Transcription factor foxq1 controls mucin gene expression and granule content in mouse stomach surface mucous cells

Foxq1 activates CB2R with oleamide to alleviate POCD

Postoperative cognitive dysfunction (POCD) is a major concern, particularly among older adults. This study used social isolation (ISO) and multiomics analyses in aged mice to investigate potential mechanisms underlying POCD development. Aged mice were divided into two groups: ISO and paired housing (PH). Oleamide and the cannabinoid receptor type 2 (CB2R) antagonist AM630 were administered intraperitoneally, while Foxq1 adeno-associated viral (AAV) vector was injected directly into the hippocampus. Intramedullary tibial surgeries were subsequently performed to establish the POCD models. Behavioral tests comprising the Y-maze, open field test, and novel object recognition were conducted 2 days after surgery. Hippocampal and serum inflammatory cytokines were assessed. Following surgery, ISO mice demonstrated intensified cognitive impairments and escalated inflammatory markers. Integrative transcriptomic and metabolomic analysis revealed elevated oleamide concentrations in the hippocampus and serum of PH mice, with associative investigations indicating a close relationship between the Foxq1 gene and oleamide levels. While oleamide administration and Foxq1 gene overexpression substantially ameliorated postoperative cognitive performance and systemic inflammation in mice, CB2R antagonist AM630 impeded these enhancements. The Foxq1 gene and oleamide may be crucial in alleviating POCD. While potentially acting through CB2R-mediated pathways, these factors may modulate neuroinflammation and attenuate proinflammatory cytokine levels within the hippocampus, substantially improving cognitive performance postsurgery. This study lays the groundwork for future research into therapeutic approaches targeting the Foxq1-oleamide-CB2R axis, with the ultimate goal of preventing or mitigating POCD.

Metabolic regulator ERRγ governs gastric stem cell differentiation into acid-secreting parietal cells

Parietal cells (PCs) produce gastric acid to kill pathogens and aid digestion. Dysregulated PC census is common in disease, yet how PCs differentiate is unclear. Here, we identify the PC progenitors arising from isthmal stem cells, using mouse models and human gastric cells, and show that they preferentially express cell-metabolism regulator and orphan nuclear receptor Estrogen-related receptor gamma (Esrrg, encoding ERRγ). Esrrg expression facilitated the tracking of stepwise molecular, cellular, and ultrastructural stages of PC differentiation. EsrrgP2ACreERT2 lineage tracing revealed that Esrrg expression commits progenitors to differentiate into mature PCs. scRNA-seq indicated the earliest Esrrg+ PC progenitors preferentially express SMAD4 and SP1 transcriptional targets and the GTPases regulating acid-secretion signal transduction. As progenitors matured, ERRγ-dependent metabolic transcripts predominated. Organoid and mouse studies validated the requirement of ERRγ for PC differentiation. Our work chronicles stem cell differentiation along a single lineage in vivo and suggests ERRγ as a therapeutic target for PC-related disorders.

Metaplastic regeneration in the mouse stomach requires a reactive oxygen species pathway

In pyloric metaplasia, mature gastric chief cells reprogram via an evolutionarily conserved process termed paligenosis to re-enter the cell cycle and become spasmolytic polypeptide-expressing metaplasia (SPEM) cells. Here, we use single-cell RNA sequencing (scRNA-seq) following injury to the murine stomach to analyze mechanisms governing paligenosis at high resolution. Injury causes induced reactive oxygen species (ROS) with coordinated changes in mitochondrial activity and cellular metabolism, requiring the transcriptional mitochondrial regulator Ppargc1a (Pgc1α) and ROS regulator Nf2el2 (Nrf2). Loss of the ROS and mitochondrial control in Ppargc1a-/- mice causes the death of paligenotic cells through ferroptosis. Blocking the cystine transporter SLC7A11(xCT), which is critical in lipid radical detoxification through glutathione peroxidase 4 (GPX4), also increases ferroptosis. Finally, we show that PGC1α-mediated ROS and mitochondrial changes also underlie the paligenosis of pancreatic acinar cells. Altogether, the results detail how metabolic and mitochondrial changes are necessary for injury response, regeneration, and metaplasia in the stomach.

The bHLH transcription factor ASCL1 promotes differentiation of endocrine cells in the stomach and is regulated by Notch signaling

Notch signaling regulates gastrointestinal stem cell proliferation and differentiation yet Notch-regulated transcriptional effectors of gastric epithelial cell differentiation are poorly understood. Here we tested the role of the bHLH transcription factor Achaete-Scute homolog 1 (ASCL1) in gastric epithelial cell differentiation, and its regulation by Notch. Newborn Ascl1 null mice showed a loss of expression of markers of neurogenin-3-dependent enteroendocrine cells, with normal expression of enterochromaffin-like cells, mucous cells, chief cells, and parietal cells. In adult mice, Ascl1 gene expression was observed in the stomach, but not the intestine, with higher expression in antral than corpus epithelium. Lineage tracing in Ascl1-CreERT2; Rosa26-LSL-tdTomato mice revealed single, scattered ASCL1+ cells in the gastric epithelium, demonstrating expression in antral gastrin- and serotonin-producing endocrine cells. ASCL1-expressing endocrine cells persisted for several weeks posttamoxifen labeling with a half-life of approximately 2 months. Lineage tracing in Gastrin-CreERT2 mice demonstrated a similar lifespan for gastrin-producing cells, confirming that gastric endocrine cells are long-lived. Finally, treatment of Ascl1-CreERT2; Rosa26-LSL-tdTomato mice with the pan-Notch inhibitor dibenzazepine increased the number of lineage-labeled cells in the gastric antrum, suggesting that Notch signaling normally inhibits Ascl1 expression. Notch regulation of Ascl1 was also demonstrated in a genetic mouse model of Notch activation, as well as Notch-manipulated antral organoid cultures, thus suggesting that ASCL1 is a key downstream Notch pathway effector promoting endocrine cell differentiation in the gastric epithelium.NEW & NOTEWORTHY Although Notch signaling is known to regulate cellular differentiation in the stomach, downstream effectors are poorly described. Here we demonstrate that the bHLH transcription factor ASCL1 is expressed in endocrine cells in the stomach and is required for formation of neurogenin-3-dependent enteroendocrine cells but not enterochromaffin-like cells. We also demonstrate that Ascl1 expression is inhibited by Notch signaling, suggesting that ASCL1 is a Notch-regulated transcriptional effector directing enteroendocrine cell fate in the mouse stomach.

Gastric epithelial stem cells in development, homeostasis and regeneration

The stem/progenitor cell pool is indispensable for the development, homeostasis and regeneration of the gastric epithelium, owing to its defining ability to self-renew whilst supplying the various functional epithelial lineages needed to digest food efficiently. A detailed understanding of the intricacies and complexities surrounding the behaviours and roles of these stem cells offers insights, not only into the physiology of gastric epithelial development and maintenance, but also into the pathological consequences following aberrations in stem cell regulation. Here, we provide an insightful synthesis of the existing knowledge on gastric epithelial stem cell biology, including the in vitro and in vivo experimental techniques that have advanced such studies. We highlight the contributions of stem/progenitor cells towards patterning the developing stomach, specification of the differentiated cell lineages and maintenance of the mature epithelium during homeostasis and following injury. Finally, we discuss gaps in our understanding and identify key research areas for future work.

