A CTX family cell adhesion molecule, JAM4, is expressed in stem cell and progenitor cell populations of both male germ cell and hematopoietic cell lineages

The Roles of Junctional Adhesion Molecules (JAMs) in Cell Migration

The review briefly summarizes the role of the family of adhesion molecules, JAMs (junctional adhesion molecules), in various cell migration, covering germ cells, epithelial cells, endothelial cells, several leukocytes, and different cancer cells. These functions affect multiple diseases, including reproductive diseases, inflammation-related diseases, cardiovascular diseases, and cancers. JAMs bind to both similar and dissimilar proteins and take both similar and dissimilar effects on different cells. Concluding relevant results provides a reference to further research.

Molecular Characterization of the Extracellular Domain of Human Junctional Adhesion Proteins

The junction adhesion molecule (JAM) family of proteins play central roles in the tight junction (TJ) structure and function. In contrast to claudins (CLDN) and occludin (OCLN), the other membrane proteins of the TJ, whose structure is that of a 4α-helix bundle, JAMs are members of the immunoglobulin superfamily. The JAM family is composed of four members: A, B, C and 4. The crystal structure of the extracellular domain of JAM-A continues to be used as a template to model the secondary and tertiary structure of the other members of the family. In this article, we have expressed the extracellular domains of JAMs fused with maltose-binding protein (MBP). This strategy enabled the work presented here, since JAM-B, JAM-C and JAM4 are more difficult targets due to their more hydrophobic nature. Our results indicate that each member of the JAM family has a unique tertiary structure in spite of having similar secondary structures. Surface plasmon resonance (SPR) revealed that heterotypic interactions among JAM family members can be greatly favored compared to homotypic interactions. We employ the well characterized epithelial cadherin (E-CAD) as a means to evaluate the adhesive properties of JAMs. We present strong evidence that suggests that homotypic or heterotypic interactions among JAMs are stronger than that of E-CADs.

Soluble JAM-C Ectodomain Serves as the Niche for Adipose-Derived Stromal/Stem Cells

Junctional adhesion molecules (JAMs) are expressed in diverse types of stem and progenitor cells, but their physiological significance has yet to be established. Here, we report that JAMs exhibit a novel mode of interaction and biological activity in adipose-derived stromal/stem cells (ADSCs). Among the JAM family members, JAM-B and JAM-C were concentrated along the cell membranes of mouse ADSCs. JAM-C but not JAM-B was broadly distributed in the interstitial spaces of mouse adipose tissue. Interestingly, the JAM-C ectodomain was cleaved and secreted as a soluble form (sJAM-C) in vitro and in vivo, leading to deposition in the fat interstitial tissue. When ADSCs were grown in culture plates coated with sJAM-C, cell adhesion, cell proliferation and the expression of five mesenchymal stem cell markers, Cd44, Cd105, Cd140a, Cd166 and Sca-1, were significantly elevated. Moreover, immunoprecipitation assay showed that sJAM-C formed a complex with JAM-B. Using CRISPR/Cas9-based genome editing, we also demonstrated that sJAM-C was coupled with JAM-B to stimulate ADSC adhesion and maintenance. Together, these findings provide insight into the unique function of sJAM-C in ADSCs. We propose that JAMs contribute not only to cell–cell adhesion, but also to cell–matrix adhesion, by excising their ectodomain and functioning as a niche-like microenvironment for stem and progenitor cells.

Homozygous deletion of 21q22.2 in a patient with hypotonia, developmental delay, cortical visual impairment, and retinopathy

21q22 contains several dosage sensitive genes that are important in neurocognitive development. Determining impacts of gene dosage alterations in this region can be useful in establishing contributions of these genes to human development and disease. We describe a 15-month-old girl with a 1,140 kb homozygous deletion in the Down Syndrome Critical Region at 21q22.2 including 4 genes; B3GALT5, IGSF5, PCP4, DSCAM, and a microRNA (MIR4760). Clinical singleton genome sequencing did not report any candidate gene variants for the patient's phenotype. She presented with hypotonia, global developmental delay, cortical visual impairment, and mild facial dysmorphism. Ophthalmological exam was suggestive of retinopathy. We propose that the absence of DSCAM and PCP4 may contribute to the patient's neurological and retinal phenotype, while the role of absent B3GALT5 and IGSF5 in her presentation remain unclear at this time.

