Absence of a PDX-1 mutation and normal gastroduodenal immunohistology in a child with pancreatic agenesis

Novel GATA6 mutations in patients with pancreatic agenesis and congenital heart malformations

Patients with pancreatic agenesis are born without a pancreas, causing permanent neonatal diabetes and pancreatic enzyme insufficiency. These patients require insulin and enzyme replacement therapy to survive, grow, and maintain normal blood glucose levels. Pancreatic agenesis is an uncommon condition but high-throughput sequencing methods provide a rare opportunity to identify critical genes that are necessary for human pancreas development. Here we present the clinical history, evaluation, and the genetic and molecular analysis from two patients with pancreatic agenesis. Both patients were born with intrauterine growth restriction, minor heart defects and neonatal diabetes. In both cases, pancreatic agenesis was confirmed by imaging studies. The patients are clinically stable with pancreatic enzymes and insulin therapy. In order identify the etiology for their disease, we performed whole exome sequencing on both patients. For each proband we identified a de novo heterozygous mutation in the GATA6 gene. GATA6 is a homeobox containing transcription factor involved in both early development of the pancreas and heart. In vitro functional analysis of one of the variants revealed that the mutation creates a premature stop codon in the coding sequence resulting in the production of a truncated protein with loss of activity. These results show how genetic mutations in GATA6 may lead to functional inactivity and pancreatic agenesis in humans.

Neonatal diabetes, gallbladder agenesis, duodenal atresia, and intestinal malrotation caused by a novel homozygous mutation in RFX6

Recently, bi-allelic mutations in the transcription factor RFX6 were described as the cause of a rare condition characterized by neonatal diabetes with pancreatic and biliary hypoplasia and duodenal/jejunal atresia. A male infant developed severe hyperglycemia (446 mg/dL) within 24 h of birth. Acute abdominal concerns by day five necessitated exploratory surgery that revealed duodenal atresia, gallbladder agenesis, annular pancreas and intestinal malrotation. He also exhibited chronic diarrhea and feeding intolerance, cholestatic jaundice, and subsequent liver failure. He died of sepsis at four months old while awaiting liver transplantation. The phenotype of neonatal diabetes with intestinal atresia and biliary agenesis clearly pointed to RFX6 as the causative gene; indeed, whole exome sequencing revealed a novel homozygous RFX6 mutation c.779A>C; p.Lys260Thr (K260T). This missense mutation also changes the consensus 5' splice donor site before intron 7 and is thus predicted to cause disruption in splicing. Both parents, who were not known to be related, were heterozygous carriers. Targeted genetic testing based on consideration of phenotypic features may reveal a cause among the many genes now associated with heterogeneous forms of monogenic neonatal diabetes. Our study demonstrates the feasibility of using modern sequencing technology to identify one such rare cause. Continued research is needed to determine the possible cost-effectiveness of this approach, especially when clear phenotypic clues are absent. Further study of patients with RFX6 mutations should clarify its role in pancreatic, intestinal and enteroendocrine cellular development and explain features such as the diarrhea exhibited in our case.

Clinical characterization of a newly described neonatal diabetes syndrome caused by RFX6 mutations

Mutations in the RFX6 gene were recently described to underlie a distinct autosomal recessive syndrome of neonatal diabetes comprising intestinal atresia and hepatobiliary abnormalities. Until now, only six patients harboring RFX6 mutations have been reported. We report on a new case due to a novel homozygous splice site mutation and update on the clinical outcome of a previously reported patient. In addition we review the clinical and molecular features of all RFX6 mutated cases to better characterize the syndrome. Our results suggest that despite the early postnatal fulminant course, patients who survive may expect a relatively favorable prognosis.

Defining the cancer master switch

BACKGROUND

Recent research has focused on signaling cascades and their interactions yielding considerable insight into which genetic pathways are targeted and how they tend to be altered in tumors. Therapeutic interventions now can be designed based on the knowledge of pathways vital to tumor growth and survival. These critical targets for intervention, master switches for cancer, are termed so because the tumor attempts to "flip the switch" in a way that promotes its survival, whereas molecular therapy aims to "switch off" signals important for tumor-related processes.

METHODS

Literature review.