SOX9 Governs Gastric Mucous Neck Cell Identity and Is Required for Injury-Induced Metaplasia

BACKGROUND & AIMS

Acute and chronic gastric injury induces alterations in differentiation within the corpus of the stomach called pyloric metaplasia. Pyloric metaplasia is characterized by the death of parietal cells and reprogramming of mitotically quiescent zymogenic chief cells into proliferative, mucin-rich spasmolytic polypeptide-expressing metaplasia (SPEM) cells. Overall, pyloric metaplastic units show increased proliferation and specific expansion of mucous lineages, both by proliferation of normal mucous neck cells and recruitment of SPEM cells. Here, we identify Sox9 as a potential gene of interest in the regulation of mucous neck and SPEM cell identity in the stomach.

METHODS

We used immunostaining and electron microscopy to characterize the expression pattern of SRY-box transcription factor 9 (SOX9) during murine gastric development, homeostasis, and injury in homeostasis, after genetic deletion of Sox9 and after targeted genetic misexpression of Sox9 in the gastric epithelium and chief cells.

RESULTS

SOX9 is expressed in all early gastric progenitors and strongly expressed in mature mucous neck cells with minor expression in the other principal gastric lineages during adult homeostasis. After injury, strong SOX9 expression was induced in the neck and base of corpus units in SPEM cells. Adult corpus units derived from Sox9-deficient gastric progenitors lacked normal mucous neck cells. Misexpression of Sox9 during postnatal development and adult homeostasis expanded mucous gene expression throughout corpus units including within the chief cell zone in the base. Sox9 deletion specifically in chief cells blunts their reprogramming into SPEM.

CONCLUSIONS

Sox9 is a master regulator of mucous neck cell differentiation during gastric development. Sox9 also is required for chief cells to fully reprogram into SPEM after injury.

Dynamic transcriptome and LC-MS/MS analysis revealed the important roles of taurine and glutamine metabolism in response to environmental salinity changes in gills of rainbow trout (Oncorhynchus mykiss)

Recently, the frequent salinity fluctuation has become a growing threat to fishes. However, the dynamic patterns of gene expression in response to salinity changes remain largely unexplored. In the present study, 18 RNA-Seq datasets were generated from gills of rainbow trout at different salinities, including 0 ‰, 6 ‰, 12 ‰, 18 ‰, 24 ‰ and 30 ‰. Based on the strict thresholds, we have identified 63, 1411, 2096, 1031 and 1041 differentially expressed genes in gills of rainbow trout through pairwise comparisons. Additionally, weighted gene co-expression network analysis was performed to construct 18 independent modules with distinct expression patterns. Of them, green and tan modules were found to be tightly related to salinity changes, several hub genes of which are known as the important regulators in taurine and glutamine metabolism. To further investigate their potential roles in response to salinity changes, taurine, glutamine, and their metabolism-related glutamic acid and α-ketoglutaric acid were accurately quantitated using liquid chromatography-tandem mass spectrometry analysis. Results clearly showed that their concentrations were closely associated with salinity changes. These findings suggested that taurine and glutamine play important roles in response to salinity changes in gills of rainbow trout, providing new insights into the molecular mechanism of fishes in salinity adaptation.

Cell plasticity in regeneration in the stomach and beyond

Recent studies using cell lineage-tracing techniques, organoids, and single-cell RNA sequencing analyses have revealed: 1) adult organs use cell plasticity programs to recruit progenitor cells to regenerate tissues after injury, and 2) plasticity is far more common than previously thought, even in homeostasis. Here, we focus on the complex interplay of normal stem cell differentiation and plasticity in homeostasis and after injury, using the gastric epithelium as a touchstone. We also examine common features of regenerative programs and discuss the evolutionarily conserved, stepwise process of paligenosis which reprograms mature cells into progenitors that can repair damaged tissue. Finally, we discuss how conserved plasticity programs may help us better understand pathological processes like metaplasia.

Identification of testicular Foxq1 as a critical modulator of lactate metabolism in mouse Sertoli cells

Postmeiotic germ cells require the lactate produced by the adjacent Sertoli cells (SCs) as their sole energy fuels. Lactate production in SCs is elaborately regulated by monitoring the transcription of the lactate dehydrogenase A (Ldha) gene. However, the transcription factors that are responsible for the control of Ldha transcription in SCs remain ill defined. Herein, the expression of forkhead box Q1 (FOXQ1), a central modulator of glucose metabolism in liver, was demonstrated in mouse testis throughout postnatal development, with maximum levels in adult specimens. At this age, FOXQ1 was immunolocalized in the nuclei of the functionally mature SCs. Testicular levels of FOXQ1 were overtly modulated by germ cells (GCs)-derived IL-1α, in a dose- and time-dependent manner. To further clarify the biological functions of FOXQ1, we disrupted the mouse Foxq1 gene using a Cas9/RNA-mediated gene targeting strategy. Foxq1^-/- males were subfertile and showed oligoasthenozoospermia due to lactate deficiency. Moreover, we provided the molecular evidence that FOXQ1 may regulate lactate production by directly targeting the transactivation of the Ldha gene in SCs. From a functional standpoint, overexpression of the exogenous Ldha ameliorated Foxq1 deficiency-impaired lactate synthesis in the SCs^Foxq1-/- cells. Thus, these findings collectively underscore a reproductive facet of this recently characterized transcription factor, which may operate as a novel transcriptional integrator linking energy homeostasis and nursery function in SCs.

Modelling hereditary diffuse gastric cancer initiation using transgenic mouse-derived gastric organoids and single-cell sequencing

Hereditary diffuse gastric cancer (HDGC) is a cancer syndrome caused by germline variants in CDH1, the gene encoding the cell-cell adhesion molecule E-cadherin. Loss of E-cadherin in cancer is associated with cellular dedifferentiation and poor prognosis, but the mechanisms through which CDH1 loss initiates HDGC are not known. Using single-cell RNA sequencing, we explored the transcriptional landscape of a murine organoid model of HDGC to characterize the impact of CDH1 loss in early tumourigenesis. Progenitor populations of stratified squamous and simple columnar epithelium, characteristic of the mouse stomach, showed lineage-specific transcriptional programs. Cdh1 inactivation resulted in shifts along the squamous differentiation trajectory associated with aberrant expression of genes central to gastrointestinal epithelial differentiation. Cytokeratin 7 (CK7), encoded by the differentiation-dependent gene Krt7, was a specific marker for early neoplastic lesions in CDH1 carriers. Our findings suggest that deregulation of developmental transcriptional programs may precede malignancy in HDGC. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Annotation of chromatin states in 66 complete mouse epigenomes during development

The morphologically and functionally distinct cell types of a multicellular organism are maintained by their unique epigenomes and gene expression programs. Phase III of the ENCODE Project profiled 66 mouse epigenomes across twelve tissues at daily intervals from embryonic day 11.5 to birth. Applying the ChromHMM algorithm to these epigenomes, we annotated eighteen chromatin states with characteristics of promoters, enhancers, transcribed regions, repressed regions, and quiescent regions. Our integrative analyses delineate the tissue specificity and developmental trajectory of the loci in these chromatin states. Approximately 0.3% of each epigenome is assigned to a bivalent chromatin state, which harbors both active marks and the repressive mark H3K27me3. Highly evolutionarily conserved, these loci are enriched in silencers bound by polycomb repressive complex proteins, and the transcription start sites of their silenced target genes. This collection of chromatin state assignments provides a useful resource for studying mammalian development.