Lack of whey acidic protein (WAP) four-disulfide core domain protease inhibitor 2 (WFDC2) causes neonatal death from respiratory failure in mice

Respiratory failure is a life-threatening problem for pre-term and term infants, yet many causes remain unknown. Here, we present evidence that whey acidic protein (WAP) four-disulfide core domain protease inhibitor 2 (Wfdc2), a protease inhibitor previously unrecognized in respiratory disease, may be a causal factor in infant respiratory failure. Wfdc2 transcripts are detected in the embryonic lung and analysis of a Wfdc2-GFP knock-in mouse line shows that both basal and club cells, and type II alveolar epithelial cells (AECIIs), express Wfdc2 neonatally. Wfdc2-null-mutant mice display progressive atelectasis after birth with a lethal phenotype. Mutant lungs have multiple defects, including impaired cilia and the absence of mature club cells from the tracheo-bronchial airways, and malformed lamellar bodies in AECIIs. RNA sequencing shows significant activation of a pro-inflammatory pathway, but with low-quantity infiltration of mononuclear cells in the lung. These data demonstrate that Wfdc2 function is vitally important for lung aeration at birth and that gene deficiency likely causes failure of the lung mucosal barrier.

Transendothelial migration (TEM) of in vitro generated dendritic cell vaccine in cancer immunotherapy

Many efforts have been made to improve the efficacy of dendritic cell (DC) vaccines in DC-based cancer immunotherapy. One of these efforts is to deliver a DC vaccine more efficiently to the regional lymph nodes (rLNs) to induce stronger anti-tumor immunity. Together with chemotaxis, transendothelial migration (TEM) is believed to be a critical and indispensable step for DC vaccine migration to the rLNs after administration. However, the mechanism underlying the in vitro-generated DC TEM in DC-based cancer immunotherapy has been largely unknown. Currently, junctional adhesion molecules (JAMs) were found to play an important role in the TEM of in vitro generated DC vaccines. This paper reviews the TEM of DC vaccines and TEM-associated JAM molecules.

Junctional adhesion molecules mediate transendothelial migration of dendritic cell vaccine in cancer immunotherapy

In vitro generated dendritic cells (DCs) have been studied in cancer immunotherapy for decades. However, the detailed molecular mechanism underlying transendothelial migration (TEM) of DC vaccine across the endothelial barrier to regional lymph nodes (LNs) remains largely unknown. Here, we found that junctional adhesion molecule (JAM)-Like (JAML) is involved in the TEM of mouse bone marrow-derived DCs (BMDCs). Treatment with an anti-JAML antibody or JAML knock-down significantly reduced the TEM activity of BMDCs, leading to impairment of DC-based cancer immunotherapy. We found that the interaction of JAML of BMDCs with the coxsackie and adenovirus receptor of endothelial cells plays a crucial role in the TEM of BMDCs. On the other hand, human monocyte-derived DCs (MoDCs) did not express the JAML protein but still showed normal TEM activity. We found that MoDCs express only JAM1 and that the homophilic interaction of JAM1 is essential for MoDC TEM across a HUVEC monolayer. Our findings suggest that specific JAM family members play an important role in the TEM of in vitro-generated mouse and human DCs from the inoculation site to regional LNs in DC-based cancer immunotherapy.

