SOX9 specifies the pyloric sphincter epithelium through mesenchymal-epithelial signals

Diverse functions of SOX9 in liver development and homeostasis and hepatobiliary diseases

The liver is the central organ for digestion and detoxification and has unique metabolic and regenerative capacities. The hepatobiliary system originates from the foregut endoderm, in which cells undergo multiple events of cell proliferation, migration, and differentiation to form the liver parenchyma and ductal system under the hierarchical regulation of transcription factors. Studies on liver development and diseases have revealed that SRY-related high-mobility group box 9 (SOX9) plays an important role in liver embryogenesis and the progression of hepatobiliary diseases. SOX9 is not only a master regulator of cell fate determination and tissue morphogenesis, but also regulates various biological features of cancer, including cancer stemness, invasion, and drug resistance, making SOX9 a potential biomarker for tumor prognosis and progression. This review systematically summarizes the latest findings of SOX9 in hepatobiliary development, homeostasis, and disease. We also highlight the value of SOX9 as a novel biomarker and potential target for the clinical treatment of major liver diseases.

Essential Role of BMP4 Signaling in the Avian Ceca in Colorectal Enteric Nervous System Development

The enteric nervous system (ENS) is principally derived from vagal neural crest cells that migrate caudally along the entire length of the gastrointestinal tract, giving rise to neurons and glial cells in two ganglionated plexuses. Incomplete migration of enteric neural crest-derived cells (ENCDC) leads to Hirschsprung disease, a congenital disorder characterized by the absence of enteric ganglia along variable lengths of the colorectum. Our previous work strongly supported the essential role of the avian ceca, present at the junction of the midgut and hindgut, in hindgut ENS development, since ablation of the cecal buds led to incomplete ENCDC colonization of the hindgut. In situ hybridization shows bone morphogenetic protein-4 (BMP4) is highly expressed in the cecal mesenchyme, leading us to hypothesize that cecal BMP4 is required for hindgut ENS development. To test this, we modulated BMP4 activity using embryonic intestinal organ culture techniques and retroviral infection. We show that overexpression or inhibition of BMP4 in the ceca disrupts hindgut ENS development, with GDNF playing an important regulatory role. Our results suggest that these two important signaling pathways are required for normal ENCDC migration and enteric ganglion formation in the developing hindgut ENS.

High-resolution ultrasound and speckle tracking: a non-invasive approach to assess in vivo gastrointestinal motility during development

Gastrointestinal motor activity has been extensively studied in adults; however, only few studies have investigated fetal motor skills. It is unknown when the gastrointestinal tract starts to contract during the embryonic period and how this function evolves during development. Here, we adapted a non-invasive high-resolution echography technique combined with speckle tracking analysis to examine the gastrointestinal tract motor activity dynamics during chick embryo development. We provided the first recordings of fetal gastrointestinal motility in living embryos without anesthesia. We found that, although gastrointestinal contractions appear very early during development, they become synchronized only at the end of the fetal period. To validate this approach, we used various pharmacological inhibitors and BAPX1 gene overexpression in vivo. We found that the enteric nervous system determines the onset of the synchronized contractions in the stomach. Moreover, alteration of smooth muscle fiber organization led to an impairment of this functional activity. Altogether, our findings show that non-invasive high-resolution echography and speckle tracking analysis allows visualization and quantification of gastrointestinal motility during development and highlight the progressive acquisition of functional and coordinated gastrointestinal motility before birth.

Microanalysis of the stomach of southern white-breasted hedgehog (Erinaceus concolor): Histological, histochemical, immunohistochemical, and scanning electron microscopic studies

This study was designed to provide more detailed knowledge on the stomach histochemistry and immunohistochemistry in the southern white-breasted hedgehog (Erinaceus concolor). Two animals were used in the present work. Periodic acid Schiff's (PAS) and Alcian blue were used for histochemical purposes. SOX9, gastrin, serotonin, and glucagon markers were traced immunohistochemically. The mucosa was extremely folded in the fundus with numerous opening of glands. The body and pylorus mucosa were almost smooth and equipped with gastric gland openings. A simple columnar epithelium covered the stomach entirely. Cardiac glands region was mucus secreting with both positive and negative reactions to PAS. Fundic mucosa was contained cardiac glands near to the cardia, and toward the body it was divided into the light and dark zones. These zones and body contained proper gastric gland, which constituted of parietal, chief, and mucous neck cells. These glands contained PAS-positive cells on their basal portions. The pyloric glands were mucus secreting but negative for PAS. All gastric glands were Alcian blue-negative, but epithelium showed moderate reaction especially in the pylorus. SOX and gastrin were express highly in the body and fundus. The expression of serotonin and glucagon was rare. Comparatively, some similarities between the stomach of hedgehog and dog can be assumed. The present findings provide additional information concerning the histochemical characteristics and endocrine cells distribution in the stomach of the southern white-breasted hedgehog (Erinaceus concolor). Further detailed studies are required to enhance the current knowledge on histophysiology of the digestive system in this species as a pet and exotic animal.

Functional human gastrointestinal organoids can be engineered from three primary germ layers derived separately from pluripotent stem cells

Human organoid model systems lack important cell types that, in the embryo, are incorporated into organ tissues during development. We developed an organoid assembly approach starting with cells from the three primary germ layers-enteric neuroglial, mesenchymal, and epithelial precursors-that were derived separately from human pluripotent stem cells (PSCs). From these three cell types, we generated human antral and fundic gastric tissue containing differentiated glands surrounded by layers of smooth muscle containing functional enteric neurons that controlled contractions of the engineered antral tissue. Using this experimental system, we show that human enteric neural crest cells (ENCCs) promote mesenchyme development and glandular morphogenesis of antral stomach organoids. Moreover, ENCCs can act directly on the foregut to promote a posterior fate, resulting in organoids with a Brunner's gland phenotype. Thus, germ layer components that are derived separately from PSCs can be used for tissue engineering to generate complex human organoids.

SOX9: An emerging driving factor from cancer progression to drug resistance

Dysregulation of transcription factors is one of the common problems in the pathogenesis of human cancer. Among them, SOX9 is one of the critical transcription factors involved in various diseases, including cancer. The expression of SOX9 is regulated by microRNAs (miRNAs), methylation, phosphorylation, and acetylation. Interestingly, SOX9 acts as a proto-oncogene or tumor suppressor gene, relying upon kinds of cancer. Recent studies have reported the critical role of SOX9 in the regulation of the tumor microenvironment (TME). Additionally, activation of SOX9 signaling or SOX9 regulated signaling pathways play a crucial role in cancer development and progression. Accumulating evidence also suggests that SOX9 acquires stem cell features to induce epithelial-mesenchymal transition (EMT). Moreover, SOX9 has been broadly studied in the field of cancer stem cell (CSC) and EMT in the last decades. However, the link between SOX9 and cancer drug resistance has only recently been discovered. Furthermore, its differential expression could be a potential biomarker for tumor prognosis and progression. This review outlined the various biological implications of SOX9 in cancer progression and cancer drug resistance and elucidated its signaling network, which could be a potential target for designing novel anticancer drugs.

