20. A trial of glyburide commenced on DOL #9 while on Insulin drip, yielded minimal response, prompting a transition to short-acting insulin for correction of hyperglycemia (&amp;gt;250 mg/dL). C-peptide level during sulfonylurea (SU) trial remained low (0.5 ng/mL). The infant required 2 to 3 corrections per day with 0.05 units of Lispro Insulin, with the last dose administered at 44 days. She did not receive any long-acting Insulin. As of her last follow-up at the endocrine clinic at 57 days of age, the infant is thriving well and has normal blood glucose levels. The 6q24 Methylation-MLPA study showed duplication of 6q24 on the paternally inherited chromosome 6. Significantly, she never encountered hypoglycemia during her hospital stay. The C-peptide increased to 0.8 ng/ml at DOL#37 and had normalized to 1.3 ng/mL by DOL#57 indicating remission of TNDM. Conclusion: 6q24-related TNDM may often be characterized by features such as small for gestational age (SGA), macroglossia, umbilical hernia, cardiac and renal abnormalities. Early presentation of hyperglycemia with this phenotype must prompt its diagnostic evaluation. Early resolution by 1.5 months as seen in our case is uncommon. Uniquely, we used C-peptide as a tracking tool to guide resolution and manage insulin therapy. Presentation: 6/3/2024

Neonatal diabetes mellitus – manifestation of GATA-6 syndrome

GATA6 syndrome is an unusual genetic disorder that presents complications during pregnancy, congenital heart defects, neonatal diabetes, and severe pancreatic dysfunction. The cause of the syndrome is a de novo mutation in the GATA6 gene, located on chromosome 18. We present the case of a patient who exhibited congenital heart defects and severe hyperglycemia from the neonatal period, caused by pancreatic agenesis. The diagnosis was established based on molecular genetic analyses. Insulin and pancreatic enzyme replacement therapy provide a favorable prognosis in pancreatic agenesis, significantly reducing neonatal mortality associated with this drastic diagnosis.

Management Strategies for Children and Adolescents with Diabetes Mellitus

The principles of treatment for diabetes in children and adolescents cannot simply be derived from care routinely provided to adults with diabetes. The major consideration is that the epidemiology, pathophysiology, developmental considerations, and response to treatment of pediatric diabetes are often different from those of adult diabetes. Second, recommended treatments for children and adolescents with type 1 diabetes (T1DM), type 2 diabetes (T2DM), and other pediatric conditions such as monogenic diabetes (neonatal diabetes and MODY [maturity-onset diabetes of the young]) also differ. HbA1c goals in T1DM and T2DM must be individualized and reassessed over time. A HbA1c &lt; 7% is appropriate for many children and adolescents with T1DM. In a case with hypoglycemia, hypoglycemic unawareness, lack of access to analog insulins, advanced insulin delivery technology and/or continuous glucose monitoring, a less stringent HbA1c &lt; 7.5% will be required. A reasonable HbA1c goal for T2DM is &lt; 7%. If possible, a strict HbA1c target of &lt; 6.5% can be implemented. Metformin is the first-line treatment of choice in T2DM. In a case with ketosis or HbA1c &gt; 8.5%, insulin will be required with once daily basal insulin (0.25~0.5 IU/kg). If the glycemic goal is not attained, the addition of a second agent is considered in adult patients but might not be applicable or safe in pediatric cases. Therefore, the efficacy and safety of these drugs used in adult patients, including glucagon-like peptide-1 receptor agonists and sodium glucose cotransporter 2 inhibitors, should be evaluated in pediatric patients worldwide.

