Single-cell transcriptome analysis defines heterogeneity of the murine pancreatic ductal tree
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Curated by eLife
Evaluation Summary:
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Their analysis unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic inflammation. Finally, such detailed analysis of the pancreatic duct tree is relevant also in the context of cancer biology and might help elucidating the transition from pancreatitis to pancreatic cancer and/or different predisposition to cancer.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. The reviewers remained anonymous to the authors.)
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Abstract
To study disease development, an inventory of an organ's cell types and understanding of physiologic function is paramount. Here, we performed single-cell RNA-sequencing to examine heterogeneity of murine pancreatic duct cells, pancreatobiliary cells, and intrapancreatic bile duct cells. We describe an epithelial-mesenchymal transitory axis in our three pancreatic duct subpopulations and identify osteopontin as a regulator of this fate decision as well as human duct cell dedifferentiation. Our results further identify functional heterogeneity within pancreatic duct subpopulations by elucidating a role for geminin in accumulation of DNA damage in the setting of chronic pancreatitis. Our findings implicate diverse functional roles for subpopulations of pancreatic duct cells in maintenance of duct cell identity and disease progression and establish a comprehensive road map of murine pancreatic duct cell, pancreatobiliary cell, and intrapancreatic bile duct cell homeostasis.
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Author Response:
Reviewer #1 (Public Review):
The study by Hendley et al takes advantage of duct-specific DBA-lectin expression to purify pancreatic ductal populations that were then subjected to scRNA-seq analysis. The ability to enrich for this relatively low abundant pancreatic cell population resulted in a more robust dataset that had been generated previously from whole pancreas analyses. The manuscript catalogs several different gene clusters that delineate heterogeneous subpopulations of three different pancreatic ductal subpopulations in mice: mouse pancreatic ductal cells, pancreatobiliary cells, and intra pancreatic bile duct cells. Additional comparisons of the resulting data sets with published embryonic and adult datasets is a strength of the study and allows the authors to subclassify the different ductal cell …
Author Response:
Reviewer #1 (Public Review):
The study by Hendley et al takes advantage of duct-specific DBA-lectin expression to purify pancreatic ductal populations that were then subjected to scRNA-seq analysis. The ability to enrich for this relatively low abundant pancreatic cell population resulted in a more robust dataset that had been generated previously from whole pancreas analyses. The manuscript catalogs several different gene clusters that delineate heterogeneous subpopulations of three different pancreatic ductal subpopulations in mice: mouse pancreatic ductal cells, pancreatobiliary cells, and intra pancreatic bile duct cells. Additional comparisons of the resulting data sets with published embryonic and adult datasets is a strength of the study and allows the authors to subclassify the different ductal cell populations and facilitates the identification of potentially novel subpopulations. Pseudotime analysis also identified gene programs that led the authors to speculate the existence of an EMT axis in pancreatic ducts. Overall, the data analyses is strong, but the authors tend to draw conclusions that are not fully supported by the presented data.
The second half of this study focuses on three candidate proteins that were identified in the transcriptome analysis - Anxa3, SPP1 and Geminin. Crispr-Cas9 was used to delete each gene in an immortalized human duct cell line (HPDE). Deletion of each gene resulted in increased proliferation; SPP1 mutant cells also displayed abnormal morphology. Additional functional studies of the cell lines or in mouse models suggested a role for SPP1 in maintaining the ductal phenotype and Geminin in protecting ductal cells from DNA damage, respectively. Although the provided phenotypic analysis suggest important functional roles for these proteins, follow up studies will be required to fully understand the role of these genes in homeostatic or cancer conditions.
Strengths:
- Enrichment of pancreatic ductal populations enhanced the robustness of the scRNA-Seq dataset
- Quality of the sequencing data and extensive computational analysis is extremely good and more comprehensive than previously published datasets
- Comparative analysis with existing mouse and human data sets
- Use of human ductal cell lines and mouse models to begin to explore the function of candidate ductal genes.
Weaknesses:
- There are many suppositions based on gene expression changes that are somewhat overstated.
- The conclusion that there is an EMT axis in pancreatic ducts is not fully supported by the gene expression and immunofluorescence data
- A good rationale for choosing Anxa3, SPP1 and Geminin for additional functional analysis is not provided. In addition, it isn't clear why Anxa3 function isn't pursued further.
- Although extensive models (transplanted cells for SPP1 and mouse conditional KOs for Geminin) were generated, the functional analysis for each gene is preliminary; additional longer term studies will be necessary to fully understand the role of these proteins in pancreatic duct development and cancer.
We would like to thank the Reviewer for their fair and thoughtful review of our manuscript. We agree with the comments and have addressed them as described in detail below. In particular, we have focused on streamlining the presentation and description of our bioinformatic analysis, providing additional rationale for using the particular genes we focused on in the follow-up analyses, and including additional data to support the EMT axis.
