N-cadherin gene maps to human chromosome 18 and is not linked to the E-cadherin gene

Doxorubicin and topotecan resistance in ovarian cancer: Gene expression and microenvironment analysis in 2D and 3D models

This study explores the mechanisms underlying chemotherapy resistance in ovarian cancer (OC) using doxorubicin (DOX) and topotecan (TOP)-resistant cell lines derived from the drug-sensitive A2780 ovarian cancer cell line. Both two-dimensional (2D) monolayer cell cultures and three-dimensional (3D) spheroid models were employed to examine the differential drug responses in these environments. The results revealed that 3D spheroids demonstrated significantly higher resistance to DOX and TOP than 2D cultures, suggesting a closer mimicry of in vivo tumour conditions. Molecular analyses identified overexpression of essential drug resistance-related genes, including MDR1 and BCRP, and extracellular matrix (ECM) components, such as MYOT and SPP1, which were more pronounced in resistant cell lines. MDR1 and BCRP overexpression contribute to chemotherapy resistance in OC by expelling drugs like DOX and TOP. Targeting these transporters with inhibitors or gene silencing could improve drug efficacy, making them key therapeutic targets to enhance treatment outcomes for drug-resistant OC. The study further showed that EMT-associated markers, including VIM, SNAIL1, and SNAIL2, were upregulated in the 3D spheroids, reflecting a more mesenchymal phenotype. These findings suggest that factors beyond gene expression, such as spheroid architecture, cell-cell interactions, and drug penetration, contribute to the enhanced resistance observed in 3D cultures. These results highlight the importance of 3D cell culture models for a more accurate representation of tumour drug resistance mechanisms in ovarian cancer, providing valuable insights for therapeutic development.

Severe and post-COVID-19 are associated with high expression of vimentin and reduced expression of N-cadherin

SARS-CoV-2 penetrates human cells via its spike protein, which mainly interacts with ACE2 receptors, triggering viral replication and an exacerbated immune response characterized by a cytokine storm. Vimentin III, an intermediate filament protein predominantly found in mesenchymal cells, has garnered considerable attention in recent research due to its multifaceted biological roles and significance in the endothelial-mesenchymal transition (EndMT) during various fibrotic processes. However, the pathophysiological mechanisms linking vimentin to SARS-CoV-2 remain incompletely elucidated. In this study, we determined the expression profiles of vimentin in three cohorts: patients admitted to the intensive care unit with SARS-CoV-2 infection, individuals in the 6-12 month convalescent phase post-infection and COVID-19 negative controls. Our objective was to assess the association between peripheral blood biomarkers implicated in endothelial dysfunction and genes related to fibrosis. Serum levels of vimentin and N-cadherin were determined by ELISA, while vimentin gene expression was determined by qRT-PCR. In addition, we examined the correlation between clinical parameters and serum levels of vimentin and N-cadherin in severe COVID-19 patients and healthy counterparts. Our findings revealed elevated serum vimentin levels and increased gene expression in severe COVID-19 patients compared to healthy controls. Conversely, serum N-cadherin levels were diminished in both acute and convalescent stages of severe COVID-19 relative to healthy individuals. Notably, associations were observed between C-reactive protein, lactate dehydrogenase, lymphocyte count and vimentin levels in severe COVID-19 patients, indicative of endothelial dysfunction. Furthermore, our study identified vimentin and N-cadherin as potential diagnostic markers via ROC analysis. Overall, delineating the dysregulation of vimentin and N-cadherin due to SARS-CoV-2 infection in disease pathogenesis and tissue homeostasis offers novel insights for clinical management and targeted therapeutic interventions.

Atractylodin Induces Apoptosis and Inhibits the Migration of A549 Lung Cancer Cells by Regulating ROS-Mediated Signaling Pathways

Atractylodin (ATR) has anticancer effects on some tumor cells by inducing apoptosis, but its mechanism in lung cancer remains unclear. This study investigates the inhibitory effect of ATR on A549 lung cancer cells. Cell viability was detected by the Cell Counting Kit-8 assay, and results showed that ATR could significantly inhibit the proliferation of A549 cells. Apoptosis was detected by Annexin V-FITC/PI staining, and apoptosis rate and mitochondrial membrane potential were detected by flow cytometry. Results showed that the effect of ATR on the apoptosis of A549 cells was negatively correlated with the change in mitochondrial membrane potential. Western blot analysis showed that ATR regulated apoptosis induced by mitogen-activated protein kinase, signal transducer and activator of transcription 3, and nuclear factor kappa B signaling pathways. Analyses of reactive oxygen species (ROS), cell cycle, and cell migration showed that ATR induced intracellular ROS accumulation as an initiation signal to induce cell cycle arrest regulated by the AKT signaling pathway and cell migration inhibition regulated by the Wnt signaling pathway. Results showed that ATR can inhibit cell proliferation, induce cell apoptosis, induce cell cycle arrest, and inhibit the migration of A549 cells (p < 0.05 was considered statistically significant, * p < 0.05, ** p < 0.01 and *** p < 0.001).

Role of Neural (N)-Cadherin in Breast Cancer Cell Stemness and Dormancy in the Bone Microenvironment

Breast cancer cells that interact with spindle-shaped N-Cadherin+ Osteoblasts (SNOs) are recognised to become dormant through a Notch2-dependent mechanism. We found that Notch2High human BrCa MDA-MB231 (MDA) cells also expressed high level of N-Cadherin. This prompted us to hypothesize that N-Cadherin could have a role in MDA-SNO interaction. Of note, the expression of N-Cadherin in MDA cells reduced tumour incidence and bone osteolysis in BrCa mouse model. Moreover, similarly to Notch2High MDA cells, the N-CadherinHigh MDA cells revealed a high expression of the canonical Haematopoietic Stem cell (HSC) markers, suggesting an HSC mimicry, associated with higher ability to form mammospheres. Interestingly, N-CadherinHigh MDA cells showed greater capacity to adhere to SNOs, while the inhibition of SNO-mediating MDA cell proliferation was unremarkable. To investigate whether these features were shared by mouse BrCa, we used the 4T1 cell line in which N-Cadherin expression was abolished and then rescued. At variance with MDA cells, 4T1 cells expressing N-Cadherin revealed that the latter was associated with a lower expression of the HSC marker, Cxcr4, along with a lower capacity to form mammospheres. Furthermore, the rescue of N-Cadherin expression increased cell-cell adhesion and reduced proliferation of 4T1 cells when they were co-plated with SNOs. In conclusion, we demonstrated that: (i) N-CadherinHigh and Notch2High MDA cells showed similar HSC mimicry and dormancy features; (ii) N-Cadherin mediated BrCa-SNO adhesion; (iii) N-Cadherin had a positive Notch2-dependent role on SNO-induced dormancy and HSC mimicry in MDA cells, and a negative role in 4T1 cell stemness and HSC mimicry.