BMP Signaling in Development, Stem Cells, and Diseases of the Gastrointestinal Tract

The bone morphogenetic protein (BMP) pathway is essential for the morphogenesis of multiple organs in the digestive system. Abnormal BMP signaling has also been associated with disease initiation and progression in the gastrointestinal (GI) tract and associated organs. Recent studies using animal models, tissue organoids, and human pluripotent stem cells have significantly expanded our understanding of the roles played by BMPs in the development and homeostasis of GI organs. It is clear that BMP signaling regulates GI function and disease progression that involve stem/progenitor cells and inflammation in a tissue-specific manner. In this review we discuss these new findings with a focus on the esophagus, stomach, and intestine.

PROX1 is a specific and dynamic marker of sacral neural crest cells in the chicken intestine

The enteric nervous system (ENS) is a complex network constituted of neurons and glial cells that ensures the intrinsic innervation of the gastrointestinal tract. ENS cells originate from vagal and sacral neural crest cells that are initially located at the border of the neural tube. In birds, sacral neural crest cells (sNCCs) first give rise to an extramural ganglionated structure (the so-called Nerve of Remak [NoR]) and to the pelvic plexus. Later, sNCCs enter the colon mesenchyme to colonize and contribute to the intrinsic innervation of the caudal part of the gut. However, no specific sNCC marker has been described. Here, we report the expression pattern of prospero-related homeobox 1 (PROX1) in the developing chick colon. PROX1 is a homeobox domain transcription factor that plays a role in cell type specification in various tissues. Using in situ hybridization and immunofluorescence techniques, we showed that PROX1 is expressed in sNCCs localized in the NoR and in the pelvic plexus. Then, using real-time quantitative PCR we found that PROX1 displays a strong and highly dynamic expression pattern during NoR development. Moreover, we demonstrated using in vivo cell tracing, that sNCCs are the source of the PROX1-positive cells within the NoR. Our results indicate that PROX1 is the first marker that specifically identifies sNCCs. This might help to better identify the role of the different neural crest cell populations in distal gut innervation, and consequently to improve the diagnosis of diseases linked to incomplete ENS formation, such as Hirschsprung's disease.

TGF-β Family Signaling in Ductal Differentiation and Branching Morphogenesis

Epithelial cells contribute to the development of various vital organs by generating tubular and/or glandular architectures. The fully developed forms of ductal organs depend on processes of branching morphogenesis, whereby frequency, total number, and complexity of the branching tissue define the final architecture in the organ. Some ductal tissues, like the mammary gland during pregnancy and lactation, disintegrate and regenerate through periodic cycles. Differentiation of branched epithelia is driven by antagonistic actions of parallel growth factor systems that mediate epithelial-mesenchymal communication. Transforming growth factor-β (TGF-β) family members and their extracellular antagonists are prominently involved in both normal and disease-associated (e.g., malignant or fibrotic) ductal tissue patterning. Here, we discuss collective knowledge that permeates the roles of TGF-β family members in the control of the ductal tissues in the vertebrate body.

Translating Developmental Principles to Generate Human Gastric Organoids

Gastric diseases, including peptic ulcer disease and gastric cancer, are highly prevalent in human beings. Despite this, the cellular biology of the stomach remains poorly understood relative to other gastrointestinal organs such as the liver, intestine, and colon. In particular, little is known about the molecular basis of stomach development and the differentiation of gastric lineages. Although animal models are useful for studying gastric development, function, and disease, there are major structural and physiological differences in human stomachs that render these models insufficient. To look at gastric development, function, and disease in a human context, a model system of the human stomach is imperative. This review details how this was achieved through the directed differentiation of human pluripotent stem cells in a 3-dimensional environment into human gastric organoids (HGOs). Similar to previous work that has generated human intestine, colon, and lung tissue in vitro, HGOs were generated in vitro through a step-wise differentiation designed to mimic the temporal-spatial signaling dynamics that control stomach development in vivo. HGOs can be used for a variety of purposes, including genetic modeling, drug screening, and potentially even in future patient transplantation. Moreover, HGOs are well suited to study the development and interactions of nonepithelial cell types, such as endothelial, neuronal, and mesenchymal, which remain almost completely unstudied. This review discusses the basics of stomach morphology, function, and developmental pathways involved in generating HGOs. We also highlight important gaps in our understanding of how epithelial and mesenchymal interactions are essential for the development and overall function of the human stomach.

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.

Analyses of Sox-B and Sox-E Family Genes in the Cephalopod Sepia officinalis: Revealing the Conserved and the Unusual

Cephalopods provide an unprecedented opportunity for comparative studies of the developmental genetics of organ systems that are convergent with analogous vertebrate structures. The Sox-family of transcription factors is an important class of DNA-binding proteins that are known to be involved in many aspects of differentiation, but have been largely unstudied in lophotrochozoan systems. Using a degenerate primer strategy we have isolated coding sequence for three members of the Sox family of transcription factors from a cephalopod mollusk, the European cuttlefish Sepia officinalis: Sof-SoxE, Sof-SoxB1, and Sof-SoxB2. Analyses of their expression patterns during organogenesis reveals distinct spatial and temporal expression domains. Sof-SoxB1 shows early ectodermal expression throughout the developing epithelium, which is gradually restricted to presumptive sensory epithelia. Expression within the nervous system appears by mid-embryogenesis. Sof-SoxB2 expression is similar to Sof-SoxB1 within the developing epithelia in early embryogenesis, however appears in largely non-overlapping expression domains within the central nervous system and is not expressed in the maturing sensory epithelium. In contrast, Sof-SoxE is expressed throughout the presumptive mesodermal territories at the onset of organogenesis. As development proceeds, Sof-SoxE expression is elevated throughout the developing peripheral circulatory system. This expression disappears as the circulatory system matures, but expression is maintained within undifferentiated connective tissues throughout the animal, and appears within the nervous system near the end of embryogenesis. SoxB proteins are widely known for their role in neural specification in numerous phylogenetic lineages. Our data suggests that Sof-SoxB genes play similar roles in cephalopods. In contrast, Sof-SoxE appears to be involved in the early stages of vasculogenesis of the cephalopod closed circulatory system, a novel role for a member of this gene family.

LIX1 regulates YAP1 activity and controls the proliferation and differentiation of stomach mesenchymal progenitors

BACKGROUND

Smooth muscle cell (SMC) plasticity maintains the balance between differentiated SMCs and proliferative mesenchymal progenitors, crucial for muscular tissue homeostasis. Studies on the development of mesenchymal progenitors into SMCs have proven useful in identifying molecular mechanisms involved in digestive musculature plasticity in physiological and pathological conditions.

