Epithelial V-like antigen (EVA), a novel member of the immunoglobulin superfamily, expressed in embryonic epithelia with a potential role as homotypic adhesion molecule in thymus histogenesis

Transcriptomic analysis reveals the effects of maternal exposure to bisphenol AF on hypothalamic development in male neonatal mice

Fragmented data suggest that bisphenol AF (BPAF), a chemical widely used in a variety of products, might have potential impacts on the hypothalamus. Here, we employed male neonatal mice following maternal exposure to explore the effects of low-dose BPAF on hypothalamic development by RNA-sequencing. We found that maternal exposure to approximately 50 µg/(kg·day) BPAF from postanal day (PND) 0 to PND 15 altered the hypothalamic transcriptome, primarily involving the pathways and genes associated with extracellular matrix (ECM) and intercellular adhesion, neuroendocrine regulation, and neurological processes. Further RNA analysis confirmed the changes in the expression levels of concerned genes. Importantly, we further revealed that low-dose BPAF posed a stimulatory impact on pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus and induced the browning of inguinal white adipose tissue. All findings indicate that developmental exposure to low-dose BPAF could interfere with hypothalamic development and thereby lead to alterations in the metabolism. Interestingly, 5000 µg/(kg·day) BPAF caused slighter, non-significant or even inverse alterations than the low dose of 50 µg/(kg·day), displaying a dose-independent effect. Further observations suggest that the the dose-independent effects of BPAF might be associated with oxidative stress and inflammatory responses caused by the high dose. Overall, our study highlights a risk of low-dose BPAF to human neuroendocrine regulation and metabolism.

MPZL2 variant analysis with whole exome sequencing in a cohort of Chinese hearing loss patients

BACKGROUND

Hearing loss is a genetically heterogeneous disease with more than 100 genes identified. Pathogenic variants in the MPZL2 gene cause autosomal recessive non-syndromic hearing loss. MPZL2 patients showed mild to moderate progressive hearing loss with onset age around 10 years old. To date, four pathogenic variants have been identified.

AIMS

To explore the clinical characteristics and variants of MPZL2-related hearing loss, and summarize the prevalence rate in overall hearing loss patients.

MATERIAL AND METHODS

To determine the prevalence of MPZL2-related hearing loss in the Chinese population, we analyzed MPZL2 variants of whole exome sequencing data derived from a cohort of 385 hearing loss patients.

RESULTS

Overall, homozygous MPZL2 variants were identified in 5 sporadic cases (diagnostic rate = 1.30%). A novel missense variant c.52C > T;p.Leu18Phe was identified in one other patient with compound heterozygous mutations in MPZL2, but the pathogenicity was uncertain according to the American College of Medical Genetics guidelines (2015). A patient homozygous for the c.220C > T,p.Gln74Ter variant showed congenital profound hearing loss at all frequencies, a phenotype different from previous reports.

CONCLUSIONS

Our results enriched the mutation and phenotype spectrum of MPZL2-related hearing loss. Comparisons between allele frequencies of MPZL2:c.220C > T;p.Gln74Ter and other common deafness variants suggested that MPZL2:c.220C > T;p.Gln74Ter should be included in the group of common deafness variants for prescreening.

A novel MPZL2 c. 68delC variant is associated with progressive hearing loss in Chinese population and literature review

Objective

Methods

Results

Conclusion

KLF5 Is Activated by Gene Amplification in Gastric Cancer and Is Essential for Gastric Cell Proliferation

Gastric cancer is the third leading cause of cancer death worldwide. In this study, we tried to clarify the function of KLF5 in gastric cancer. Copy number variation (CNV) and the expression of KLF5 were interrogated in public datasets. The clinical significance of KLF5 amplification and gene expression in gastric cancer were evaluated. The function of KLF5 in cell proliferation was studied in gastric cancer cell lines and organoids. We found that KLF5 amplification mainly occurred in the chromosome instable tumors (CIN) and was significantly associated with TP53 mutation. In addition, higher KLF5 expression correlated with more locally invasive gastric cancer and higher T stage. Next, a KLF5 gene expression signature was curated. The genes in the signature were involved in cell development, cell cycle regulation, cell death, suggesting potential roles played by KLF5. Functional studies using siRNAs revealed that KLF5 was essential for the proliferation of gastric cancer cells. Finally, using gastric organoid models, we revealed that the proliferation of organoids was significantly inhibited after the down regulation of KLF5. Our study revealed that KLF5 was amplified and over-expressed in gastric cancer, and it may play an oncogene-like role in gastric cancer by supporting cell proliferation.

Rare deleterious germline variants and risk of lung cancer

Recent studies suggest that rare variants exhibit stronger effect sizes and might play a crucial role in the etiology of lung cancers (LC). Whole exome plus targeted sequencing of germline DNA was performed on 1045 LC cases and 885 controls in the discovery set. To unveil the inherited causal variants, we focused on rare and predicted deleterious variants and small indels enriched in cases or controls. Promising candidates were further validated in a series of 26,803 LCs and 555,107 controls. During discovery, we identified 25 rare deleterious variants associated with LC susceptibility, including 13 reported in ClinVar. Of the five validated candidates, we discovered two pathogenic variants in known LC susceptibility loci, ATM p.V2716A (Odds Ratio [OR] 19.55, 95%CI 5.04-75.6) and MPZL2 p.I24M frameshift deletion (OR 3.88, 95%CI 1.71-8.8); and three in novel LC susceptibility genes, POMC c.*28delT at 3' UTR (OR 4.33, 95%CI 2.03-9.24), STAU2 p.N364M frameshift deletion (OR 4.48, 95%CI 1.73-11.55), and MLNR p.Q334V frameshift deletion (OR 2.69, 95%CI 1.33-5.43). The potential cancer-promoting role of selected candidate genes and variants was further supported by endogenous DNA damage assays. Our analyses led to the identification of new rare deleterious variants with LC susceptibility. However, in-depth mechanistic studies are still needed to evaluate the pathogenic effects of these specific alleles.

Epithelial V-like antigen 1 promotes hepatocellular carcinoma growth and metastasis via the ERBB-PI3K-AKT pathway

The role of epithelial V‐like antigen 1 (EVA1) has been well studied in thymic development and homostasis; however, its putative relationship with cancer remains largely unknown. Therefore, here we investigated the role of EVA1 in hepatocellular carcinoma. Interestingly, EVA1 expression was significantly increased in hepatocellular carcinoma (HCC) and was also associated with a poor prognosis and recurrence in HCC patients. Overexpression of EVA1 promoted cell growth, invasion and migration in vitro. Consistently, knockdown of EVA1 expression inhibited proliferation and migration in vitro, while repressing metastasis of HCC cells in vivo. RNA‐seq analysis indicated that EVA1 is able to upregulate the expression of genes in the ERBB3‐PI3K pathway. Accordingly, an increased level of AKT phosphorylation was detected in HCC cells after EVA1 overexpression. LY294002, a PI3K inhibitor, inhibited AKT phosphorylation and rescued the tumor‐promoting effect of EVA1 overexpression. Altogether, the present study has revealed the oncogenic role of EVA1 during HCC progression and metastasis through the ERBB‐PI3K‐AKT signaling pathway, reiterating the potential use of EVA1 as a therapeutic target and/or prognostic marker for HCC.