CONCLUSIONS

Defining useful targets for therapy depends on identifying pathways that are crucial for tumor growth, survival, and metastasis. Because not all signaling cascades are created equal, selecting master switches or targets for intervention needs to be done in a systematic fashion. This discussion proposes a set of criteria to define what it means to be a cancer master switch and provides examples to illustrate their application.

Pancreatic hypoplasia presenting with neonatal diabetes mellitus in association with congenital heart defect and developmental delay

Congenital pancreatic hypoplasia is a rare cause of neonatal diabetes. We report on a series of three patients with pancreatic agenesis and congenital heart defects. All had abdominal scan evidence of pancreatic agenesis. In addition, Patient 1 had a ventricular septal defect, patent ductus arteriosus and pulmonary artery stenosis; Patient 2 had a truncus arteriosus and Patient 3 had tetralogy of Fallot. Two of the three patients have developmental delay. All three patients were isolated cases within the family. Investigations included sequencing of GCK, ABCC8, IPF1, NEUROD1, PTF1A, HNF1B, INS, ISL1, NGN3, HHEX, G6PC2, TCF7L2, SOX4, FOXP3 (Patients 1 and 2), GATA4 and KCNJ11 genes (all three patients), but no mutations were found. Genetic investigation to exclude paternal UPD 6, methylation aberrations and duplications of 6q24 was also negative in all three. 22q11 deletion was excluded in all three patients. Array CGH in Patient (1) showed a approximately 250 kb, paternally inherited duplication of chromosome 12q [arr cgh 12q24.33 (B35:CHR12:131808577-132057649++) pat], not found in the other two patients. Permanent neonatal diabetes mellitus due to pancreatic hypoplasia with congenital heart defects has been reported before and may represent a distinct condition. We discuss this rare association and review previously reported literature.

Neonatal diabetes mellitus due to pancreas agenesis: a new case report and review of the literature

Neonatal diabetes mellitus (NDM) is a rare condition (1:400,000 neonates) defined as hyperglycemia occurring in the first months of life, lasting more than 2 wk and requiring insulin for management. We here report on a 33-month-old girl with pancreatic agenesis, an extremely rare cause of permanent neonatal diabetes mellitus (PNDM). Timely diagnosis and adequate treatment of both endocrine and exocrine insufficiency may permit survival and normal development.

A further example of a distinctive autosomal recessive syndrome comprising neonatal diabetes mellitus, intestinal atresias and gall bladder agenesis

We report a patient born to consanguineous parents as a further example of a recently described phenotype comprising neonatal diabetes, intestinal atresias and gall bladder agenesis. Other reports have described cases with overlapping patterns including malrotation, biliary atresia and pancreatic hypoplasia (e.g. as described by Martínez-Frías). We propose that these cases may represent variations of the same syndrome. It is likely that this disorder is inherited as an autosomal recessive trait. Our case is the first to have neonatal diabetes without a demonstrable structural pancreatic abnormality, showing that a deficit in pancreatic function is involved. We sequenced genes with a recognized role in monogenic forms of diabetes, including KCNJ11, ABCC8, GCK, IPF1, HNF1beta, NeuroD1 and TCF7L2, as well as a novel candidate gene, HNF6, known to be involved in hepatobiliary and pancreatic development, but did not identify mutations.

Neonatal and late-onset diabetes mellitus caused by failure of pancreatic development: report of 4 more cases and a review of the literature

OBJECTIVE

Permanent neonatal diabetes mellitus caused by developmental failure of the pancreas is rare. Thus far, only a few genetic causes have been reported. We now report the clinical and genetic aspects of 4 more cases of permanent neonatal diabetes mellitus caused by pancreatic agenesis or hypoplasia.

PATIENTS AND METHODS

All 4 of the patients were from consanguineous kinships, and all presented with diabetes mellitus and pancreatic exocrine insufficiency. Three patients had pancreatic agenesis, and 1 had pancreatic hypoplasia on computed tomography scan. DNA was extracted from blood samples of patients and unaffected family members. Specific genes were amplified by polymerase chain reaction and characterized by DNA sequencing.

