Two novel GATA6 mutations cause childhood-onset diabetes mellitus, pancreas malformation and congenital heart disease

GATA6 regulates WNT and BMP programs to pattern precardiac mesoderm during the earliest stages of human cardiogenesis

Haploinsufficiency for GATA6 is associated with congenital heart disease (CHD) with variable comorbidity of pancreatic or diaphragm defects, although the etiology of disease is not well understood. Here, we used cardiac directed differentiation from human embryonic stem cells (hESCs) as a platform to study GATA6 function during early cardiogenesis. GATA6 loss-of-function hESCs had a profound impairment in cardiac progenitor cell (CPC) specification and cardiomyocyte (CM) generation due to early defects during the mesendoderm and lateral mesoderm patterning stages. Profiling by RNA-seq and CUT&RUN identified genes of the WNT and BMP programs regulated by GATA6 during early mesoderm patterning. Furthermore, interactome analysis detected GATA6 binding with developmental transcription factors and chromatin remodelers suggesting cooperative regulation of cardiac lineage gene accessibility. We show that modulating WNT and BMP inputs during the first 48 hours of cardiac differentiation is sufficient to partially rescue CPC and CM defects in GATA6 heterozygous and homozygous mutant hESCs. This study provides evidence of the regulatory functions for GATA6 directing human precardiac mesoderm patterning during the earliest stages of cardiogenesis to further our understanding of haploinsufficiency causing CHD and the co-occurrence of cardiac and other organ defects caused by human GATA6 mutations.

Monogenic Diabetes with GATA6 Mutations: Characterization of a Novel Family and a Comprehensive Analysis of the GATA6 Clinical and Genetics Traits

Monogenic diabetes caused by GATA6 mutations were almost described as neonatal diabetes, and the phenotypic spectrum has expanded since then. Our study underscores the broad phenotypic spectrum by reporting a de novo GATA6 mutation in a family. Furthermore, we reviewed related literature to summarize the clinical and genetic characteristics of monogenic diabetes with GATA6 mutations (n = 39) in order to improve clinicians' understanding of the disease. We conclude that the GATA6 missense mutation (c. 749G > T, p. Gly250Val) is not reported presently, characterized by adult-onset diabetes with pancreatic dysplasia and located in transcriptional activation region. Carries with GATA6 mutations (n = 55) have a variable spectrum of diabetes, ranging from neonatal (72.7%), childhood-onset (20%) to adults-onset (7.5%). 83.5% of patients with abnormal pancreatic development. Heart and hepatobillary defects are the most common abnormalities of extrapancreatic features. Most mutations with GATA6 are loss of function (LOF, 71.8%) and located in functional region. Functional studies mostly support loss-of-function as the pathophysiological mechanism. In conclusion, there are various types of diabetes with GATA6 mutations, which can also occur in adult diabetes. Phenotypic defects with GATA6 mutations are most frequently malformations of pancreas and heart. This highlights the importance of comprehensive clinical evaluation of identified carriers to evaluate their full phenotypic spectrum.

GATA4 and GATA6 loss-of-expression is associated with extinction of the classical programme and poor outcome in pancreatic ductal adenocarcinoma

OBJECTIVE

GATA6 is a key regulator of the classical phenotype in pancreatic ductal adenocarcinoma (PDAC). Low GATA6 expression associates with poor patient outcome. GATA4 is the second most expressed GATA factor in the pancreas. We assessed whether, and how, GATA4 contributes to PDAC phenotype and analysed the association of expression with outcome and response to chemotherapy.

DESIGN

We analysed PDAC transcriptomic data, stratifying cases according to GATA4 and GATA6 expression and identified differentially expressed genes and pathways. The genome-wide distribution of GATA4 was assessed, as well as the effects of GATA4 knockdown. A multicentre tissue microarray study to assess GATA4 and GATA6 expression in samples (n=745) from patients with resectable was performed. GATA4 and GATA6 levels were dichotomised into high/low categorical variables; association with outcome was assessed using univariable and multivariable Cox regression models.