MPZL2 is a novel gene associated with autosomal recessive nonsyndromic moderate hearing loss

While recent studies have revealed a substantial portion of the genes underlying human hearing loss, the extensive genetic landscape has not been completely explored. Here, we report a loss-of-function variant (c.72delA) in MPZL2 in three unrelated multiplex families from Turkey and Iran with autosomal recessive nonsyndromic hearing loss. The variant co-segregates with moderate sensorineural hearing loss in all three families. We show a shared haplotype flanking the variant in our families implicating a single founder. While rare in other populations, the allele frequency of the variant is ~ 0.004 in Ashkenazi Jews, suggesting that it may be an important cause of moderate hearing loss in that population. We show that Mpzl2 is expressed in mouse inner ear, and the protein localizes in the auditory inner and outer hair cells, with an asymmetric subcellular localization. We thus present MPZL2 as a novel gene associated with sensorineural hearing loss.

MPZL2, Encoding the Epithelial Junctional Protein Myelin Protein Zero-like 2, Is Essential for Hearing in Man and Mouse

In a Dutch consanguineous family with recessively inherited nonsyndromic hearing impairment (HI), homozygosity mapping combined with whole-exome sequencing revealed a MPZL2 homozygous truncating variant, c.72del (p.Ile24Metfs^∗22). By screening a cohort of phenotype-matched subjects and a cohort of HI subjects in whom WES had been performed previously, we identified two additional families with biallelic truncating variants of MPZL2. Affected individuals demonstrated symmetric, progressive, mild to moderate sensorineural HI. Onset of HI was in the first decade, and high-frequency hearing was more severely affected. There was no vestibular involvement. MPZL2 encodes myelin protein zero-like 2, an adhesion molecule that mediates epithelial cell-cell interactions in several (developing) tissues. Involvement of MPZL2 in hearing was confirmed by audiometric evaluation of Mpzl2-mutant mice. These displayed early-onset progressive sensorineural HI that was more pronounced in the high frequencies. Histological analysis of adult mutant mice demonstrated an altered organization of outer hair cells and supporting cells and degeneration of the organ of Corti. In addition, we observed mild degeneration of spiral ganglion neurons, and this degeneration was most pronounced at the cochlear base. Although MPZL2 is known to function in cell adhesion in several tissues, no phenotypes other than HI were found to be associated with MPZL2 defects. This indicates that MPZL2 has a unique function in the inner ear. The present study suggests that deleterious variants of Mplz2/MPZL2 affect adhesion of the inner-ear epithelium and result in loss of structural integrity of the organ of Corti and progressive degeneration of hair cells, supporting cells, and spiral ganglion neurons.

CLCA2 Interactor EVA1 Is Required for Mammary Epithelial Cell Differentiation

CLCA2 is a p53-, p63-inducible transmembrane protein that is frequently downregulated in breast cancer. It is induced during differentiation of human mammary epithelial cells, and its knockdown causes epithelial-to-mesenchymal transition (EMT). To determine how CLCA2 promotes epithelial differentiation, we searched for interactors using membrane dihybrid screening. We discovered a strong interaction with the cell junctional protein EVA1 (Epithelial V-like Antigen 1) and confirmed it by co-immunoprecipitation. Like CLCA2, EVA1 is a type I transmembrane protein that is regulated by p53 and p63. It is thought to mediate homophilic cell-cell adhesion in diverse epithelial tissues. We found that EVA1 is frequently downregulated in breast tumors and breast cancer cell lines, especially those of mesenchymal phenotype. Moreover, knockdown of EVA1 in immortalized human mammary epithelial cells (HMEC) caused EMT, implying that EVA1 is essential for epithelial differentiation. Both EVA1 and CLCA2 co-localized with E-cadherin at cell-cell junctions. The interacting domains were delimited by deletion analysis, revealing the site of interaction to be the transmembrane segment (TMS). The primary sequence of the CLCA2 TMS was found to be conserved in CLCA2 orthologs throughout mammals, suggesting that its interaction with EVA1 co-evolved with the mammary gland. A screen for other junctional interactors revealed that CLCA2 was involved in two different complexes, one with EVA1 and ZO-1, the other with beta catenin. Overexpression of CLCA2 caused downregulation of beta catenin and beta catenin-activated genes. Thus, CLCA2 links a junctional adhesion molecule to cytosolic signaling proteins that modulate proliferation and differentiation. These results may explain how attenuation of CLCA2 causes EMT and why CLCA2 and EVA1 are frequently downregulated in metastatic breast cancer cell lines.

Eva1 Maintains the Stem-like Character of Glioblastoma-Initiating Cells by Activating the Noncanonical NF-κB Signaling Pathway

Glioblastoma (GBM)-initiating cells (GIC) are a tumorigenic subpopulation that are resistant to radio- and chemotherapies and are the source of disease recurrence. Therefore, the identification and characterization of GIC-specific factors is critical toward the generation of effective GBM therapeutics. In this study, we investigated the role of epithelial V-like antigen 1 (Eva1, also known as myelin protein zero-like 2) in stemness and GBM tumorigenesis. Eva1 was prominently expressed in GICs in vitro and in stem cell marker (Sox2, CD15, CD49f)-expressing cells derived from human GBM tissues. Eva1 knockdown in GICs reduced their self-renewal and tumor-forming capabilities, whereas Eva1 overexpression enhanced these properties. Eva1 deficiency was also associated with decreased expression of stemness-related genes, indicating a requirement for Eva1 in maintaining GIC pluripotency. We further demonstrate that Eva1 induced GIC proliferation through the activation of the RelB-dependent noncanonical NF-κB pathway by recruiting TRAF2 to the cytoplasmic tail. Taken together, our findings highlight Eva1 as a novel regulator of GIC function and also provide new mechanistic insight into the role of noncanonical NF-κB activation in GIC, thus offering multiple potential therapeutic targets for preclinical investigation in GBM.

A monoclonal antibody against the extracellular domain of mouse and human epithelial V-like antigen 1 reveals a restricted expression pattern among CD4- CD8- thymocytes

Expression of transcripts for the homotypic adhesion protein epithelial V-like antigen 1 (EVA1), also known as myelin protein zero like-2 (Mpzl2), is known to be present in thymic stromal cells. However, protein expression within different thymic subsets, stromal and/or lymphoid, has not been characterized due a lack of specific reagents. To address this, we generated a hybridoma (G9P3-1) secreting a monoclonal antibody (G9P3-1Mab), reactive against both human and mouse EVA1. The G9P3-1Mab was generated by immunizing Mpzl2-deficient gene-targeted mice with the extracellular domain of EVA1, followed by a conventional hybridoma fusion protocol, illustrating the feasibility of using gene-targeted mice to generate monoclonal antibodies with multiple species cross-reactivity. We confirmed expression of EVA1 on cortical and medullary epithelial cell subsets and revealed a restricted pattern of expression on CD4- CD8- double negative (DN) cell subsets, with the highest level of expression on DN3 (CD44(low)CD25(+)) thymocytes. G9P3-1MAb is a valuable reagent to study thymic T cell development and is likely useful for the analysis of pathological conditions affecting thymopoiesis, such as thymic involution caused by stress or aging.