Junctional Adhesion Molecule-A Is Highly Expressed on Human Hematopoietic Repopulating Cells and Associates with the Key Hematopoietic Chemokine Receptor CXCR4

Hematopoietic stem/progenitor cells (HSPCs) reside in specialized bone marrow microenvironmental niches, with vascular elements (endothelial/mesenchymal stromal cells) and CXCR4-CXCL12 interactions playing particularly important roles for HSPC entry, retention, and maintenance. The functional effects of CXCL12 are dependent on its local concentration and rely on complex HSPC-niche interactions. Two Junctional Adhesion Molecule family proteins, Junctional Adhesion Molecule-B (JAM)-B and JAM-C, are reported to mediate HSPC-stromal cell interactions, which in turn regulate CXCL12 production by mesenchymal stromal cells (MSCs). Here, we demonstrate that another JAM family member, JAM-A, is most highly expressed on human hematopoietic stem cells with in vivo repopulating activity (p < .01 for JAM-A(high) compared to JAM-A(Int or Low) cord blood CD34(+) cells). JAM-A blockade, silencing, and overexpression show that JAM-A contributes significantly (p < .05) to the adhesion of human HSPCs to IL-1β activated human bone marrow sinusoidal endothelium. Further studies highlight a novel association of JAM-A with CXCR4, with these molecules moving to the leading edge of the cell upon presentation with CXCL12 (p < .05 compared to no CXCL12). Therefore, we hypothesize that JAM family members differentially regulate CXCR4 function and CXCL12 secretion in the bone marrow niche. Stem Cells 2016;34:1664-1678.

Dynamic equilibrium of heterogeneous and interconvertible multipotent hematopoietic cell subsets

Populations of hematopoietic stem cells and progenitors are quite heterogeneous and consist of multiple cell subsets with distinct phenotypic and functional characteristics. Some of these subsets also appear to be interconvertible and oscillate between functionally distinct states. The multipotent hematopoietic cell line EML has emerged as a unique model to study the heterogeneity and interconvertibility of multipotent hematopoietic cells. Here we describe extensive phenotypic and functional heterogeneity of EML cells which stems from the coexistence of multiple cell subsets. Each of these subsets is phenotypically and functionally heterogeneous, and displays distinct multilineage differentiation potential, cell cycle profile, proliferation kinetics, and expression pattern of HSC markers and some of the key lineage-associated transcription factors. Analysis of their maintenance revealed that on a population level all EML cell subsets exhibit cell-autonomous interconvertible properties, with the capacity to generate all other subsets and re-establish complete parental EML cell population. Moreover, all EML cell subsets generated during multiple cell generations maintain their distinct phenotypic and functional signatures and interconvertible properties. The model of EML cell line suggests that interconvertible multipotent hematopoietic cell subsets coexist in a homeostatically maintained dynamic equilibrium which is regulated by currently unknown cell-intrinsic mechanisms.

JAM-related proteins in mucosal homeostasis and inflammation

Mucosal surfaces are lined by epithelial cells that form a physical barrier protecting the body against external noxious substances and pathogens. At a molecular level, the mucosal barrier is regulated by tight junctions (TJs) that seal the paracellular space between adjacent epithelial cells. Transmembrane proteins within TJs include junctional adhesion molecules (JAMs) that belong to the cortical thymocyte marker for Xenopus family of proteins. JAM family encompasses three classical members (JAM-A, JAM-B, and JAM-C) and related molecules including JAM4, JAM-like protein, Coxsackie and adenovirus receptor (CAR), CAR-like membrane protein and endothelial cell-selective adhesion molecule. JAMs have multiple functions that include regulation of endothelial and epithelial paracellular permeability, leukocyte recruitment during inflammation, angiogenesis, cell migration, and proliferation. In this review, we summarize the current knowledge regarding the roles of the JAM family members in the regulation of mucosal homeostasis and leukocyte trafficking with a particular emphasis on barrier function and its perturbation during pathological inflammation.