Xenopus epidermal and endodermal epithelia as models for mucociliary epithelial evolution, disease, and metaplasia

The Xenopus embryonic epidermis is a powerful model to study mucociliary biology, development, and disease. Particularly, the Xenopus system is being used to elucidate signaling pathways, transcription factor functions, and morphogenetic mechanisms regulating cell fate specification, differentiation and cell function. Thereby, Xenopus research has provided significant insights into potential underlying molecular mechanisms for ciliopathies and chronic airway diseases. Recent studies have also established the embryonic epidermis as a model for mucociliary epithelial remodeling, multiciliated cell trans-differentiation, cilia loss, and mucus secretion. Additionally, the tadpole foregut epithelium is lined by a mucociliary epithelium, which shows remarkable features resembling mammalian airway epithelia, including its endodermal origin and a variable cell type composition along the proximal-distal axis. This review aims to summarize the advantages of the Xenopus epidermis for mucociliary epithelial biology and disease modeling. Furthermore, the potential of the foregut epithelium as novel mucociliary model system is being highlighted. Additional perspectives are presented on how to expand the range of diseases that can be modeled in the frog system, including proton pump inhibitor-associated pneumonia as well as metaplasia in epithelial cells of the airway and the gastroesophageal region.

Signalling codes for the maintenance and lineage commitment of embryonic gastric epithelial progenitors

The identity of embryonic gastric epithelial progenitors is unknown. We used single-cell RNA-sequencing, genetic lineage tracing and organoid assays to assess whether Axin2- and Lgr5-expressing cells are gastric progenitors in the developing mouse stomach. We show that Axin2 ⁺ cells represent a transient population of embryonic epithelial cells in the forestomach. Lgr5 ⁺ cells generate both glandular corpus and squamous forestomach organoids ex vivo Only Lgr5 ⁺ progenitors give rise to zymogenic cells in culture. Modulating the activity of the WNT, BMP and Notch pathways in vivo and ex vivo, we found that WNTs are essential for the maintenance of Lgr5 ⁺ epithelial cells. Notch prevents differentiation of the embryonic epithelial cells along all secretory lineages and hence ensures their maintenance. Whereas WNTs promote differentiation of the embryonic progenitors along the zymogenic cell lineage, BMPs enhance their differentiation along the parietal lineage. In contrast, WNTs and BMPs are required to suppress differentiation of embryonic gastric epithelium along the pit cell lineage. Thus, coordinated action of the WNT, BMP and Notch pathways controls cell fate determination in the embryonic gastric epithelium.

Single-cell transcriptomes of pancreatic preinvasive lesions and cancer reveal acinar metaplastic cells' heterogeneity

Acinar metaplasia is an initial step in a series of events that can lead to pancreatic cancer. Here we perform single-cell RNA-sequencing of mouse pancreas during the progression from preinvasive stages to tumor formation. Using a reporter gene, we identify metaplastic cells that originated from acinar cells and express two transcription factors, Onecut2 and Foxq1. Further analyses of metaplastic acinar cell heterogeneity define six acinar metaplastic cell types and states, including stomach-specific cell types. Localization of metaplastic cell types and mixture of different metaplastic cell types in the same pre-malignant lesion is shown. Finally, single-cell transcriptome analyses of tumor-associated stromal, immune, endothelial and fibroblast cells identify signals that may support tumor development, as well as the recruitment and education of immune cells. Our findings are consistent with the early, premalignant formation of an immunosuppressive environment mediated by interactions between acinar metaplastic cells and other cells in the microenvironment.

A Metformin-Responsive Metabolic Pathway Controls Distinct Steps in Gastric Progenitor Fate Decisions and Maturation

Cellular metabolism plays important functions in dictating stem cell behaviors, although its role in stomach epithelial homeostasis has not been evaluated in depth. Here, we show that the energy sensor AMP kinase (AMPK) governs gastric epithelial progenitor differentiation. Administering the AMPK activator metformin decreases epithelial progenitor proliferation and increases acid-secreting parietal cells (PCs) in mice and organoids. AMPK activation targets Krüppel-like factor 4 (KLF4), known to govern progenitor proliferation and PC fate choice, and PGC1α, which we show controls PC maturation after their specification. PC-specific deletion of AMPKα or PGC1α causes defective PC maturation, which could not be rescued by metformin. However, metformin treatment still increases KLF4 levels and suppresses progenitor proliferation. Thus, AMPK activates KLF4 in progenitors to reduce self-renewal and promote PC fate, whereas AMPK-PGC1α activation within the PC lineage promotes maturation, providing a potential suggestion for why metformin increases acid secretion and reduces gastric cancer risk in humans.

HNF4α pathway mapping identifies wild-type IDH1 as a targetable metabolic node in gastric cancer

OBJECTIVE

Gastric cancer (GC) is a leading cause of cancer mortality. Previous studies have shown that hepatocyte nuclear factor-4α (HNF4α) is specifically overexpressed in GC and functionally required for GC development. In this study, we investigated, on a genome-wide scale, target genes of HNF4α and oncogenic pathways driven by HNF4α and HNF4α target genes.

DESIGN

We performed HNF4α chromatin immunoprecipitation followed by sequencing across multiple GC cell lines, integrating HNF4α occupancy data with (epi)genomic and transcriptome data of primary GCs to define HNF4α target genes of in vitro and in vivo relevance. To investigate mechanistic roles of HNF4α and HNF4α targets, we performed cancer metabolic measurements, drug treatments and functional assays including murine xenograft experiments.

RESULTS

Gene expression analysis across 19 tumour types revealed HNF4α to be specifically upregulated in GCs. Unbiased pathway analysis revealed organic acid metabolism as the top HNF4α-regulated pathway, orthogonally supported by metabolomic analysis. Isocitrate dehydrogenase 1 (IDH1) emerged as a convergent HNF4α direct target gene regulating GC metabolism. We show that wild-type IDH1 is essential for GC cell survival, and that certain GC cells can be targeted by IDH1 inhibitors.

CONCLUSIONS

Our results highlight a role for HNF4α in sustaining GC oncogenic metabolism, through the regulation of IDH1. Drugs targeting wild-type IDH1 may thus have clinical utility in GCs exhibiting HNF4α overexpression, expanding the role of IDH1 in cancer beyond IDH1/2 mutated malignancies.

Exploring disease-specific methylated CpGs in human male genital abnormalities by using methylated-site display-amplified fragment length polymorphism (MSD-AFLP)

The incidence of male reproductive system disorders, especially hypospadias, has been increasing in developed countries since the latter half of the 20th century. Endocrine-disrupting chemicals from the environment are considered to be involved in hypospadias onset through epigenetic alterations. This pilot study aimed to explore disease-specific methylated CpGs in human patient samples using the methylated-site display-amplified fragment length polymorphism (MSD-AFLP) technique developed by our research group [1]. We compared clinical samples from hypospadias and phimosis patients. Foreskin and blood samples were collected from one- to two-year-old patients with hypospadias (N = 3) and phimosis (N = 3) during surgical treatment. MSD-AFLP analysis showed significantly decreased CpG-methylation levels of genes such as MYH11 and increased CpG-methylation levels of genes such as PLA2G15 in hypospadias patients. Hierarchical clustering analysis showed that genes with significantly altered CpG levels were more markedly altered in DNA from blood than from foreskin. Because of the small number of samples, further investigation is necessary to elucidate the association between variations in CpG levels in foreskin and blood DNA and male genital abnormalities. However, our MSD-AFLP method appears to be a useful tool for exploring disease-specific methylated-CpGs in human epidemiological studies.

Gene expression profile data of the developing small intestine of Id2-deficient mice

This article contains data related to the research article entitled “Id2 determines intestinal identity through repression of the foregut transcription factor, Irx5” [1]. Id2 deficient (Id2^−/−) mice developed gastric tumors and heterotopic squamous epithelium in the small intestine. These tumors and heterotopic tissues were derived from ectopic gastric cells and squamous cells formed in the small intestine respectively during development. In this study, microarray data of the developing small intestine of Id2^−/− mice was analyzed.