The Use of Transcriptional Profiling to Improve Personalized Diagnosis and Management of Cutaneous T-cell Lymphoma (CTCL)

PURPOSE

Although many patients with mycosis fungoides presenting with stage I disease enjoy an indolent disease course and normal life expectancy, about 15% to 20% of them progress to higher stages and most ultimately succumb to their disease. Currently, it is not possible to predict which patients will progress and which patients will have a stable disease. Previously, we conducted microarray analyses with RT-PCR validation of gene expression in biopsy specimens from 60 patients with stage I-IV cutaneous T-cell lymphoma (CTCL), identified three distinct clusters based upon transcription profile, and correlated our molecular findings with 6 years of clinical follow-up.

EXPERIMENTAL DESIGN

We test by RT-PCR within our prediction model the expression of about 240 genes that were previously reported to play an important role in CTCL carcinogenesis. We further extend the clinical follow-up of our patients to 11 years. We compare the expression of selected genes between mycosis fungoides/Sézary syndrome and benign inflammatory dermatoses that often mimic this cancer.

RESULTS

Our findings demonstrate that 52 of the about 240 genes can be classified into cluster 1-3 expression patterns and such expression is consistent with their suggested biologic roles. Moreover, we determined that 17 genes (CCL18, CCL26, FYB, T3JAM, MMP12, LEF1, LCK, ITK, GNLY, IL2RA, IL26, IL22, CCR4, GTSF1, SYCP1, STAT5A, and TOX) are able to both identify patients who are at risk of progression and also distinguish mycosis fungoides/Sézary syndrome from benign mimickers.

CONCLUSIONS

This study, combined with other gene expression analyses, prepares the foundation for the development of personalized molecular approach toward diagnosis and treatment of CTCL.

Gene expression profiling for the purposes of biomarker discovery in oral potentially malignant lesions: a systematic review

Early and accurate diagnosis of oral potentially malignant lesions (OPML) is of critical importance in preventing malignant transformation. Although histopathological interpretation of the degree of epithelial dysplasia is considered the gold standard for diagnosis, this method is subjective and lacks sensitivity. Therefore, many attempts have been made to identify objective molecular biomarkers to improve diagnosis. Microarray technology has the advantage of screening the expression of the whole genome making it one of the best tools for searching for novel biomarkers. However, microarray studies of OPMLs are limited, and no review has been published to highlight and compare their findings. In this paper, we systematically review all studies that have incorporated microarray analyses in the investigation of gene profile alterations in OPMLs and suggest a set of commonly dysregulated genes across multiple gene expression profile studies. This list of common genes may help focus selection of markers for further analysis regarding their importance in the diagnosis and prognosis of OPMLs.

Epithelial V-like antigen mediates efficacy of anti-alpha₄ integrin treatment in a mouse model of multiple sclerosis

Natalizumab inhibits the transmigration of activated T lymphocytes into the brain and is highly efficacious in multiple sclerosis (MS). However, from a pharmacogenomic perspective, its efficacy and safety in specific patients remain unclear. Here our goal was to analyze the effects of epithelial V-like antigen (EVA) on anti-alpha₄ integrin (VLA4) efficacy in a mouse model of MS, experimental autoimmune encephalomyelitis (EAE). EVA has been previously characterized in human CD4 T lymphocytes, mouse thymic development, and choroid plexus epithelial cells. Further analysis here demonstrated expression in B lymphocytes and an increase in EVA⁺ lymphocytes following immunization. Following active induction of EAE using the MOG^35–55 active immunization model, EVA deficient mice developed more severe EAE and white matter tissue injury as compared to wild type controls. This severe EAE phenotype did not respond to anti-VLA4 treatment. In both the control antibody and anti-VLA4 conditions, these mice demonstrated persistent CNS invasion of mature B lymphocyte (CD19⁺, CD21⁺, sIgG⁺), increased serum autoantibody levels, and extensive complement and IgG deposition within lesions containing CD5⁺IgG⁺ cells. Wild type mice treated with control antibody also demonstrated the presence of CD19⁺, CD21⁺, sIgG⁺ cells within the CNS during peak EAE disease severity and detectable serum autoantibody. In contrast, wild type mice treated with anti-VLA4 demonstrated reduced serum autoantibody levels as compared to wild type controls and EVA-knockout mice. As expected, anti-VLA4 treatment in wild type mice reduced the total numbers of all CNS mononuclear cells and markedly decreased CD4 T lymphocyte invasion. Treatment also reduced the frequency of CD19⁺, CD21⁺, sIgG⁺ cells in the CNS. These results suggest that anti-VLA4 treatment may reduce B lymphocyte associated autoimmunity in some individuals and that EVA expression is necessary for an optimal therapeutic response. We postulate that these findings could optimize the selection of treatment responders.

Genetic ablation of myelin protein zero-like 3 in mice increases energy expenditure, improves glycemic control, and reduces hepatic lipid synthesis

Obesity continues to be a global health problem, and thus it is imperative that new pathways regulating energy balance be identified. Recently, it was reported: (Hayashi K, Cao T, Passmore H, Jourdan-Le Saux C, Fogelgren B, Khan S, Hornstra I, Kim Y, Hayashi M, Csiszar K. J Invest Dermatol 123: 864-871, 2004) that mice carrying a missense mutation in myelin protein zero-like 3 (Mpzl3rc) have reduced body weight. To determine how Mpzl3 controls energy balance in vivo, we generated mice deficient in myelin protein zero-like 3 (Mpzl3-KO). Interestingly, KO mice were hyperphagic yet had reduced body weight and fat mass. Moreover, KO mice were highly resistant to body weight and fat mass gain after exposure to a high-fat, energy-dense diet. These effects on body weight and adiposity were driven, in part, by a pronounced increase in whole body energy expenditure levels in KO mice. KO mice also had reduced blood glucose levels during an intraperitoneal glucose challenge and significant reductions in circulating insulin levels suggesting an increase in insulin sensitivity. In addition, there was an overall increase in oxidative capacity and contractile force in skeletal muscle isolated from KO mice. Hepatic triglyceride levels were reduced by 92% in livers of KO mice, in part due to a reduction in de novo lipid synthesis. Interestingly, Mpzl3 mRNA expression in liver was increased in diet-induced obese mice. Moreover, KO mice exhibited an increase in insulin-stimulated Akt signaling in the liver, further demonstrating that Mpzl3 can regulate insulin sensitivity in this tissue. We have determined that Mpzl3 has a novel physiological role in controlling body weight regulation, energy expenditure, glycemic control, and hepatic triglyceride synthesis in mice.