RESULTS

Here, we show that Limb Expression 1 (LIX1) molecularly defines the population of mesenchymal progenitors in the developing stomach. Using in vivo functional approaches in the chick embryo, we demonstrate that LIX1 is a key regulator of stomach SMC development. We show that LIX1 is required for stomach SMC determination to regulate the expression of the pro-proliferative gene YAP1 and mesenchymal cell proliferation. However, as stomach development proceeds, sustained LIX1 expression has a negative impact on further SMC differentiation and this is associated with a decrease in YAP1 activity.

CONCLUSIONS

We demonstrate that expression of LIX1 must be tightly regulated to allow fine-tuning of the transcript levels and state of activation of the pro-proliferative transcriptional coactivator YAP1 to regulate proliferation rates of stomach mesenchymal progenitors and their differentiation. Our data highlight dual roles for LIX1 and YAP1 and provide new insights into the regulation of cell density-dependent proliferation, which is essential for the development and homeostasis of organs.

Epithelial Splicing Regulatory Protein 1 (ESRP1) is a new regulator of stomach smooth muscle development and plasticity

In vertebrates, stomach smooth muscle development is a complex process that involves the tight transcriptional or post-transcriptional regulation of different signalling pathways. Here, we identified the RNA-binding protein Epithelial Splicing Regulatory Protein 1 (ESRP1) as an early marker of developing and undifferentiated stomach mesenchyme. Using a gain-of-function approach, we found that in chicken embryos, sustained expression of ESRP1 impairs stomach smooth muscle cell (SMC) differentiation and FGFR2 splicing profile. ESRP1 overexpression in primary differentiated stomach SMCs induced their dedifferentiation, promoted specific-FGFR2b splicing and decreased FGFR2c-dependent activity. Moreover, co-expression of ESRP1 and RBPMS2, another RNA-binding protein that regulates SMC plasticity and Bone Morphogenetic Protein (BMP) pathway inhibition, synergistically promoted SMC dedifferentiation. Finally, we also demonstrated that ESRP1 interacts with RBPMS2 and that RBPMS2-mediated SMC dedifferentiation requires ESRP1. Altogether, these results show that ESRP1 is expressed also in undifferentiated stomach mesenchyme and demonstrate its role in SMC development and plasticity.

Porcine SOX9 Gene Expression Is Influenced by an 18 bp Indel in the 5'-Untranslated Region

Sex determining region Y-box 9 (SOX9) is an important regulator of sex and skeletal development and is expressed in a variety of embryonal and adult tissues. Loss or gain of function resulting from mutations within the coding region or chromosomal aberrations of the SOX9 locus lead to a plethora of detrimental phenotypes in humans and animals. One of these phenotypes is the so-called male-to-female or female-to-male sex-reversal which has been observed in several mammals including pig, dog, cat, goat, horse, and deer. In 38,XX sex-reversal French Large White pigs, a genome-wide association study suggested SOX9 as the causal gene, although no functional mutations were identified in affected animals. However, besides others an 18bp indel had been detected in the 5′-untranslated region of the SOX9 gene by comparing affected animals and controls. We have identified the same indel (Δ18) between position +247bp and +266bp downstream the transcription start site of the porcine SOX9 gene in four other pig breeds; i.e., German Large White, Laiwu Black, Bamei, and Erhualian. These animals have been genotyped in an attempt to identify candidate genes for porcine inguinal and/or scrotal hernia. Because the 18bp segment in the wild type 5′-UTR harbours a highly conserved cAMP-response element (CRE) half-site, we analysed its role in SOX9 expression in vitro. Competition and immunodepletion electromobility shift assays demonstrate that the CRE half-site is specifically recognized by CREB. Both binding of CREB to the wild type as well as the absence of the CRE half-site in Δ18 reduced expression efficiency in HEK293T, PK–15, and ATDC5 cells significantly. Transfection experiments of wild type and Δ18 SOX9 promoter luciferase constructs show a significant reduction of RNA and protein levels depending on the presence or absence of the 18bp segment. Hence, the data presented here demonstrate that the 18bp indel in the porcine SOX9 5′-UTR is of functional importance and may therefore indeed be a causative variation in SOX9 associated traits.

Mesenchymal-epithelial interactions during digestive tract development and epithelial stem cell regeneration

The gastrointestinal tract develops from a simple and uniform tube into a complex organ with specific differentiation patterns along the anterior-posterior and dorso-ventral axes of asymmetry. It is derived from all three germ layers and their cross-talk is important for the regulated development of fetal and adult gastrointestinal structures and organs. Signals from the adjacent mesoderm are essential for the morphogenesis of the overlying epithelium. These mesenchymal-epithelial interactions govern the development and regionalization of the different gastrointestinal epithelia and involve most of the key morphogens and signaling pathways, such as the Hedgehog, BMPs, Notch, WNT, HOX, SOX and FOXF cascades. Moreover, the mechanisms underlying mesenchyme differentiation into smooth muscle cells influence the regionalization of the gastrointestinal epithelium through interactions with the enteric nervous system. In the neonatal and adult gastrointestinal tract, mesenchymal-epithelial interactions are essential for the maintenance of the epithelial regionalization and digestive epithelial homeostasis. Disruption of these interactions is also associated with bowel dysfunction potentially leading to epithelial tumor development. In this review, we will discuss various aspects of the mesenchymal-epithelial interactions observed during digestive epithelium development and differentiation and also during epithelial stem cell regeneration.

Enteric neural crest cells regulate vertebrate stomach patterning and differentiation

In vertebrates, the digestive tract develops from a uniform structure where reciprocal epithelial-mesenchymal interactions pattern this complex organ into regions with specific morphologies and functions. Concomitant with these early patterning events, the primitive GI tract is colonized by the vagal enteric neural crest cells (vENCCs), a population of cells that will give rise to the enteric nervous system (ENS), the intrinsic innervation of the GI tract. The influence of vENCCs on early patterning and differentiation of the GI tract has never been evaluated. In this study, we report that a crucial number of vENCCs is required for proper chick stomach development, patterning and differentiation. We show that reducing the number of vENCCs by performing vENCC ablations induces sustained activation of the BMP and Notch pathways in the stomach mesenchyme and impairs smooth muscle development. A reduction in vENCCs also leads to the transdifferentiation of the stomach into a stomach-intestinal mixed phenotype. In addition, sustained Notch signaling activity in the stomach mesenchyme phenocopies the defects observed in vENCC-ablated stomachs, indicating that inhibition of the Notch signaling pathway is essential for stomach patterning and differentiation. Finally, we report that a crucial number of vENCCs is also required for maintenance of stomach identity and differentiation through inhibition of the Notch signaling pathway. Altogether, our data reveal that, through the regulation of mesenchyme identity, vENCCs act as a new mediator in the mesenchymal-epithelial interactions that control stomach development.