RESULTS

GATA4 messenger RNA is enriched in classical, compared with basal-like tumours. We classified samples in 4 groups as high/low for GATA4 and GATA6. Reduced expression of GATA4 had a minor transcriptional impact but low expression of GATA4 enhanced the effects of GATA6 low expression. GATA4 and GATA6 display a partially overlapping genome-wide distribution, mainly at promoters. Reduced expression of both proteins in tumours was associated with the worst patient survival. GATA4 and GATA6 expression significantly decreased in metastases and negatively correlated with basal markers.

CONCLUSIONS

GATA4 and GATA6 cooperate to maintain the classical phenotype. Our findings provide compelling rationale to assess their expression as biomarkers of poor prognosis and therapeutic response.

Genetic syndromes with diabetes: A systematic review

Previous reviews and clinical guidelines have identified 10-20 genetic syndromes associated with diabetes, but no systematic review has been conducted to date. We provide the first comprehensive catalog for syndromes with diabetes mellitus. We conducted a systematic review of MEDLINE, Embase, CENTRAL, PubMed, OMIM, and Orphanet databases for case reports, case series, and observational studies published between 1946 and January 15, 2020, that described diabetes mellitus in adults and children with monogenic or chromosomal syndromes. Our literature search identified 7,122 studies, of which 160 fulfilled inclusion criteria. Our analysis of these studies found 69 distinct diabetes syndromes. Thirty (43.5%) syndromes included diabetes mellitus as a cardinal clinical feature, and 56 (81.2%) were fully genetically elucidated. Sixty-three syndromes (91.3%) were described more than once in independent case reports, of which 59 (93.7%) demonstrated clinical heterogeneity. Syndromes associated with diabetes mellitus are more numerous and diverse than previously anticipated. While knowledge of the syndromes is limited by their low prevalence, future reviews will be needed as more cases are identified. The genetic etiologies of these syndromes are well elucidated and provide potential avenues for future gene identification efforts, aid in diagnosis and management, gene therapy research, and developing personalized medicine treatments.

Genome Editing Human Pluripotent Stem Cells to Model β-Cell Disease and Unmask Novel Genetic Modifiers

A mechanistic understanding of the genetic basis of complex diseases such as diabetes mellitus remain elusive due in large part to the activity of genetic disease modifiers that impact the penetrance and/or presentation of disease phenotypes. In the face of such complexity, rare forms of diabetes that result from single-gene mutations (monogenic diabetes) can be used to model the contribution of individual genetic factors to pancreatic β-cell dysfunction and the breakdown of glucose homeostasis. Here we review the contribution of protein coding and non-protein coding genetic disease modifiers to the pathogenesis of diabetes subtypes, as well as how recent technological advances in the generation, differentiation, and genome editing of human pluripotent stem cells (hPSC) enable the development of cell-based disease models. Finally, we describe a disease modifier discovery platform that utilizes these technologies to identify novel genetic modifiers using induced pluripotent stem cells (iPSC) derived from patients with monogenic diabetes caused by heterozygous mutations.

A Missense Mutation in IRS1 is Associated with the Development of Early-Onset Type 2 Diabetes