Inactivation of the RB family prevents thymus involution and promotes thymic function by direct control of Foxn1 expression

RB family genes control T cell production and promote thymic involution through reducing Foxn1 expression in thymic epithelial cells.

Thymic involution during aging is a major cause of decreased production of T cells and reduced immunity. Here we show that inactivation of Rb family genes in young mice prevents thymic involution and results in an enlarged thymus competent for increased production of naive T cells. This phenotype originates from the expansion of functional thymic epithelial cells (TECs). In RB family mutant TECs, increased activity of E2F transcription factors drives increased expression of Foxn1, a central regulator of the thymic epithelium. Increased Foxn1 expression is required for the thymic expansion observed in Rb family mutant mice. Thus, the RB family promotes thymic involution and controls T cell production via a bone marrow–independent mechanism, identifying a novel pathway to target to increase thymic function in patients.

Compensatory upregulation of myelin protein zero-like 2 expression in spermatogenic cells in cell adhesion molecule-1-deficient mice

The cell adhesion molecule-1 (Cadm1) is a member of the immunoglobulin superfamily. In the mouse testis, Cadm1 is expressed in the earlier spermatogenic cells up to early pachytene spermatocytes and also in elongated spermatids, but not in Sertoli cells. Cadm1-deficient mice have male infertility due to defective spermatogenesis, in which detachment of spermatids is prominent while spermatocytes appear intact. To elucidate the molecular mechanisms of the impaired spermatogenesis caused by Cadm1 deficiency, we performed DNA microarray analysis of global gene expression in the testis compared between Cadm1-deficient and wild-type mice. Out of the 25 genes upregulated in Cadm1-deficient mice, we took a special interest in myelin protein zero-like 2 (Mpzl2), another cell adhesion molecule of the immunoglobulin superfamily. The levels of Mpzl2 mRNA increased by 20-fold and those of Mpzl2 protein increased by 2-fold in the testis of Cadm1-deficient mice, as analyzed with quantitative PCR and western blotting, respectively. In situ hybridization and immunohistochemistry demonstrated that Mpzl2 mRNA and protein are localized in the earlier spermatogenic cells but not in elongated spermatids or Sertoli cells, in both wild-type and Cadm1-deficient mice. These results suggested that Mpzl2 can compensate for the deficiency of Cadm1 in the earlier spermatogenic cells.

Gene expression signatures differentiate adenocarcinoma of lung and breast origin in effusions

Lung and breast adenocarcinoma at advanced stages commonly involve the serosal cavities, giving rise to malignant effusions. The aim of the present study was to compare the global gene expression patterns of metastases from these 2 malignancies, to expand and improve the diagnostic panel of biomarkers currently available for their differential diagnosis, as well as to define type-specific biological targets. Gene expression profiles of 7 breast and 4 lung adenocarcinoma effusions were analyzed using the HumanRef-8 BeadChip from Illumina. Differentially expressed candidate genes were validated using quantitative real-time polymerase chain reaction and immunohistochemistry. Unsupervised hierarchical clustering using all 54,675 genes in the array separated lung from breast adenocarcinoma samples. We identified 289 unique probes that were significantly differentially expressed in the 2 cancers by greater than 2-fold using moderated t statistics, of which 65 and 224 were overexpressed in breast and lung adenocarcinoma, respectively. Genes overexpressed in breast adenocarcinoma included TFF1, TFF3, FOXA1, CA12, PITX1, RARRES1, CITED4, MYC, TFAP2A, EFHD1, TOB1, SPDEF, FASN, and TH. Genes overexpressed in lung adenocarcinoma included TITF1, SFTPG, MMP7, EVA1, GPR116, HOP, SCGB3A2, and MET. The differential expression of 15 genes was validated by quantitative real-time PCR, and differences in 8 gene products were confirmed by immunohistochemistry. Expression profiling distinguishes breast adenocarcinoma from lung adenocarcinoma and identifies genes that are differentially expressed in these 2 tumor types. The molecular signatures unique to these cancers may facilitate their differential diagnosis and may provide a molecular basis for therapeutic target discovery.

Grainyhead-like 2 regulates neural tube closure and adhesion molecule expression during neural fold fusion

Defects in closure of embryonic tissues such as the neural tube, body wall, face and eye lead to severe birth defects. Cell adhesion is hypothesized to contribute to closure of the neural tube and body wall; however, potential molecular regulators of this process have not been identified. Here we identify an ENU-induced mutation in mice that reveals a molecular pathway of embryonic closure. Line2F homozygous mutant embryos fail to close the neural tube, body wall, face, and optic fissure, and they also display defects in lung and heart development. Using a new technology of genomic sequence capture and high-throughput sequencing of a 2.5Mb region of the mouse genome, we discovered a mutation in the grainyhead-like 2 gene (Grhl2). Microarray analysis revealed Grhl2 affects the expression of a battery of genes involved in cell adhesion and E-cadherin protein is drastically reduced in tissues that require Grhl2 function. The tissue closure defects in Grhl2 mutants are similar to that of AP-2α null mutants and AP-2α has been shown to bind to the promoter of E-cadherin. Therefore, we tested for a possible interaction between these genes. However, we find that Grhl2 and AP-2α do not regulate each other's expression, E-cadherin expression is normal in AP-2α mutants during neural tube closure, and Grhl2;AP-2α trans-heterozygous embryos are morphologically normal. Taken together, our studies point to a complex regulation of neural tube fusion and highlight the importance of comparisons between these two models to understand more fully the molecular pathways of embryonic tissue closure.

Selective ablation of the androgen receptor in mouse sertoli cells affects sertoli cell maturation, barrier formation and cytoskeletal development

The observation that mice with a selective ablation of the androgen receptor (AR) in Sertoli cells (SC) (SCARKO mice) display a complete block in meiosis supports the contention that SC play a pivotal role in the control of germ cell development by androgens. To delineate the physiological and molecular mechanism responsible for this control, we compared tubular development in pubertal SCARKO mice and littermate controls. Particular attention was paid to differences in SC maturation, SC barrier formation and cytoskeletal organization and to the molecular mediators potentially involved. Functional analysis of SC barrier development by hypertonic perfusion and lanthanum permeation techniques and immunohistochemical analysis of junction formation showed that SCARKO mice still attempt to produce a barrier separating basal and adluminal compartment but that barrier formation is delayed and defective. Defective barrier formation was accompanied by disturbances in SC nuclear maturation (immature shape, absence of prominent, tripartite nucleoli) and SC polarization (aberrant positioning of SC nuclei and cytoskeletal elements such as vimentin). Quantitative RT-PCR was used to study the transcript levels of genes potentially related to the described phenomena between day 8 and 35. Differences in the expression of SC genes known to play a role in junction formation could be shown from day 8 for Cldn11, from day 15 for Cldn3 and Espn, from day 20 for Cdh2 and Jam3 and from day 35 for ZO-1. Marked differences were also noted in the transcript levels of several genes that are also related to cell adhesion and cytoskeletal dynamics but that have not yet been studied in SC (Actn3, Ank3, Anxa9, Scin, Emb, Mpzl2). It is concluded that absence of a functional AR in SC impedes the remodeling of testicular tubules expected at the onset of spermatogenesis and interferes with the creation of the specific environment needed for germ cell development.

