Localization of human homeodomain transcription factor insulin promoter factor 1 (IPF1) to chromosome band 13q12.1

Unlocking β-cell restoration: The crucial role of PDX1 in diabetes therapy

Diabetes has been a significant healthcare problem worldwide for a considerable period. The primary objective of diabetic treatment plans is to control the symptoms associated with the pathology. To effectively combat diabetes, it is crucial to comprehend the disease's etiology, essential factors, and the relevant processes involving β-cells. The development of the pancreas, maturation, and maintenance of β-cells, and their role in regular insulin function are all regulated by PDX1. Therefore, understanding the regulation of PDX1 and its interactions with signaling pathways involved in β-cell differentiation and proliferation are crucial elements of alternative diabetes treatment strategies. The present review aims to explore the protective role of PDX1 in β-cell proliferation through signaling pathways. The main keywords chosen for this review include "PDX1 for β-cell mass," "β-cell proliferation," "β-cell restoration via PDX1," and "mechanism of PDX1 in β-cells." A comprehensive literature search was conducted using various internet search engines, such as PubMed, Science Direct, and other publication databases. We summarize several approaches to generating β-cells from alternative cell sources, employing PDX1 under various modified growth conditions and different transcriptional factors. Our analysis highlights the unique potential of PDX1 as a promising target in molecular and cell-based therapies for diabetes.

PDX1 is the cornerstone of pancreatic β-cell functions and identity

Diabetes has been a worldwide healthcare problem for many years. Current methods of treating diabetes are still largely directed at symptoms, aiming to control the manifestations of the pathology. This creates an overall need to find alternative measures that can impact on the causes of the disease, reverse diabetes, or make it more manageable. Understanding the role of key players in the pathogenesis of diabetes and the related β-cell functions is of great importance in combating diabetes. PDX1 is a master regulator in pancreas organogenesis, the maturation and identity preservation of β-cells, and of their role in normal insulin function. Mutations in the PDX1 gene are correlated with many pancreatic dysfunctions, including pancreatic agenesis (homozygous mutation) and MODY4 (heterozygous mutation), while in other types of diabetes, PDX1 expression is reduced. Therefore, alternative approaches to treat diabetes largely depend on knowledge of PDX1 regulation, its interaction with other transcription factors, and its role in obtaining β-cells through differentiation and transdifferentiation protocols. In this article, we review the basic functions of PDX1 and its regulation by genetic and epigenetic factors. Lastly, we summarize different variations of the differentiation protocols used to obtain β-cells from alternative cell sources, using PDX1 alone or in combination with various transcription factors and modified culture conditions. This review shows the unique position of PDX1 as a potential target in the genetic and cellular treatment of diabetes.

PDX-1: A Promising Therapeutic Target to Reverse Diabetes

The pancreatic duodenum homeobox-1 (PDX-1) is a transcription factor encoded by a Hox-like homeodomain gene that plays a crucial role in pancreatic development, β-cell differentiation, and the maintenance of mature β-cell functions. Research on the relationship between PDX-1 and diabetes has gained much attention because of the increasing prevalence of diabetes melitus (DM). Recent studies have shown that the overexpression of PDX-1 regulates pancreatic development and promotes β-cell differentiation and insulin secretion. It also plays a vital role in cell remodeling, gene editing, and drug development. Conversely, the absence of PDX-1 increases susceptibility to DM. Therefore, in this review, we summarized the role of PDX-1 in pancreatic development and the pathogenesis of DM. A better understanding of PDX-1 will deepen our knowledge of the pathophysiology of DM and provide a scientific basis for exploring PDX-1 as a potential target for treating diabetes.