Expression of N-cadherin by skeletal muscle in the degenerationand the degeneration/regeneration processes after nerve injury

We investigated the expression of N-cadherin by skeletal muscle during the degeneration and degeneration/regeneration processes using the rat sciatic nerve and gastrocnemius muscle model. The right sciatic nerve was exposed in the mid-thigh region, and the nerve was transsected with small scissors. After then, nerve was sutured (sutured group), or both edges of the resected nerve were turned and sutured to the muscle of each side (unsutured group). At various periods up to 24 weeks after the operation the middle portion of the gastrocnemius muscle of the treated hindlimbs was removed. Expression of N-cadherin was detected by western blot analysis and immunofluorescent staining with an anti N-cadherin antibody. In the both groups, the degree of expression had already increased by the end of the first postoperative week, but there were no significant differences between the first and second postoperative weeks between the two groups. However, the values recorded at the fourth, sixth, ninth, and twelfth postoperative weeks were significantly higher in the unsutured group than in the sutured group. Immunofluorescent staining was present around the muscular membrane in all specimens including the control. These results indicated that there was a difference in the kinetics of expression of N-cadherin in skeletal muscle between the degeneration and degeneration/regeneration processes of the muscle after injury to the nerve. It was also clear that N-cadherin has a role at the surface of the muscle cell in skeletal muscle, not in the satellite and inflammatory cells, in both groups.

Establishment of the mouse model by rabbit antiserum specific to EC1-2 or EC3-4 epitopes for studying the pathogenesis of pemphigus vulgaris

The research goal was to establish the neonatal mouse model by specific rabbit anti EC1-2 or EC3-4 antiserum for the purpose of studying pemphigus vulgaris (PV) pathogenesis. RNA was extracted from human keratinocytes. The cDNAs was synthesized by reverse transcription. Amplified EC1-2 or EC3-4 genes were inserted into pGEX-4T expression plasmids to constitute the recombinant plasmids, and transformed into E.coli. for the expression of the fusion proteins. The purified fusion proteins were used to immunize New Zealand white rabbits to obtain the specific anti EC1-2 or EC3-4 antisera. IgG fractions from the antisera were purified and passively transferred intradermally into the upper back skin of neonatal BALB/c mice. Histologic, ultrastructural, and immunofluorescence features of PV were evaluated in these mice. PV features were shown in the mice injected with anti EC1-2 antibody, erythema on the flanks and positive Nikolsky sign. The histology showed intraepidermal vesicle formation and acantholytic cells within. Acantholysis, but no clinical symptoms, was seen in the mice treated with the antibody specific to EC3-4. Additionally, skin sections from the abdomen from these neonatal mice were cryo-sectioned for direct-immunofluorescence. FITC-conjugated IgG antibody deposit between the keratinocytes throughout the epidermis. The indirect immunofluorescence with monkey esophagus showed the presence of anti-intracellular antibody with a titer of 1:40. On electronic microscopy, intercellular spaces (ICS) were widened and the desmosomes were split or dissolved. A novel PV mouse model was established by treatment with the specific rabbit antiserum. These data confirmed that both EC1-2 and EC3-4 are pathogenic epitopes in PVA, but EC1-2 is more dominant.

Localization and expression of R-cadherin in skeletal muscle following nerve injury

Rats in which the sciatic nerves were cut were divided into two groups: animals with nerve sutured and animals with nerve not sutured. In the unsutured group, the levels of R-cadherin expression increased and then decreased to values lower than those of controls. In the sutured group, the levels of R-cadherin expression increased and then decreased to almost control values. These results suggest that R-cadherin plays some role in cells of normal and regenerating muscles.

Involvement of E-cadherin in the Development of Erythroid Cells; Subject Heading

The cadherins represent a large family of structurally and functionally related cell adhesion molecules involved in morphogenesis of multicellular organisms and maintenance of solid tissues. In the hematopoietic system, however, almost nothing was known about the involvement of this family. PCR screening of RNA of human bone marrow mononuclear cells with specific primers for different classical cadherins revealed that members of this family are also expressed by bone marrow cells. Here we report that E-cadherin, which is mainly expressed by cells of epithelial origin, plays a critical role in the development of human erythrocytes. FACS analysis with human E-cadherin-specific antibodies and the use of immunoaffinity columns revealed that expression of E-cadherin is restricted to defined maturation stages of the erythropoietic cell lineage. Erythroblasts and normoblasts express E-cadherin, but mature erythrocytes do not. Lymphoid and all the other myeloid cell lineages do not express E-cadherin at any developmental stage. The differentiation of the erythroid lineage in vitro could be influenced by addition of anti-E-cadherin antibodies in a concentration dependent manner indicating a direct involvement of this cell adhesion molecule in the differentiation process. In line with these in vitro data is the finding that E-cadherin is down regulated during erythroleukemia on the developing erythroid cells. Our results suggest an unanticipated function of E-cadherin in the hematopoietic system.

The cadherin superfamily: diversity in form and function

Over recent years cadherins have emerged as a growing superfamily of molecules, and a complex picture of their structure and their biological functions is becoming apparent. Variation in their extracellular region leads to the large potential for recognition properties of this superfamily. This is demonstrated strikingly by the recently discovered FYN-binding CNR-protocadherins; these exhibit alternative expression of the extracellular portion, which could lead to distinct cell recognition in different neuronal populations, whereas their cytoplasmic part, and therefore intracellular interactions, is constant. Diversity in the cytoplasmic moiety of the cadherins imparts specificity to their interactions with cytoplasmic components; for example, classical cadherins interact with catenins and the actin filament network, desmosomal cadherins interact with catenins and the intermediate filament system and CNR-cadherins interact with the SRC-family kinase FYN. Recent evidence suggests that CNR-cadherins, 7TM-cadherins and T-cadherin, which is tethered to the membrane by a GPI anchor, all localise to lipid rafts, specialised cell membrane domains rich in signalling molecules. Originally thought of as cell adhesion molecules, cadherin superfamily molecules are now known to be involved in many biological processes, such as cell recognition, cell signalling, cell communication, morphogenesis, angiogenesis and possibly even neurotransmission.

Adhesion Molecules as Diagnostic Tools in Tumor Pathology

Adhesion molecules are transmembrane glycoproteins mediating cell-cell and cell extracellular matrix interactions. They control a number of fundamental biological processes including cell migration, differentiation, proliferation, and apoptosis. In the last decade there has been an increasing interest in the exploitation of these molecules as diagnostic and/or prognostic markers in tumor pathology. For example, a large number of studies have shown that loss of E-cadherin expression correlates with high tumor grade and advanced tumor stage in a number of malignancies. The analysis of adhesion molecule profile in a routine clinical setting needs further investigation in prospective multicenter studies. Int J Surg Pathol 8(3):191-200, 2000

Clustered cadherin genes: a sequence-ready contig for the desmosomal cadherin locus on human chromosome 18