Single-cell transcriptome analysis identifies distinct cell types and niche signaling in a primary gastric organoid model

The diverse cellular milieu of the gastric tissue microenvironment plays a critical role in normal tissue homeostasis and tumor development. However, few cell culture model can recapitulate the tissue microenvironment and intercellular signaling in vitro. We used a primary tissue culture system to generate a murine p53 null gastric tissue model containing both epithelium and mesenchymal stroma. To characterize the microenvironment and niche signaling, we used single cell RNA sequencing (scRNA-Seq) to determine the transcriptomes of 4,391 individual cells. Based on specific markers, we identified epithelial cells, fibroblasts and macrophages in initial tissue explants during organoid formation. The majority of macrophages were polarized towards wound healing and tumor promotion M2-type. During the course of time, the organoids maintained both epithelial and fibroblast lineages with the features of immature mouse gastric stomach. We detected a subset of cells in both lineages expressing Lgr5, one of the stem cell markers. We examined the lineage-specific Wnt signaling activation, and identified that Rspo3 was specifically expressed in the fibroblast lineage, providing an endogenous source of the R-spondin to activate Wnt signaling. Our studies demonstrate that this primary tissue culture system enables one to study gastric tissue niche signaling and immune response in vitro.

A revised airway epithelial hierarchy includes CFTR-expressing ionocytes

The airways of the lung are the primary sites of disease in asthma and cystic fibrosis. Here we study the cellular composition and hierarchy of the mouse tracheal epithelium by single-cell RNA-sequencing (scRNA-seq) and in vivo lineage tracing. We identify a rare cell type, the Foxi1+ pulmonary ionocyte; functional variations in club cells based on their location; a distinct cell type in high turnover squamous epithelial structures that we term 'hillocks'; and disease-relevant subsets of tuft and goblet cells. We developed 'pulse-seq', combining scRNA-seq and lineage tracing, to show that tuft, neuroendocrine and ionocyte cells are continually and directly replenished by basal progenitor cells. Ionocytes are the major source of transcripts of the cystic fibrosis transmembrane conductance regulator in both mouse (Cftr) and human (CFTR). Knockout of Foxi1 in mouse ionocytes causes loss of Cftr expression and disrupts airway fluid and mucus physiology, phenotypes that are characteristic of cystic fibrosis. By associating cell-type-specific expression programs with key disease genes, we establish a new cellular narrative for airways disease.

Patterning the gastrointestinal epithelium to confer regional-specific functions

The gastrointestinal (GI) tract, in simplest terms, can be described as an epithelial-lined muscular tube extending along the cephalocaudal axis from the oral cavity to the anus. Although the general architecture of the GI tract organs is conserved from end to end, the presence of different epithelial tissue structures and unique epithelial cell types within each organ enables each to perform the distinct digestive functions required for efficient nutrient assimilation. Spatiotemporal regulation of signaling pathways and downstream transcription factors controls GI epithelial morphogenesis during development to confer essential regional-specific epithelial structures and functions. Here, we discuss the fundamental functions of each GI tract organ and summarize the diversity of epithelial structures present along the cephalocaudal axis of the GI tract. Next, we discuss findings, primarily from genetic mouse models, that have defined the roles of key transcription factors during epithelial morphogenesis, including p63, SOX2, SOX15, GATA4, GATA6, HNF4A, and HNF4G. Additionally, we examine how the Hedgehog, WNT, and BMP signaling pathways contribute to defining unique epithelial features along the cephalocaudal axis of the GI tract. Lastly, we examine the molecular mechanisms controlling regionalized cytodifferentiation of organ-specific epithelial cell types within the GI tract, concentrating on the stomach and small intestine. The delineation of GI epithelial patterning mechanisms in mice has provided fundamental knowledge to guide the development and refinement of three-dimensional GI organotypic culture models such as those derived from directed differentiation of human pluripotent stem cells and those derived directly from human tissue samples. Continued examination of these pathways will undoubtedly provide vital insights into the mechanisms of GI development and disease and may afford new avenues for innovative tissue engineering and personalized medicine approaches to treating GI diseases.

Genetic analysis of zebrafish homologs of human FOXQ1, foxq1a and foxq1b, in innate immune cell development and bacterial host response

FOXQ1 is a member of the forkhead-box transcription factor family that has important functions in development, cancer, aging, and many cellular processes. The role of FOXQ1 in cancer biology has raised intense interest, yet much remains poorly understood. We investigated the possible function of the two zebrafish orthologs (foxq1a and foxq1b) of human FOXQ1 in innate immune cell development and function. We employed CRISPR-Cas9 targeted mutagenesis to create null mutations of foxq1a and foxq1b in zebrafish. Using a combination of molecular, cellular, and embryological approaches, we characterized single and double foxq1a bcz11 and foxq1b bcz18 mutants. This study provides the first genetic mutant analyses of zebrafish foxq1a and foxq1b. Interestingly, we found that foxq1a, but not foxq1b, was transcriptionally regulated during a bacterial response, while the expression of foxq1a was detected in sorted macrophages and upregulated in foxq1a-deficient mutants. However, the transcriptional response to E. coli challenge of foxq1a and foxq1b mutants was not significantly different from that of their wildtype control siblings. Our data shows that foxq1a may have a role in modulating bacterial response, while both foxq1a and foxq1b are not required for the development of macrophages, neutrophils, and microglia. Considering the implicated role of FOXQ1 in a vast number of cancers and biological processes, the foxq1a and foxq1b null mutants from this study provide useful genetic models to further investigate FOXQ1 functions.

FOXQ1 regulates senescence-associated inflammation via activation of SIRT1 expression

Cellular senescence is an initial barrier to tumor development that prevents the proliferation of premalignant cells. However, some of the features of senescent cells seem to promote tumor progression via senescence-associated secretory phenotype (SASP). Here, we demonstrated that the protein level of forkhead box Q1 (FOXQ1), which highly overexpresses in several kinds of tumors, was significantly downregulated during both replicative and oncogene-induced senescence. Moreover, overexpression of FOXQ1 delayed senescence, whereas FOXQ1 silence led to premature senescence in human fibroblasts. Furthermore, we identified that FOXQ1 upregulated SIRT1 expression through transcriptional regulation via directly binding to the SIRT1 promoter. Finally, we showed that FOXQ1 remarkably inhibited the replicative senescence through depressing the expression of the inflammatory cytokines interleukin-6 (IL-6) and IL-8 via modulation of SIRT1-NF-κB pathway. In addition, FOXQ1 overexpressed in human esophageal cancer cells and ablation of FOXQ1 restrained the tumourigenic ability of the esophageal cancer cells (EC109 and EC9706) in a mouse xenograft model in vivo. Taken together, these findings uncover a previously unidentified role of FOXQ1 regulating SASP and tumor development at same time.

Up-Regulation of FOXC2 and FOXQ1 Is Associated with The Progression of Gastric-Type Adenocarcinoma

OBJECTIVE

Forkhead box (FOX) proteins are important regulators of the epithelial-to-mesenchymal transition (EMT), which is the main mechanism of cancer metastasis. Different studies have shown their potential involvement in progression of cancer in different tissues such as breast, ovary and colorectum. In this study, we aimed to analyze the expression of genes encoding two FOX proteins in gastric adenocarcinoma.

MATERIALS AND METHODS

In this experimental case-control study, the expression of FOXC2 and FOXQ1 was examined in 31 gastric adenocarcinoma tumors and 31 normal adjacent gastric tissues by reverse transcription polymerase chain reaction (PCR).

RESULTS

The expression of both genes was significantly up-regulated in gastric adenocarcinoma tumors compared with the normal tissues (P<0.05). The differential expression of these two genes was also correlated with the grade of tumors (P<0.01).

CONCLUSION

We show that up-regulation of FOXC2 and FOXQ1 are likely to be involved in the progression of gastric adenocarcinoma.