Monogenic Defects of Beta Cell Function: From Clinical Suspicion to Genetic Diagnosis and Management of Rare Types of Diabetes

Monogenic defects of beta cell function refer to a group of rare disorders that are characterized by early-onset diabetes mellitus due to a single gene mutation affecting insulin secretion. It accounts for up to 5% of all pediatric diabetes cases and includes transient or permanent neonatal diabetes, maturity-onset diabetes of the young (MODY), and various syndromes associated with diabetes. Causative mutations have been identified in genes regulating the development or function of the pancreatic beta cells responsible for normal insulin production and/or release. To date, more than 40 monogenic diabetes subtypes have been described, with those caused by mutations in HNF1A and GCK genes being the most prevalent. Despite being caused by a single gene mutation, each type of monogenic diabetes, especially MODY, can appear with various clinical phenotypes, even among members of the same family. This clinical heterogeneity, its rarity, and the fact that it shares some features with more common types of diabetes, can make the clinical diagnosis of monogenic diabetes rather challenging. Indeed, several cases of MODY or syndromic diabetes are accurately diagnosed in adulthood, after having been mislabeled as type 1 or type 2 diabetes. The recent widespread use of more reliable sequencing techniques has improved monogenic diabetes diagnosis, which is important to guide appropriate treatment and genetic counselling. The current review aims to summarize the latest knowledge on the clinical presentation, genetic confirmation, and therapeutic approach of the various forms of monogenic defects of beta cell function, using three imaginary clinical scenarios and highlighting clinical and laboratory features that can guide the clinician in reaching the correct diagnosis.

Modelling human diabetes ex vivo: a glance at maturity onset diabetes of the young.

Diabetes is a complex metabolic disease which most commonly has a polygenic origin; however, in rare cases, diabetes may be monogenic. This is indeed the case in both Maturity Onset Diabetes of the Young (MODY) and neonatal diabetes. These disease subtypes are believed to be simpler than Type 1 (T1D) and Type 2 Diabetes (T2D), which allows for more precise modelling. During the three last decades, many studies have focused on rodent models. These investigations provided a wealth of knowledge on both pancreas development and beta cell function. In particular, they allowed the establishment of a hierarchy of the transcription factors and highlighted the role of microenvironmental factors in the control of progenitor cell proliferation and differentiation. Transgenic mice also offered the possibility to decipher the mechanisms that define the functional identity of the pancreatic beta cells. Despite such interest in transgenic mice, recent data have also indicated that important differences exist between mice and human. To overcome these limitations, new human models are necessary. In the present review, we describe these ex vivo models, which are created using stem cells and organoids, and represent an important step toward islet cell therapy and drug discovery.

Insulin Delivery Technology for Treatment of Infants with Neonatal Diabetes Mellitus: A Systematic Review.

Neonatal diabetes mellitus is a rare disorder of glucose metabolism with onset within the first 6months of life. The initial treatment is based on insulin infusion. The technologies for diabetes treatment can be very helpful, even if guidelines are still lacking. The current study aimed to provide a comprehensive review of the literature about the safety and efficacy of insulin treatment with technology for diabetes to support clinicians in the management of infants with neonatal diabetes mellitus. A total of 22 papers were included, most of them case reports or case series. The first infants with neonatal diabetes mellitus treated with insulin pumps were described nearly two decades ago. Over the years, continuous glucose monitoring systems were added to treat these individuals, allowing for a better customization of insulin administration. Insulin was diluted in some cases to further minimize the doses. Improvement in technology for diabetes prompted clinicians to use new devices and algorithms for insulin delivery in infants with neonatal diabetes as well. These systems are safe and effective, may shorten hospital stay, and help clinicians weaning insulin during the remission phase in the transient forms or switching from insulin to sulfonylurea when suggested by the molecular diagnosis. New technologies for insulin delivery in infants with neonatal diabetes can be used safely and closed-loop algorithms can work properly in these situations, optimizing blood glucose control.

IER3IP1-mutations cause microcephaly by selective inhibition of ER-Golgi transport

Mutations in the IER3IP1 (Immediate Early Response-3 Interacting Protein 1) gene can give rise to MEDS1 (Microcephaly with Simplified Gyral Pattern, Epilepsy, and Permanent Neonatal Diabetes Syndrome-1), a severe condition leading to early childhood mortality. The small endoplasmic reticulum (ER)-membrane protein IER3IP1 plays a non-essential role in ER-Golgi transport. Here, we employed secretome and cell-surface proteomics to demonstrate that the absence of IER3IP1 results in the mistrafficking of proteins crucial for neuronal development and survival, including FGFR3, UNC5B and SEMA4D. This phenomenon correlates with the distension of ER membranes and increased lysosomal activity. Notably, the trafficking of cargo receptor ERGIC53 and KDEL-receptor 2 are compromised, with the latter leading to the anomalous secretion of ER-localized chaperones. Our investigation extended to in-utero knock-down of Ier3ip1 in mouse embryo brains, revealing a morphological phenotype in newborn neurons. In summary, our findings provide insights into how the loss or mutation of a 10 kDa small ER-membrane protein can cause a fatal syndrome.