The versatile functions of Sox9 in development, stem cells, and human diseases

The transcription factor Sox9 was first discovered in patients with campomelic dysplasia, a haploinsufficiency disorder with skeletal deformities caused by dysregulation of Sox9 expression during chondrogenesis. Since then, its role as a cell fate determiner during embryonic development has been well characterized; Sox9 expression differentiates cells derived from all three germ layers into a large variety of specialized tissues and organs. However, recent data has shown that ectoderm- and endoderm-derived tissues continue to express Sox9 in mature organs and stem cell pools, suggesting its role in cell maintenance and specification during adult life. The versatility of Sox9 may be explained by a combination of post-transcriptional modifications, binding partners, and the tissue type in which it is expressed. Considering its importance during both development and adult life, it follows that dysregulation of Sox9 has been implicated in various congenital and acquired diseases, including fibrosis and cancer. This review provides a summary of the various roles of Sox9 in cell fate specification, stem cell biology, and related human diseases. Ultimately, understanding the mechanisms that regulate Sox9 will be crucial for developing effective therapies to treat disease caused by stem cell dysregulation or even reverse organ damage.

Role of SOX2 in foregut development in relation to congenital abnormalities

The uptake of the two essential ingredients for life, oxygen and nutrients, occurs primarily through the oral cavity, but these two lifelines need to be separated with high accuracy once inside the body. The two systems, the gas exchange pulmonary system and the gastro-intestinal feeding system, are derived from the same primitive embryonic structure during development, the foregut, which need to be separated before birth. In certain newborns, this separation occurs not or insufficiently, leading to life threatening conditions, sometimes incompatible with life. The development of the foregut, trachea and lungs is influenced and coordinated by a multitude of signaling cascades and transcription factors. In this review, we will highlight the development of the foregut and pulmonary system and focus on associated congenital abnormalities in light of known genetic alterations with specific attention to the transcription factor SOX2.

Homodimerization of RBPMS2 through a new RRM-interaction motif is necessary to control smooth muscle plasticity

In vertebrates, smooth muscle cells (SMCs) can reversibly switch between contractile and proliferative phenotypes. This involves various molecular mechanisms to reactivate developmental signaling pathways and induce cell dedifferentiation. The protein RBPMS2 regulates early development and plasticity of digestive SMCs by inhibiting the bone morphogenetic protein pathway through its interaction with NOGGIN mRNA. RBPMS2 contains only one RNA recognition motif (RRM) while this motif is often repeated in tandem or associated with other functional domains in RRM-containing proteins. Herein, we show using an extensive combination of structure/function analyses that RBPMS2 homodimerizes through a particular sequence motif (D-x-K-x-R-E-L-Y-L-L-F: residues 39–51) located in its RRM domain. We also show that this specific motif is conserved among its homologs and paralogs in vertebrates and in its insect and worm orthologs (CPO and MEC-8, respectively) suggesting a conserved molecular mechanism of action. Inhibition of the dimerization process through targeting a conserved leucine inside of this motif abolishes the capacity of RBPMS2 to interact with the translational elongation eEF2 protein, to upregulate NOGGIN mRNA in vivo and to drive SMC dedifferentiation. Our study demonstrates that RBPMS2 possesses an RRM domain harboring both RNA-binding and protein-binding properties and that the newly identified RRM-homodimerization motif is crucial for the function of RBPMS2 at the cell and tissue levels.

Aberrant expression of SOX9 is associated with gastrokine 1 inactivation in gastric cancers

BACKGROUND

SOX9 belongs to the SOX [sry-related high-mobility group (HMG) box] family and acts as a transcription factor that plays a central role in the development and differentiation of multiple cell lineages. The aim of this study was to determine whether the GKN1 gene is involved in the development of gastric cancer by regulating SOX9.

METHODS

The effect of GKN1 and β-catenin on SOX9 expression was examined in GKN1 and β-catenin-transfected AGS and MKN-1 gastric cancer cells. SOX9 expression was also determined in gastric cancer tissues and cell lines by Western blot analysis and immunohistochemistry.

RESULTS

Ectopic expression of β-catenin induced increased expression of SOX9 in AGS cells, whereas GKN1 decreased expression of SOX9 in AGS and MKN-1 cells. In addition, we found an inverse correlation between expression of SOX9 and GKN1 in gastric cancer tissues and cell lines. In immunohistochemistry, nuclear SOX9 expression was detected in 64 (34.6 %) of 185 gastric carcinomas and its expression was closely associated with GKN1 immunonegativity. There was no significant relationship between altered expression of SOX9 protein and clinicopathological parameters including overall survival.

CONCLUSION

These data suggest that aberrant SOX9 expression by GKN1 inactivation may be involved in the development of sporadic gastric cancers as an early event.

LIM homeodomain transcription factor Isl1 directs normal pyloric development by targeting Gata3

Background

Abnormalities in pyloric development or in contractile function of the pylorus cause reflux of duodenal contents into the stomach and increase the risk of gastric metaplasia and cancer. Abnormalities of the pyloric region are also linked to congenital defects such as the relatively common neonatal hypertrophic pyloric stenosis, and primary duodenogastric reflux. Therefore, understanding pyloric development is of great clinical relevance. Here, we investigated the role of the LIM homeodomain transcription factor Isl1 in pyloric development.

Results

Examination of Isl1 expression in developing mouse stomach by immunohistochemistry, whole mount in situ hybridization and real-time quantitative PCR demonstrated that Isl1 is highly expressed in developing mouse stomach, principally in the smooth muscle layer of the pylorus. Isl1 expression was also examined by immunofluorescence in human hypertrophic pyloric stenosis where the majority of smooth muscle cells were found to express Isl1. Isl1 function in embryonic stomach development was investigated utilizing a tamoxifen-inducible Isl1 knockout mouse model. Isl1 deficiency led to nearly complete absence of the pyloric outer longitudinal muscle layer at embryonic day 18.5, which is consistent with Gata3 null mouse phenotype. Chromatin immunoprecipitation, luciferase assays, and electrophoretic mobility shift assays revealed that Isl1 ensures normal pyloric development by directly targeting Gata3.

Conclusions

This study demonstrates that the Isl1-Gata3 transcription regulatory axis is essential for normal pyloric development. These findings are highly clinically relevant and may help to better understand pathways leading to pyloric disease.

Expression of SOX9 in intraductal papillary mucinous neoplasms of the pancreas

OBJECTIVES

SRY (sex determining region Y) box 9 (SOX9) plays a key role in the embryologic development, differentiation, and maintenance of organs in the pancreas as well as progression of several kinds of tumors. The aim of the present study was to evaluate the expression and potential role of SOX9 in intraductal papillary mucinous neoplasms (IPMNs) of the pancreas.

METHODS

The authors selected 27 pathological tissues from 19 IPMN cases to assess the expression of SOX9 by means of immunohistochemistry and analyzed the expression pattern of SOX9 with 78 lesions obtained from these tissues stained by SOX9.