Signal initiation in biological systems: the properties and detection of transient extracellular protein interactions

Extracellular glycoprotein interactions are not detected by most high throughput assays creating “blind-spots” in protein interaction maps. This review examines this problem and discusses recent advances that have begun to address it.

Individual cells within biological systems frequently coordinate their functions through signals initiated by specific extracellular protein interactions involving receptors that bridge the cellular membrane. Due to their biochemical nature, these membrane-embedded receptor proteins are difficult to manipulate and their interactions are characterised by very weak binding strengths that cannot be detected using popular high throughput assays. This review will provide a general outline of the biochemical attributes of receptor proteins focussing in particular on the biophysical properties of their transient interactions. Methods that are able to detect these weak extracellular binding events and especially those that can be used for identifying novel interactions will be compared. Finally, I discuss the feasibility of constructing a complete and accurate extracellular protein interaction map, and the methods that are likely to be useful in achieving this goal.

Epithelial to mesenchymal transition contributes to drug resistance in pancreatic cancer

A better understanding of drug resistance mechanisms is required to improve outcomes in patients with pancreatic cancer. Here, we characterized patterns of sensitivity and resistance to three conventional chemotherapeutic agents with divergent mechanisms of action [gemcitabine, 5-fluorouracil (5-FU), and cisplatin] in pancreatic cancer cells. Four (L3.6pl, BxPC-3, CFPAC-1, and SU86.86) were sensitive and five (PANC-1, Hs766T, AsPC-1, MIAPaCa-2, and MPanc96) were resistant to all three agents based on GI(50) (50% growth inhibition). Gene expression profiling and unsupervised hierarchical clustering revealed that the sensitive and resistant cells formed two distinct groups and differed in expression of specific genes, including several features of "epithelial to mesenchymal transition" (EMT). Interestingly, an inverse correlation between E-cadherin and its transcriptional suppressor, Zeb-1, was observed in the gene expression data and was confirmed by real-time PCR. Independent validation experiment using five new pancreatic cancer cell lines confirmed that an inverse correlation between E-cadherin and Zeb-1 correlated closely with resistance to gemcitabine, 5-FU, and cisplatin. Silencing Zeb-1 in the mesenchymal lines not only increased the expression of E-cadherin but also other epithelial markers, such as EVA1 and MAL2, and restored drug sensitivity. Importantly, immunohistochemical analysis of E-cadherin and Zeb-1 in primary tumors confirmed that expression of the two proteins was mutually exclusive (P = 0.012). Therefore, our results suggest that Zeb-1 and other regulators of EMT may maintain drug resistance in human pancreatic cancer cells, and therapeutic strategies to inhibit Zeb-1 and reverse EMT should be evaluated.

The human orthologue of murine Mpzl3 with predicted adhesive and immune functions is a potential candidate gene for immune-related hereditary hair loss

We have recently reported a mutation within the conserved immunoglobulin V-type domain of the predicted adhesion protein Mpzl3 (MIM 611707) in rough coat (rc) mice with severe skin abnormalities and progressive cyclic hair loss. In this study, we tested the hypothesis that the human orthologue MPZL3 on chromosome 11q23.3 is a candidate for similar symptoms in humans. The predicted conserved MPZL3 protein has two transmembrane motifs flanking an extracellular Ig-like domain. The R100Q rc mutation is within the Ig-domain recognition loop that has roles in T-cell receptors and cell adhesion. Results of the rc mouse study, 3D structure predictions, homology with Myelin Protein Zero and EVA1, comprehensive database analyses of polymorphisms and mutations within the human MPZL3 gene and its cell, tissue expression and immunostaining pattern indicate that homozygous or compound heterozygous mutations of MPZL3 might be involved in immune-mediated human hereditary disorders with hair loss.

Phosphorylation and localization of protein-zero related (PZR) in cultured endothelial cells

Protein-zero related (PZR) is an immunoglobulin V (IgV)-type immunoreceptor with two immunoreceptor tyrosine-based inhibitory motifs (ITIMs). PZR interacts with Src homology 2 domain-containing tyrosine phosphatase (SHP-2) via its tyrosine-phosphorylated ITIMs, for which c-Src is a putative kinase. Towards elucidating PZR function in endothelial cells (ECs), the authors cloned PZR from bovine aortic endothelial cells (BAECs) and characterized it. Mature bovine PZR had 94.8% and 92.7% sequence identity with canine and human proteins, respectively, and the two ITIM sequences were conserved among higher vertebrates. PZR was expressed in many cell types and was localized to cell contacts and intracellular granules in BAECs and mesothelioma (REN) cells. Coimmunoprecipitation revealed that PZR, Grb-2-associated binder-1 (Gab1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) were three major SHP-2-binding proteins in BAECs. H(2)O(2) enhanced PZR tyrosine phosphorylation and PZR/SHP-2 interaction in ECs in a dose-and time-dependent manner. To see if tyrosine kinases other than Src are also capable of phosphorylating PZR, the authors cotransfected HEK293 cells with PZR and one of several tyrosine kinases and found that c-Src, c-Fyn, c-Lyn, Csk, and c-Abl, but not c-Fes, phosphorylated PZR and increased PZR/SHP-2 interaction. These results suggest that PZR is a cell adhesion protein that may be involved in SHP-2-dependent signaling at interendothelial cell contacts.

Epithelial V-like antigen regulates permeability of the blood-CSF barrier

Epithelial V-like antigen (EVA), a CD3-binding immunoglobulin-like protein, regulates embryonic thymic development. Here we demonstrate that EVA is expressed in choroid plexus from mature immune competent and lymphocyte-deficient (RAG-/-) mice. Choroid plexus epithelial cells from RAG-/- mice demonstrated reduced junctional integrity and enhanced permeability that was associated with decreased expression of E-cadherin and EVA mRNA as compared to wild-type mice. Following iv infusion of an anti-CD3 antibody (145-2C11) that also binds EVA, expression of E-cadherin and EVA mRNA approached levels seen in wild-type mice. Immuno-fluorescent staining for cadherin also revealed decreased expression in untreated RAG-/- mice that could be increased by 145-2C11 treatment. Expression of mouse EVA in HEK-293 cells followed by challenge with 145-2C11 resulted in increased cytosolic calcium that was not seen in control cells. These results suggest that EVA expressed in choroid plexus cells may regulate the permeability of the blood-CSF barrier.