We describe the assembly of a cosmid and PAC contig of approximately 700 kb on human chromosome 18q12 spanning the DSC and DSG genes coding for the desmocollins and desmogleins. These are members of the cadherin superfamily of calcium-dependent cell adhesion proteins present in the desmosome type of cell junction found especially in epithelial cells. They provide the strong cell-cell adhesion generated by this type of cell junction for which expression of both a desmocollin and a desmoglein is required. In the autoimmune skin diseases pemphigus foliaceous and pemphigus vulgaris (PV), where the autoantigens are, respectively, encoded by the DSG1 and DSG3 genes, severe areas of acantholysis (cell separation), potentially life-threatening in the case of PV, are evident. Dominant mutations in the DSG1 gene causing striate palmoplantar keratoderma result in hyperkeratosis of the skin on the parts of the body where pressure and abrasion are greatest, viz., on the palms and soles. These genes are also candidate tumor suppressor genes in squamous cell carcinomas and other epithelial cancers. We have screened two chromosome 18-specific cosmid libraries by hybridization with previously isolated YAC clones and DSC and DSG cDNAs, and a whole genome PAC library, both by hybridization with the YACs and by screening by PCR using cDNA sequences and YAC end sequence. The contigs were extended by further PCR screens using STSs generated by vectorette walking from the ends of the cosmids and PACs, together with sequence from PAC ends. Despite screening of two libraries, the cosmid contig still had four gaps. The PAC contig filled these gaps and in fact covered the whole locus. The positions of 45 STSs covering the whole of this region are presented. The desmocollin and desmoglein genes, which are about 30-35 kb in size, are quite well separated at approximately 20-30 kb apart and are arranged in two clusters, one DSC cluster and one DSG cluster, which are transcribed outward from the interlocus region. The order of the genes is correlated with the spatial order of gene expression in the developing mouse embryo, and this, and previous transgenic experiments, suggests that long-range genetic elements that coordinate expression of these genes may be present. The complete bacterial clone contig described in this paper is thus a resource not only for future sequencing but also for investigations into the control of expression of these clustered genes.

A potential role of R-cadherin in striated muscle formation

We have examined the murine embryonic expression pattern of the cell adhesion molecule R-cadherin in muscle, kidney, thymus, and lung. In developing muscle, R-cadherin was first seen at 10.5-11.5 days postcoitum in the somitic myotome. Consistently, we found R-cadherin expressed at the highest levels in the myotome, early skeletal muscle, and smooth muscle (both vascular and visceral), while very low levels of R-cadherin were detected in the heart. The expression pattern and subcellular localization of R-cadherin in developing skeletal muscle indicate a possible role in myoblast cell-cell interactions during both primary and secondary myogenesis. In the developing kidney, R-cadherin was first detected at 10.5 days postcoitum in the mesonephric epithelial tubule cells. In the metanephric kidney, it was specifically expressed in the pretubular aggregates, comma- and S-shaped bodies, proximal tubules, and collecting ducts. Thus, in the kidney, R-cadherin was associated with the mesenchymal-epithelial transition. R-cadherin was also found in other developing epithelia, for example in the thymic epithelial cells. In the lung, R-cadherin was expressed at the highest levels in the smooth muscle surrounding the lung epithelial tubules. To test whether R-cadherin can direct formation of tissues, we constitutively expressed R-cadherin in E-cadherin-/- ES cells and examined histogenesis in teratomas derived from these cells. R-cadherin exclusively rescued formation of striated muscle and epithelia in the teratomas. R-cadherin's ability to form epithelia in vivo was substantiated by its ability to rescue formation of cystic embryoid bodies in vitro. By comparing our data with the previously reported embryonic expression patterns and histogenetic activities of E- and N-cadherin, we suggest that R-cadherin plays an important role in the formation of striated muscle and possibly also of epithelia.

Hormonal regulation of N-cadherin mRNA levels in rat granulosa cells

We have examined the ability of hormones to modulate the steady-state levels of N-cadherin mRNA transcripts in aggregated and dispersed rat granulosa cell populations. Estradiol and follicle-stimulating hormone (FSH) had no effect on the levels of N-cadherin mRNA transcripts in aggregated granulosa cells. In contrast, these two hormones stimulated N-cadherin mRNA levels in dispersed granulosa cells. This is the first report that estradiol and FSH are capable of regulating N-cadherin mRNA levels. The results also suggest that the N-cadherin mRNA levels in dispersed and aggregated granulosa cells are regulated by different mechanisms.

Identification of novel cadherins expressed in human melanoma cells

Cadherin molecules are essential for tissue morphogenesis and are also related to cancer invasion and metastasis. Although normal melanocytes express E- and P-cadherin, the activity and expression of E- and P-cadherin in melanoma cells are still unknown. We measured the homophilic adhesion activity of human normal epidermal melanocytes and the melanoma cell lines MeWo and A375. The melanoma cells showed stronger homophilic adhesion activity than did the melanocytes, despite the lower expression of E- and P-cadherin in the melanoma cells. This result suggested that melanoma cells expressed other types of homophilic adhesion molecules. Using degenerate primers to amplify multiple cadherin subtypes, we performed a polymerase chain reaction (PCR) with the first strand of cDNAs generated by reverse transcription of the mRNAs of the melanoma cells, and we isolated two known cadherin fragments, N-cadherin and PC42, and six novel cadherin fragments, cadherins ME1-ME6. The reverse transcriptase-PCR using specific primers of cadherins including E-, P-, and N-cadherins, PC42, and cadherins ME1-ME6 revealed that the melanoma cells expressed more kinds of cadherin molecules than did the melanocytes. Such cadherins may play an important role in melanoma cell-cell adhesion.

Lineage restriction of the myogenic conversion factor myf-5 in the brain

myf-5 is one of four transcription factors belonging to the MyoD family that play key roles in skeletal muscle determination and differentiation. We have shown earlier by gene targeting nlacZ into the murine myf-5 locus that myf-5 expression in the developing mouse embryo is closely associated with the restriction of precursor muscle cells to the myogenic lineage. We now identify unexpected expression of this myogenic factor in subdomains of the brain. myf-5 expression begins to be detected at embryonic day 8 (E8) in the mesencephalon and coincides with the appearance of the first differentiated neurons; expression in the secondary prosencephalon initiates at E10 and is confined to the ventral domain of prosomere p4, later becoming restricted to the posterior hypothalamus. This expression is observed throughout embryogenesis. No other member of the MyoD family is detected in these regions, consistent with the lack of myogenic conversion. Furthermore, embryonic stem cells expressing the myf-5/nlacZ allele yield both skeletal muscle and neuronal cells when differentiated in vitro. These observations raise questions about the role of myf-5 in neurogenesis as well as myogenesis, and introduce a new lineage marker for the developing brain.