Anamnestic, clinical, laboratory and molecular genetic characteristics of patients with neonatal diabetes mellitus

BACKGROUND: Currently, there is an increase in the incidence of diabetes mellitus throughout the world, including the steadily increasing number of rare, genetically determined forms of diabetes. Of particular interest are monogenic forms, including neonatal diabetes mellitus, which is a rare heterogeneous disease that manifests, as a rule, in the first 6 months of a child’s life, characterized by a severe labile course and a high risk of complications. Neonatal diabetes mellitus is a rare heterogeneous disease that usually manifests itself in the first 6 months of a child’s life, characterized by a severe, labile course and a high risk of complications. Currently, more than 25 genes are known, mutations in which cause both permanent and transient neonatal diabetes mellitus, as well as syndromic variants of this disease, which are of particular interest due to their severity and polymorphic clinical picture. In this regard, timely verification of the diagnosis is of particular importance. AIM: The aim of this study is to increase the efficiency of diagnosis of neonatal diabetes mellitus based on the analysis of anamnestic, clinical, laboratory and molecular genetic characteristics of patients. MATERIALS AND METHODS: 14 patients with transient and permanent neonatal diabetes mellitus were examined. RESULTS: 11 (78.6%) patients had isolated neonatal diabetes, in three of them the disease was verified in the structure of hereditary syndromes (Wolcott–Rallison syndrome, IPEX syndrome and Donohue syndrome). According to molecular genetic analysis, 14 variants were found in the genes ABCC8, KCNJ11, GCK, GATA6, WFS1, CACNA1D, EIF2AK3, FOXP3, PAX4, INSR, IGF1R, three of which were not previously described in the literature. CONCLUSIONS: The clinical heterogeneity identified in patients is determined primarily by the diversity of verified variants in causative genes. New variants in the CACNA1D and IGF1R genes that may be associated with the development of NDM, remain poorly understood and require further research.

CRISPR screening uncovers a long-range enhancer for ONECUT1 in pancreatic differentiation and links a diabetes risk variant

Functional enhancer annotation is critical for understanding tissue-specific transcriptional regulation and prioritizing disease-associated non-coding variants. However, unbiased enhancer discovery in disease-relevant contexts remains challenging. To identify enhancers pertinent to diabetes, we conducted a CRISPR interference (CRISPRi) screen in the human pluripotent stem cell (hPSC) pancreatic differentiation system. Among the enhancers identified, we focused on an enhancer we named ONECUT1e-664kb, ∼664 kb from the ONECUT1 promoter. Previous studies have linked ONECUT1 coding mutations to pancreatic hypoplasia and neonatal diabetes. We found that homozygous deletion of ONECUT1e-664kb in hPSCs leads to a near-complete loss of ONECUT1 expression and impaired pancreatic differentiation. ONECUT1e-664kb contains a type 2 diabetes-associated variant (rs528350911) disrupting a GATA motif. Introducing the risk variant into hPSCs reduced binding of key pancreatic transcription factors (GATA4, GATA6, and FOXA2), supporting its causal role in diabetes. This work highlights the utility of unbiased enhancer discovery in disease-relevant settings for understanding monogenic and complex disease.

Deletion of RFX6 impairs iPSC-derived islet organoid development and survival, with no impact on PDX1+/NKX6.1+ progenitors.

