gas7: A gene expressed preferentially in growth-arrested fibroblasts and terminally differentiated Purkinje neurons affects neurite formation

CD2 distinguishes two subsets of human plasmacytoid dendritic cells with distinct phenotype and functions

Plasmacytoid dendritic cells (pDCs) are key regulators of antiviral immunity. They rapidly secrete IFN-alpha and cross-present viral Ags, thereby launching adaptive immunity. In this study, we show that activated human pDCs inhibit replication of cancer cells and kill them in a contact-dependent fashion. Expression of CD2 distinguishes two pDC subsets with distinct phenotype and function. Both subsets secrete IFN-alpha and express granzyme B and TRAIL. CD2(high) pDCs uniquely express lysozyme and can be found in tonsils and in tumors. Both subsets launch recall T cell responses. However, CD2(high) pDCs secrete higher levels of IL12p40, express higher levels of costimulatory molecule CD80, and are more efficient in triggering proliferation of naive allogeneic T cells. Thus, human blood pDCs are composed of subsets with specific phenotype and functions.

Validation of candidate causal genes for obesity that affect shared metabolic pathways and networks

A major task in dissecting the genetics of complex traits is to identify causal genes for disease phenotypes. We previously developed a method to infer causal relationships among genes through the integration of DNA variation, gene transcription, and phenotypic information. Here we validated our method through the characterization of transgenic and knockout mouse models of candidate genes that were predicted to be causal for abdominal obesity. Perturbation of eight out of the nine genes, with Gas7, Me1 and Gpx3 being novel, resulted in significant changes in obesity related traits. Liver expression signatures revealed alterations in common metabolic pathways and networks contributing to abdominal obesity and overlapped with a macrophage-enriched metabolic network module that is highly associated with metabolic traits in mice and humans. Integration of gene expression in the design and analysis of traditional F2 intercross studies allows high confidence prediction of causal genes and identification of involved pathways and networks.

Involvement of Gas7 along the ERK1/2 MAP kinase and SOX9 pathway in chondrogenesis of human marrow-derived mesenchymal stem cells

OBJECTIVE

The growth-arrest-specific protein, Gas7, has been shown to be involved in reorganization of the cytoskeleton and for inducing changes in cell shape during cell differentiation. The goals of this study were to investigate the novel role of human Gas7 (hGas7) in chondrogenic differentiation of human mesenchymal stem cells (hMSCs) and to identify the relationship between hGas7, extracellular signal-regulated kinase (ERK1/2) and SOX9 in the chondrogenic pathway.

METHODS

Bone marrow-derived hMSCs were induced to undergo chondrogenic differentiation with transforming growth factor-beta1 (TGF-beta1) in an aggregate culture system. The expression of hGas7 and SOX9 and phosphorylation of ERK1/2 at multiple time points were investigated. Chondrogenic capacity was evaluated by the size of aggregates, by glycosaminoglycan content, and by type II collagen and proteoglycan deposition after interfering with expression of hGas7, ERK1/2 or SOX9. To delineate the functional role of these genes in chondrogenesis, inhibition of individual gene's expression in hMSCs, by antisense oligonucleotides or interference RNA (siRNA), and the effect on chondrogenic differentiation were also investigated.

RESULTS

Treatment of hMSCs with TGF-beta1 resulted in a transient up-regulation of hGas7b, one of the hGas7 isoforms (day 3-day 5), a transient phosphorylation of ERK1/2 (0.5-4 h) and an up-regulation of SOX9 (2 h to day 14). Transient expression of hGas7b was also detected in hMSCs by reverse transcription-polymerase chain reaction at day 2 and day 3 following TGF-beta1 treatment. Interference with hGas7b production by hGas7b-specific antisense oligonucleotide or inhibition of p-ERK with PD98059, a specific inhibitor of ERK signaling pathway, or interference with SOX9 production by SOX9 siRNA all caused adverse effects of chondrogenic differentiation of hMSCs. Meanwhile, inhibition of p-ERK or SOX9 both blocked the expression of hGas7b. However, the p-ERK and SOX9 pathway was not affected by inhibition of hGas7b.

CONCLUSION

These results provide evidence that the transient expression of hGas7b, regulated by activation of ERK1/2 and SOX9 pathway, is essential for chondrogenic differentiation of hMSCs.