Intercellular adhesion molecules (ICAMs) and spermatogenesis

BACKGROUND

During the seminiferous epithelial cycle, restructuring takes places at the Sertoli-Sertoli and Sertoli-germ cell interface to accommodate spermatogonia/spermatogonial stem cell renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation since developing germ cells, in particular spermatids, move 'up and down' the seminiferous epithelium. Furthermore, preleptotene spermatocytes differentiated from type B spermatogonia residing at the basal compartment must traverse the blood-testis barrier (BTB) to enter the adluminal compartment to prepare for meiosis at Stage VIII of the epithelial cycle, a process also accompanied by the release of sperm at spermiation. These cellular events that take place at the opposite ends of the epithelium are co-ordinated by a functional axis designated the apical ectoplasmic specialization (ES)-BTB-basement membrane. However, the regulatory molecules that co-ordinate cellular events in this axis are not known.

METHODS

Literature was searched at http://www.pubmed.org and http://scholar.google.com to identify published findings regarding intercellular adhesion molecules (ICAMs) and the regulation of this axis.

RESULTS

Members of the ICAM family, namely ICAM-1 and ICAM-2, and the biologically active soluble ICAM-1 (sICAM-1) are the likely regulatory molecules that co-ordinate these events. sICAM-1 and ICAM-1 have antagonistic effects on the Sertoli cell tight junction-permeability barrier, involved in Sertoli cell BTB restructuring, whereas ICAM-2 is restricted to the apical ES, regulating spermatid adhesion during the epithelial cycle. Studies in other epithelia/endothelia on the role of the ICAM family in regulating cell movement are discussed and this information has been evaluated and integrated into studies of these proteins in the testis to create a hypothetical model, depicting how ICAMs regulate junction restructuring events during spermatogenesis.

CONCLUSIONS

ICAMs are crucial regulatory molecules of spermatogenesis. The proposed hypothetical model serves as a framework in designing functional experiments for future studies.

Function of junctional adhesion molecules (JAMs) in leukocyte migration and homeostasis

Homeostasis is a word widely used in the scientific community to refer to the property of a system to maintain its uniformity and functionality. In living organisms, the word refers to the concept enunciated 150 years ago by C. Bernard by which external variations must be compensated for in order to maintain internal conditions compatible with life. This is especially true in the case of highly dynamic system such as the hematopoietic system that requires the coordinated control of cell proliferation and death within specialized microenvironments that are anatomically distinct. As a consequence, hematopoietic cell adhesion and migration must be tightly controlled in order for hematopoietic cells to reach and to be maintained in appropriate microenvironments. The junctional adhesion molecules (JAMs) are adhesion molecules that belong to the immunoglobulin superfamily (IgSf) and that have been initially identified as important players controlling vascular permeability and leukocyte transendothelial migration. This involves the regulated localization of the JAMs at lateral endothelial cell/cell borders and their interaction with leukocyte integrins. More recently, some of the JAM family members have also been found to be expressed by stromal cells and to regulate chemokine secretion within lymphoid organs, acting not only on leukocyte transendothelial migration, but also on hematopoietic cell retention within specialized microenvironments. This review summarizes recent progress in understanding the role of the JAMs in leukocyte adhesion and migration to tentatively draw an integrated view of the homeostatic function of the JAMs within the hematopoietic system.

Adhesion protein VSIG1 is required for the proper differentiation of glandular gastric epithelia

VSIG1, a cell adhesion protein of the immunoglobulin superfamily, is preferentially expressed in stomach, testis, and certain gastric, esophageal and ovarian cancers. Here, we describe the expression patterns of three alternatively spliced isoforms of mouse Vsig1 during pre- and postnatal development of stomach and potential function of Vsig1 in differentiation of gastric epithelia. We show that isoforms Vsig1A and Vsig1B, which differ in the 3′untranslated region, are expressed in the early stages of stomach development. Immunohistochemical analysis revealed that VSIG1 is restricted to the adherens junction of the glandular epithelium. The shorter transcript Vsig1C is restricted to the testis, encodes an N-terminal truncated protein and is presumably regulated by an internal promoter, which is located upstream of exon 1b. To determine whether the 5′ flanking region of exon 1a specifically targets the expression of Vsig1 to stomach epithelia, we generated and analyzed transgenic mice. The 4.8-kb fragment located upstream of exon 1a was sufficient to direct the expression of the reporter gene to the glandular epithelia of transgenic stomach. To determine the role of VSIG1 during the development of stomach epithelia, an X-linked Vsig1 was inactivated in embryonic stem cells (ESCs). Although Vsig1^−/Y ESCs were only able to generate low coat color chimeric mice, no male chimeras transmitted the targeted allele to their progeny suggesting that the high contribution of Vsig1^−/Y cells leads to the lethality of chimeric embryos. Analysis of chimeric stomachs revealed the differentiation of VSIG1-null cells into squamous epithelia inside the glandular region. These results suggest that VSIG1 is required for the establishment of glandular versus squamous epithelia in the stomach.

