A recent study has shown that deletion of beta-catenin within the pancreatic epithelium results in a loss of pancreas mass. Here, we show that ectopic stabilization of beta-catenin within mouse pancreatic epithelium can have divergent effects on both organ formation and growth. Robust stabilization of beta-catenin during early organogenesis drives changes in hedgehog and Fgf10 signaling and induces a loss of Pdx1 expression in early pancreatic progenitor cells. Together, these perturbations in early pancreatic specification culminate in a severe reduction of pancreas mass and postnatal lethality. By contrast, inducing the stabilized form of beta-catenin at a later time point in pancreas development causes enhanced proliferation that results in a dramatic increase in pancreas organ size. Taken together, these data suggest a previously unappreciated temporal/spatial role for beta-catenin signaling in the regulation of pancreas organ growth.
"During weeks 3-4, the hepatic diverticulum develops into the liver,
biliary system, the two ends of the main pancreatic duct, and part of the head of the
pancreas. Studies have shown that the classical Wnt/β-catenin signal pathway plays an
important role in the development of the pancreas and intrahepatic duct (4,5). However, research into the role of the Wnt/β-catenin pathway in the development of the
common bile duct is lacking. "
[Show abstract][Hide abstract] ABSTRACT: β-catenin and c-myc play important roles in the development of tissues and organs. However, little is known about their expression patterns during the development of the human common bile duct. Immunohistochemistry was used to detect β-catenin and c-myc expression in common bile duct samples from postmortem tissues of 14 premature infants and 6 spontaneously aborted fetuses. The expression of β-catenin and c-myc was also analyzed by Western blot. The samples were divided into four groups based on the stage of human fetal development: 12, 13-27, 28-37, and >37 weeks. The Image-Pro Plus v. 6.0 image analysis software was used to calculate the mean qualifying score (MQS). At fetal stages 12, 13-27, 28-37, and >37 weeks, MQS of β-catenin were 612.52±262.13, 818.38±311.73, 706.33±157.19, and 350.69±110.19, respectively. There was a significant difference in MQS among the four groups (ANOVA, P=0.0155) and between the scores at >37 and 13-27 weeks (Student-Newman-Keuls, P<0.05). At fetal stages 12, 13-27, 28-37, and >37 weeks, the MQS of c-myc were 1376.64±330.04, 1224.18±171.66, 1270.24±320.75, and 741.04±219.19, respectively. There was a significant difference in MQS among the four groups (ANOVA, P=0.0087) and between the scores at >37 and 12 weeks, >37 and 13-27 weeks, and >37 and 28-37 weeks (all P<0.05, Student-Newman-Keuls). Western blots showed that β-catenin and c-myc expression were significantly higher in fetal than in postnatal control duct tissue (P<0.05). c-myc and β-catenin are involved in the normal development of the human common bile duct.
Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas / Sociedade Brasileira de Biofisica ... [et al.] 07/2014; 47(7):594-599. DOI:10.1590/1414-431X20142765 · 1.01 Impact Factor
"Here, we find that Dicer function remains important throughout pancreatic development and plays a role in regulating acinar identity and viability. Our model utilizes a driver line that initiates Dicer recombination in the developing pancreas at a later embryonic stage than the Cre driver used by Lynn and colleagues. We observe minimal gross effects on pancreatic development, suggesting stage sensitive requirements for miRNA processing on establishing and expanding exocrine and endocrine progenitors. However, the acinar cells that do develop are unstable both in regards to their terminal differentiation and viability. "
[Show abstract][Hide abstract] ABSTRACT: miRNA levels are altered in pancreatic ductal adenocarcinoma (PDA), the most common and lethal pancreatic malignancy, and intact miRNA processing is essential for lineage specification during pancreatic development. However, the role of miRNA processing in PDA has not been explored. Here we study the role of miRNA biogenesis in PDA development by deleting the miRNA processing enzyme Dicer in a PDA mouse model driven by oncogenic Kras. We find that loss of Dicer accelerates Kras driven acinar dedifferentiation and acinar to ductal metaplasia (ADM), a process that has been shown to precede and promote the specification of PDA precursors. However, unconstrained ADM also displays high levels of apoptosis. Dicer loss does not accelerate development of Kras driven PDA precursors or PDA, but surprisingly, we observe that mouse PDA can develop without Dicer, although at the expense of proliferative capacity. Our data suggest that intact miRNA processing is involved in both constraining pro-tumorigenic changes in pancreatic differentiation as well as maintaining viability during PDA initiation.
PLoS ONE 05/2014; 9(5):e95486. DOI:10.1371/journal.pone.0095486 · 3.23 Impact Factor
"The fact that β-catenin is essentially dispensable before E12.5 may explain the previous paradoxical finding that early activation of β-catenin actually causes pancreas agenesis (Heiser et al., 2006). "
[Show abstract][Hide abstract] ABSTRACT: Pancreatic exocrine and endocrine lineages arise from multipotent pancreatic progenitor cells (MPCs). Exploiting the mechanisms that govern expansion and differentiation of these cells could enhance efforts to generate β-cells from stem cells. Although our prior work indicates that the canonical Wnt signaling component β-catenin is required qualitatively for exocrine acinar but not endocrine development, precisely how this requirement plays out at the level of MPCs and their lineage-restricted progeny is unknown. In addition, the contribution of β-catenin function to β-cell development remains controversial. To resolve the potential roles of β-catenin in development of MPCs and β-cells, we generated pancreas- and pre-endocrine-specific β-catenin knockout mice. Pancreas-specific loss of β-catenin produced not only a dramatic reduction in acinar cell numbers, but also a significant reduction in β-cell mass. The loss of β-cells is due not to a defect in the differentiation of endocrine precursors, but instead correlates with an early and specific loss of MPCs. In turn, this reflects a novel role for β-catenin in maintaining proximal-distal patterning of the early epithelium, such that distal MPCs resort to a proximal, endocrine-competent "trunk" fate when β-catenin is deleted. Moreover, β-catenin maintains proximal-distal patterning, in part, by inhibiting Notch signaling. Subsequently, β-catenin is required for proliferation of both distal and proximal cells, driving overall organ growth. In distinguishing two distinct roles for β-catenin along the route of β-cell development, we suggest that temporally appropriate positive and negative manipulation of this molecule could enhance expansion and differentiation of stem cell-derived MPCs.
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