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Silencing Mist1 Gene Expression Is Essential for Recovery from Acute Pancreatitis.

Karki A, Humphrey SE, Steele RE, Hess DA, Taparowsky EJ, Konieczny SF - PLoS ONE (2015)

Bottom Line: Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses.We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells.The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, the Purdue Center for Cancer Research, and the Bindley Bioscience Center, Purdue University, West Lafayette, IN, 47907-2057, United States of America.

ABSTRACT
Acinar cells of the exocrine pancreas are tasked with synthesizing, packaging and secreting vast quantities of pro-digestive enzymes to maintain proper metabolic homeostasis for the organism. Because the synthesis of high levels of hydrolases is potentially dangerous, the pancreas is prone to acute pancreatitis (AP), a disease that targets acinar cells, leading to acinar-ductal metaplasia (ADM), inflammation and fibrosis-events that can transition into the earliest stages of pancreatic ductal adenocarcinoma. Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses. In this study, we examined the importance of the acinar-specific maturation transcription factor MIST1 to AP damage and organ recovery. Analysis of wild-type and Mist1 conditional mice revealed that Mist1 gene transcription and protein accumulation were dramatically reduced as acinar cells underwent ADM alterations during AP episodes. To test if loss of MIST1 function was primarily responsible for the damaged status of the organ, mice harboring a Cre-inducible Mist1 transgene (iMist1) were utilized to determine if sustained MIST1 activity could alleviate AP damage responses. Unexpectedly, constitutive iMist1 expression during AP led to a dramatic increase in organ damage followed by acinar cell death. We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells. The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

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Mist1CreERT/+/LSL-Mist1myc mice (iMist1) exhibit acinar-specific Mist1myc expression upon CreERT2 activity.(A) Diagram outlining the time course of the study. (B) Tam treatment of iMist1 mice leads to rapid accumulation of nuclear MIST1myc protein exclusively in pancreatic acinar cells. (C) Quantification of MIST1myc+ acinar cells following Tam induction. (D) RT-qPCR analysis reveals no deleterious effects on general pancreas properties from Mist1myc induction. See DiRenzo et al. [33] for a full characterization of the iMist1 model. ***p ≤ 0.001. n.s.—not significant.
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pone.0145724.g005: Mist1CreERT/+/LSL-Mist1myc mice (iMist1) exhibit acinar-specific Mist1myc expression upon CreERT2 activity.(A) Diagram outlining the time course of the study. (B) Tam treatment of iMist1 mice leads to rapid accumulation of nuclear MIST1myc protein exclusively in pancreatic acinar cells. (C) Quantification of MIST1myc+ acinar cells following Tam induction. (D) RT-qPCR analysis reveals no deleterious effects on general pancreas properties from Mist1myc induction. See DiRenzo et al. [33] for a full characterization of the iMist1 model. ***p ≤ 0.001. n.s.—not significant.

Mentions: Our studies have shown that Mist1 expression is transiently silenced during the peak of AP damage and that Mist1 re-expression is not required for the pancreas to recover from an AP episode. Nonetheless, given the importance of MIST1 to normal acinar cell polarity and secretory function [33, 46–49, 72, 74], we investigated if sustained MIST1 protein expression could be used to limit the initial AP damage response. Previous studies have shown that formation of ADM and PanIN lesions is significantly attenuated when Mist1 expression is maintained in the presence of oncogenic KRASG12D [26, 39]. Therefore, we hypothesized that a similar lessening of AP damage might be achieved by maintaining MIST1 transcriptional activity. For these studies, we utilized a Cre-inducible LSL-Mist1myc (iMist1myc) transgenic mouse model (S5 Fig) [33] and generated Mist1CreERT/+/iMist1myc offspring. Administering Tam to Mist1CreERT/+/iMist1myc mice induced iMist1myc transgene expression in 94.7% pancreatic acinar cells (Fig 5A–5C). Despite elevated levels of MIST1, Mist1CreERT/+/iMist1myc mice exhibited a completely normal pancreas phenotype with no significant changes in the expression of acinar and ductal genes (Fig 5D, data not shown) [33].