Protocadherin Pcdh2 shows properties similar to, but distinct from, those of classical cadherins

Cell adhesion and several other properties of a recently identified cadherin-related protein, protocadherin Pcdh2, were characterized. A chimeric Pcdh2 in which the original cytoplasmic domain was replaced with the cytoplasmic domain of E-cadherin was expressed in mouse L cells. The expressed protein had a molecular mass of about 150 kDa and was localized predominantly at the cell periphery, as was the wild-type Pcdh2. In a conventional cell aggregation assay, the transfectants showed cell aggregation activity comparable to that of classical cadherins. This activity was Ca(2+)-dependent and was inhibited by the addition of anti-Pcdh2 antibody, indicating that the chimeric Pcdh2, and probably the wild-type Pcdh2, has Ca(2+)-dependent cell aggregation activity. Mixed cell aggregation assay using L cells and different types of transfectants showed that the activity of Pcdh2 was homophilic and molecular type specific and that Pcdh2 was transfectants did not aggregate with other types of transfectants or with L cells. In immunoprecipitation, the chimeric Pcdh2 co-precipitated with a 105 kDa and a 95 kDa protein, whereas wild-type Pcdh2 co-precipitated with no major protein. Pcdh2 was easily solubilized with non-ionic detergent, in contrast to the case of classical cadherins. On immunofluorescence microscopy, the somas of Purkinje cells were diffusely stained with anti-human Pcdh2 antibody. Mouse Pcdh1 and Pcdh2 were mapped to a small segment of chromosome 18, suggesting that various protocadherins form a gene cluster at this region. The present results suggest that Pcdh2, and possibly other protocadherins as well as protocadherin-related proteins such as Drosophila fat, mediate Ca(2+)-dependent and specific homophilic cell-cell interaction in vivo and play an important role in cell adhesion, cell recognition, and/or some other basic cell processes.

Expression of N-cadherin and alpha-catenin in astrocytomas and glioblastomas

We examined levels of mRNA and protein for N-cadherin, the predominant cadherin in neural tissues, and mRNA levels for the cadherin-associated protein, alpha-catenin, in a series of gliomas and in glioblastoma cell lines. mRNA levels for N-cadherin and alpha-catenin were significantly higher in glioblastomas than in low-grade astrocytomas or normal brain, while the levels of intact N-cadherin protein were similar in glioblastomas, low-grade astrocytomas and brain. In addition, there was no consistent relationship between invasiveness and expression of N-cadherin and alpha-catenin in highly invasive vs minimally invasive tumours within the same histopathological grade. To assess further the relationship between cadherin expression and neural tumour invasion, we measured N-cadherin expression, calcium-dependent cell adhesion and motility of several glioblastoma cell lines. While all N-cadherin-expressing lines were adhesive, no correlation was seen between the level of N-cadherin expression and cell motility. Together, these findings imply that, in contrast to the role played by E-cadherin in carcinomas, N-cadherin does not restrict the invasion of glioblastomas.

Expressed cadherin pseudogenes are localized to the critical region of the spinal muscular atrophy gene

Low-copy repeats have been associated with genomic rearrangements and have been implicated in the generation of mutations in several diseases. Here we characterize a subset of low-copy repeats in the spinal muscular atrophy (SMA) region in human chromosome 5q13. We show that this repeated sequence, named c41-cad, is a highly expressed pseudogene derived from an intact neuronal cadherin gene, Br-cadherin, situated on 5p13-14. Br-cadherin is expressed specifically in the brain, whereas the c41-cad transcripts are 10-15 times more abundant and are present in all tissues examined. We speculate that the c41-cad repeats, separately or in concert with other repeats in the SMA region, are involved in the pathogenesis of SMA by promoting rearrangements and deletions.

Phylogenetic analysis of the cadherin superfamily

Cadherins are a multigene family of proteins which mediate homophilic calcium-dependent cell adhesion and are thought to play an important role in morphogenesis by mediating specific intercellular adhesion. Different lines of experimental evidence have recently indicated that the site responsible for mediating adhesive interactions is localized to the first extracellular domain of cadherin. Based upon an analysis of the sequence of this domain, I show that cadherins can be classified into three groups with distinct structural features. Furthermore, using this sequence information a phylogenetic tree relating the known cadherins was assembled. This is the first such tree to be published for the cadherins. One cadherin subtype, neural cadherin (N-cadherin), shows very little sequence divergence between species, whereas all other cadherin subtypes show more substantial divergence, suggesting that selective pressure upon this domain may be greater for N-cadherin than for other cadherins. Phylogenetic analysis also suggests that the gene duplications which established the main branches leading to the different cadherin subtypes occurred very early in their history. These duplications set the stage for the diversified superfamily we now observe.

Adhesion molecules. I: Keratinocyte-keratinocyte interactions; cadherins and pemphigus

During the last few years, considerable progress has been made in our understanding of the structure and function of cadherins and of the pathophysiology of pemphigus. Cadherins are a multiple gene family of Ca(++)-dependent cell adhesion molecules with a typical single-spanning transmembrane structure. Cadherins have two major subfamilies, classic cadherin and desmosomal cadherin. Classic cadherins, including E-, P-, and N-cadherins, are characterized by a homophilic binding specificity. They localize at adherens junctions and mediate physiologic interaction with the involvement of cytoplasmic anchoring molecules, catenins, and the actin-based cytoskeleton network. Desmosomal cadherins, the desmocollins and desmogleins, localize at desmosomes and are linked to the intermediate keratin filaments network via plakoglobin and desmoplakin. Molecular cloning has demonstrated that the autoantigens of both pemphigus vulgaris and pemphigus foliaceus are members of the desmoglein subfamily of the cadherin supergene family. Thus, pemphigus is characterized as an anti-cadherin autoimmune disease. Furthermore, a baculovirus recombinant protein of pemphigus vulgaris antigen was capable of absorbing out the pathogenic autoantibodies from patients' sera, providing a possibility of antigen-specific therapeutic strategies for pemphigus.

Similarities in structure and expression between mouse P-cadherin, chicken B-cadherin and frog XB/U-cadherin

By immunological methods, we show that the monoclonal antibody 6D5 which reacts specifically with Xenopus laevis XB/U-cadherin, also binds to mouse P-cadherin and to chicken B-cadherin but not to the respective E-cadherins (L-CAM) or other "classical" cadherins in these species. In the first extracellular domain, three amino acid residues are identified that are shared by frog XB/U-cadherin, chicken B-cadherin and mammalian P-cadherins but not by the other "classical" cadherins. With few exceptions, the other cadherins possess residues at these positions that are also characteristic of each type of cadherin. Moreover, the expression patterns of P-, B-, and XB/U-cadherin in mouse, chicken and frog are more similar to each other than they are to those of the E-cadherins, L-CAM or other classical cadherins. Taken together, our results suggest that mammalian P-cadherins, chicken B-cadherin and frog XB/U-cadherin are closely related, if not homologous, molecules. A number of differences in the expression patterns between P-, B-, and XB/U-cadherin indicate that these molecules assume differential morphogenetic roles in different species.

Structure and distribution of N-cadherin in developing zebrafish embryos: morphogenetic effects of ectopic over-expression

N-cadherin cDNA was cloned from a zebrafish embryonic cDNA library. Analysis of the deduced amino acid sequence of this molecule (ZN-cadherin) revealed a high degree of homology to N-cadherins of other species, except that its pre-sequence is considerably shorter. Nevertheless, following transfection into chinese hamster ovary (CHO) cells, the expressed protein was functionally active, namely participated in calcium-dependent intercellular interactions. Moreover, ectopic over-expression of ZN-cadherin, following mRNA microinjection into 2-4 cell embryos, caused microaggregation and uneven segregation of deep cells, resulting in distorted embryos. Developmental Northern and Western blot analyses indicated that both the mRNA and the protein first appear at gastrulation. In-situ hybridization showed that ZN-cadherin mRNA was initially present in all deep cells, and later became restricted to various epithelial and neural tissues. Whole-mount immunostaining indicated that while ZN-cadherin was already present at 50% epiboly, it became associated with cell junctions only 4-5 h later. In developing somites ZN-cadherin expression was prominent but transient. High levels of the protein were detected in epithelial somites and its expression was apparently down regulated concomitantly with the onset of myogenesis.