JAM-B regulates maintenance of hematopoietic stem cells in the bone marrow

In adult mammals, hematopoietic stem cells (HSCs) reside in the bone marrow (BM) and are maintained in a quiescent and undifferentiated state through adhesive interactions with specialized microenvironmental niches. Although junctional adhesion molecule-C (JAM-C) is expressed by HSCs, its function in adult hematopoiesis remains elusive. Here, we show that HSCs adhere to JAM-B expressed by BM stromal cells in a JAM-C dependent manner. The interaction regulates the interplay between HSCs and BM stromal cells as illustrated by the decreased pool of quiescent HSCs observed in jam-b deficient mice. We further show that this is probably because of alterations of BM stromal compartments and changes in SDF-1α BM content in jam-b(-/-) mice, suggesting that JAM-B is an active player in the maintenance of the BM stromal microenvironment.

Dysadherin can enhance tumorigenesis by conferring properties of stem-like cells to hepatocellular carcinoma cells

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is associated with a high potential for metastasis and disease recurrence, even after surgical resection. The cancer stem cell (CSC) hypothesis proposes that CSCs are responsible for chemo-resistance, recurrence, and metastasis. Dysadherin is a prognostic indicator of metastasis and poor survival in many different cancer types. In this study, we investigated the possible link between dysadherin and CSC in HCC.

METHODS

We analyzed the functional implications of dysadherin on cancer stemness by modification of the dysadherin gene in HCC cell lines.

RESULTS

The transfection of dysadherin cDNA into the liver cancer cell line PLC/PRF/5 enhanced the properties of CSCs, including anti-apoptosis, their sphere-forming ability, side population phenotype, and tumor initiation ability in vivo. Furthermore, knockdown of dysadherin in the liver cancer cell line SK-Hep1 suppressed its stem cell-like properties.

CONCLUSIONS

These results show that dysadherin give rise to properties of CSC in HCC. Therefore, these findings suggest that dysadherin may be a potential molecular prognostic marker of HCC and may aid in the development of more effective therapies.

Vascular and epithelial junctions: a barrier for leucocyte migration

Rapid mobilization of leucocytes through endothelial and epithelial barriers is key in immune system reactivity. The underlying mechanisms that regulate these processes have been the basis for many recent studies. Traditionally, leucocyte extravasation had been believed to occur through a paracellular route, which involves localized disruption of endothelial cell junctions. However, more recently, a transcellular route has been described involving the passage through the endothelial cell body. Leucocytes are also able to migrate through epithelium to monitor mucosal tissues and microenvironments. A number of adhesion molecules are known to regulate transmigration of leucocytes through epithelial and endothelial layers. Paracellular and transcellular leucocyte transmigration are regulated by adhesion molecules such as PECAM-1 (platelet-endothelial cell adhesion molecule 1), CD99, VE-cadherin (vascular endothelial cadherin) and JAM (junctional adhesion molecule) proteins. The purpose of this review is to discuss the role of these molecules in leucocyte transmigration and how they contribute to the different mechanisms that regulate leucocyte trafficking.