RESULTS

SOX9 was expressed in the normal pancreas, IPMN, and pancreatic ductal adenocarcinoma. SOX9-positive cells were confined to the lower portions of the papillary structures of IPMN. However, SOX9 was expressed in the entire epithelium once the neoplasms advanced to high-grade dysplasia and invasive carcinoma. The expression pattern of SOX9 was similar to that of CD44 in the normal pancreas and IPMN. Double staining of SOX9 and CD44 detected colocalization of SOX9 and CD44 in IPMN.

CONCLUSIONS

Changes in the SOX9 expression pattern may be involved in the mechanisms of the malignant progression of IPMN.

Proper development of the outer longitudinal smooth muscle of the mouse pylorus requires Nkx2-5 and Gata3

BACKGROUND & AIMS

Infantile hypertrophic pyloric stenosis is a common birth anomaly characterized by obstruction of the pyloric lumen. A genome-wide association study implicated NKX2-5, which encodes a transcription factor that is expressed in embryonic heart and pylorus, in the pathogenesis of infantile hypertrophic pyloric stenosis. However, the function of the NKX2-5 in pyloric smooth muscle development has not been examined directly. We investigated the pattern of Nkx2-5 during the course of murine pyloric sphincter development and examined coexpression of Nkx2-5 with Gata3 and Sox9-other transcription factors with pyloric-specific mesenchymal expression. We also assessed pyloric sphincter development in mice with disruption of Nkx2-5 or Gata3.

METHODS

We used immunofluorescence analysis to compare levels of NKX2-5, GATA3, and SOX9 in different regions of smooth muscle cells. Pyloric development was assessed in mice with conditional or germline deletion of Nkx2-5 or Gata3, respectively.

RESULTS

Gata3, Nkx2-5, and Sox9 are coexpressed in differentiating smooth muscle cells of a distinct fascicle of the pyloric outer longitudinal muscle. Expansion of this fascicle coincides with development of the pyloric sphincter. Disruption of Nkx2-5 or Gata3 causes severe hypoplasia of this fascicle and alters pyloric muscle shape. Although expression of Sox9 requires Nkx2-5 and Gata3, there is no apparent hierarchical relationship between Nkx2-5 and Gata3 during pyloric outer longitudinal muscle development.

CONCLUSIONS

Nkx2-5 and Gata3 are independently required for the development of a pyloric outer longitudinal muscle fascicle, which is required for pyloric sphincter morphogenesis in mice. These data indicate that regulatory changes that alter Nkx2-5 or Gata3 expression could contribute to pathogenesis of infantile hypertrophic pyloric stenosis.

Environmental concentration of nonylphenol alters the development of urogenital and visceral organs in avian model

Nonylphenol (NP) is an endocrine disruptor with harmful effects including feminization and carcinogenesis on various organisms. This substance is a degradation product of nonylphenol ethoxylates (NPEO) that is used in several industrial and agricultural processes. In this paper, we examined the assessment of NP exposure on chick embryo development, using a concentration consistent with the environmental concentrations of NP. With this aim, NP (between 0.1 and 50 μg/egg) was injected into the yolk of egg through a small needle hole in the shell. We report the effect of NP on chick reproductive system development although the effect we observed is lower than those observed by exposition to other endocrine disruptors. However, histological analysis highlighted a decrease of intraluminal seminiferous surface area in 64.12% of case (P=0.0086) and an heterogeneous organization of the renal tubules when 10 μg/egg were injected. Moreover, an impairment of liver development with an abnormal bile spillage was observed when higher concentration of NP was injected (50 μg/egg).

Recent advances in the molecular and genetic understanding of congenital gastrointestinal malformations

Major developmental paradigms are highly conserved among vertebrates. The contribution of developmental biology to the understanding of human disease and regeneration has soared recently. We review advances in the molecular and genetic understanding of gastrointestinal development using evidence from both mammalian and nonmammalian models. When appropriate, we highlight relevance and applicability to human disease.

The postnatal role of Sox9 in cartilage

Sox9 is an essential transcription factor for the differentiation of the chondrocytic lineage during embryonic development. To test whether Sox9 continues to play a critical role in cartilaginous tissues in the adult mice, we used an inducible, genetic strategy to disrupt the Sox9 gene postnatally in these tissues. The postnatal inactivation of Sox9 led to stunted growth characterized by decreased proliferation, increased cell death, and dedifferentiation of growth plate chondrocytes. Upon postnatal Sox9 inactivation in the articular cartilage, the sulfated proteoglycan and aggrecan content of the uncalcified cartilage were rapidly depleted and the degradation of aggrecan was accompanied by higher ADAMTS5 immunostaining and increased detection of the aggrecan neoepitope, NITEGE. In spite of the severe loss of Collagen 2a1 mRNA, the Collagen II protein persisted in the articular cartilage, and no histopathological signs of osteoarthritis were observed. The homeostasis of the intervertebral disk (IVD) was dramatically altered upon Sox9 depletion, resulting in disk compression and subsequent degeneration. Inactivation of Sox9 in the IVD markedly reduced the expression of several genes encoding extracellular matrix proteins, as well as some of the enzymes responsible for their posttranslational modification. Furthermore, the loss of Sox9 in the IVD decreased the expression of cytokines, cell-surface receptors, and ion channels, suggesting that Sox9 coordinates a large genetic program that is instrumental for the proper homeostasis of the cells contained in the IVD postnatally. Our results indicate that Sox9 has an essential role in the physiological control of cartilaginous tissues in adult mice. © 2012 American Society for Bone and Mineral Research.

The RNA-binding protein RBPMS2 regulates development of gastrointestinal smooth muscle

BACKGROUND & AIMS

Gastrointestinal development requires regulated differentiation of visceral smooth muscle cells (SMCs) and their contractile activities; alterations in these processes might lead to gastrointestinal neuromuscular disorders. Gastrointestinal SMC development and remodeling involves post-transcriptional modification of messenger RNA. We investigated the function of the RNA-binding protein for multiple splicing 2 (RBPMS2) during normal development of visceral smooth muscle in chicken and expression of its transcript in human pathophysiological conditions.

METHODS

We used avian replication-competent retroviral misexpression approaches to analyze the function of RBPMS2 in vivo and in primary cultures of chicken SMCs. We analyzed levels of RBPMS2 transcripts in colon samples from pediatric patients with Hirschsprung's disease and patients with chronic pseudo obstruction syndrome (CIPO) with megacystis.

RESULTS

RBPMS2 was expressed strongly during the early stage of visceral SMC development and quickly down-regulated in differentiated and mature SMCs. Misexpression of RBPMS2 in differentiated visceral SMCs induced their dedifferentiation and reduced their contractility by up-regulating expression of Noggin, which reduced activity of bone morphogenetic protein. Visceral smooth muscles from pediatric patients with CIPO expressed high levels of RBPMS2 transcripts, compared with smooth muscle from patients without this disorder.