Molecular cloning of cDNA for XTCAD-1, a novel Xenopus cadherin, and its expression in adult tissues and embryos of Xenopus laevis

We have isolated from a Xenopus tailbud cDNA library a novel cadherin cDNA, denoted as XTCAD-1, which contained an open reading frame including the entire coding region. XTCAD-1 codes for 714 amino acids (molecular mass: 96 kDa), which include five characteristic extracellular cadherin motifs, a single putative transmembrane domain, and a cytoplasmic domain. In each domain, XTCAD-1 shared extensive homologies with other cadherins, and was related to EP-, E-, and P-cadherins more closely than to N- and M-cadherins. In adult Xenopus, XTCAD-1 mRNA was strongly expressed in intestine/stomach, kidney and skin, which are respectively derived from endoderm, mesoderm, and ectoderm. In Xenopus embryogenesis, expression of XTCAD-1 mRNA was first detected at blastula stage, and the level of the expression increased gradually during gastrula stage, reached a peak at tailbud stage and then decreased slightly at tadpole stage. These results suggest that in Xenopus laevis XTCAD-1 plays an important role in the maintenance of adult tissues that contain epithelial cells abundantly and also in morphogenesis in early embryonic development.

Adhesion molecules: novel molecular tools in tumor pathology

Cell adhesion is a key process, elementary in the establishment of tissue architecture and differentiation. In neoplasia, in which there is a disruption of tissue architecture and a derangement in differentiation, it has been postulated that changes in cell-cell and cell-matrix interactions account for the ability of cancer cells to transgress normal tissue boundaries and disperse to distant sites. Complex and coordinated reductions and increases in adhesion have been proposed to be necessary for tumor invasion and metastasis. This hypothesis has fueled the interest of cancer research teams to evaluate the expression of various adhesion molecules in a wide range of human malignancies in the hope of pinpointing some of the cell adhesion alterations underlying tumor behavior. To date, a multitude of transmembrane glycoproteins, including cell-cell adhesion molecules (CAMs) and cell-matrix or substratum adhesion molecules (SAMs), have been identified; their structure, molecular genetics, and biochemistry have been elucidated, and we are beginning to understand their normal function. A few of these, on the basis of current evidence, seem to be promising candidate molecules for a role in neoplasia. This article aims to summarize recent developments in this field of adhesion research as well as the clinical applications in diagnostic pathology arising from it. First, by way of introduction, a summary of the biochemical and functional characterization of each family of adhesion receptors will be presented, followed by a presentation of the experimental data implicating them in the control of invasion, metastasis, and differentiation.

Developmental regulation of M-cadherin in the terminal differentiation of skeletal myoblasts

Cadherins form a large family of membrane glycoproteins which mediate homophilic calcium-dependent cell adhesion. They are thought to mediate the initial calcium-dependent cell adhesion which precedes the plasma membrane fusion of skeletal myoblasts. Two cadherin subtypes are known to be expressed in mammalian skeletal myoblasts: muscle cadherin (M-cadherin) and neural cadherin (N-cadherin). In the present study we demonstrate that 1) the expression of M- and N-cadherin is differentially regulated during myoblast differentiation in vitro, 2) the expression of M-cadherin but not N-cadherin is inhibited by 5-bromo-2'-deoxyuridine (BUdR), an agent which selectively inhibits skeletal myoblast differentiation, and 3) fusion and differentiation-competent rat L6 myoblasts do not express detectable levels of N-cadherin mRNA. In vivo, M-cadherin mRNA was detectable exclusively in skeletal muscle. M-cadherin mRNA levels peaked during the secondary myogenic wave in rat hindlimb muscle, becoming barely detectable in 1-week-old and adult rats. These observations indicate that M-cadherin is unique in two ways: It is the first cadherin to be included in the family of skeletal muscle-specific genes, and it shows peak levels of expression in developing skeletal muscle tissue. Taken together, these results suggest that M-cadherin plays an important role in skeletal myogenesis.

Spatial and temporal relationships between cadherins and PECAM-1 in cell-cell junctions of human endothelial cells

The integrity of the endothelial layer, which lines the entire cavity of the vascular system, depends on tight adhesion of the cells to the underlying basement membrane as well as to each other. It has been previously shown that such interactions occur via membrane receptors that determine the specificity, topology, and mechanical properties of the surface adhesion. Cell-cell junctions between endothelial cells, in culture and in situ, involve both Ca(2+)-dependent and -independent mechanisms that are mediated by distinct adhesion molecules. Ca(2+)-dependent cell-cell adhesion occurs mostly via members of the cadherin family, which locally anchor the microfilament system to the plasma membrane, in adherens junctions. Ca(2+)-independent adhesions were reported to mainly involve members of the Ig superfamily. In this study, we performed three-dimensional microscopic analysis of the relative subcellular distributions of these two endothelial intercellular adhesion systems. We show that cadherins are located at adjacent (usually more apical), yet clearly distinct domains of the lateral plasma membrane, compared to PECAM-1. Moreover, cadherins were first organized in adherens junctions within 2 h after seeding of endothelial cells, forming multiple lateral patches which developed into an extensive belt-like structure over a period of 24 h. PECAM-1 became associated with surface adhesions significantly later and became progressively associated with the cadherin-containing adhesions. Cadherins and PECAM-1 also differed in their detergent extractability, reflecting differences in their mode of association with the cytoskeleton. Moreover, the two adhesion systems could be differentially modulated since short treatment with the Ca2+ chelator EGTA, disrupted the cadherin junctions leaving PECAM-1 apparently intact. These results confirm that endothelial cells possess distinct intercellular contact mechanisms that differ in their spatial and temporal organization as well as in their functional properties.