Reviewer #2 (Public Review):
In this study the authors address the heterogeneity of the mouse ductal cell at the single cell level and conduct functional studies for selected marker genes. They isolated duct cells using the DBA lectin as a molecular surface marker. This is an noteworthy approach as it does not rely on the specificity and expression levels of reporter lines. Isolated cells contained a majority of non-duct cells that were identified by their transcriptomic profile and excluded from further analysis. The transcriptomic profiles of bona fide duct cells were then subjected to standard analyses for differentially expressed genes, activated pathways and lineage relationships. Of particular interest is the comparison of these data with human data from a recently published study that used a different sorting strategy for duct cells. As more studies at the single cell level are conducted, these types of comparisons need to become part of them in order to derive commonalities and identify deficits due to methodological or technological limitations. The study was by necessity descriptive up to this point and the authors addressed this with functional studies on SPP1 and GMNN which suggested that SPP1 is necessary for the maintenance of the ductal differentiated phenotype whereas GMNN protects cells against DNA damage during increased proliferation triggered by chronic pancreatitis.
It is an interesting study, but there are caveats, particularly concerning the functional studies. The functional analysis of SPP1 needs to be strengthened and some findings on the the analysis of GMNN clarified. There is also an over reliance on the outcome of pathways analyses and upstream regulators which are often treated as actual findings rather than possibilities to be explored in this or future studies. The single cell RNA Seq analysis would benefit from reducing speculation and restrict descriptions to the essential features of each cluster. Main figures for this analysis could also be simplified along the same lines.
We thank the reviewer for appreciating our study as “interesting” and for considering our investigations as a “noteworthy approach”. We are glad that the reviewer acknowledges our efforts in delivering a manuscript with necessary descriptive bioinformatics analysis followed up with functional studies for select subpopulation markers. Conversely, we took the constructive criticism seriously and added new data to further substantiate our claims.
Reviewer #3 (Public Review):
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Using a DBA+ lectin sorting strategy murine pancreatic duct, intrapancreatic bile duct, and pancreatobiliary cells were isolated and subjected to scRNA-seq. Computational analysis of the datasets unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Furthermore, the authors compared these clusters to previously reported mouse and human pancreatic duct populations and focused on the functional properties of selected duct genes, including Spp1, Anxa3 and Geminin. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic inflammation. Finally, such detailed analysis of the pancreatic duct tree is relevant also in the context of cancer biology and might help elucidating the transition from pancreatitis to pancreatic cancer and/or different predisposition to cancer.
The study is very well done, with careful controls and well-designed experiments.
We thank the reviewer for appreciating our study as “very well done” as well as envisaging the potential relevance of our findings to cancer biology.
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Reviewer #3 (Public Review):
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Using a DBA+ lectin sorting strategy murine pancreatic duct, intrapancreatic bile duct, and pancreatobiliary cells were isolated and subjected to scRNA-seq. Computational analysis of the datasets unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Furthermore, the authors compared these clusters to previously reported mouse and human pancreatic duct populations and focused on the functional properties of selected duct genes, including Spp1, Anxa3 and Geminin. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic …
Reviewer #3 (Public Review):
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Using a DBA+ lectin sorting strategy murine pancreatic duct, intrapancreatic bile duct, and pancreatobiliary cells were isolated and subjected to scRNA-seq. Computational analysis of the datasets unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Furthermore, the authors compared these clusters to previously reported mouse and human pancreatic duct populations and focused on the functional properties of selected duct genes, including Spp1, Anxa3 and Geminin. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic inflammation. Finally, such detailed analysis of the pancreatic duct tree is relevant also in the context of cancer biology and might help elucidating the transition from pancreatitis to pancreatic cancer and/or different predisposition to cancer.
The study is very well done, with careful controls and well-designed experiments.
-
Reviewer #2 (Public Review):
In this study the authors address the heterogeneity of the mouse ductal cell at the single cell level and conduct functional studies for selected marker genes. They isolated duct cells using the DBA lectin as a molecular surface marker. This is an noteworthy approach as it does not rely on the specificity and expression levels of reporter lines. Isolated cells contained a majority of non-duct cells that were identified by their transcriptomic profile and excluded from further analysis. The transcriptomic profiles of bona fide duct cells were then subjected to standard analyses for differentially expressed genes, activated pathways and lineage relationships. Of particular interest is the comparison of these data with human data from a recently published study that used a different sorting strategy for duct …
Reviewer #2 (Public Review):
In this study the authors address the heterogeneity of the mouse ductal cell at the single cell level and conduct functional studies for selected marker genes. They isolated duct cells using the DBA lectin as a molecular surface marker. This is an noteworthy approach as it does not rely on the specificity and expression levels of reporter lines. Isolated cells contained a majority of non-duct cells that were identified by their transcriptomic profile and excluded from further analysis. The transcriptomic profiles of bona fide duct cells were then subjected to standard analyses for differentially expressed genes, activated pathways and lineage relationships. Of particular interest is the comparison of these data with human data from a recently published study that used a different sorting strategy for duct cells. As more studies at the single cell level are conducted, these types of comparisons need to become part of them in order to derive commonalities and identify deficits due to methodological or technological limitations. The study was by necessity descriptive up to this point and the authors addressed this with functional studies on SPP1 and GMNN which suggested that SPP1 is necessary for the maintenance of the ductal differentiated phenotype whereas GMNN protects cells against DNA damage during increased proliferation triggered by chronic pancreatitis.