Excess of genomic defects in a woolly mammoth on Wrangel island

Woolly mammoths (Mammuthus primigenius) populated Siberia, Beringia, and North America during the Pleistocene and early Holocene. Recent breakthroughs in ancient DNA sequencing have allowed for complete genome sequencing for two specimens of woolly mammoths (Palkopoulou et al. 2015). One mammoth specimen is from a mainland population 45,000 years ago when mammoths were plentiful. The second, a 4300 yr old specimen, is derived from an isolated population on Wrangel island where mammoths subsisted with small effective population size more than 43-fold lower than previous populations. These extreme differences in effective population size offer a rare opportunity to test nearly neutral models of genome architecture evolution within a single species. Using these previously published mammoth sequences, we identify deletions, retrogenes, and non-functionalizing point mutations. In the Wrangel island mammoth, we identify a greater number of deletions, a larger proportion of deletions affecting gene sequences, a greater number of candidate retrogenes, and an increased number of premature stop codons. This accumulation of detrimental mutations is consistent with genomic meltdown in response to low effective population sizes in the dwindling mammoth population on Wrangel island. In addition, we observe high rates of loss of olfactory receptors and urinary proteins, either because these loci are non-essential or because they were favored by divergent selective pressures in island environments. Finally, at the locus of FOXQ1 we observe two independent loss-of-function mutations, which would confer a satin coat phenotype in this island woolly mammoth.

We observe an excess of detrimental mutations, consistent with genomic meltdown in woolly mammoths on Wrangel Island just prior to extinction. We observe an excess of deletions, an increase in the proportion of deletions affecting gene sequences, and an excess of premature stop codons in response to evolution under low effective population sizes. Large numbers of olfactory receptors appear to have loss of function mutations in the island mammoth. These results offer genetic support within a single species for nearly-neutral theories of genome evolution. We also observe two independent loss of function mutations at the FOXQ1 locus, likely conferring a satin coat in this unusual woolly mammoth.

Notch as a Driver of Gastric Epithelial Cell Proliferation

The gastric epithelium is sustained by a population of stem cells that replenish the various mature epithelial lineages throughout adulthood. Regulation of stem and progenitor cell proliferation occurs via basic developmental signaling pathways, including the Notch pathway, which recently was described to promote gastric stem cell proliferation in both mice and human beings. Current cancer theory proposes that adult stem cells that maintain gastrointestinal tissues accumulate mutations that promote cancerous growth, and that basic signaling pathways, such as Notch, which stimulate stem cell proliferation, can promote tumorigenesis. Accordingly, constitutive Notch activation leads to unchecked cellular proliferation and gastric tumors in genetic mouse models. Furthermore, there is emerging evidence suggesting that the Notch pathway may be activated in some human gastric cancers, supporting a potential role for Notch in gastric tumorigenesis. In this review, we first summarize the current understanding of gastric stem cells defined by genetic mouse studies, followed by discussion of the literature regarding Notch pathway regulation of gastric stem cell function in the mouse and human beings. Notch action to maintain gastric epithelial cell homeostasis and the cellular consequences of dysregulated signaling to promote tumorigenesis are discussed, including studies associating Notch activation with human gastric cancer. Finally, we compare and contrast Notch function in the stomach with other gastrointestinal tissues, including the intestine, to highlight the sensitivity of the stomach to Notch-induced tumors.

The hepatic FOXQ1 transcription factor regulates glucose metabolism in mice

AIM/HYPOTHESIS

Hepatic forkhead box q1 (FOXQ1) expression levels are regulated by nutritional and pathophysiological status. In this study we investigated the role of FOXQ1 in the regulation of hepatic gluconeogenesis.

METHODS

We used multiple mouse and cell models to study the role of FOXQ1 in regulating expression of gluconeogenic genes, and cellular and hepatic glucose production.

RESULTS

Expression of hepatic FOXQ1 was regulated by fasting in normal mice and was dysregulated in diabetic mice. Overexpression of FOXQ1 in primary hepatocytes inhibited expression of gluconeogenic genes and decreased cellular glucose output. Hepatic FOXQ1 rescue in db/db and high-fat diet-induced obese mice markedly decreased blood glucose level and improved glucose intolerance. In contrast, wild-type C57 mice with hepatic FOXQ1 deficiency displayed increased blood glucose levels and impaired glucose tolerance. Interestingly, studies into molecular mechanisms indicated that FOXQ1 interacts with FOXO1, thereby blocking FOXO1 activity on hepatic gluconeogenesis, preventing it from directly binding to insulin response elements mapped in the promoter region of gluconeogenic genes.

CONCLUSIONS/INTERPRETATION

FOXQ1 is a novel factor involved in regulating hepatic gluconeogenesis, and the decreased FOXQ1 expression in liver may contribute to the development of type 2 diabetes.

Stomach development, stem cells and disease

The stomach, an organ derived from foregut endoderm, secretes acid and enzymes and plays a key role in digestion. During development, mesenchymal-epithelial interactions drive stomach specification, patterning, differentiation and growth through selected signaling pathways and transcription factors. After birth, the gastric epithelium is maintained by the activity of stem cells. Developmental signals are aberrantly activated and stem cell functions are disrupted in gastric cancer and other disorders. Therefore, a better understanding of stomach development and stem cells can inform approaches to treating these conditions. This Review highlights the molecular mechanisms of stomach development and discusses recent findings regarding stomach stem cells and organoid cultures, and their roles in investigating disease mechanisms.

Identification of additional risk loci for stroke and small vessel disease: a meta-analysis of genome-wide association studies

BACKGROUND

Genetic determinants of stroke, the leading neurological cause of death and disability, are poorly understood and have seldom been explored in the general population. Our aim was to identify additional loci for stroke by doing a meta-analysis of genome-wide association studies.

METHODS

For the discovery sample, we did a genome-wide analysis of common genetic variants associated with incident stroke risk in 18 population-based cohorts comprising 84 961 participants, of whom 4348 had stroke. Stroke diagnosis was ascertained and validated by the study investigators. Mean age at stroke ranged from 45·8 years to 76·4 years, and data collection in the studies took place between 1948 and 2013. We did validation analyses for variants yielding a significant association (at p<5 × 10(-6)) with all-stroke, ischaemic stroke, cardioembolic ischaemic stroke, or non-cardioembolic ischaemic stroke in the largest available cross-sectional studies (70 804 participants, of whom 19 816 had stroke). Summary-level results of discovery and follow-up stages were combined using inverse-variance weighted fixed-effects meta-analysis, and in-silico lookups were done in stroke subtypes. For genome-wide significant findings (at p<5 × 10(-8)), we explored associations with additional cerebrovascular phenotypes and did functional experiments using conditional (inducible) deletion of the probable causal gene in mice. We also studied the expression of orthologs of this probable causal gene and its effects on cerebral vasculature in zebrafish mutants.

FINDINGS

We replicated seven of eight known loci associated with risk for ischaemic stroke, and identified a novel locus at chromosome 6p25 (rs12204590, near FOXF2) associated with risk of all-stroke (odds ratio [OR] 1·08, 95% CI 1·05-1·12, p=1·48 × 10(-8); minor allele frequency 21%). The rs12204590 stroke risk allele was also associated with increased MRI-defined burden of white matter hyperintensity-a marker of cerebral small vessel disease-in stroke-free adults (n=21 079; p=0·0025). Consistently, young patients (aged 2-32 years) with segmental deletions of FOXF2 showed an extensive burden of white matter hyperintensity. Deletion of Foxf2 in adult mice resulted in cerebral infarction, reactive gliosis, and microhaemorrhage. The orthologs of FOXF2 in zebrafish (foxf2b and foxf2a) are expressed in brain pericytes and mutant foxf2b(-/-) cerebral vessels show decreased smooth muscle cell and pericyte coverage.