Differential effects of over-expressed neural cell adhesion molecule isoforms on myoblast fusion

We have used a transfection based approach to analyze the role of neural cell adhesion molecule (NCAM) in myogenesis at the stage of myoblast fusion to form multinucleate myotubes. Stable cell lines of myogenic C2 cells were isolated that express the transmembrane 140- or 180-kD NCAM isoforms or the glycosylphosphatidylinositol (GPI) linked isoforms of 120 or 125 kD. We found that expression of the 140-kD transmembrane isoform led to a potent enhancement of myoblast fusion. The 125-kD GPI-linked NCAM also enhanced the rate of fusion but less so when a direct comparison of cell surface levels of the 140-kD transmembrane form was carried out. While the 180-kD transmembrane NCAM isoform was effective in promoting C2 cell fusion similar to the 140-kD isoform, the 120-kD isoform did not have an effect on fusion parameters. It is possible that these alterations in cell fusion are associated with cis NCAM interactions in the plane of the membrane. While all of the transfected human NCAMs (the transmembrane 140- and 180-kD isoforms and the 125- and 120-kD GPI isoforms) could be clustered in the plane of the plasma membrane by species-specific antibodies there was a concomitant clustering of the endogenous mouse NCAM protein in all cases except with the 120-kD human isoform. These studies show that different isoforms of NCAM can undergo specific interactions in the plasma membrane which are likely to be important in fusion. While the transmembrane and the 125-kD GPI-anchored NCAMs are capable of enhancing fusion the 120-kD GPI NCAM is not. Thus it is likely that interactions associated with NCAM intracellular domains and also the muscle specific domain (MSD) region in the extracellular domain of the GPI-linked 125-kD NCAM are important. In particular this is the first role ascribed to the O-linked carbohydrate containing MSD region which is specifically expressed in skeletal muscle.

Molecular biology of cadherins in the nervous system

Cadherins are cell-cell adhesion molecules belonging to the Ca(2+)-dependent cadherin superfamily. In the last few years the number of cadherins identified in the nervous system has increased considerably. Cadherins are integral membrane glycoproteins. They are structurally closely related and interspecies homologies are high. The function is mediated through a homophilic binding mechanism, and intracellular proteins, directly or indirectly connected to the cadherins and the cytoskeleton, are necessary for cadherin activity. Cadherins have been implicated in segregation and aggregation of tissues at early developmental stages and in growth and guidance of axons during nervous system development. These functions are modified by changes in type(s) and amount of cadherins expressed at different developmental stages. The regulatory elements guiding cadherin expression are currently being elucidated.

T-cadherin 2: molecular characterization, function in cell adhesion, and coexpression with T-cadherin and N-cadherin

Cadherins are integral membrane glycoproteins that mediate calcium-dependent, homophilic cell-cell adhesion and are implicated in controlling tissue morphogenesis. T-cadherin is anchored to the membrane through a glycosyl phosphatidylinositol (Ranscht B, Dours-Zimmermann MT: Neuron 7:391-402, 1991) and expressed in a restricted pattern in developing embryos (Ranscht B, Bronner-Fraser M: Development 111:15-22, 1991). We report here the molecular and functional characterization of the T-cadherin isoform, T-cadherin 2 (Tcad-2) and the expression of the corresponding mRNA. Tcad-2 cDNA differs in its 3' nucleotide sequence from T-cadherin cDNA and encodes a protein in which the carboxy terminal Leu of T-cadherin is substituted by Lys and extended by the amino acids SerPheProTyrVal. By RNase protection, mRNAs encoding the T-cadherin isoforms are coexpressed in heart, muscle, liver, skin, somites, and in neural tissue. Many tissues contain both T-cadherin and Tcad-2 mRNAs in conjunction with N-cadherin transcripts, and T-cadherins and N-cadherin proteins are coexpressed on the surface of individual neurons in vitro. Expression in Chinese hamster ovary cells (CHO) revealed that Tcad-2 is a glycosyl phosphatidylinositol-anchored membrane protein that functions in calcium-dependent, homophilic cell adhesion. The identification of a functional T-cadherin isoform and the coexpression of T-cadherins and N-cadherin by individual cells suggest that specific adhesive interactions of embryonic cells may involve a complex interplay between multiple cadherins.

Molecular cloning and characterization of the human E-cadherin cDNA

E-cadherin is a Ca(2+)-dependent cell adhesion molecule involved in cell-cell interaction. In its normal physiological function it plays an important role in embryonic development and tissue morphogenesis. Recent studies have shown that in cancer development E-cadherin can act as a suppressor of invasion. Indeed, in several kinds of carcinomas allelic loss of the E-cadherin/Uvomorulin locus and decreased E-cadherin expression have been described. The importance of E-cadherin in human cancer development may be substantiated by molecular analysis of the E-cadherin transcript. Therefore, we isolated and characterized the human E-cadherin cDNA. Comparison of the nucleotide and deduced amino acid sequences revealed that the human E-cadherin is highly homologous to the mouse E-cadherin (uvomorulin) and to other members of the cadherin family.

Human genes containing polymorphic trinucleotide repeats

Expansions of trinucleotide repeats within gene transcripts are responsible for fragile X syndrome, myotonic dystrophy and spinal and bulbar muscular atrophy. To identify other human genes with similar features as candidates for triplet repeat expansion mutations, we screened human cDNA libraries with repeat probes and searched databases for transcribed genes with repeats. From both strategies, 40 genes were identified and 14 characterized. Five were found to contain repeats which are highly polymorphic including the N-cadherin, BCR, glutathione-S-transferase and Na+/K+ ATPase (beta-subunit) genes. These data demonstrate the occurrence of other human loci which may undergo this novel mechanism of mutagenesis giving rise to genetic disease.

The gene for the cell adhesion molecule M-cadherin maps to mouse chromosome 8 and human chromosome 16q24.1-qter and is near the E-cadherin (uvomorulin) locus in both species

A mouse myotube-derived cDNA encoding the Ca(2+)-dependent cell adhesion molecule M-cadherin was used to study the segregation of the corresponding gene Cdh3 in a mouse interspecific backcross. Cdh3 was found to be unlinked to the N-cadherin gene but linked to the E-cadherin (uvomorulin) locus on chromosome 8 in a region of conserved synteny with human chromosome 16q. The gene order cen-Junb-Um-Tat-(Cdh3/Aprt) was determined. The human homologue CDH3 was mapped to chromosome 16q24.1-qter by analyzing human/mouse somatic cell hybrids.

Genomic structure and chromosomal mapping of the mouse N-cadherin gene

N-cadherin is a member of the cadherin cell-cell adhesion receptor family that includes P-, E-, and R-cadherin and liver cell adhesion molecule (L-CAM). In this study, we determined the structure of the mouse N-cadherin gene by analyzing overlapping genomic clones obtained from a mouse genomic library. This gene consists of 16 exons that disperse over greater than 200 kilobases of genomic DNA. This large size of the N-cadherin gene, compared with its cDNA (4.3 kilobases), is ascribed to the fact that the first and second introns are 34.2 kilobases and greater than 100 kilobases long, respectively. When the N-cadherin gene was compared with that of L-CAM and P-cadherin, the exon-intron boundaries were found to be fully conserved between them, except that the P-cadherin first exon includes the first and second exons of the other two genes. Also, the second intron, which is equivalent to the first intron in P-cadherin, is exceptionally large and this structural feature is conserved in all of these genes. An interesting feature of the N-cadherin gene is that this gene has an extra 16th exon that is almost identical to the other exon, 100% in the coding region and 99% in the 3' untranslated region in the nucleotide level. We also determined the chromosomal localization of the N-cadherin gene by interspecific backcross analysis and found that this gene is localized in the proximal region of mouse chromosome 18. The E- and P-cadherin genes are tightly linked and located on chromosome 8 in this species. Thus, N-cadherin is unlinked to these other cadherin loci.