CONCLUSIONS

Expression of RBPMS2 is present in visceral SMC precursors. Sustained expression of RBPMS2 inhibits the expression of markers of SMC differentiation by inhibiting bone morphogenetic protein activity, and stimulates SMC proliferation. RBPMS2 transcripts are up-regulated in patients with CIPO; alterations in RBPMS2 function might be involved in digestive motility disorders, particularly those characterized by the presence of muscular lesions (visceral myopathies).

Immunohistochemical analysis of bone morphological protein signaling pathway in human myometrium

We assessed by immunohistochemistry the expression of the phosphorylated (activated) form of Smad1 and 5 (P-SMAD1/5), of Noggin and of two smooth muscle cell markers (α-SMA and SM22) in a series of human myometrium samples and in a smooth muscle cell line derived from human myometrium (HUt-SMC, PromoCell, USA). Myometrium samples were removed from two cadavers (a fetus at 26 weeks of gestation and a neonate) and from ten non-menopausal women who underwent hysterectomy for adenomyosis and leiomyoma. P-SMAD1/5 expression was never detected in myometrium (both normal and pathological specimens), but only as a nuclear positive staining in glandular and luminal epithelial cells in sections in which also the endometrial mucosa was present. Noggin was strongly expressed especially in myometrium and adenomyosis samples from non-menopausal patients in comparison to the neonatal and fetal myometrium specimens in which muscle cells were less positive. In more than 95% of HUt-SMCs, α-SMA and Desmin were co-expressed, indicating a pure smooth muscle phenotype. When progesterone was added to the culture medium, no P-SMAD1/5 expression was detected, whereas the expression Noggin and SM22, a marker of differentiated smooth muscle cells, increased by 3 fold (p=0.002) and 4.3 fold (p=0.001), respectively (p=0.002). Our results suggest that, in non-menopausal normal human myometrium, the BMP pathway might be inhibited and that this inhibition might be enhanced by progesterone, which increases the differentiation of smooth muscle cells (SM22 levels). These findings could help in the identification of new mechanisms that regulate uterine motility.

SOX9 is expressed in normal stomach, intestinal metaplasia, and gastric carcinoma in humans

BACKGROUND

SOX9 is a marker for stem cells in the intestine and overexpression of SOX9 is found in some types of cancer. However, the expression of SOX9 in normal stomach, precancerous intestinal metaplasia, and gastric carcinoma has not yet been clarified. This study aimed to investigate SOX9 expression in the corpus and pyloric regions of the normal human stomach, premalignant intestinal metaplasia, and gastric carcinoma by using immunohistochemistry.

METHODS

We evaluated SOX9 expression in 46 clinical samples (early gastric well-differentiated adenocarcinoma including surrounding intestinal metaplasia) resected under esophagogastroduodenoscopy.

RESULTS

A small amount of SOX9 was expressed in the neck/isthmus of the corpus region and SOX9 expression was predominantly restricted to the neck/isthmus of the pyloric region in normal human stomach. In the intestinal metaplastic mucosa, SOX9- and PCNA-positive cells were located at the base of the intestinal metaplastic mucosa. Almost all of the gastric carcinoma cells expressed SOX9.

CONCLUSION

SOX9 is expressed in intestinal metaplasia and gastric carcinoma in humans.

Epithelial BMP signaling is required for proper specification of epithelial cell lineages and gastric endocrine cells

Bone morphogenetic protein (BMP) signaling within the gastrointestinal tract is complex. BMP ligands and their receptors are expressed in both epithelial and mesenchymal compartments, suggesting bidirectional signaling between these two entities. Despite an increasing interest in BMP signaling in gut physiology and pathologies, the distinct contribution of BMP signaling in the epithelium vs. the mesenchyme in gastrointestinal homeostasis remains to be established. We aimed to investigate the role of epithelial BMP signaling in gastric organogenesis, gland morphogenesis, and maintenance of epithelial cell functions. Using the Cre/loxP system, we generated a mouse model with an early deletion during development of BMP receptor 1A (Bmpr1a) exclusively in the foregut endoderm. Bmpr1a(ΔGEC) mice showed no severe abnormalities in gastric organogenesis, gland epithelial proliferation, or morphogenesis, suggesting only a minor role for epithelial BMP signaling in these processes. However, early loss of BMP signaling in foregut endoderm did impact on gastric patterning, leading to an anteriorization of the stomach. In addition, numbers of parietal cells were reduced in Bmpr1a(ΔGEC) mice. Epithelial BMP deletion significantly increased the numbers of chromogranin A-, ghrelin-, somatostatin-, gastrin-, and serotonin-expressing gastric endocrine cells. Cancer never developed in young adult (<100 days) Bmpr1a-inactivated mice although a marker of spasmolytic polypeptide-expressing metaplasia was upregulated. Using this model, we have uncovered that BMP signaling negatively regulates the proliferation and commitment of endocrine precursor cells. Our data also indicate that loss of BMP signaling in epithelial gastric cells alone is not sufficient to induce gastric neoplasia.

An EGFR-ERK-SOX9 signaling cascade links urothelial development and regeneration to cancer

Like many carcinomas, urothelial carcinoma (UroCa) is associated with chronic injury. A better understanding of this association could inform improved strategies for preventing and treating this disease. We investigated the expression, regulation, and function of the transcriptional regulator SRY-related high-mobility group box 9 (Sox9) in urothelial development, injury repair, and cancer. In mouse bladders, Sox9 levels were high during periods of prenatal urothelial development and diminished with maturation after birth. In adult urothelial cells, Sox9 was quiescent but was rapidly induced by a variety of injuries, including exposure to the carcinogen cyclophosphamide, culture with hydrogen peroxide, and osmotic stress. Activation of extracellular signal-regulated kinases 1/2 (ERK1/2) was required for Sox9 induction in urothelial injury and resulted from activation of the epidermal growth factor receptor (Egfr) by several Egfr ligands that were dramatically induced by injury. In UroCa cell lines, SOX9 expression was constitutively upregulated and could be suppressed by EGFR or ERK1/2 blockade. Gene knockdown showed a role for SOX9 in cell migration and invasion. Accordingly, SOX9 protein levels were preferentially induced in invasive human UroCa tissue samples (n = 84) compared with noninvasive cancers (n = 56) or benign adjacent urothelium (n = 49). These results identify a novel, potentially oncogenic signaling axis linking urothelial injury to UroCa. Inhibiting this axis is feasible through a variety of pharmacologic approaches and may have clinical utility.

Aberrant epithelial-mesenchymal Hedgehog signaling characterizes Barrett's metaplasia

BACKGROUND & AIMS

The molecular mechanism underlying epithelial metaplasia in Barrett's esophagus remains unknown. Recognizing that Hedgehog signaling is required for early esophageal development, we sought to determine if the Hedgehog pathway is reactivated in Barrett's esophagus, and if genes downstream of the pathway could promote columnar differentiation of esophageal epithelium.