Large-scale screening for novel low-affinity extracellular protein interactions

Extracellular protein-protein interactions are essential for both intercellular communication and cohesion within multicellular organisms. Approximately a fifth of human genes encode membrane-tethered or secreted proteins, but they are largely absent from recent large-scale protein interaction datasets, making current interaction networks biased and incomplete. This discrepancy is due to the unsuitability of popular high-throughput methods to detect extracellular interactions because of the biochemical intractability of membrane proteins and their interactions. For example, cell surface proteins contain insoluble hydrophobic transmembrane regions, and their extracellular interactions are often highly transient, having half-lives of less than a second. To detect transient extracellular interactions on a large scale, we developed AVEXIS (avidity-based extracellular interaction screen), a high-throughput assay that overcomes these technical issues and can detect very transient interactions (half-lives <or= 0.1 sec) with a low false-positive rate. We used it to systematically screen for receptor-ligand pairs within the zebrafish immunoglobulin superfamily and identified novel ligands for both well-known and orphan receptors. Genes encoding receptor-ligand pairs were often clustered phylogenetically and expressed in the same or adjacent tissues, immediately implying their involvement in similar biological processes. Using AVEXIS, we have determined the first systematic low-affinity extracellular protein interaction network, supported by independent biological data. This technique will now allow large-scale extracellular protein interaction mapping in a broad range of experimental contexts.

Molecular dissection of prethymic progenitor entry into the T lymphocyte developmental pathway

Notch signaling activates T lineage differentiation from hemopoietic progenitors, but relatively few regulators that initiate this program have been identified, e.g., GATA3 and T cell factor-1 (TCF-1) (gene name Tcf7). To identify additional regulators of T cell specification, a cDNA library from mouse Pro-T cells was screened for genes that are specifically up-regulated in intrathymic T cell precursors as compared with myeloid progenitors. Over 90 genes of interest were identified, and 35 of 44 tested were confirmed to be more highly expressed in T lineage precursors relative to precursors of B and/or myeloid lineage. To a remarkable extent, however, expression of these T lineage-enriched genes, including zinc finger transcription factor, helicase, and signaling adaptor genes, was also shared by stem cells (Lin(-)Sca-1(+)Kit(+)CD27(-)) and multipotent progenitors (Lin(-)Sca-1(+)Kit(+)CD27(+)), although down-regulated in other lineages. Thus, a major fraction of these early T lineage genes are a regulatory legacy from stem cells. The few genes sharply up-regulated between multipotent progenitors and Pro-T cell stages included those encoding transcription factors Bcl11b, TCF-1 (Tcf7), and HEBalt, Notch target Deltex1, Deltex3L, Fkbp5, Eva1, and Tmem131. Like GATA3 and Deltex1, Bcl11b, Fkbp5, and Eva1 were dependent on Notch/Delta signaling for induction in fetal liver precursors, but only Bcl11b and HEBalt were up-regulated between the first two stages of intrathymic T cell development (double negative 1 and double negative 2) corresponding to T lineage specification. Bcl11b was uniquely T lineage restricted and induced by Notch/Delta signaling specifically upon entry into the T lineage differentiation pathway.

EVA regulates thymic stromal organisation and early thymocyte development

Epithelial V-like antigen (EVA) is an immunoglobulin-like adhesion molecule identified in a screen for molecules developmentally regulated at the DN to DP progression in thymocyte development. We show that EVA is expressed during the early stages of thymus organogenesis in both fetal thymic epithelia and T cell precursors, and is progressively downregulated from day 16.5 of embryonic development. In the postnatal thymus, EVA expression is restricted to epithelial cells and is distributed throughout both cortical and medullary thymic regions. Transgenic overexpression of EVA in the thymus cortex resulted in a modified stromal environment, which elicited an increase in organ size and absolute cell number. Although peripheral T lymphocyte numbers are augmented throughout life, no imbalance either in the repertoire, or in the different T cell subsets was detected. Collectively, these data suggest a role for EVA in structural organisation of the thymus and early lymphocyte development.

Mutation in Mpzl3, a novel [corrected] gene encoding a predicted [corrected] adhesion protein, in the rough coat (rc) mice with severe skin and hair abnormalities

The rough coat (rc), an autosomal-recessive mutation, arose spontaneously in C57BL/6J mice. Homozygous rc mice develop severe skin and hair abnormalities, including cyclic and progressive hair loss and sebaceous gland hypertrophy. The rc locus was previously mapped to Chromosome 9. To elucidate the genetic basis underlying the rc phenotype development, we carried out positional cloning, and mapped the rc locus to a 246-kb interval. We identified a missense mutation within a novel open reading frame in the rc/rc mice, which is predicted to encode a cell adhesion molecule with the highest homology to myelin protein zero (MPZ) and myelin protein zero-like 2 (MPZL2, also called epithelial V-like antigen). We therefore named this gene Mpzl3 (myelin protein zero-like 3). The mutation in the rc/rc mice occurred at a highly conserved residue within the conserved Ig-like V-type domain, thus likely altering the MPZL3 protein function. Reverse transcriptase-PCR and Western blot analyses revealed expression of the Mpzl3 gene in various adult organs, including the skin. Using indirect immunofluorescence, we detected MPZL3 protein in the keratinocytes and sebocytes in the skin. Results from this study identified a novel gene encoding a predicted adhesion protein whose mutation in the rc/rc mice likely caused the rc phenotype.

Variable domains and a VpreB-like molecule are present in a jawless vertebrate

Immunoglobulins (Igs) and T cell antigen receptors (TCRs) that undergo somatic diversification have not been identified in the two extant orders of jawless vertebrates, which occupy essential positions in terms of understanding the evolution of the emergence of adaptive immunity. Using a single motif-dependent PCR-based approach coupled with a vector that allows selection of cDNAs encoding secretion signal sequences, four different genes encoding Ig V-type domains were identified in the sea lamprey (Petromyzon marinus). One of the predicted proteins encoded by these genes shares structural characteristics with mammalian VpreB molecules, including the absence of a recognizable transmembrane region, a relatively high proportion of charged amino acids in its C-terminal tail and distinctive features of its secretion signal peptide. This is the first indication of a molecule related to the B cell receptor (BCR) complex in a species that diverged prior to the jawed vertebrates in which RAG-mediated adaptive immunity is first encountered.

Mycophenolate mofetil increases adhesion capacity of tumor cells in vitro

BACKGROUND

The immunosuppressive drug mycophenolate mofetil (MMF) reduces expression of the heterophilic binding elements intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 and thereby prevents attachment of alloactivated leukocytes to donor endothelium. The authors speculated that MMF might further diminish receptors of the immunoglobulin superfamily which, however, act as homophilic binding elements. Because decrease of homophilic adhesion receptors correlates with tumor dissemination and metastasis, MMF could trigger development or recurrence of neoplastic tumors.

METHODS

The authors analyzed the influence of MMF on homotypic adhesion receptors and its consequence for tumor cell attachment to an endothelial cell monolayer. Neuroblastoma (NB) cells, which self-aggregate by means of the homophilic-binding element neural cell adhesion molecule (NCAM), were used. Effects of MMF on the 140- and 180-kDa NCAM isoforms were investigated quantitatively by flow cytometry, Western blot, and reverse-transcriptase (RT) polymerase chain reaction (PCR). The relevance of NCAM for tumor cell binding was proven by treating NB with NCAM antisense oligonucleotides.