RESULTS

Several genes that encode transcription factors that have known roles in pancreas development were characterized in the affected children and unaffected family members. These genes include Pdx1, the master regulator of pancreas development and beta-cell differentiation, and other transcription factors that are expressed early in pancreas development, namely, Ptf1a, Sox9, Sox17, Hnf6, and HlxB9. Several novel polymorphisms were found in our patients. However, these were also present in unaffected individuals. No disease-causing mutations were found in any of these genes.

CONCLUSIONS

These findings add to the 4 cases already in the literature in which the Pdx1 structural gene has been found to be normal in patients with pancreatic agenesis or hypoplasia. The analysis here has been extended to include the screening of 4 other candidate genes in addition to promoter elements upstream of the Pdx1. Two of the cases occurred in a sibling pair, and 2 were isolated, so there may be more than 1 etiology in the cases reported here.

Neonatal diabetes: how research unravelling the genetic puzzle has both widened our understanding of pancreatic development whilst improving children's quality of life

It has become increasingly apparent over the last few years that the seemingly ubiquitous auto-immune aetiology to pre-pubertal diabetes does not apply to those diagnosed under 6 months of age. In this age group, disease appears, in the vast majority of cases, to be conferred by single gene disorders mainly related to pancreatic development. The unravelling of these disorders has resulted in a far greater understanding of pancreatic development and some startling changes in treatment, resulting in improved quality of life and diabetes control. The progress made in our scientific and clinical understanding of these extremely rare diseases is a perfect example of how studying seemingly rare illnesses can improve our overall knowledge of much more common conditions.

Unusual case of neonatal diabetes mellitus due to congenital pancreas agenesis

Congenital absence of the pancreas is an extremely rare condition. We participated in the care of a patient with an unusual presentation of neonatal diabetes attributable to agenesis of the pancreas. Additional clinical features of the patient included cardiac septal defects, gall bladder agenesis and duodenal malrotation. Appropriate institution of insulin, exocrine pancreatic supplements and surgical repair of the cardiac and intestinal anomalies resulted in the infant's survival. Of the reported cases of congenital pancreas agenesis, two cases have been ascribed to mutations in the insulin promoter factor-1(Ipf-1) gene. Deletion of the Ipf-1-homolog pdx-1 in mice results in the failure of pancreas to develop. Analysis of both exons of the Ipf-1 coding sequence from the presented patient's genomic DNA, however, did not identify a mutation. These results suggest that a congenital or genetic perturbation occurred in this infant most likely before the appearance of dorsal pancreatic bud in the 3 mm long embryonic stage, around the embryonic day 25 in human development, before the onset of Ipf-1 expression.

Ductuloinsular tumors of the pancreas: endocrine tumors with entrapped nonneoplastic ductules

Rare pancreatic neoplasms have been reported that show both endocrine and exocrine differentiation in the neoplastic components. In addition, pancreatic endocrine tumors may contain small, cytologically bland ductules intimately admixed with the endocrine component. It was recently suggested that these ductules represent an intrinsic part of the tumor, ie, that the ductules are neoplastic, and the term "ductulo-insular tumors of the pancreas" was proposed. In the present study, the nature of the ductular component of 16 cases of ductule-containing pancreatic endocrine tumors was investigated at the molecular level. Molecular genetic changes often present in ductal pancreatic neoplasms were not found by immunohistochemistry for DPC4, p53, and ERBB2 and by sequence analysis of KRAS codon 12. An X-chromosome inactivation clonality assay of one such tumor from a female patient indicated that the neuroendocrine component was monoclonal, contrasting with the ductular component that was polyclonal. The lymph node and liver metastases from three patients only contained the neuroendocrine component, and no ductules were observed. Although certain morphologic features of ductule-containing endocrine tumors are reminiscent of the embryonic development of the human pancreas, none of the tumors expressed PDX-1, a transcription factor essential in pancreatic organ development. Based on our results, it is suggested that the ductular component occasionally found in pancreatic endocrine tumors is the result of entrapment of preexisting nonneoplastic ductules and that the tumors are otherwise not distinctive from conventional pancreatic endocrine tumors. Although the phenomenon is rare, it is important to recognize and to distinguish these tumors from true mixed ductal-endocrine neoplasms, which are generally more clinically aggressive. "Pancreatic endocrine tumors with entrapped ductules" would be the preferred nomenclature since it better reflects the nonneoplastic nature of the ductules.