METHODS

Immunohistochemistry, immunofluorescence, and quantitative real-time polymerase chain reaction were used to analyze clinical specimens, human esophageal cell lines, and mouse esophagi. Human esophageal squamous epithelial (HET-1A) and adenocarcinoma (OE33) cells were subjected to acid treatment and used in transfection experiments. Swiss Webster mice were used in a surgical model of bile reflux injury. An in vivo transplant culture system was created using esophageal epithelium from Sonic hedgehog transgenic mice.

RESULTS

Marked up-regulation of Hedgehog ligand expression, which can be induced by acid or bile exposure, occurs frequently in Barrett's epithelium and is associated with stromal expression of the Hedgehog target genes PTCH1 and BMP4. BMP4 signaling induces expression of SOX9, an intestinal crypt transcription factor, which is highly expressed in Barrett's epithelium. We further show that expression of Deleted in Malignant Brain Tumors 1, the human homologue of the columnar cell factor Hensin, occurs in Barrett's epithelium and is induced by SOX9. Finally, transgenic expression of Sonic hedgehog in mouse esophageal epithelium induces expression of stromal Bmp4, epithelial Sox9, and columnar cytokeratins.

CONCLUSIONS

Epithelial Hedgehog ligand expression may contribute to the initiation of Barrett's esophagus through induction of stromal BMP4, which triggers reprogramming of esophageal epithelium in favor of a columnar phenotype.

Dynamic patterning at the pylorus: formation of an epithelial intestine-stomach boundary in late fetal life

In the adult mouse, distinct morphological and transcriptional differences separate stomach from intestinal epithelium. Remarkably, the epithelial boundary between these two organs is literally one cell thick. This discrete junction is established suddenly and precisely at embryonic day (E) 16.5, by sharpening a previously diffuse intermediate zone. In the present study, we define the dynamic transcriptome of stomach, pylorus, and intestinal tissues between E14.5 and E16.5. We show that establishment of this boundary is concomitant with the induction of over a thousand genes in intestinal epithelium, and these gene products provide intestinal character. Hence, we call this process intestinalization. We identify specific transcription factors (Hnf4 gamma, Creb3l3, and Tcfec) and examine signaling pathways (Hedgehog and Wnt) that may play a role in this process. Finally, we define a unique expression domain at the pylorus itself and detect novel pylorus-specific patterns for the transcription factor Gata3 and the secreted protein nephrocan.

Vertebrate endoderm development and organ formation

The endoderm germ layer contributes to the respiratory and gastrointestinal tracts and to all of their associated organs. Over the past decade, studies in vertebrate model organisms, including frog, fish, chick, and mouse, have greatly enhanced our understanding of the molecular basis of endoderm organ development. We review this progress with a focus on early stages of endoderm organogenesis including endoderm formation, gut tube morphogenesis and patterning, and organ specification. Lastly, we discuss how developmental mechanisms that regulate endoderm organogenesis are used to direct differentiation of embryonic stem cells into specific adult cell types, which function to alleviate disease symptoms in animal models.

Dividing the tubular gut: generation of organ boundaries at the pylorus

The discrete organs that comprise the gastrointestinal tract (esophagus, stomach, small intestine, and large intestine) arise embryonically by regional differentiation of a single tube that is initially morphologically similar along its length. Regional organ differentiation programs, for example, for stomach or intestine, involve signaling cross-talk between epithelium and mesenchyme and result in the formation of precise boundaries between organs, across which dramatic differences in both morphology and gene expression are seen. The pylorus is a unique area of the gut tube because it not only marks an important organ boundary in the tubular gut (the stomach/intestinal boundary) but is also the hub for the development of multiple accessory organs (liver, pancreas, gall bladder, and spleen). This chapter examines: (a) our current understanding of the molecular and morphogenic processes that underlie the generation of the dramatic epithelial tissue boundary that compartmentalizes stomach and intestine; (b) the tissue interactions that promote development of the accessory organs in this area; and (c) the molecular interactions that specify patterning of the pyloric sphincter. Though the focus here is primarily on the mouse as a model organism, the molecular underpinnings of organ patterning near the pylorus are shared by chick and frog. Thus, further study of these conserved developmental programs could potentially shed light on the mechanisms underlying human pyloric malformations such as infantile hypertrophic pyloric stenosis.

Six2 activity is required for the formation of the mammalian pyloric sphincter

The functional activity of Six2, a member of the so/Six family of homeodomain-containing transcription factors, is required during mammalian kidney organogenesis. We have now determined that Six2 activity is also necessary for the formation of the pyloric sphincter, the functional gate at the stomach-duodenum junction that inhibits duodenogastric reflux. Our data reveal that several genes known to be important for pyloric sphincter formation in the chick (e.g., Bmp4, Bmpr1b, Nkx2.5, Sox9, and Gremlin) also appear to be required for the formation of this structure in mammals. Thus, we propose that Six2 activity regulates this gene network during the genesis of the pyloric sphincter in the mouse.

Gonadal sex differentiation and expression of Sox9a2, Dmrt1, and Foxl2 in Oryzias luzonensis

Oryzias luzonensis is closely related to the medaka, O. latipes. The sex of both species is determined by an XX-XY system. However, the testis determining gene (DMY/Dmrt1bY) found in O. latipes does not exist in O. luzonensis. Instead, a different gene is thought to act as a testis determining gene. In this study, we focused the gonadal sex differentiation process in O. luzonensis under different testis determining gene. First, we observed the gonadal development of O. luzonensis histologically. We then analyzed the expression of Sox9a2/Sox9b, Dmrt1, and Foxl2 during early development. Our results suggest that the sexual differentiation of germ cells in O. luzonensis is initiated later than in O. latipes. However, the timing of the sexual differentiation of the supporting cell linage is similar between the species.

The role of the visceral mesoderm in the development of the gastrointestinal tract

The gastrointestinal (GI) tract forms from the endoderm (which gives rise to the epithelium) and the mesoderm (which develops into the smooth muscle layer, the mesenchyme, and numerous other cell types). Much of what is known of GI development has been learned from studies of the endoderm and its derivatives, because of the importance of epithelial biology in understanding and treating human diseases. Although the necessity of epithelial-mesenchymal cross talk for GI development is uncontested, the role of the mesoderm remains comparatively less well understood. The transformation of the visceral mesoderm during development is remarkable; it differentiates from a very thin layer of cells into a complex tissue comprising smooth muscle cells, myofibroblasts, neurons, immune cells, endothelial cells, lymphatics, and extracellular matrix molecules, all contributing to the form and function of the digestive system. Understanding the molecular processes that govern the development of these cell types and elucidating their respective contribution to GI patterning could offer insight into the mechanisms that regulate cell fate decisions in the intestine, which has the unique property of rapid cell renewal for the maintenance of epithelial integrity. In reviewing evidence from both mammalian and nonmammalian models, we reveal the important role of the visceral mesoderm in the ontogeny of the GI tract.