Homozygous mutations in RFX6 lead to neonatal diabetes accompanied by a hypoplastic pancreas, whereas heterozygous mutations cause MODY. Recent studies have also shown RFX6 variants to be linked with type 2 diabetes. Despite RFX6's known function in islet development, its specific role in diabetes pathogenesis remains unclear. Here, we aimed to understand the mechanisms underlying the impairment of pancreatic islet development and subsequent hypoplasia due to loss-of-function mutations in RFX6. We examined regulatory factor X6 (RFX6) expression during human embryonic stem cell (hESC) differentiation into pancreatic islets and re-analysed a single-cell RNA-seq dataset to identify RFX6-specific cell populations during islet development. Furthermore, induced pluripotent stem cell (iPSC) lines lacking RFX6 were generated using CRISPR/Cas9. Various approaches were then employed to explore the consequences of RFX6 loss across different developmental stages. Subsequently, we evaluated transcriptional changes resulting from RFX6 loss through RNA-seq of pancreatic progenitors (PPs) and endocrine progenitors (EPs). RFX6 expression was detected in PDX1+ cells in the hESC-derived posterior foregut (PF). However, in the PPs, RFX6 did not co-localise with pancreatic and duodenal homeobox 1 (PDX1) or NK homeobox 1 (NKX6.1) but instead co-localised with neurogenin 3, NK2 homeobox 2 and islet hormones in the EPs and islets. Single-cell analysis revealed high RFX6 expression levels in endocrine clusters across various hESC-derived pancreatic differentiation stages. Upon differentiating iPSCs lacking RFX6 into pancreatic islets, a significant decrease in PDX1 expression at the PF stage was observed, although this did not affect PPs co-expressing PDX1 and NKX6.1. RNA-seq analysis showed the downregulation of essential genes involved in pancreatic endocrine differentiation, insulin secretion and ion transport due to RFX6 deficiency. Furthermore, RFX6 deficiency resulted in the formation of smaller islet organoids due to increased cellular apoptosis, linked to reduced catalase expression, implying a protective role for RFX6. Overexpression of RFX6 reversed defective phenotypes in RFX6-knockout PPs, EPs and islets. These findings suggest that pancreatic hypoplasia and reduced islet cell formation associated with RFX6 mutations are not due to alterations in PDX1+/NKX6.1+ PPs but instead result from cellular apoptosis and downregulation of pancreatic endocrine genes. RNA-seq datasets have been deposited in the Zenodo repository with accession link (DOI: https://doi.org/10.5281/zenodo.10656891 ).

Precision treatment of beta-cell monogenic diabetes: a systematic review

BackgroundBeta-cell monogenic forms of diabetes have strong support for precision medicine. We systematically analyzed evidence for precision treatments for GCK-related hyperglycemia, HNF1A-, HNF4A- and HNF1B-diabetes, and mitochondrial diabetes (MD) due to m.3243 A > G variant, 6q24-transient neonatal diabetes mellitus (TND) and SLC19A2-diabetes.MethodsThe search of PubMed, MEDLINE, and Embase for individual and group level data for glycemic outcomes using inclusion (English, original articles written after 1992) and exclusion (VUS, multiple diabetes types, absent/aggregated treatment effect measures) criteria. The risk of bias was assessed using NHLBI study-quality assessment tools. Data extracted from Covidence were summarized and presented as descriptive statistics in tables and text.ResultsThere are 146 studies included, with only six being experimental studies. For GCK-related hyperglycemia, the six studies (35 individuals) assessing therapy discontinuation show no HbA1c deterioration. A randomized trial (18 individuals per group) shows that sulfonylureas (SU) were more effective in HNF1A-diabetes than in type 2 diabetes. Cohort and case studies support SU’s effectiveness in lowering HbA1c. Two cross-over trials (each with 15–16 individuals) suggest glinides and GLP-1 receptor agonists might be used in place of SU. Evidence for HNF4A-diabetes is limited. Most reported patients with HNF1B-diabetes (N = 293) and MD (N = 233) are on insulin without treatment studies. Limited data support oral agents after relapse in 6q24-TND and for thiamine improving glycemic control and reducing/eliminating insulin requirement in SLC19A2-diabetes.ConclusionThere is limited evidence, and with moderate or serious risk of bias, to guide monogenic diabetes treatment. Further evidence is needed to examine the optimum treatment in monogenic subtypes.