It is an interesting study, but there are caveats, particularly concerning the functional studies. The functional analysis of SPP1 needs to be strengthened and some findings on the the analysis of GMNN clarified. There is also an over reliance on the outcome of pathways analyses and upstream regulators which are often treated as actual findings rather than possibilities to be explored in this or future studies. The single cell RNA Seq analysis would benefit from reducing speculation and restrict descriptions to the essential features of each cluster. Main figures for this analysis could also be simplified along the same lines.
-
Reviewer #1 (Public Review):
The study by Hendley et al takes advantage of duct-specific DBA-lectin expression to purify pancreatic ductal populations that were then subjected to scRNA-seq analysis. The ability to enrich for this relatively low abundant pancreatic cell population resulted in a more robust dataset that had been generated previously from whole pancreas analyses. The manuscript catalogs several different gene clusters that delineate heterogeneous subpopulations of three different pancreatic ductal subpopulations in mice: mouse pancreatic ductal cells, pancreatobiliary cells, and intra pancreatic bile duct cells. Additional comparisons of the resulting data sets with published embryonic and adult datasets is a strength of the study and allows the authors to subclassify the different ductal cell populations and facilitates …
Reviewer #1 (Public Review):
The study by Hendley et al takes advantage of duct-specific DBA-lectin expression to purify pancreatic ductal populations that were then subjected to scRNA-seq analysis. The ability to enrich for this relatively low abundant pancreatic cell population resulted in a more robust dataset that had been generated previously from whole pancreas analyses. The manuscript catalogs several different gene clusters that delineate heterogeneous subpopulations of three different pancreatic ductal subpopulations in mice: mouse pancreatic ductal cells, pancreatobiliary cells, and intra pancreatic bile duct cells. Additional comparisons of the resulting data sets with published embryonic and adult datasets is a strength of the study and allows the authors to subclassify the different ductal cell populations and facilitates the identification of potentially novel subpopulations. Pseudotime analysis also identified gene programs that led the authors to speculate the existence of an EMT axis in pancreatic ducts. Overall, the data analyses is strong, but the authors tend to draw conclusions that are not fully supported by the presented data.
The second half of this study focuses on three candidate proteins that were identified in the transcriptome analysis - Anxa3, SPP1 and Geminin. Crispr-Cas9 was used to delete each gene in an immortalized human duct cell line (HPDE). Deletion of each gene resulted in increased proliferation; SPP1 mutant cells also displayed abnormal morphology. Additional functional studies of the cell lines or in mouse models suggested a role for SPP1 in maintaining the ductal phenotype and Geminin in protecting ductal cells from DNA damage, respectively. Although the provided phenotypic analysis suggest important functional roles for these proteins, follow up studies will be required to fully understand the role of these genes in homeostatic or cancer conditions.
Strengths:
Enrichment of pancreatic ductal populations enhanced the robustness of the scRNA-Seq dataset
Quality of the sequencing data and extensive computational analysis is extremely good and more comprehensive than previously published datasets
Comparative analysis with existing mouse and human data sets
Use of human ductal cell lines and mouse models to begin to explore the function of candidate ductal genes.
Weaknesses:
There are many suppositions based on gene expression changes that are somewhat overstated.
The conclusion that there is an EMT axis in pancreatic ducts is not fully supported by the gene expression and immunofluorescence data
A good rationale for choosing Anxa3, SPP1 and Geminin for additional functional analysis is not provided. In addition, it isn't clear why Anxa3 function isn't pursued further.
Although extensive models (transplanted cells for SPP1 and mouse conditional KOs for Geminin) were generated, the functional analysis for each gene is preliminary; additional longer term studies will be necessary to fully understand the role of these proteins in pancreatic duct development and cancer.
-
Evaluation Summary:
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Their analysis unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic inflammation. Finally, such detailed analysis of the pancreatic duct tree is relevant also in the context of cancer biology and might help elucidating the transition from pancreatitis to pancreatic cancer and/or different predisposition to cancer.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes …
Evaluation Summary:
In this study, the authors present a high-resolution single-cell transcriptomic atlas of the pancreatic ductal tree. Their analysis unveiled important heterogeneity within the pancreatic ductal tree and identified unique cellular states. Overall, the results presented here suggest distinct functional roles for subpopulations of duct cells in maintenance of duct cell identity and implication in chronic pancreatic inflammation. Finally, such detailed analysis of the pancreatic duct tree is relevant also in the context of cancer biology and might help elucidating the transition from pancreatitis to pancreatic cancer and/or different predisposition to cancer.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. The reviewers remained anonymous to the authors.)
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