Autoantibodies against the amino-terminal cadherin-like binding domain of pemphigus vulgaris antigen are pathogenic

Complementary DNA cloning of the 130-kD pemphigus vulgaris (PV) autoantigen (PVA) has indicated that it is a member of the cadherin family of Ca(2+)-dependent cell adhesion molecules. By homology with typical cadherins, PVA has five extracellular domains (EC1 through EC5). To localize immunogenic domains and to determine whether antibodies against them might be pathogenic, we produced beta-galactosidase fusion proteins with cDNA encoding different portions of the extracellular domains of PVA (EC1-2, EC3-5, and each individual domain). Immunoblot analysis of these fusion proteins with 23 PV patients' sera demonstrated that major immunogenic regions of PVA are located on the EC1, EC2, and EC4 domains. IgG was affinity-purified from PV sera on fusion proteins representing the amino (EC1-2) and carboxy (EC3-5) terminus of the extracellular PVA, and injected into neonatal mice. PV IgG affinity-purified on the EC1-2 fusion protein caused suprabasilar acantholysis, the typical histological finding of PV, but IgG affinity-purified on the EC3-5 fusion protein or beta-galactosidase alone did not. These results indicate that at least one pathogenic epitope, which is sufficient to cause suprabasilar acantholysis in neonatal mice, is located on the amino-terminal region of PVA, an area thought to be important in cadherin homophilic adhesion.

A molecular genetic linkage map of mouse chromosome 18 reveals extensive linkage conservation with human chromosomes 5 and 18

An interspecific backcross between C57BL/6J and Mus spretus was used to generate a molecular genetic linkage map of mouse chromosome 18 that includes 23 molecular markers and spans approximately 86% of the estimated length of the chromosome. The Apc, Camk2a, D18Fcr1, D18Fcr2, D18Leh1, D18Leh2, Dcc, Emb-rs3, Fgfa, Fim-2/Csfmr, Gnal, Grl-1, Grp, Hk-1rs1, Ii, Kns, Lmnb, Mbp, Mcc, Mtv-38, Palb, Pdgfrb, and Tpl-2 genes were mapped relative to each other in one interspecific backcross. A second interspecific backcross and a centromere-specific DNA satellite probe were used to determine the distance of the most proximal chromosome 18 marker to the centromere. The interspecific map extends the known regions of linkage homology between mouse chromosome 18 and human chromosomes 5 and 18 and identifies a new homology segment with human chromosome 10p. It also provides molecular access to many regions of mouse chromosome 18 for the first time.

A developmentally regulated switch in neuronal responsiveness to NCAM and N-cadherin in the rat hippocampus

Monolayers of control 3T3 fibroblasts and 3T3 cells expressing transfected NCAM or N-cadherin have been used as a culture substratum for rat hippocampal neurons. Both NCAM and N-cadherin are expressed in the hippocampus through embryonic day 17 (E17) to postnatal day 4 (PND4); however, whereas E17 neurons responded to transfected NCAM by extending considerably longer neurites, PND4 neurons responded very poorly. The converse was true for responsiveness to N-cadherin. These data demonstrate a switch in neuronal responsiveness to NCAM and N-cadherin in the developing hippocampus. NCAM-dependent neurite outgrowth from E17 neurons was largely dependent on the presence of alpha 2–8-linked polysialic acid (PSA) on neuronal NCAM. NCAM-dependent neurite outgrowth could be fully inhibited by pertussis toxin or a combination of L- and N-type calcium channel antagonists thus providing direct evidence concerning the nature of the second messenger pathway activated in primary neurons by cell adhesion molecules (CAMs).

The human gene (DSG2) coding for HDGC, a second member of the desmoglein subfamily of the desmosomal cadherins, is, like DSG1 coding for desmoglein DGI, assigned to chromosome 18

Desmoglein is a transmembrane glycoprotein of the cadherin superfamily present in the desmosomal junction in vertebrate epithelial cells. At least two variants of desmoglein are differentially expressed in human tissues: DGI, a characteristic desmosomal protein; and HDGC, which is, for example, expressed in the simple epithelium of the colon. Using a PCR assay, we were able to assign DSG2, the gene coding for desmoglein HDGC, to chromosome 18, the same chromosomal localization to which we have previously assigned DSG1 coding for desmoglein DGI.

Structure and interactions of desmosomal and other cadherins

The cadherin superfamily of cell-cell adhesion molecules is now known to include proteins of the desmosome as well as of the adherens type of junction. The desmosomal cadherins consist of two families of proteins, the desmocollins and the desmogleins, both of which are represented by different isoforms which are differentially expressed in epidermis. The desmocollins are quite similar to the classic cadherins in overall structure, but with alternatively spliced variants; the desmogleins have extra cytoplasmic sequences added onto the basic cadherin structure. The cytoplasmic domains are specialized for binding to 'mediator' proteins, such as plakoglobin, which interconnect to the intermediate filament system rather than the actin filaments as do the classic cadherins.

Expression of NCAM isoforms during skeletal myogenesis in the mouse embryo

We have examined the developmental patterns of neural cell adhesion molecule (NCAM) gene expression in embryonic mouse skeletal muscle cells by in situ hybridization. Moreover, by utilising exon-specific cRNA probes, we have examined tissue specific splicing of the NCAM gene. We show that there is a distinct sequence of NCAM isoform expression during skeletal muscle development. Since NCAMs are also expressed in other cell types, particularly neurons, NCAM mRNAs have been colocalised with acetylcholine receptor alpha (AChR alpha) gene transcripts to identify muscle-specific expression. NCAM is first detected in somites as they first form, prior to their differentiation into muscle and nonmuscle compartments. Myotomes, the first skeletal muscle masses to form in the embryo, express mRNAs for the transmembrane 180 and 140 kDa isoforms of NCAM. Both of these transcripts are also detected in the neural tube, and their spatial pattern of expression changes with development. Transcripts containing the muscle-specific domain (MSD) of the NCAM gene are not detected prior to 11 days postcoitum (p.c.), at a time when rostral somites already contain well-developed myotomes. As the level of MSD mRNAs increases at 12 days p.c., the 140 and 180 kDa transcript levels decrease in skeletal muscle masses. The level of all NCAM isoform transcripts declines between 13 and 15 days p.c. in muscle. However, the 180 and 140 kDa NCAM isoforms are expressed at a high level in neural tissue and in other locations in the developing embryo such as in smooth muscle, around vibrissae follicles, and in the perichondrial zone of digits.

The human gene (DSG3) coding for the pemphigus vulgaris antigen is, like the genes coding for the other two known desmogleins, assigned to chromosome 18

Pemphigus vulgaris (PV) is a potentially lethal skin disease in which epidermal blisters occur as the result of the loss of cell-cell adhesion caused by the action of autoantibodies against a keratinocyte cell surface glycoprotein, the PV antigen (PVA). This latter protein is a member of the desmoglein subfamily of the cadherin superfamily of cell-cell adhesion molecules, present in the desmosome type of intercellular junction. The other two known desmogleins are DGI, which is a target antigen in another autoantibody-mediated blistering disease of the epidermis, pemphigus foliaceous, and HDGC, which is expressed in the basal layer of the epidermis and in the simple epithelium of, for example, the colon. Genes coding for DGI (DSG1) and HDGC (DSG2) have previously been assigned to human chromosome 18. We now present evidence, using a polymerase chain reaction assay, that DSG3, the gene coding for PVA, is assigned to the same chromosome.