RESULTS

MMF profoundly increased the number of adherent NB cells, with a maximum effect at 0.1 microM, compared with controls. Decrease of NCAM on the cell surface was detected by flow cytometry. Western blot and RT-PCR demonstrated reduced protein and RNA levels of the 140- and 180-kDa isoforms. Treatment of NB cells with NCAM antisense oligonucleotides showed that reduced NCAM expression leads to enhanced tumor cell adhesion.

CONCLUSIONS

MMF decreases NCAM receptors, which is associated with enhanced tumor cell invasiveness. The authors conclude that an MMF-based immunosuppressive regimen might increase the risk of tumor metastasis if this process is predominantly conveyed by means of homophilic adhesion proteins.

JAML, a novel protein with characteristics of a junctional adhesion molecule, is induced during differentiation of myeloid leukemia cells

Retinoic acid induces clinical remission in acute promyelocytic leukemia (APL) by triggering differentiation of leukemia promyelocytes. Here, we have characterized a gene encoding a member of the immunoglobulin superfamily, among novel retinoic acid-induced genes identified in APL cells. This protein, which was named JAML (junctional adhesion molecule-like), contains 2 extracellular immunoglobulin-like domains, a transmembrane segment, and a cytoplasmic tail. JAML mRNA is expressed in hematopoietic tissues and is prominently expressed in granulocytes. The fact that JAML protein is localized at the cell plasma membrane in the areas of cell-cell contacts, whereas it is not detected at free cell borders, suggests that JAML is engaged in homophilic interactions. Furthermore, a conserved dimerization motif among JAM members was shown to be important for JAML localization at the cell membrane. Finally, exogenous expression of JAML in myeloid leukemia cells resulted in enhanced cell adhesion to endothelial cells. Altogether, our results point to JAML as a novel member of the JAM family expressed on leukocytes with a possible role in leukocyte transmigration.

Expression of protein zero is increased in lesioned axon pathways in the central nervous system of adult zebrafish

The immunoglobulin superfamily molecule protein zero (P0) is important for myelin formation and may also play a role in adult axon regeneration, since it promotes neurite outgrowth in vitro. Moreover, it is expressed in the regenerating central nervous system (CNS) of fish, but not in the nonregenerating CNS of mammals. We identified a P0 homolog in zebrafish. Cell type-specific expression of P0 begins in the ventromedial hindbrain and the optic chiasm at 3-5 days of development. Later (at 4 weeks) expression has spread throughout the optic system and spinal cord. This is consistent with a role for P0 in CNS myelination during development. In the adult CNS, glial cells constitutively express P0 mRNA. After an optic nerve crush, expression is increased within 2 days in the entire optic pathway. Expression peaks at 1 to 2 months and remains elevated for at least 6 months postlesion. After enucleation, P0 mRNA expression is also upregulated but fails to reach the high levels observed in crush-lesioned animals at 4 weeks postlesion. Spinal cord transection leads to increased expression of P0 mRNA in the spinal cord caudal to the lesion site. The glial upregulation of P0 mRNA expression after a lesion of the adult zebrafish CNS suggests roles for P0 in promoting axon regeneration and remyelination after injury.

Keratinocyte growth factor preserves normal thymopoiesis and thymic microenvironment during experimental graft-versus-host disease

Thymus-dependent reconstitution of the peripheral T-cell compartment is critical for the successful outcome of bone marrow transplantation. However, graft-versus-host disease (GVHD) affects thymic stromal function and thus prevents normal T-cell maturation and selection. To determine whether cytoprotection of thymic epithelial cells (TECs) by keratinocyte growth factor (KGF) averts GVHD-related injury to the thymus, a nonirradiated murine parent-->F(1) transplantation model was investigated. Administration of KGF between days -3 and +3 of GVHD induction preserved normal thymic size, cellularity, and thymocyte phenotype when measured 2 weeks after transplantation and compared with saline-treated parent-->F(1) mice that received allogeneic transplants. Moreover, the characteristic GVHD-induced impairment in cell cycle progression of pro- and pre-T cells was prevented by KGF. However, the normal phenotypic and functional status of the thymus did not correlate with the higher number of GVHD-inducing mature donor T cells in thymi of KGF-treated mice. Importantly, extensive analysis of the different TEC populations within the thymic cortex and medulla revealed an almost normal stromal architecture and composition in GVHD mice treated with KGF. These observations are likely to reflect an indirect effect of KGF on thymopoiesis as KGF-receptor expression was demonstrated to be restricted to TECs. Thus, pharmacologic doses of KGF appear to exert a potent effect on TEC function, which in turn allows for normal T lymphopoiesis to occur during acute GVHD.

Identification of a promiscuous T-cell epitope in Mycobacterium tuberculosis Mce proteins

The characterization of Mycobacterium tuberculosis antigens inducing CD4(+) T-cell responses could critically contribute to the development of subunit vaccines for M. tuberculosis. Here we performed computational analysis by using T-cell epitope prediction software (known as TEPITOPE) to predict promiscuous HLA-DR ligands in the products of the mce genes of M. tuberculosis. The analysis of the proliferative responses of CD4(+) T cells from patients with pulmonary tuberculosis to selected peptides displaying promiscuous binding to HLA-DR in vitro led us to the identification of a peptide that induced proliferation of CD4(+) cells from 50% of the tested subjects. This study demonstrates that a systematic computational approach can be used to identify T-cell epitopes in proteins expressed by an intracellular pathogen.

Relevance of the tumor antigen in the validation of three vaccination strategies for melanoma

Many preclinical studies of cancer immunotherapy are based on the testing of a single vaccination strategy in several tumor models. Moreover, most of those studies used xenogeneic Ags, which, owing to their high immunogenicity, may not represent realistic models for the validation of cancer immunotherapies. To address these issues, we compared the vaccination efficacy of three well established strategies (i.e., naked DNA; peptide-pulsed dendritic cells (DC), or a mixture of peptide and the Escherichia coli toxin LTR72) using the xenogeneic OVA or the naturally expressed tyrosinase-related protein 2 (TRP-2) tumor Ag in the B16 melanoma model. C57BL/6 mice received one to three s.c. injections of peptide-pulsed DC or DNA, or one to four mucosal administrations of peptide-toxin mixture. One to 2 wk later, the animals were challenged s.c. with B16 or B16 cells expressing OVA (B16-OVA). Vaccination of mice with OVA induced in all cases melanoma-specific CTL and protection against B16-OVA. When TRP-2 was used, all three vaccines elicited B16-specific CTL, but only DC pulsed with the immunodominant T cell epitope TRP-2181-188 allowed protection against B16. Even more importantly, a vaccination regimen with TRP-2-pulsed DC, started 24 h after the injection of a lethal number of B16 cells, caused a therapeutic effect in 60% of the challenged animals. Our results strongly emphasize the relevance of the tumor Ag in the definition of immunotherapeutic strategies for cancer, and support the use of peptide-pulsed DC as cancer vaccine in humans.