INTERPRETATION

We identified common variants near FOXF2 that are associated with increased stroke susceptibility. Epidemiological and experimental data suggest that FOXF2 mediates this association, potentially via differentiation defects of cerebral vascular mural cells. Further expression studies in appropriate human tissues, and further functional experiments with long follow-up periods are needed to fully understand the underlying mechanisms.

FUNDING

NIH, NINDS, NHMRC, CIHR, European national research institutions, Fondation Leducq.

Stomach Organ and Cell Lineage Differentiation: from Embryogenesis to Adult Homeostasis

Gastric diseases cause considerable worldwide burden. However, the stomach is still poorly understood in terms of the molecular-cellular processes that govern its development and homeostasis. In particular, the complex relationship between the differentiated cell types located within the stomach and the stem and progenitor cells that give rise to them is significantly understudied relative to other organs. In this review, we will highlight the current state of the literature relating to specification of gastric cell lineages from embryogenesis to adulthood. Special emphasis is placed on substantial gaps in knowledge about stomach specification that we think should be tackled to advance the field. For example, it has long been assumed that adult gastric units have a granule-free stem cell that gives rise to all differentiated lineages. Here we will point out that there are also other models that fit all extant data, such as long-lived lineage-committed progenitors that might serve as a source of new cells during homeostasis.

Notch signaling regulates gastric antral LGR5 stem cell function

The major signaling pathways regulating gastric stem cells are unknown. Here we report that Notch signaling is essential for homeostasis of LGR5(+) antral stem cells. Pathway inhibition reduced proliferation of gastric stem and progenitor cells, while activation increased proliferation. Notch dysregulation also altered differentiation, with inhibition inducing mucous and endocrine cell differentiation while activation reduced differentiation. Analysis of gastric organoids demonstrated that Notch signaling was intrinsic to the epithelium and regulated growth. Furthermore, in vivo Notch manipulation affected the efficiency of organoid initiation from glands and single Lgr5-GFP stem cells, suggesting regulation of stem cell function. Strikingly, constitutive Notch activation in LGR5(+) stem cells induced tissue expansion via antral gland fission. Lineage tracing using a multi-colored reporter demonstrated that Notch-activated stem cells rapidly generate monoclonal glands, suggesting a competitive advantage over unmanipulated stem cells. Notch activation was associated with increased mTOR signaling, and mTORC1 inhibition normalized NICD-induced increases in proliferation and gland fission. Chronic Notch activation induced undifferentiated, hyper-proliferative polyps, suggesting that aberrant activation of Notch in gastric stem cells may contribute to gastric tumorigenesis.

Profiling of embryonic stem cell differentiation

Embryonic stem (ES) cells have been shown to recapitulate normal developmental stages. They are therefore a highly useful tool in the study of developmental biology. Profiling of ES cell-derived cells has yielded important information about the characteristics of differentiated cells, and allowed the identification of novel marker genes and pathways of differentiation. In this review, we focus on recent results from profiling studies of mouse embryos, human islets, and human ES cell-derived differentiated cells from several research groups. Global gene expression data from mouse embryos have been used to identify novel genes or pathways involved in the developmental process, and to search for transcription factors that regulate direct reprogramming. We introduce gene expression databases of human pancreas cells (Beta Cell Gene Atlas, EuroDia database), and summarize profiling studies of islet- or human ES cell-derived pancreatic cells, with a focus on gene expression, microRNAs, epigenetics, and protein expression. Then, we describe our gene expression profile analyses and our search for novel endoderm, or pancreatic, progenitor marker genes. We differentiated mouse ES cells into mesendoderm, definitive endoderm (DE), mesoderm, ectoderm, and Pdx1-expressing pancreatic lineages, and performed DNA microarray analyses. Genes specifically expressed in DE, and/or in Pdx1-expressing cells, were extracted and their expression patterns in normal embryonic development were studied by in situ hybridization. Out of 54 genes examined, 27 were expressed in the DE of E8.5 mouse embryos, and 15 genes were expressed in distinct domains in the pancreatic buds of E14.5 mouse embryos. Akr1c19, Aebp2, Pbxip1, and Creb3l1 were all novel, and none has been described as being expressed, either in the DE, or in the pancreas. By introducing the profiling results of ES cell-derived cells, the benefits of using ES cells to study early embryonic development will be discussed.

Forkhead box Q1 promotes hepatocellular carcinoma metastasis by transactivating ZEB2 and VersicanV1 expression

Forkhead box Q1 (FoxQ1) is a master regulator of tumor metastasis. However, the molecular mechanism of FoxQ1 in regulating hepatocellular carcinoma (HCC) metastasis remains unknown. Here we report a novel function for FoxQ1 in modifying the tumor microenvironment to promote HCC metastasis. FoxQ1 expression was an independent and significant risk factor for the recurrence and survival in two independent cohorts totaling 1,002 HCC patients. FoxQ1 induced epithelial-mesenchymal transition (EMT) through the transactivation of ZEB2 expression by directly binding to the ZEB2 promoter. Knockdown of ZEB2 decreased FoxQ1-enhanced HCC metastasis, whereas up-regulation of ZEB2 rescued the decreased metastasis induced by FoxQ1 knocking down. Additionally, serial deletion, site-directed mutagenesis, and a chromatin immunoprecipitation assays showed that VersicanV1, which promoted HCC metastasis and macrophage attraction, was a direct transcriptional target of FoxQ1. FoxQ1-induced VersicanV1 expression promoted the secretion of chemokine (C-C motif) ligand 2 (CCL2) from HCC cells. Chemotaxis assay showed that the culture media from FoxQ1-overexpressing HCC cells increased the migratory activity of the macrophages. Inhibition of VersicanV1 and CCL2 expression significantly inhibited FoxQ1-mediated macrophage migration. In animal studies, the up-regulation of FoxQ1 in HCC cells promoted HCC metastasis and intratumoral tumor associated macrophage (TAM) infiltration, whereas knockdown of VersicanV1 reduced FoxQ1-mediated HCC metastasis and intratumoral TAM infiltration. Depletion of macrophages using clodronate liposomes dramatically decreased FoxQ1-enhanced HCC metastasis. In human HCC tissues, FoxQ1 expression was positively correlated with ZEB2 and VersicanV1 expression and intratumoral TAM infiltration. Patients with positive coexpression of FoxQ1 and ZEB2, FoxQ1, and VersicanV1, or FoxQ1 and intratumoral TAMs were associated with poorer prognosis.

CONCLUSION

FoxQ1 promotes HCC metastasis by transactivating ZEB2 and VersicanV1 expression, resulting in the induction of EMT and the recruitment of macrophage infiltration.

FOXQ1, a novel target of the Wnt pathway and a new marker for activation of Wnt signaling in solid tumors

Background

The forkhead box transcription factor FOXQ1 has been shown to be upregulated in colorectal cancer (CRC) and metastatic breast cancer and involved in tumor development, epithelial-mesenchymal transition and chemoresistance. Yet, its transcriptional regulation is still unknown.

Methods

FOXQ1 mRNA and protein expression were analysed in a panel of CRC cell lines, and laser micro-dissected human biopsy samples by qRT-PCR, microarray GeneChip® U133 Plus 2.0 and western blots. FOXQ1 regulation was assayed by chromatin immunoprecipitation and luciferase reporter assays.

Results

FOXQ1 was robustly induced in CRC compared to other tumors, but had no predictive value with regards to grade, metastasis and survival in CRC. Prototype-based gene coexpression and gene set enrichment analysis showed a significant association between FOXQ1 and the Wnt pathway in tumors and cancer cell lines from different tissues. In vitro experiments confirmed, on a molecular level, FOXQ1 as a direct Wnt target. Analysis of known Wnt targets identified FOXQ1 as the most suitable marker for canonical Wnt activation across a wide panel of cell lines derived from different tissues.