There could be an overlap of monogenic diabetes and early-onset type 2 diabetes mellitus. Precise diagnosis of early-onset diabetes has proven valuable for understanding the mechanism of diabetes and selecting optimal therapy. The majority of maturity onset diabetes of the young (MODY) pathogenic genes in China is still unknown. In this study, a family with suspected MODY was enrolled. Whole-exome sequencing (WES) was used to analyze the variants of the proband. Variants were filtered according to their frequency, location, functional consequences, and bioinformatics software. Candidate pathogenic variants were validated by Sanger sequencing and tested for cosegregation in other members of the family and nonrelated healthy controls. KEGG (Kyoto Encyclopedia of Genes and Genomes) and PPI (protein-protein interaction) analysis were conducted using the DAVID (Database for Annotation, Visualization, and Integrated Discovery) and the STRING online analysis tools for the candidate pathogenic gene. A total of 123291 variants including 105344 SNPs and 17947 InDels were found in WES. A likely pathogenic rare missense heterozygous mutation in diabetes genes (c.2137C > T, p.His713Tyr in IRS1) was identified, which was a cosegregate in this family and not in nonrelated healthy controls. The position of the mutation in the aminoacid sequence of the gene is highly conserved among the species. 2 significantly enriched KEGG pathways were identified including bta04930, type II diabetes mellitus (GCK, INS, PDX1, ABCC8, and IRS1), and bta04910, insulin signaling pathway (GCK, INS, and IRS1). PPI analysis displayed that IRS1 interacts with 3 known pathogenic proteins including INS, KCNJ11, and GCK. We conclude that WES could be an initial option for genetic testing in patients with early-onset diabetes. IRS1 p.His713Tyr is implicated as a possible pathogenic mutation in monogenic diabetes, which might require further validation, and the precise molecular mechanism underlying the influence of IRS1 p.His713Tyr on the development of diabetes remains to be determined in the further prospective studies.

GATA factors in pancreas development and disease

There is an urgent need for the development of novel therapeutics options for diabetic patients given the high prevalence of diabetes worldwide and that, currently, there is no cure for this disease. The transplantation of pancreatic islets that contain insulin-producing cells is a promising therapeutic alternative, particularly for type 1 diabetes. However, the shortage of organ donors constitutes a major limitation for this approach; thus, developing alternative sources of insulin-producing cells is of critical importance. In the last decade, our knowledge of the molecular mechanisms controlling embryonic pancreas development has significantly advanced. More importantly, this knowledge has provided the basis for the in vitro generation of insulin-producing cells from stem cells. Recent studies have revealed that GATA transcription factors are involved in various stages of pancreas formation and in the adult ß cell function. Here, we review the fundamental role of GATA transcription factors in pancreas morphogenesis and their association with congenital diseases associated with pancreas.

GATA6 mutations: Characterization of two novel patients and a comprehensive overview of the GATA6 genotypic and phenotypic spectrum

The first human mutations in GATA6 were described in a cohort of patients with persistent truncus arteriosus, and the phenotypic spectrum has expanded since then. This study underscores the broad phenotypic spectrum by presenting two patients with de novo GATA6 mutations, both exhibiting complex cardiac defects, pancreatic, and other abnormalities. Furthermore, we provided a detailed overview of all published human genetic variation in/near GATA6 published to date and the associated phenotypes (n = 78). We conclude that the most common phenotypes associated with a mutation in GATA6 were structural cardiac and pancreatic abnormalities, with a penetrance of 87 and 60%, respectively. Other common malformations were gallbladder agenesis, congenital diaphragmatic hernia, and neurocognitive abnormalities, mostly developmental delay. Fifty-eight percent of the mutations were de novo, and these patients more often had an anomaly of intracardiac connections, an anomaly of the great arteries, and hypothyroidism, compared with those with inherited mutations. Functional studies mostly support loss-of-function as the pathophysiological mechanism. In conclusion, GATA6 mutations give a wide range of phenotypic defects, most frequently malformations of the heart and pancreas. This highlights the importance of detailed clinical evaluation of identified carriers to evaluate their full phenotypic spectrum.

A case of immune-mediated type 1 diabetes mellitus due to congenital rubella ınfection

Congenital rubella infection is a transplacental infection that can cause intrauterine growth retardation, cataracts, patent ductus arteriosus, hearing loss, microcephaly, thrombocytopenia, and severe fetal injury. It has been shown that type 1 diabetes mellitus develops in 12%-20% of patients with congenital rubella infection, and disorders in the oral glucose tolerance test is observed in 40% of patients. No biochemical or serological markers exist which could indicate that type 1 diabetes was caused by a congenital rubella infection. We report a 13-year-old male patient who was admitted to our hospital with complaints of new-onset polyuria, polydipsia, urination, and weight loss. In addition, he was found to have neurosensory hearing loss, patent ductus arteriosus, and microcephaly. Immunemediated type 1 diabetes mellitus was considered due to the fact that the autoantibodies of diabetes mellitus were positive.