Encapsulation and Transplantation of Pancreatic Progenitor Cells

Type 1 diabetes, characterized by autoimmune destruction of pancreatic beta cells, affects 41 million people worldwide. Beta cell replacement therapies have immense potential as a treatment option because pancreatic progenitors derived from human pluripotent stem cells can provide a near limitless supply of transplantable tissue. The key limitation of this approach is the need for lifelong use of immunosuppressive drugs that have undesirable side effects. Microencapsulation is an option for providing protection for transplanted cells from mechanical stress and immune attack. Traditionally, pluripotent cells are differentiated on a 2D matrix before being transferred into an immunoisolation device. Here, we describe a method of differentiating pluripotent stem cells into pancreatic progenitors while the cells are encapsulated in alginate microspheres. This method provides several advantages including the need for fewer steps compared to the traditional approach, protection against mechanical/physical damage during differentiation in bioreactors, and immune-protection of cells once transplanted into the host.

Investigating the role of transcription factors of pancreas development in pancreatic cancer

Pancreatic cancer (PC) is the seventh most common cause of cancer-related deaths worldwide that kills more than 300,000 people every year. Prognosis of PC is very poor with a five-year survival rate about 5%. The most common and highly observed type of PC is pancreatic ductal adenocarcinoma (PDAC). It is preceded by the progression of precursor lesions such as Pancreatic Intraepithelial Neoplasia (PanIN), Intraductal Papillary Neoplasm (IPMN) and Mucinous Cystic Neoplasm (MCN). PanIN is the most common among these premalignant lesions. Genes orchestrating the origin and differentiation of cells during organogenesis have the tendency to produce tumor cells in response to activating or inactivating mutations. Based on the following premise, we discuss the role of transcription factors (TFs) of pancreas development and cell fate differentiation in PC. Pancreas/duodenum homeobox protein 1 (PDX1), Pancreas transcription factor 1 subunit alpha (PTF1A), Nuclear receptor subfamily 5 group A member 2 (NR5A2), Hepatocyte nuclear factor 1-alpha (HNF1A) and Hepatocyte nuclear factor 1-beta (HNF1B) play vital role in the development and differentiation of pancreatic precursor cells. Mutated KRAS induces abnormalities in the regular function of these TFs which in turn cause abnormal cell growth and proliferation that leads to cancer. Thus, these TFs are highly susceptible for the origin of PC. Therefore, we propose that these TFs can be treated as therapeutic targets for the development of anticancer drugs.

Quantitative Evaluation of Serum Proteins Uncovers a Protein Signature Related to Maturity-Onset Diabetes of the Young (MODY)

Maturity-onset diabetes of the young (MODY) is an inherited monogenic type of diabetes. Genetic mutations in MODY often cause nonsynonymous changes that directly lead to the functional distortion of proteins and the pathological consequences. Herein, we proposed that the inherited mutations found in a MODY family could cause a disturbance of protein abundance, specifically in serum. The serum samples were collected from a Uyghur MODY family through three generations, and the serum proteins after depletion treatment were examined by quantitative proteomics to characterize the MODY-related serum proteins followed by verification using target quantification of proteomics. A total of 32 serum proteins were preliminarily identified as the MODY-related. Further verification test toward the individual samples demonstrated the 12 candidates with the significantly different abundance in the MODY patients. A comparison of the 12 proteins among the sera of type 1 diabetes, type 2 diabetes, MODY, and healthy subjects was conducted and revealed a protein signature related with MODY composed of the serum proteins such as SERPINA7, APOC4, LPA, C6, and F5.

Changes on the Pancreas in Experimental Diabetes and the Effect of Lycopene on These Changes: Pdx-1, Ngn-3, and Nestin Expressions

The aim of the present study was to investigate changes occurring in the number of beta cells, as well as the expressions of Ngn-3, nestin and Pdx-1 of pancreatic progenitor cells in the pancreas of experimentally-induced adult diabetic rats and to determine the effect of orally-administered lycopene on these changes. Following the administration of 50 mg/kg streptozotocin to rats, four groups of animals were established: control + corn oil, control + lycopene, diabetic + corn oil and diabetic + lycopene. The animals in the control + lycopene and diabetic + lycopene groups received 4 mg/kg lycopene for a period of four weeks. The expressions of insulin, Ngn-3, nestin, and Pdx-1 were determined through immunohistochemistry in sections taken from pancreas tissue samples at the end of the experiment. The number of insulin-positive cells was found to be significantly low in the diabetic groups compared to the control groups. In addition, the presence of Ngn-3 and nestin-positive cells within the exocrine pancreas surrounding the islands was noted in the diabetic groups. Lycopene, in general did not have any effect in any of the parameters analyzed in the present study. It is suggested that these cells would function as stem cells to replace the lost beta-cell population. It is also suggested that it is possible to demonstrate the antioxidant effects of lycopene in the pancreas of diabetic rats by increasing the dose and duration of lycopene administration. Anat Rec, 300:2200-2207, 2017. © 2017 Wiley Periodicals, Inc.