Conclusions

Our data show that FOXQ1 is one of the most over-expressed genes in CRC and a direct target of the canonical Wnt pathway. It is a potential new marker for detection of early CRC and Wnt activation in tumors of different origins.

Gastrokines: stomach-specific proteins with putative homeostatic and tumor suppressor roles

During the past decade, a new family of stomach-specific proteins has been recognized. Known as "gastrokines" (GKNs), these secreted proteins are products of gastric mucus-producing cell lineages. GKNs are highly conserved in physical structure, and emerging data point to convergent functions in the modulation of gastric mucosal homeostasis and inflammation. While GKNs are highly prevalent in the normal stomach, frequent loss of GKN expression in gastric cancers, coupled with established antiproliferative activity, suggests putative tumor suppressor roles. Conversely, ectopic expression of GKNs in reparative lesions of Crohn's disease alludes to additional activity in epithelial wound healing and/or repair. Modes of action remain unsolved, but the recent demonstration of a GKN2-trefoil factor 1 heterodimer implicates functional interplay with trefoil factors. This review aims to provide a historical account of GKN biology and encapsulate the rapidly accumulating evidence supporting roles in gastric epithelial homeostasis and tumor suppression.

Novel cell surface genes expressed in the stomach primordium during gastrointestinal morphogenesis of mouse embryos

The mechanisms of gastrointestinal morphogenesis in mammals are not well understood. This is partly due to the lack of appropriate markers that are expressed with spatiotemporal specificity in the gastrointestinal tract during development. Using mouse embryos, we surveyed markers of the prospective stomach region during gastrointestinal morphogenesis. The initiation of organ bud formation occurs at E10.5 in mice. These primordia for the digestive organs protrude from a tube-like structured endoderm and have their own distinct morphogenesis. We identified 3 cell surface genes -Adra2a, Fzd5, and Trpv6 - that are expressed in the developing stomach region during gastrointestinal morphogenesis using a microarray-based screening. These novel genes will be useful in expanding our understanding of the mechanisms of gastrointestinal development.

An expression profile analysis of ES cell-derived definitive endodermal cells and Pdx1-expressing cells

Background

We developed an efficient in vitro method to differentiate mouse ES cells into the definitive endoderm (DE) and then Pdx1-expressing pancreatic lineages using mesodermal-derived supporting cells, M15. Using this method, resulting ES cell-derived DE and Pdx1-expressing cells were isolated by cell sorting, and their gene expression profiles were investigated with DNA microarray. Genes that were specifically expressed in DE and/or in Pdx1-expressing cells were extracted and their expression patterns in normal embryonic development were studied.

Results

Genes whose expression increased in DE and Pdx1 positive cells compared to the undifferentiated ES cells were chosen and in situ hybridizations were performed. Out of 54 genes examined, 27 were expressed in the DE of E8.5 mouse embryos and 15 genes were expressed in distinct domains in the pancreatic buds of E14.5 embryos. Among those genes expressed were Foxq1, CpM, Foxp4, Pcdh1, and Zmiz1, which were previously reported in other endodermal tissues. Genes, such as Parm1, Tmem184a, Hipk2 and Sox4 were reported to be expressed during early pancreatic development. Nptx2, C2cd4b, Tcf7l2 and Kiss1r were reported to be associated with beta cell or pancreatic functions in the adult. Akr1c19, Aebp2, Pbxip1 and Creb3l1, were novel and have not been described as being expressed either in DE or the pancreas.

Conclusions

We identified 27 genes, including 4 novel genes expressed in DE and pancreatic progenitor cells during normal development using an ES cell in vitro differentiation system. These results showed that DE cells and Pdx1/GFP-expressing cells obtained from our M15 based differentiation method mimic cells during the normal developmental processes. Additionally, ES cells are an excellent model for studies of early developmental processes.

The Forkhead factor FoxQ1 influences epithelial differentiation

The Forkhead family of transcription factors comprises numerous members and is implicated in various cellular functions, including cell growth, apoptosis, migration, and differentiation. In this study, we identified the Forkhead factor FoxQ1 as increased in expression during TGF-β1 induced changes in epithelial differentiation, suggesting functional roles of FoxQ1 for epithelial plasticity. The repression of FoxQ1 in mammary epithelial cells led to a change in cell morphology characterized by an increase in cell size, pronounced cell-cell contacts, and an increased expression of several junction proteins (e.g., E-cadherin). In addition, FoxQ1 knock-down cells revealed rearrangements in the actin-cytoskeleton and slowed down cell cycle G1-phase progression. Furthermore, repression of FoxQ1 enhanced the migratory capacity of coherent mammary epithelial cells. Gene expression profiling of NM18 cells indicated that FoxQ1 is a relevant downstream mediator of TGF-β1-induced gene expression changes. This included the differential expression of transcription factors involved in epithelial plasticity, for example, Ets-1, Zeb1, and Zeb2. In summary, this study has elucidated the functional impact of FoxQ1 on epithelial differentiation.

XBP1 controls maturation of gastric zymogenic cells by induction of MIST1 and expansion of the rough endoplasmic reticulum

BACKGROUND & AIMS

The transition of gastric epithelial mucous neck cells (NCs) to digestive enzyme-secreting zymogenic cells (ZCs) involves an increase in rough endoplasmic reticulum (ER) and formation of many large secretory vesicles. The transcription factor MIST1 is required for granulogenesis of ZCs. The transcription factor XBP1 binds the Mist1 promoter and induces its expression in vitro and expands the ER in other cell types. We investigated whether XBP1 activates Mist1 to regulate ZC differentiation.

METHODS

Xbp1 was inducibly deleted in mice using a tamoxifen/Cre-loxP system; effects on ZC size and structure (ER and granule formation) and gastric differentiation were studied and quantified for up to 13 months after deletion using morphologic, immunofluorescence, quantitative reverse-transcriptase polymerase chain reaction, and immunoblot analyses. Interactions between XBP1 and the Mist1 promoter were studied by chromatin immunoprecipitation from mouse stomach and in XBP1-transfected gastric cell lines.

RESULTS

Tamoxifen-induced deletion of Xbp1 (Xbp1Δ) did not affect survival of ZCs but prevented formation of their structure. Xbp1Δ ZCs shrank 4-fold, compared with those of wild-type mice, with granulogenesis and cell shape abnormalities and disrupted rough ER. XBP1 was required and sufficient for transcriptional activation of MIST1. ZCs that developed in the absence of XBP1 induced ZC markers (intrinsic factor, pepsinogen C) but showed abnormal retention of progenitor NC markers.

CONCLUSIONS

XBP1 controls the transcriptional regulation of ZC structural development; it expands the lamellar rough ER and induces MIST1 expression to regulate formation of large granules. XBP1 is also required for loss of mucous NC markers as ZCs form.