Silencing Mist1 Gene Expression Is Essential for Recovery from Acute Pancreatitis.

Karki A, Humphrey SE, Steele RE, Hess DA, Taparowsky EJ, Konieczny SF - PLoS ONE (2015)

Mist1CreERT/+/LSL-Mist1myc mice (iMist1) exhibit acinar-specific Mist1myc expression upon CreERT2 activity.(A) Diagram outlining the time course of the study. (B) Tam treatment of iMist1 mice leads to rapid accumulation of nuclear MIST1myc protein exclusively in pancreatic acinar cells. (C) Quantification of MIST1myc+ acinar cells following Tam induction. (D) RT-qPCR analysis reveals no deleterious effects on general pancreas properties from Mist1myc induction. See DiRenzo et al. [33] for a full characterization of the iMist1 model. ***p ≤ 0.001. n.s.—not significant.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4696804&req=5

pone.0145724.g005: Mist1CreERT/+/LSL-Mist1myc mice (iMist1) exhibit acinar-specific Mist1myc expression upon CreERT2 activity.(A) Diagram outlining the time course of the study. (B) Tam treatment of iMist1 mice leads to rapid accumulation of nuclear MIST1myc protein exclusively in pancreatic acinar cells. (C) Quantification of MIST1myc+ acinar cells following Tam induction. (D) RT-qPCR analysis reveals no deleterious effects on general pancreas properties from Mist1myc induction. See DiRenzo et al. [33] for a full characterization of the iMist1 model. ***p ≤ 0.001. n.s.—not significant.
Mentions: Our studies have shown that Mist1 expression is transiently silenced during the peak of AP damage and that Mist1 re-expression is not required for the pancreas to recover from an AP episode. Nonetheless, given the importance of MIST1 to normal acinar cell polarity and secretory function [33, 46–49, 72, 74], we investigated if sustained MIST1 protein expression could be used to limit the initial AP damage response. Previous studies have shown that formation of ADM and PanIN lesions is significantly attenuated when Mist1 expression is maintained in the presence of oncogenic KRASG12D [26, 39]. Therefore, we hypothesized that a similar lessening of AP damage might be achieved by maintaining MIST1 transcriptional activity. For these studies, we utilized a Cre-inducible LSL-Mist1myc (iMist1myc) transgenic mouse model (S5 Fig) [33] and generated Mist1CreERT/+/iMist1myc offspring. Administering Tam to Mist1CreERT/+/iMist1myc mice induced iMist1myc transgene expression in 94.7% pancreatic acinar cells (Fig 5A–5C). Despite elevated levels of MIST1, Mist1CreERT/+/iMist1myc mice exhibited a completely normal pancreas phenotype with no significant changes in the expression of acinar and ductal genes (Fig 5D, data not shown) [33].

Bottom Line: Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses.We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells.The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, the Purdue Center for Cancer Research, and the Bindley Bioscience Center, Purdue University, West Lafayette, IN, 47907-2057, United States of America.

ABSTRACT
Acinar cells of the exocrine pancreas are tasked with synthesizing, packaging and secreting vast quantities of pro-digestive enzymes to maintain proper metabolic homeostasis for the organism. Because the synthesis of high levels of hydrolases is potentially dangerous, the pancreas is prone to acute pancreatitis (AP), a disease that targets acinar cells, leading to acinar-ductal metaplasia (ADM), inflammation and fibrosis-events that can transition into the earliest stages of pancreatic ductal adenocarcinoma. Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses. In this study, we examined the importance of the acinar-specific maturation transcription factor MIST1 to AP damage and organ recovery. Analysis of wild-type and Mist1 conditional mice revealed that Mist1 gene transcription and protein accumulation were dramatically reduced as acinar cells underwent ADM alterations during AP episodes. To test if loss of MIST1 function was primarily responsible for the damaged status of the organ, mice harboring a Cre-inducible Mist1 transgene (iMist1) were utilized to determine if sustained MIST1 activity could alleviate AP damage responses. Unexpectedly, constitutive iMist1 expression during AP led to a dramatic increase in organ damage followed by acinar cell death. We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells. The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

Show MeSH
Related in: MedlinePlus