The Construction of Regulatory Network for Insulin-Mediated Genes by Integrating Methods Based on Transcription Factor Binding Motifs and Gene Expression Variations

Type 2 diabetes mellitus is a complex metabolic disorder associated with multiple genetic, developmental and environmental factors. The recent advances in gene expression microarray technologies as well as network-based analysis methodologies provide groundbreaking opportunities to study type 2 diabetes mellitus. In the present study, we used previously published gene expression microarray datasets of human skeletal muscle samples collected from 20 insulin sensitive individuals before and after insulin treatment in order to construct insulin-mediated regulatory network. Based on a motif discovery method implemented by iRegulon, a Cytoscape app, we identified 25 candidate regulons, motifs of which were enriched among the promoters of 478 up-regulated genes and 82 down-regulated genes. We then looked for a hierarchical network of the candidate regulators, in such a way that the conditional combination of their expression changes may explain those of their target genes. Using Genomica, a software tool for regulatory network construction, we obtained a hierarchical network of eight regulons that were used to map insulin downstream signaling network. Taken together, the results illustrate the benefits of combining completely different methods such as motif-based regulatory factor discovery and expression level-based construction of regulatory network of their target genes in understanding insulin induced biological processes and signaling pathways.

In-vitro generation of human adipose tissue derived insulin secreting cells: up-regulation of Pax-6, Ipf-1 and Isl-1

We present a study of up-regulation of genes responsible for pancreatic development in glucose-sensitive insulin-secreting mesenchymal stem cells (IS-MSC) generated and differentiated from human adipose tissue (h-AD), with use of our specific differentiation media and without use of any xenogenic material. Anterior wall abdominal fat was collected from 56 volunteers and cultured in self-designed proliferation medium for 10 days. Cells were harvested by trypsinization and differentiated into insulin-expressing cells using self-designed differentiation medium for 3 days followed by evaluation for transcriptional factors Pax-6, Ipf-1, Isl-1, C-peptide and insulin secretion. Generated IS-MSC showed expression of Pax-6, Pdx-6 and Isl-1. Non-differentiated MSC as well as their further culture in absence of differentiation medium were used as negative controls. Generated 56 IS-MSC cell-lines were glucose responsive i.e. mean C-Peptide and insulin secretion levels were measured 0.41 ng/ml and 13.13 μU/ml, respectively, in absence of glucose which rose to 1.18 ng/ml and 83.42 μU/ml, respectively, following glucose challenge (p < 0.001). The mean rise in C-peptide and insulin secretion levels was 2.88 and 6.35 fold, respectively. To conclude insulin-secreting h-AD-MSC can be generated safely and effectively with application of specific differentiation media without xenogeneic material/any genetic modification, showing expression of transcriptional factors Pax-6, Ipf-1 and Isl-1.

Maternal obesity during the preconception and early life periods alters pancreatic development in early and adult life in male mouse offspring