Requirement of the epithelium-specific Ets transcription factor Spdef for mucous gland cell function in the gastric antrum

Mucus-secreting cells of the stomach epithelium provide a protective barrier against damage that might result from bacterial colonization or other stimuli. Impaired barrier function contributes to chronic inflammation and cancer. Knock-out mice for the epithelium-specific transcription factor Spdef (also called Pdef) have defects in terminal differentiation of intestinal and bronchial secretory cells. We sought to determine the physiologic function of Spdef in the stomach, another site of significant levels of Spdef expression. We used in situ hybridization and immunohistochemistry to localize Spdef-expressing cells in the mouse stomach; targeted gene disruption to generate mice lacking Spdef; and histologic, immunologic, and transcriptional profiling approaches to determine the requirements of Spdef in stomach epithelial homeostasis. In wild-type mice, Spdef RNA and protein are expressed predominantly in mucous gland cells of the antrum and in mucous neck cells of the glandular corpus. Within 1.5 years, nearly half of homozygous mutant mice developed profound mucosal hyperplasia of the gastric antrum. Submucosal infiltration of inflammatory cells preceded antral hyperplasia by several weeks. The absence of Spdef impaired terminal maturation of antral mucous gland cells, as reflected in reduced expression of Muc6 and Tff2 and reduced numbers of secretory granules. Antral gene expression abnormalities overlapped significantly with those in Spdef(-/-) colon, including genes implicated in secretory granule traffic and functions. Spdef is required for terminal maturation of antral mucous gland cells to protect animals from gastric inflammation and resulting hyperplasia. These requirements parallel Spdef functions in secretory intestinal cells and suggest a common molecular mechanism for maturation of gastrointestinal secretory lineages.

2,3,7,8-Tetrachlorodibenzo-p-dioxin upregulates FoxQ1b in zebrafish jaw primordium

Vertebrate jaw development can be disrupted by exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-a potent activator of the aryl hydrocarbon receptor (AHR) transcription factor required for transducing the toxic effects of TCDD. We used zebrafish (Danio rerio) embryos to investigate transcriptional responses to TCDD with the goal of discovering novel, jaw-specific genes affected by TCDD exposure. Our results uncovered a novel target of TCDD-activated Ahr belonging to the evolutionarily conserved family of forkhead box transcription factors. Quantitative real-time polymerase chain reaction analysis demonstrated that FoxQ1b was upregulated by TCDD 7- and 10-fold at 24 and 48 h postfertilization (hpf), respectively. The rate of TCDD-induced FoxQ1b expression was more rapid than that of Cyp1a, a known direct target of TCDD-activated Ahr. TCDD-mediated induction of FoxQ1b was suppressed in the presence of an Ahr antagonist, alpha-naphthoflavone, as well as following knockdown of Ahr2 expression using an Ahr2-specific morpholino antisense oligonucleotide. In situ hybridization analysis of FoxQ1b expression at 48 hpf demonstrated that FoxQ1b is specifically expressed in the jaw primordium where it discretely outlines a developing jaw structure known as Meckel's cartilage--a conserved structure in all jawed vertebrates that develops abnormally in the presence of TCDD. These results identify a novel target of TCDD-activated Ahr and suggest that FoxQ1b may play a role in craniofacial abnormalities induced by developmental exposure to TCDD.

FOXQ1 is overexpressed in colorectal cancer and enhances tumorigenicity and tumor growth

Forkhead box Q1 (FOXQ1) is a member of the forkhead transcription factor family, and it has recently been proposed to participate in gastric acid secretion and mucin gene expression in mice. However, the role of FOXQ1 in humans and especially in cancer cells remains unknown. We found that FOXQ1 mRNA is overexpressed in clinical specimens of colorectal cancer (CRC; 28-fold/colonic mucosa). A microarray analysis revealed that the knockdown of FOXQ1 using small interfering RNA resulted in a decrease in p21(CIP1/WAF1) expression, and a reporter assay and a chromatin immunoprecipitation assay showed that p21 was one of the target genes of FOXQ1. Stable FOXQ1-overexpressing cells (H1299/FOXQ1) exhibited elevated levels of p21 expression and inhibition of apoptosis induced by doxorubicin or camptothecin. Although cellular proliferation was decreased in H1299/FOXQ1 cells in vitro, H1299/FOXQ1 cells significantly increased tumorigenicity [enhanced green fluorescent protein (EGFP): 2/15, FOXQ1: 7/15] and enhanced tumor growth (437 +/- 301 versus 1735 +/- 769 mm3, P < 0.001) in vivo. Meanwhile, stable p21 knockdown of H1299/FOXQ1 cells increased tumor growth, suggesting that FOXQ1 promotes tumor growth independent of p21. Microarray analysis of H1299/EGFP and H1299/FOXQ1 revealed that FOXQ1 overexpression upregulated several genes that have positive roles for tumor growth, including VEGFA, WNT3A, RSPO2, and BCL11A. CD31 and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining of the tumor specimens showed that FOXQ1 overexpression mediated the angiogenic and antiapoptotic effect in vivo. In conclusion, FOXQ1 is overexpressed in CRC and enhances tumorigenicity and tumor growth presumably through its angiogenic and antiapoptotic effects. Our findings show that FOXQ1 is a new member of the cancer-related FOX family.

Capn8 promoter directs the expression of Cre recombinase in gastric pit cells of transgenic mice

Gastric pit cells are high-turnover epithelial cells of the gastric mucosa. They secrete mucus to protect the gastric epithelium from acid and pepsin. To investigate the genetic mechanisms underlying the physiological functions of gastric pit cells, we generated a transgenic mouse line, namely, Capn8-Cre, in which the expression of Cre recombinase was controlled by the promoter of the intracellular Ca(2+)-regulated cysteine protease calpain-8. To test the tissue distribution and excision activity of Cre recombinase, the Capn8-Cre transgenic mice were bred with the ROSA26 reporter strain and a mouse strain that carries Smad4 conditional alleles (Smad4(Co/Co)). Multiple-tissue PCR and LacZ staining demonstrated that Capn8-Cre transgenic mouse expressed Cre recombinase in the gastric pit cells. Cre recombinase activity was also detected in the liver and skin tissues. These data suggest that the Capn8-Cre mouse line described here could be used to dissect gene function in gastric pit cells.

The gastric mucosa development and differentiation

The development and differentiation of the gastric mucosa are controlled by a complex interplay of signaling proteins and transcriptional regulators. This process is complicated by the fact that the stomach is derived from two germ layers, the endoderm and the mesoderm, with the first giving rise to the mature epithelium and the latter contributing the smooth muscle required for peristalsis. Reciprocal epithelial-mesenchymal interactions dictate the formation of the stomach during fetal development, and also contribute to its continuous regeneration and differentiation throughout adult life. In this chapter, we discuss the discoveries that have been made in different model systems, from zebrafish to human, which show that the Hedgehog, Wnt, Notch, bone morphogenetic protein, and fibroblast growth factor (FGF) signaling systems play essential roles during various stages of stomach development.

How form follows functional genomics: gene expression profiling gastric epithelial cells with a particular discourse on the parietal cell

The cellular composition and morphology of the stomach epithelium have been described in detail; however, the molecular mechanisms that regulate the differentiation of the various cell lineages as well as the function of mature gastric cells are far less clear. Recently, dissection of the molecular anatomy of the stomach has been boosted by the advent of functional genomics, which allows investigators to determine patterns of gene expression across virtually the entire cellular transcriptome. In this review, we discuss the impact of functional genomic studies on the understanding of gastric epithelial physiology. We show how functional genomic studies have uncovered genes that are useful as new cell lineage-specific markers of differentiation and provide new insights into cell physiology. For example, vascular endothelial growth factor B (Vegfb) has been identified as a parietal cell-specific marker that may allow parietal cells to regulate the mucosal vascular network. We also discuss how functional genomics has identified aberrantly expressed genes in disease states. Human epididymis 4 (HE4), for example, was recently identified as a metaplasia-induced gene product in mice based on microarray analysis. Finally, we will examine how analysis of higher-order patterns of gene expression can go beyond simply identifying individual genes to show how cells work as integrated systems. Specifically, we show how application of a Gene Ontology (GO) analysis of gene expression patterns from multiple tissues identifies the gastric parietal cell as an outlier, unlike other differentiated cell lineages in the stomach or elsewhere in the body.