Coxsackievirus and adenovirus receptor is up-regulated in migratory germ cells during passage of the blood-testis barrier

The coxsackievirus and adenovirus receptor (CAR) is a cell adhesion molecule expressed in epithelial tight junctions and other cell-cell contacts. Using indirect immunofluorescence, quantitative RT-PCR, and Western blots, the expression and distribution of CAR in developing and adult testis are examined. CAR is highly expressed in both Sertoli and germ cells during perinatal and postnatal development, followed by a rapid down-regulation of both mRNA and protein levels. Interestingly, we find that CAR is a previously unknown downstream target for FSH because CAR mRNA levels were induced in primary cultures of FSH-stimulated Sertoli cells. In contrast to other epithelia, CAR is not a general component of tight junctions in the seminiferous epithelium, and Sertoli cells in the adult testis do not express CAR. Instead, CAR expression is stage dependent and specifically found in migratory germ cells. RT-PCR also demonstrated the presence of junctional adhesion molecule-like (JAML) in the testis. JAML was previously reported by others to form a functional complex with CAR regulating transepithelial migration of leukocytes. The expression of JAML in the testis suggests that a similar functional complex might be present during germ cell migration across the blood-testis barrier. Finally, an intermediate compartment occupied by CAR-positive, migrating germ cells and flanked by two occludin-containing junctions is identified. Together, these results implicate a function for CAR in testis morphogenesis and in migration of germ cells across the blood-testis barrier during spermatogenesis.

JAM Family and Related Proteins in Leukocyte Migration (Vestweber Series)

Exploring the role of junctional adhesion molecules (JAMs) has proven to be varied and controversial. The purpose of this review is to discuss the new and exciting roles of these IgSF molecules and how they have evolved to contribute to diverse functions from development to inflammation. In particular, recent research has focused on JAM subfamily members JAM-A, -B, and -C with newly described roles in leukocyte trafficking during inflammation and angiogenesis. However, research on all JAM family members has demonstrated recurring themes with striking similarities in the many diverse processes they are now known to regulate.

Transmembrane proteins of tight junctions

Tight junctions contribute to the paracellular barrier, the fence dividing plasma membranes, and signal transduction, acting as a multifunctional complex in vertebrate epithelial and endothelial cells. The identification and characterization of the transmembrane proteins of tight junctions, claudins, junctional adhesion molecules (JAMs), occludin and tricellulin, have led to insights into the molecular nature of tight junctions. We provide an overview of recent progress in studies on these proteins and highlight their roles and regulation, as well as their functional significance in human diseases.

Mouse embryonic stem cell-derived embryoid bodies generate progenitors that integrate long term into renal proximal tubules in vivo

The metanephric kidney is a mesodermal organ that develops as a result of reciprocal interactions between the ureteric bud and the blastema. The generation of embryonic stem (ES) cell-derived progenitors offers potential for regenerative therapies but is often limited by development of tumor formation. Because brachyury (T) denotes mesoderm specification, a mouse ES cell line with green fluorescence protein (GFP) knocked into the functional T locus as well as lacZ in the ROSA26 locus (LacZ/T/GFP) was used in cell selection and lineage tracing. In the absence of leukemia inhibitory factor, mouse ES cells give rise to embryoid bodies that can differentiate into mesoderm. Culture conditions were optimized (4 d, 10 ng/ml Activin-A) to generate maximal numbers of renal progenitor populations identified by expression of the specific combination of renal markers cadherin-11, WT-1, Pax-2, and Wnt-4. LacZ/T/GFP+ cells were further enriched by FACS selection. Five days after injection of LacZ/T/GFP+ cells into embryonic kidney explants in organ culture, beta-galactosidase immunohistochemistry showed incorporation into blastemal cells of the nephrogenic zone. After a single injection into developing live newborn mouse kidneys, co-localization studies showed that the LacZ/T/GFP+ cells were stably integrated into proximal tubules with normal morphology and normal polarization of alkaline phosphatase and aquaporin-1 for 7 mo, without teratoma formation. It is concluded that defined differentiation of ES cells into embryoid bodies with Activin-A and selection for T expression provides a means to isolate and purify renal proximal tubular progenitor cells with the potential for safe use in regenerative therapies.