Maternal obesity induced by a high fat (HF) diet may program susceptibility in offspring, altering pancreatic development and causing later development of chronic degenerative diseases, such as obesity and diabetes. Female mice were fed standard chow (SC) or an HF diet for 8 weeks prior to mating and during the gestational and lactational periods. The male offspring were assessed at birth, at 10 days, and at 3 months of age. The body mass (BM) gain was 50% greater before pregnancy and 80% greater during pregnancy in HF dams than SC dams. Dams fed an HF diet showed higher oral glucose tolerance test (OGTT), blood pressure, serum corticosterone, and insulin levels than dams fed SC. At 10 days of age and at 3 mo old the HF offspring showed greater BM and higher blood glucose levels than the SC offspring. The mean diameter of the islets had increased by 37% in the SC offspring and by 155% in the HF offspring at 10 days of age. The islet mass ratio (IM/PM) was 88% greater in the HF offspring at 10 days of age, and 107% greater at 3 mo of age, compared to the values obtained at birth. The HF offspring had a beta cell mass (BCM)/PM ratio 54% lower than SC offspring at birth. However, HF offspring displayed a 146% increase in the BCM/PM ratio at 10 days of age, and 112% increase at 3 months of age than values at birth. A 3 mo of age, the HF offspring showed a greater OGTT and higher levels of than SC offspring. In conclusion, a maternal HF diet consumed during the preconceptional period and throughout the gestational and lactational periods in mice results in dramatic alterations in the pancreata of the offspring.

Parallel retention of Pdx2 genes in cartilaginous fish and coelacanths

The Pdx1 or Ipf1 gene encodes an important homeodomain-containing protein with key roles in pancreas development and function. Mutations in human PDX1 are implicated in developmental defects and disease of the pancreas. Extensive research, including genome sequencing, has indicated that Pdx1 is the only member of its gene family in mammals, birds, amphibians, and ray-finned fish, and with the exception of teleost fish, this gene forms part of the ParaHox gene cluster along with Gsx1 and Cdx2. The ParaHox cluster, however, is a remnant of a 4-fold genome duplication; the three other ParaHox paralogues lack a Pdx-like gene in all vertebrate genomes examined to date. We have used bacterial artificial chromosome cloning and synteny analysis to show that the ancestor of living jawed vertebrates in fact had more ParaHox genes, including two Pdx genes (Pdx1 and Pdx2). Surprisingly, the two Pdx genes have been retained in parallel in two quite distantly related lineages, the cartilaginous fish (sharks, skates, and chimeras) and the Indonesian coelacanth, Latimeria menadoensis. The Pdx2 gene has been lost independently in ray-finned fish and in tetrapods.

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.

PDX-1 and the pancreas

Many transcription factors are critical for ensuring proper embryonic development of the endocrine pancreas and normal islet function. The transcription factor pancreatic duodenal homeobox 1 (PDX-1) is uniformly expressed in early pancreatic buds of embryos as well as the beta and delta cells of the islets of Langerhans. PDX-1 has also been found in dispersed endocrine cells of the duodenum in adults and plays a key role in pancreas formation. It has been reported that null mutation of PDX-1 in mice results in a failure of the pancreatic bud to expand; thus, the mice die 2-3 days after birth from hyperglycemia and dehydration. Heterozygous PDX-1 mice developed a pancreas but were diabetic. It has been shown that PDX-1 is required for maintaining the pancreatic islet functions by activating gene transcriptions including insulin, somatostatin (SST), islet amyloid polypeptide, glucose transporter type 2, and glucokinase. PDX-1 serves a dual role in pancreatic development. It initially contributes to pancreatic formation during embryogenesis and subsequently regulates the pancreatic islet cell physiology in mature islet cells. Understanding the underlying molecular mechanisms of pancreas formation, especially the function of PDX-1, may contribute to the enhanced treatment and prevention of debilitating diseases such as diabetes, insulinomas, and pancreatic carcinomas.

Regulation of pdx-1 gene expression

The homeodomain-containing transcription factor pancreatic duodenal homeobox 1 (PDX-1) plays a key role in pancreas development and in beta-cell function. Upstream sequences of the gene up to about -6 kb show islet-specific activity in transgenic mice. Attempts to identify functional regulatory elements involved in the controlled expression of the pdx-1 gene led to the identification of distinct distal beta-cell-specific enhancers in human and rat genes. Three additional sequences, conserved between the mouse and the human 5'-flanking regions, two of which are also found in the chicken gene, conferred beta-cell-specific expression on a reporter gene, albeit to different extents. A number of transcription factors binding to and modulating the transcriptional activity of the regulatory elements were identified, such as hepatocyte nuclear factor (HNF)-3beta, HNF-1alpha, SP1/3, and, interestingly, PDX-1 itself. A fourth conserved region was localized to the proximal promoter around an E-box motif and was found to bind members of the upstream stimulatory factor (USF) family of transcription factors. We postulate that disruption of pdx-1 cis-acting regulatory sequences and/or mutations or functional impairment of transcription factors controlling the expression of the gene can lead to diabetes.