Calcium dependence of A-CAM function in human renal epithelium

Previously we have used immunocytochemistry to identify A-CAM as a major cell adhesion molecule in human renal tubular epithelium. In this study, we demonstrate the calcium dependence of cell-cell adhesion and A-CAM function in cultured human renal epithelial cells. Separation of adjacent cells was seen within 1 min following sequestration of calcium from the culture medium with EDTA. This loss of intracellular adhesion in low calcium conditions was accompanied by the disappearance of A-CAM immunoreactivity. The changes were reversible and on return to normal calcium concentrations, A-CAM immunoreactivity reappeared and cell adhesion was re-established. The time course of this recovery was slow, taking 2-3 h. These results demonstrate the calcium dependence of cell adhesion in cultured human renal epithelial cells and confirm the adhesive function of the immunoreactive A-CAM molecule.

Neural cell adhesion molecule (NCAM) and N-cadherin mRNA during development and aging: selective reduction in the 7.4-kb and 6.7-kb NCAM mRNA levels in the hippocampus of adult and old rats

By examining the time course, from E15 to 720 days of age, for changes in the prevalence of mRNAs coding for neural cell adhesion molecule (NCAM), N-cadherin and alpha-tubulin in rat hippocampus and forebrain, it was concluded that (i) the NCAM 7.4-, 6.7-, 5.2-, 4.3- and 2.9-kb mRNAs are differentially regulated during development and aging; (ii) the 7.4- and 6.7-kb mRNA are drastically reduced starting from day 21 onward; (iii) the E15- and day-1-specific mRNA of 4.3 kb is replaced with the 5.2-kb mRNA starting with 21 days, thereafter the 5.2-kb message remained relatively constant over the entire life-span studied. Likewise, the 2.9-kb mRNA, which was very abundantly expressed at E15 and early postnatal stages, remained relatively constant between 180 days and 720 days; (iv) postnatal rat brains showed both qualitative and quantitative changes in N-cadherin 4.3- and 4.0-kb transcripts. The 4.3-kb mRNA was relatively abundant at 1 and 21 days postnatal stages, thereafter the signal remained very low over the entire life-span studied. The 4.0-kb message, which was specific for the E15 stage, was replaced with the 4.3-kb message; (v) as expected, the 1.8-kb mRNA coding for embryonic alpha-tubulin decreased dramatically after 1 day, but became stabilized at moderate levels during the subsequent developmental stages. At least for the NCAM gene, the regulation seems to occur post-transcriptionally, possibly at the level of RNA processing while the N-cadherin mRNA expression seems to be transcriptionally regulated.

Genes for two calcium-dependent cell adhesion molecules have similar structures and are arranged in tandem in the chicken genome

Genomic sequences immediately upstream of the translational start site for the chicken liver cell adhesion molecule (L-CAM) gene contain a second closely related gene, which, because of its location, we have designated the K-CAM gene. Less than 700 base pairs separate the presumed poly(A) site in the K-CAM gene from the translation initiation site for L-CAM. The sizes of exons 4-15 of the K-CAM gene are almost identical to those in the L-CAM gene and the exon/intron junctions occur at exactly equivalent positions in both genes. Exon 16, which includes the 3' untranslated region, is much shorter in the K-CAM gene and intron sizes and sequences are not generally conserved between the two genes. Probes from the K-CAM gene hybridized to a 3-kilobase mRNA that was present at high levels in embryonic skin, at lower levels in kidney, heart, and gizzard, and at still lower levels in brain and liver, as determined by Northern blotting. The sequence of the predicted gene product was nearly identical to that of the chicken B-cadherin cDNA, although the distribution of the K-CAM gene transcript differed from that reported for the cadherin. The proximity and identical overall structure of the K-CAM and L-CAM genes strongly suggest that they arose by gene duplication and raise the possibility that genes for other calcium-dependent CAMs may be located in clusters. Moreover, the tandem arrangement of the genes may have important implications for the regulation of their expression.

Autoantibodies against a novel epithelial cadherin in pemphigus vulgaris, a disease of cell adhesion

Pemphigus vulgaris (PV) is a life-threatening skin disease in which autoantibodies against a keratinocyte cell surface 130 kd glycoprotein, PV antigen (PVA), cause loss of cell-cell adhesion, with resultant epidermal blisters. We used affinity-purified PV IgG to isolate cDNA, containing the entire coding sequence for PVA, from human keratinocyte expression libraries. Northern blot analysis indicated PV mRNA expression only in stratified squamous epithelia. The deduced amino acid sequence of PVA was unique but showed significant homology with members of the cadherin family of Ca(2+)-dependent cell adhesion molecules, most markedly to desmoglein I. These findings demonstrate that a novel epithelial cadherin is the target of autoantibodies in PV.

Cadherin mRNAs during rat embryo development in vivo and in vitro

Whole rat embryo cultures are being used in increasing numbers of laboratories to study the mechanisms by which teratogens disturb development. The development of early somite stage embryos in vitro is very similar morphologically to that in vivo, yet few biochemical comparisons have been made. The purpose of this study was to determine the steady-state mRNA concentrations of a family of Ca(2+)-dependent cell adhesion molecules, the cadherins, during rat embryonic development in vivo and in vitro. Embryos and yolk sacs were collected on days 10, 11, and 12 of gestation (in vivo); they were also obtained from day 10 embryos after growth in culture for 24 hr (day 11 in vitro) or 45 hr (day 12 in vitro). Total RNAs isolated from embryos and yolk sacs were studied by Northern blot analysis using specific cDNA probes for three cadherins, E-cadherin, N-cadherin, and P-cadherin. Although E-cadherin mRNA was detected in embryos, it was present at much higher concentrations in yolk sacs. In addition, multiple species of E-cadherin mRNA ranging from 3.0 to 13 kb were detected. Interestingly, the concentration of the major 4.5-kb E-cadherin mRNA species in yolk sac after 45 hr in culture was increased 2.8-fold over that on day 12 of gestation in vivo. Second, two species (4.3 and 3.5 kb) of N-cadherin mRNA were detected, almost exclusively in embryos. In yolk sac, N-cadherin mRNA was detected only after 45 hr in culture. Third, P-cadherin mRNA was detected as a single 3.5-kb species, mainly in embryos. P-cadherin mRNA concentrations in yolk sac after 45 hr in culture were 5.6-fold higher than in vivo. Thus, these results demonstrate that there is a differential distribution of cadherin mRNAs in rat embryos and yolk sacs. Further, there appear to be multiple species of mRNAs for E-cadherin and N-cadherin. Finally, while whole embryo culture in vitro did not significantly alter the steady-state concentrations of cadherin mRNAs in the embryo, these concentrations were dramatically increased in the yolk sac.