Genome Editing in hPSCs Reveals GATA6 Haploinsufficiency and a Genetic Interaction with GATA4 in Human Pancreatic Development

Human disease phenotypes associated with haploinsufficient gene requirements are often not recapitulated well in animal models. Here, we have investigated the association between human GATA6 haploinsufficiency and a wide range of clinical phenotypes that include neonatal and adult-onset diabetes using CRISPR (clustered regularly interspaced short palindromic repeat)/Cas9-mediated genome editing coupled with human pluripotent stem cell (hPSC) directed differentiation. We found that loss of one GATA6 allele specifically affects the differentiation of human pancreatic progenitors from the early PDX1+ stage to the more mature PDX1+NKX6.1+ stage, leading to impaired formation of glucose-responsive β-like cells. In addition to this GATA6 haploinsufficiency, we also identified dosage-sensitive requirements for GATA6 and GATA4 in the formation of both definitive endoderm and pancreatic progenitor cells. Our work expands the application of hPSCs from studying the impact of individual gene loci to investigation of multigenic human traits, and it establishes an approach for identifying genetic modifiers of human disease.

Case report: maternal mosaicism resulting in inheritance of a novel GATA6 mutation causing pancreatic agenesis and neonatal diabetes mellitus

BACKGROUND

Haploinsufficiency of the GATA6 transcription factor gene was recently found to be the most common cause of pancreatic agenesis, a rare cause of neonatal diabetes mellitus. Although most cases are de novo, we describe three siblings with inherited GATA6 haploinsufficiency and the rare finding of parental mosaicism.

CASE PRESENTATION

The proband was born at term with severe intrauterine growth restriction, the first child of non-consanguineous parents. Diabetes occurred on day of life 1 with pancreatic exocrine insufficiency noted at several months of age. Pancreatic agenesis with absent gallbladder was confirmed when he underwent congenital diaphragmatic hernia and intestinal malrotation repair. A patent ductus arteriosus and pulmonary stenosis were repaired in infancy. Neurocognitive development has been normal. A second pregnancy was terminated due to tetralogy of Fallot and pulmonary hypoplasia secondary to congenital diaphragmatic hernia. The fetus also demonstrated severe pancreatic hypoplasia, gallbladder agenesis and intestinal rotation abnormalities. Despite severe hypoplasia, the pancreas demonstrated normal islet histology. Another sibling was found to have multiple cardiac abnormalities, requiring procedural intervention. Given the proband's spectrum of congenital anomalies, Sanger sequencing of the GATA6 gene was performed, revealing a novel heterozygous c.635_660del frameshift mutation (p.Pro212fs). The mutation is predicted to be pathogenic, resulting in inclusion of a premature stop codon and likely degradation of the gene transcript by nonsense-mediated decay. The abortus and the sibling with the cardiac defect were both found to have the mutation, while the father and remaining sibling were negative. The mother, who is healthy with no evidence of diabetes or cardiac disease, is mosaic for the mutation at a level of 11% in her peripheral leukocytes by next-generation sequencing.

CONCLUSION

We highlight a rare mechanism of pancreatic agenesis, this being only the second report of parental mosaicism for a GATA6 mutation and one of a handful of inherited cases. We also further define the phenotypic variability of GATA6 haploinsufficiency, even in individuals carrying the same mutation. Mutations in GATA6 should be strongly considered in cases of diabetes due to pancreatic hypoplasia or agenesis, and potentially affected family members should be tested regardless of phenotype.