Pancreatic Duodenal Homeobox (PDX-1) in health and disease

Insulin is expressed exclusively in the adult beta-cells of the islets of Langerhans. Pancreatic Duodenum Homeobox-1 (PDX-1) is a major regulator of transcription in these cells. It transactivates the insulin gene by binding to a specific DNA motif in its promoter region. Glucose, the main physiological regulator of insulin secretion, also regulates insulin gene transcription through PDX-1. While acute exposure to high glucose concentrations causes an increase in PDX-1 binding, and consequently in insulin mRNA levels, chronic hyperglycemia (toxic to the beta-cell) leads to a decrease in PDX-1 and insulin levels. PDX-1 is absolutely required for pancreas development. In view of the selective expression in adult beta-cells, pancreatic agenesis in both the pdx-1 null mouse and a human carrying a homozygous mutation of PDX-1 was an unexpected and remarkable finding. The homozygous clinical phenotype was neonatal diabetes mellitus (DM) and exocrine insufficiency. Heterozygosity for PDX-1 mutations was found in some individuals with a newly characterized subtype of maturity-onset diabetes of the young (MODY4) and in others with type 2 DM. This review underlines the unique role of PDX-1 in maintaining adult beta-cell-specific functions in normal and disease-related states.

Exendin-4 differentiation of a human pancreatic duct cell line into endocrine cells: involvement of PDX-1 and HNF3beta transcription factors

Exendin-4 (EX-4), a long acting agonist of GLP-1, induces an endocrine phenotype in Capan-1 cells. Under culture conditions which include serum, approximately 10% of the cells contain insulin and glucagon. When exposed to EX-4 (0.1 nM, up to 5 days), the number of cells containing insulin and glucagon increased to approximately 40%. Western blot analysis detected a progressive increase in protein levels of glucokinase and GLUT2 over 3 days of EX-4 treatment. We explored the sequence of activation of certain transcription factors known to be essential for the beta cell phenotype: PDX-1, Beta2/NeuroD, and hepatocyte nuclear factor 3beta (HNF3beta). Double immunostaining showed that PDX-1 coexisted with insulin and glucagon in EX-4-treated cells. Treatment caused an increase in PDX-1 protein levels by 24 h and induced its nuclear translocation. Beta2/NeuroD protein levels also increased progressively over 24 h. HNF3beta protein level increased twofold as early as 6 h after EX-4 treatment. EMSA results indicated that EX-4 caused a 12-fold increase in HNF3beta binding to PDX-1 promoter area II. Beta2/NeuroD protein levels progressively increased after 24 h treatment. Differentiation to insulin-producing cells was also seen when Capan-1 cells were transfected with pdx-1, with 80% of these cells expressing insulin 3 days after transfection. PDX-1 antisense totally inhibited such conversion. During the differentiation of duct cells to endocrine cells, cAMP levels (EX-4 is a ligand for the GLP-1, G-protein coupled receptor) and MAP kinase activity increased. Our results indicate that EX-4 activates adenylyl cyclase and MAP kinase which, in turn, may lead to activation of transcription factors necessary for an endocrine phenotype.

Defining the genetic contribution of type 2 diabetes mellitus

Type 2 diabetes mellitus is a common multifactorial genetic syndrome, which is determined by several different genes and environmental factors. It now affects 150 million people world wide but its incidence is increasing rapidly because of secondary factors, such as obesity, hypertension, and lack of physical activity. Many studies have been carried out to determine the genetic factors involved in type 2 diabetes mellitus. In this review we look at the different strategies used and discuss the genome wide scans performed so far in more detail. New technologies, such as microarrays, and the discovery of SNPs will lead to a greater understanding of the pathogenesis of type 2 diabetes mellitus and to better diagnostics, treatment, and eventually prevention.