Intermuscular tendons are essential for the development of vertebrate stomach

Gastrointestinal motility is ensured by the correct coordination of the enteric nervous system and the visceral smooth muscle cells (SMCs), and defective development of SMCs results in gut malformations and intestinal obstructions. In order to identify the molecular mechanisms that control the differentiation of the visceral mesenchyme into SMCs in the vertebrate stomach, we developed microarrays to analyze the gene expression profiles of undifferentiated and differentiated avian stomachs. We identify Scleraxis, a basic-helix-loop-helix transcription factor, as a new marker of stomach mesenchyme and find that expression of Scleraxis defines the presence of two tendons closely associated to the two visceral smooth muscles. Using targeted gene misexpression, we show that FGF signaling is sufficient to induce Scleraxis expression and to establish two tendon domains adjacent to the smooth muscle structures. We also demonstrate that the tendon organization is perturbed by altering Scleraxis expression or function. Moreover, using primary cells derived from stomach mesenchyme, we find that undifferentiated stomach mesenchyme can give rise to both SMCs and tendon cells. These data show that upon FGF activation, selected stomach mesenchymal cells are primed to express Scleraxis and to differentiate into tendon cells. Our findings identify a new anatomical and functional domain in the vertebrate stomach that we characterize as being two intermuscular tendons closely associated with the visceral SMC structures. We also demonstrate that the coordinated development of both tendon and smooth muscle domains is essential for the correct morphogenesis of the stomach.

Real time monitoring of BMP Smads transcriptional activity during mouse development

SUMMARY

Bone morphogenetic protein (BMP) signaling is a key pathway in the patterning and development of organisms as diverse as fruit fly and humans. However, the determination of net BMP signaling, paramount to understanding organogenesis, is limited to the analysis of fixed material. We generated a transgenic mouse that reports the transcriptional response of BMP Smad activation by coupling a well established BMP response element (BRE), isolated from the Id1 promoter, to green fluorescent protein (BRE:gfp). We monitored BMP Smad transcriptional activity in fresh and fixed BRE:gfp embryos. GFP expression was observed where expected on the basis of known signaling sites, but also in specific cell populations in which BMP signaling had been implicated but not directly demonstrated. Deletion of Smad5 reduced GFP in vivo as expected. The BRE:gfp transgenic mice are a novel tool, which will facilitate the identification of specific BMP Smad responsive cell types and allow BMP Smad signaling to be monitored in real time, supporting studies in development and disease.

Dynamic expression patterns of RhoV/Chp and RhoU/Wrch during chicken embryonic development

Rho GTPases play central roles in the control of cell adhesion and migration, cell cycle progression, growth, and differentiation. However, although most of our knowledge of Rho GTPase function comes from the study of the three classic Rho GTPases RhoA, Rac1, and Cdc42, recent studies have begun to explore the expression, regulation, and function of some of the lesser-known members of the Rho GTPase family. In the present study, we cloned the avian orthologues of RhoV (or Chp for Cdc42 homologous protein) and RhoU (or Wrch-1 for Wnt-regulated Cdc42 homolog-1) and examined their expression patterns by in situ hybridization analysis both during early chick embryogenesis and later on, during gastrointestinal tract development. Our data show that both GTPases are detected in the primitive streak, the somites, the neural crest cells, and the gastrointestinal tract with distinct territories and/or temporal expression windows. Although both proteins are 90% identical, our results indicate that cRhoV and cRhoU are distinctly expressed during chicken embryonic development.

Cellular methods in cartilage research: primary human chondrocytes in culture and chondrogenesis in human bone marrow stem cells

Work in our laboratory has focused on the in vitro culture of both human articular chondrocytes and human mesenchymal stem cells to understand what controls their ability to synthesise an appropriate cartilage-like extracellular matrix containing a predominantly collagen type II fibrillar network embedded in an aggrecan-rich ECM. This review focuses on the methodologies that we have found to be successful with cartilage and bone marrow sources of human cells and comments on the many factors which may enable improved phenotypic performance once the cells are in a fully chondrogenic environment.

Control of cell fate and differentiation by Sry-related high-mobility-group box (Sox) transcription factors

Maintain stemness, commit to a specific lineage, differentiate, proliferate, or die. These are essential decisions that every cell is constantly challenged to make in multi-cellular organisms to ensure proper development, adult maintenance, and adaptability. SRY-related high-mobility-group box (Sox) transcription factors have emerged in the animal kingdom to help cells effect such decisions. They are encoded by 20 genes in humans and mice. They share a highly conserved high-mobility-group box domain that was originally identified in SRY, the sex-determining gene on the Y chromosome, and that has derived from a canonical high-mobility-group domain characteristic of chromatin-associated proteins. The high-mobility-group box domain binds DNA in the minor groove and increases its DNA binding affinity and specificity by interacting with many types of transcription factors. It also bends DNA and may thereby confer on Sox proteins a unique and critical role in the assembly of transcriptional enhanceosomes. Sox proteins fall into eight groups. Most feature a transactivation or transrepression domain and thereby also act as typical transcription factors. Each gene has distinct expression pattern and molecular properties, often redundant with those in the same group and overlapping with those in other groups. As a whole the Sox family controls cell fate and differentiation in a multitude of processes, such as male differentiation, stemness, neurogenesis, and skeletogenesis. We review their specific molecular properties and in vivo roles, stress recent advances in the field, and suggest directions for future investigations.

Hprt-targeted transgenes provide new insights into smooth muscle-restricted promoter activity

Mouse telokin and SM22alpha promoters have previously been shown to direct smooth muscle cell-specific expression of transgenes in vivo in adult mice. However, the activity of these promoters is highly dependent on the integration site of the transgene. In the current study, we found that the ectopic expression of telokin promoter transgenes could be abolished by flanking the transgene with insulator elements from the H19 gene. However, the insulator elements did not increase the proportion of mouse lines that exhibited consistent, detectable levels of transgene expression. In contrast, when transgenes were targeted to the hprt locus, both telokin and SM22alpha promoters resulted in reproducible patterns and levels of transgene expression in all lines of mice examined. Telokin promoter transgene expression was restricted to smooth muscle tissues in adult and embryonic mice. As reported previously, SM22alpha transgenes were expressed at high levels specifically in arterial smooth muscle cells; however, in contrast to randomly integrated transgenes, the hprt-targeted SM22alpha transgenes were also expressed at high levels in smooth muscle cells in veins, bladder, and gallbladder. Using hprt-targeted transgenes, we further analyzed elements within the telokin promoter required for tissue specific activity in vivo. Analysis of these transgenes revealed that the CArG element in the telokin promoter is required for promoter activity in all tissues and that the CArG element and adjacent AT-rich region are sufficient to drive transgene expression in bladder but not intestinal smooth muscle cells.