Dysgenesis and Dysfunction of the Pancreas and Pituitary Due to FOXA2 Gene Defects

CONTEXT

Developmental disorders of the pituitary gland leading to congenital hypopituitarism can either be isolated or associated with extrapituitary abnormalities (syndromic hypopituitarism). A large number of syndromic hypopituitarism cases are linked to mutations in transcription factors. The forkhead box A2 (FOXA2) is a transcription factor that plays a key role in the central nervous system, foregut, and pancreatic development.

OBJECTIVE

This work aims to characterize 2 patients with syndromic hypopituitarism due to FOXA2 gene defects.

RESULTS

We report a novel heterozygous nonsense c.616C > T(p.Q206X) variant that leads to a truncated protein that lacks part of the DNA-binding domain of FOXA2, resulting in impaired transcriptional activation of the glucose transporter type 2 (GLUT2)-luciferase reporter. The patient is the sixth patient described in the literature with a FOXA2 mutation, and the first patient exhibiting pancreatic hypoplasia. We also report a second patient with a novel de novo 8.53 Mb deletion of 20p11.2 that encompasses FOXA2, who developed diabetes mellitus that responded to sulfonylurea treatment.

CONCLUSION

Our 2 cases broaden the molecular and clinical spectrum of FOXA2-related disease, reporting the first nonsense mutation and the first case of pancreatic dysgenesis.

Insights into the etiology and physiopathology of MODY5/HNF1B pancreatic phenotype with a mouse model of the human disease

Maturity-onset diabetes of the young type 5 (MODY5) is due to heterozygous mutations or deletion of HNF1B. No mouse models are currently available to recapitulate the human MODY5 disease. Here, we investigate the pancreatic phenotype of a unique MODY5 mouse model generated by heterozygous insertion of a human HNF1B splicing mutation at the intron-2 splice donor site in the mouse genome. This Hnf1bsp2/+ model generated with targeted mutation of Hnf1b mimicking the c.544+1G>T (T) mutation identified in humans, results in alternative transcripts and a 38% decrease of native Hnf1b transcript levels. As a clinical feature of MODY5 patients, the hypomorphic mouse model Hnf1bsp2/+ displays glucose intolerance. Whereas Hnf1bsp2/+ isolated islets showed no altered insulin secretion, we found a 65% decrease in pancreatic insulin content associated with a 30% decrease in total large islet volume and a 20% decrease in total β-cell volume. These defects were associated with a 30% decrease in expression of the pro-endocrine gene Neurog3 that we previously identified as a direct target of Hnf1b, showing a developmental etiology. As another clinical feature of MODY5 patients, the Hnf1bsp2/+ pancreases display exocrine dysfunction with hypoplasia. We observed chronic pancreatitis with loss of acinar cells, acinar-to-ductal metaplasia, and lipomatosis, with upregulation of signaling pathways and impaired acinar cell regeneration. This was associated with ductal cell deficiency characterized by shortened primary cilia. Importantly, the Hnf1bsp2/+ mouse model reproduces the pancreatic features of the human MODY5/HNF1B disease, providing a unique in vivo tool for molecular studies of the endocrine and exocrine defects and to advance basic and translational research. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Exocrine pancreatic dysfunction is common in hepatocyte nuclear factor 1β-associated renal disease and can be symptomatic

Background

Heterozygous mutations in the HNF1B gene are the most common monogenic cause of developmental kidney disease. Extrarenal phenotypes frequently occur, including diabetes mellitus and pancreatic hypoplasia; the latter is associated with subclinical exocrine dysfunction. We measured faecal elastase-1 in patients with HNF1B-associated disease regardless of diabetes status and assessed the degree of symptoms associated with pancreatic exocrine deficiency.

Methods

Faecal elastase-1 was measured in 29 patients with a known HNF1B mutation. We defined a low faecal elastase-1 concentration based on the 2.5 percentile of 99 healthy control individuals (410 μg/g stool). Symptoms related to pancreatic exocrine dysfunction were assessed and a subset of the HNF1B cohort (n  =  6) underwent pancreatic imaging.

Results

Faecal elastase-1 was below the 2.5 percentile of the control cohort in 18/29 (62%) patients with HNF1B-associated renal disease. A total of 8/29 (28%) had a measurement suggestive of exocrine pancreatic insufficiency at  <200 μg/g stool; of these, 3 suffered with abdominal pain, loose stools and/or unintentional weight loss. All three experienced symptomatic improvement and weight gain after commencing pancreatic enzyme replacement therapy. Faecal elastase-1 was low in 7/15 (47%) HNF1B patients without diabetes compared with 11/14 (79%) of those with diabetes (P  =  0.1).

Conclusions

Faecal elastase-1 deficiency is a common feature of HNF1B-associated renal disease even when diabetes is not present and pancreatic exocrine deficiency may be more symptomatic than previously suggested. Faecal elastase-1 should be measured in all patients with known HNF1B-associated disease complaining of chronic abdominal pain, loose stools or unintentional weight loss. The discovery of a low faecal elastase-1 concentration in individuals with developmental kidney disease of uncertain cause should prompt referral for HNF1B genetic testing.

A Newly-Discovered Mutation in the RFX6 Gene of the Rare Mitchell-Riley Syndrome

Mitchell-Riley syndrome is a genetic disorder characterized by neonatal diabetes, pancreatic hypoplasia, intestinal atresia and/or malrotation, biliary atresia, and gallbladder aplasia or hypoplasia. It was considered a variant of the Martinez-Frias syndrome with similar phenotypic characteristics, except for neonatal diabetes and tracheoesophageal fistula. However, the genetic mutation in (regulatory factor X on chromosome 6) RFX6 was only detected in babies who had diabetes, making it different from the previously known mutations for the disease. This is the first reported case of a classical Mitchell-Riley syndrome in the Arab peninsula along with additional features and novel mutations in the RFX6 gene.

Neonatal diabetes and protein losing enteropathy: a case report

Background

Neonatal diabetes is a rare form of monogenic diabetes with onset in the first six months of life occurring in 1/100,000 to 1/400,000 births. Both permanent and transient forms have been described. Permanent neonatal diabetes results predominantly from mutations in the KCNJ11 and ABCC8 genes. Less frequently, mutations of the GATA6 gene, located on chromosome 18 cause a form of permanent neonatal diabetes resulting from pancreatic hypoplasia or agenesis. Other anomalies associated with mutations of this gene have also been reported, most commonly congenital heart disease.

Case presentation

We report the case of a Caucasian male infant diagnosed shortly after birth with neonatal diabetes, truncus arteriosus type III, ventricular septal defect, atrial septal defect, an absent gallbladder and a right inguinal hernia. His diabetes resulted from a de novo mutation of the GATA6 gene resulting in pancreatic hypoplasia. At 20 months of age he developed protein losing enteropathy. This has not previously been associated with GATA6 mutations and it is not known if this association is causal.

Conclusion

The combination of neonatal diabetes and pancreatic agenesis/hypoplasia should alert the clinician to the possibility of a GATA6 gene abnormality. The association of protein losing enteropathy is unique to the reported case.