The ParaHox gene cluster is an evolutionary sister of the Hox gene cluster

Genes of the Hox cluster are restricted to the animal kingdom and play a central role in axial patterning in divergent animal phyla. Despite its evolutionary and developmental significance, the origin of the Hox gene cluster is obscure. The consensus is that a primordial Hox cluster arose by tandem gene duplication close to animal origins. Several homeobox genes with high sequence identity to Hox genes are found outside the Hox cluster and are known as 'dispersed' Hox-like genes; these genes may have been transposed away from an expanding cluster. Here we show that three of these dispersed homeobox genes form a novel gene cluster in the cephalochordate amphioxus. We argue that this 'ParaHox' gene cluster is an ancient paralogue (evolutionary sister) of the Hox gene cluster; the two gene clusters arose by duplication of a ProtoHox gene cluster. Furthermore, we show that amphioxus ParaHox genes have co-linear developmental expression patterns in anterior, middle and posterior tissues. We propose that the origin of distinct Hox and ParaHox genes by gene-cluster duplication facilitated an increase in body complexity during the Cambrian explosion.

Homeodomain protein IDX-1: a master regulator of pancreas development and insulin gene expression

The homeodomain protein IDX-1 appears to be a "master regulator" of pancreas development and beta-cell differentiation and function. In murine gene inactivation models and in a human subject with a homozygous mutation of the IDX-1 gene, the pancreas fails to develop. In the adult endocrine pancreas, IDX-1 is primarily expressed in beta cells, where it is a key factor in the upregulation of insulin gene transcription and appears to have a role in the regulation of the somatostatin, glucokinase, glucose transporter-2, and islet amyloid polypeptide genes. Recent studies also suggest a role for IDX-1 in the neogenesis and proliferation of beta cells. The observed functions of IDX-1 and its downregulation in parallel with insulin in glucose-toxicity models implicate IDX-1 as a potential factor contributing to the pathogenesis of diabetes mellitus. Future directions include the use of conditional gene inactivation to determine more precisely the role of IDX-1 throughout endocrine pancreas differentiation and the exploration of IDX-1 as a potential target for gene therapy of diabetes mellitus.

Pancreatic agenesis attributable to a single nucleotide deletion in the human IPF1 gene coding sequence

The homeodomain protein IPF1 (also known as IDX1, STF1 and PDX1; see Methods) is critical for development of the pancreas in mice and is a key factor for the regulation of the insulin gene in the beta-cells of the endocrine pancreas. Targeted disruption of the Ipf1 gene encoding IPF1 in transgenic mice results in a failure of the pancreas to develop (pancreatic agenesis). Here, we report the identification of a single nucleotide deletion within codon 63 of the human IPF1 gene (13q12.1) in a patient with pancreatic agenesis. The patient is homozygous for the point deletion, whereas both parents are heterozygotes for the same mutation. The deletion was not found in 184 chromosomes from normal individuals, indicating that the mutation is unlikely to be a rare polymorphism. The point deletion causes a frame shift at the C-terminal border of the transactivation domain of IPF1 resulting in the translation of 59 novel codons before termination, aminoproximal to the homeodomain essential for DNA binding. Expression of mutant IPF1 in Cos-1 cells confirms the expression of a prematurely terminated truncated protein of 16 kD. Thus, the affected patient should have no functional IPF1 protein. Given the essential role of IPF1 in pancreas development, it is likely that this autosomal recessive mutation is the cause of the pancreatic agenesis phenotype in this patient. Thus, IPF1 appears to be a critical regulator of pancreas development in humans as well as mice.

Checklist: vertebrate homeobox genes

Up to now around 170 different homeobox genes have been cloned from vertebrate genomes. A compilation of the various isolates from mouse, chick, frog, fish and man is presented in the form of a concise checklist, including the designations from the original publications. Putative homologs from different species are aligned, and key characteristics of embryonic or adult expression domains, as well as mutant phenotypes are briefly indicated.