Expression pattern of the epithelial v-like antigen (Eva) transcript suggests a possible role in placental morphogenesis

Adhesive mechanisms are considered to be of crucial importance for blastocyst adherence to the uterine wall, as well as for the interactions between embryonal and decidual tissues during hemochorial placenta formation. Epithelial V-like Antigen (Eva) is a novel homophilic adhesion molecule of the immunoglobulin superfamily, which during mouse embryonic development is expressed by various differentiating epithelia. In the present paper we describe Eva expression during mouse trophoblast invasion and placental morphogenesis, analysing day 5.5 to 18.5 postcoitum (p.c.) placentas and deciduomas by in situ hybridization. Eva transcripts were detected in spongiotrophoblast cells from 7.5 to 18.5 days p.c. Expression was uniform at early stages, but after day 11.5, p.c. became limited to the invasive subpopulation of spongiotrophoblasts (known as glycogen cells). Trophoblast giant cells did not express Eva in any of the stages analysed. Besides trophoblasts, also early postimplantation decidua was positive for Eva transcripts. In decidual tissue, Eva expression was present at day 5.5 p.c., peaked at day 7.5 p.c., and declined on successive days. The expression pattern of Eva transcripts suggests that during mouse placenta formation, its protein product may play a role in the processes of trophoblast invasion, decidual response, and trophoblast-decidual interaction.

Evidence for a stepwise evolution of the CD3 family

The three CD3 components of the TCR complex are encoded as clustered genes in mammals. The evolution of such a multimeric complex is likely to occur stepwise. The chicken CD3 cluster was entirely sequenced, and, in contrast to mammals, only two chicken CD3 genes were found to be physically linked to the unrelated genes HZW10 and epithelial V-like Ag flanking both sides of the CD3 cluster. Biochemical analyses of CD3 immunoprecipitates confirmed the presence of only two CD3 proteins and revealed an essential role for CD3gammadelta glycosylation during assembly. Functional analyses indicated that the chicken TCR/CD3 complex was efficiently down-regulated by phorbol ester treatment, demonstrating the integrity of a CD3gamma-like cytoplasmic internalization motif. These data argue for a stepwise CD3 evolution, with major differences in the TCR/CD3 structure between mammalian and nonmammalian vertebrates setting a basis for the understanding of the CD3 phylogeny and proving the ancestral nature of the CD3gammadelta protein.

Two murine and human homologs of mab-21, a cell fate determination gene involved in Caenorhabditis elegans neural development

We report the cloning and genetic characterization of one human and two murine homologs of the mab-21 cell fate specification gene. mab-21 participates in the formation of sensory organs in the male nematode tail, and is essential for other developmental functions elsewhere in the Caenorhabditis elegans embryo. The expanding mab-21 gene family, which is strikingly conserved in evolution, includes two putative Drosophila members. The two mammalian genes, encoding 41 kDa nuclear basic proteins, are expressed in partially overlapping territories in the embryonic brain, eye and limbs, as well as in neural crest derivatives. Recent genetic data implicating mab-21 as a downstream target of TGF-beta signaling, together with the distribution of mab-21 transcripts in the mouse embryo, propose these novel genes as relevant factors in various aspects of vertebrate neural development.

Molecular and cellular aspects of induced thymus development in recombinase-deficient mice

Thymus development and microenvironment organization require stage- and site-specific cross-talk between thymocyte and stroma. In this study we have used recombinase-activating gene-deficient (RAG-2(-/-)) mice to analyze regulated gene expression both in thymocytes and stromal cells following injection of anti-CD3 monoclonal antibodies as inducer of thymus development. We show that IFN-gamma, TNF-alpha and lymphotactin are transcriptionally regulated in thymocytes, whereas cytoskeletal keratin 14, IL-1alpha and TNF-alpha are regulated in the stroma, quantitatively reproducing the variations associated with beta selection of thymocytes. In addition, RAG-2(-/-) thymus development is associated with entry of epithelial cells into the cell cycle. The histochemical evidence that expanded RAG-2(-/-) thymus becomes undistinguishable from wild-type cortex further suggests that cross-talk phenomena occurring during beta selection of thymocyte are reproduced in this system.

Duplication and MHC linkage of the CTX family of genes in Xenopus and in mammals

The effects of whole genome duplications that characterize the evolution of vertebrates have been studied on the gene of the Xenopus thymocyte molecule CTX and its mammalian relatives. CTX, with an extracellular part consisting of one V and one C2 external domain, defines a new subset of the immunoglobulin superfamily and is conserved from amphibians to mammals. The number of CTX loci, their polymorphism, and their genetic linkages have been studied in several Xenopus species and in humans. In the genetically simplest species, X. tropicalis (2n = 20), the unique CTX locus is linked to the MHC. In the polyploid species, all CTX genes, unlike many other immune system genes, have remained in the genome; i.e. there are two CTX loci in the tetraploid species X. laevis (2n = 6) and six CTX loci in the dodecaploid species X. ruwenzoriensis (2n = 108). In X. laevis, one CTX gene is linked to the MHC and the other not, presumably because one set of MHC class I and II has been deleted from the corresponding linkage group. The various mammalian homologues are less related to each other than are the Xenopus CTX genes among each other, and they do not cross-hybridize with each other because they stem from the ancient polyploidization. Some human CTX homologies are on chromosomes 11 and 21, but others are on chromosomes 1, 6 and 19, which contain MHC paralogous regions; this suggests that a very ancient linkage group has been preserved.

GKLF in thymus epithelium as a developmentally regulated element of thymocyte-stroma cross-talk

Gut-enriched Krüppel-like factor (GKLF) is a transcriptional regulator expressed in differentiated epithelia. We identified GKLF transcript as a regulated element in thymic epithelium of recombinase-deficient mice during thymus development induced by anti-CD3 antibody injection. This treatment recapitulates the organogenetic process depending on productive rearrangement of T cell receptor (TCR) beta gene with thymocytes expansion and acquisition of the CD4+8+ double positive phenotype. In wildtype mice, GKLF is expressed very early in embryogenesis and becomes intensely up-regulated in thymus epithelium at day 18 of gestation when TCR beta expressing cells have selectively expanded and express both CD4 and CD8. The results presented here suggest that thymocytes may regulate GKLF transcriptionally in the cortical epithelium at the developmental check-point controlled by TCR beta gene rearrangement. Furthermore, GKLF expression in hematopoietic stroma might suggest the thus far uncharacterised participation of this factor in hematopoiesis.

Myelin protein zero and membrane adhesion

Protein zero (P0) is a member of the immunoglobulin gene superfamily (IgCAM) that is expressed at high levels in myelinated vertebrates in central (fish and amphibia) and peripheral (all species) myelin. This glycoprotein is the major adhesive component of peripheral myelin, where it mediates self-adhesion of the Schwann cell plasma membrane. Although the expression of P0 is naturally limited to Schwann cells, the molecular mechanisms of P0-mediated adhesion can be considered general and "obligatory" because, when expressed in a variety of cell lines, P0 induces strong intercellular adhesion. Modeling studies, X-ray crystallographic analysis, and experimental site-directed mutagenesis have provided excellent working models for understanding how P0 mediates adhesion at the atomic level. These models remain to be experimentally tested. However, in humans, certain mutations in P0 produce dysmyelinating disease, possibly due to disruptions in the predicted P0 lattice.