Xenopus as a model system for studying pancreatic development and diabetes

Diabetes is a chronic disease caused by the loss or dysfunction of the insulin-producing β-cells in the pancreas. To date, much of our knowledge about β-cells in humans comes from studying rare monogenic forms of diabetes. Importantly, the majority of mutations so far associated to monogenic diabetes are in genes that exert a regulatory role in pancreatic development and/or β-cell function. Thus, the identification and study of novel mutations open an unprecedented window into human pancreatic development. In this review, we summarize major advances in the genetic dissection of different types of monogenic diabetes and the insights gained from a developmental perspective. We highlight future challenges to bridge the gap between the fast accumulation of genetic data through next-generation sequencing and the need of functional insights into disease mechanisms. Lastly, we discuss the relevance and advantages of studying candidate gene variants in vivo using the Xenopus as model system.

A loss-of-function and H2B-Venus transcriptional reporter allele for Gata6 in mice

Background

The GATA-binding factor 6 (Gata6) gene encodes a zinc finger transcription factor that often functions as a key regulator of lineage specification during development. It is the earliest known marker of the primitive endoderm lineage in the mammalian blastocyst. During gastrulation, GATA6 is expressed in early cardiac mesoderm and definitive endoderm progenitors, and is necessary for development of specific mesoderm and endoderm-derived organs including the heart, liver, and pancreas. Furthermore, reactivation or silencing of the Gata6 locus has been associated with certain types of cancer affecting endodermal organs.

Results

We have generated a Gata6^H2B-Venus knock-in reporter mouse allele for the purpose of labeling GATA6-expressing cells with a bright nuclear-localized fluorescent marker that is suitable for live imaging at single-cell resolution.

Conclusions

Expression of the Venus reporter was characterized starting from embryonic stem (ES) cells, through mouse embryos and adult animals. The Venus reporter was not expressed in ES cells, but was activated upon endoderm differentiation. Gata6^{H2B-Venus/H2B-Venus} homozygous embryos did not express GATA6 protein and failed to specify the primitive endoderm in the blastocyst. However, null blastocysts continued to express high levels of Venus in the absence of GATA6 protein, suggesting that early Gata6 transcription is independent of GATA6 protein expression. At early post-implantation stages of embryonic development, there was a strong correlation of Venus with endogenous GATA6 protein in endoderm and mesoderm progenitors, then later in the heart, midgut, and hindgut. However, there were discrepancies in reporter versus endogenous protein expression in certain cells, such as the body wall and endocardium. During organogenesis, detection of Venus in specific organs recapitulated known sites of endogenous GATA6 expression, such as in the lung bud epithelium, liver, pancreas, gall bladder, stomach epithelium, and vascular endothelium. In adults, Venus was observed in the lungs, pancreas, liver, gall bladder, ovaries, uterus, bladder, skin, adrenal glands, small intestine and corpus region of the stomach. Overall, Venus fluorescent protein under regulatory control of the Gata6 locus was expressed at levels that were easily visualized directly and could endure live and time-lapse imaging techniques. Venus is co-expressed with endogenous GATA6 throughout development to adulthood, and should provide an invaluable tool for examining the status of the Gata6 locus during development, as well as its silencing or reactivation in cancer or other disease states.

Electronic supplementary material

The online version of this article (doi:10.1186/s12861-015-0086-5) contains supplementary material, which is available to authorized users.

A novel mutation in GATA6 causes pancreatic agenesis

Heterozygous mutations in GATA6 have been linked to pancreatic agenesis and cardiac malformations. The aim of this study was to describe a new mutation in GATA6 in an infant with pancreatic agenesis, associated with truncus arteriosus and absent gallbladder. Clinical data were obtained from chart review. Gene sequencing was performed on genomic DNA. The patient was a female infant diagnosed shortly after birth with a severe cardiac malformation, absent gallbladder, anomalous hepatic blood flow, unilateral hydronephrosis and hydroureter, neonatal diabetes, and pancreatic exocrine insufficiency. Despite prolonged intensive management care, she died at 3 months of age because of cardiac complications. Analysis of her genomic DNA revealed a novel missense mutation of GATA6. The novel mutation described in this case extends the list of GATA6 mutations causing pancreatic agenesis and cardiac malformations.