Roles of F-BAR/PCH proteins in the regulation of membrane dynamics and actin reorganization

The Pombe Cdc15 Homology (PCH) proteins have emerged in many species as important coordinators of signaling pathways that regulate actomyosin assembly and membrane dynamics. The hallmark of the PCH proteins is the presence of a Fes/CIP4 homology-Bin/Amphiphysin/Rvsp (F-BAR) domain; therefore they are commonly referred to as F-BAR proteins. The prototype F-BAR protein, Cdc15p of Schizosaccharomyces pombe, has a role in the formation of the contractile actomyosin ring during cytokinesis. Vertebrate F-BAR proteins have an established role in binding phospholipids and they participate in membrane deformations, for instance, during the internalization of transmembrane receptors. This way the F-BAR proteins will function as linkers between the actin polymerization apparatus and the machinery regulating membrane dynamics. Interestingly, some members of the F-BAR proteins are implicated in inflammatory or neurodegenerative disorders and the observations can be expected to have clinical implications for the treatment of the diseases.

Pombe Cdc15 homology proteins: regulators of membrane dynamics and the actin cytoskeleton

Pombe Cdc15 homology (PCH) proteins have emerged in many species as important coordinators of signalling pathways that regulate actomyosin assembly and membrane dynamics. For example, the prototype PCH protein, Cdc15p of Schizosaccharomyces pombe, has a role in assembly of the contractile ring, which is needed to separate dividing cells. Recently, mammalian PCH proteins have been found to bind phospholipids and to participate in membrane deformation. These findings suggest that PCH proteins are crucial linkers of membrane dynamics and actin polymerization, for example, during the internalization of transmembrane receptors. Intriguingly, some members of the PCH protein family are mutated in neurodegenerative and inflammatory diseases, which has implications for the identification of cures for such disorders.

Expression of the Gas7 gene and Oct4 in embryonic stem cells of mice

Oct4 is a stem cell expression marker, and persistence of its expression retains pluripotency in embryonic stem (ES) cells. Our results indicate a pattern of gradual decrease in Oct4 expression, which is prominent in the blastocyst and markedly reduced in the gastrula and neurula. The presence of POU transcription factor-like domain in Gas7 prompted us to look for its expression in the early embryonic cells. We have observed high expression of the Gas7 protein in blastocysts that gradually decreased in the neurula stages. The localization of Gas7 was initially seen throughout the blastocyst, but was later confined to dorsal ectodermal regions of the neurula, conforming with its role in neuronal differentiation. Our data reveal that Gas7 might play a role in cellular migration and cell protection in the ES cells of mouse embryo.

Evolving concepts in the pathogenesis of hairy-cell leukaemia

Hairy-cell leukaemia (HCL) has long been recognized as distinct from other chronic B-cell malignancies, but several questions remain unanswered. What is the HCL cell of origin? Why does HCL lack the hallmarks of most mature B-cell tumours (for example, chromosomal translocations and consistent lymph node involvement) and show unique features like 'hairy' morphology and bone-marrow fibrosis? Gene-expression profiling and other studies have recently provided new insights into HCL biology and have the potential to affect clinical practice.

Expression of GAS7 in childhood CNS tumors

Expression of growth arrest-specific (Gas) genes is observed during growth arrest in terminally differentiating cells during development of peripheral nerves. Gas7 is expressed predominantly in the brain and is required for neurite formation. Human GAS7 is located on chromosome 17p11.3 close to or within the putative breakpoint of isochromosome 17q (i(17q)) in medulloblastoma, indicating a potential role as a tumor suppressor gene, lost by formation of i(17q). However in the present study, the expression of GAS7 was detected in 20 of 29 childhood medulloblastoma samples regardless of the presence of i(17q). Therefore, GAS7 is not likely to be a tumor suppressor gene in medulloblastoma development.

Molecular mechanisms regulating molting in a crustacean

Crustacean growth and development is characterized by periodic shedding (ecdysis) and replacement of the rigid exoskeleton. Secretions of the X-organ sinus gland complex control the cellular events that lead to growth and molting. Western blot and ELISA results showed a progressive increase in growth arrest-specific protein (Gas7) from early postmolt stage to a maximum at late postmolt stage. Phosphorylation of ERK2, a downstream signaling protein, was also identified in the subsequent stages. ERK2 phosphorylation resulted in the expression of molt-inhibiting hormone (MIH). Specific ERK inhibitors (PD98059 and UO126) exhibited the ability to reduce the molting duration of Fenneropenaeus indicus from 12-14 days to 7-8 days, suggesting that the ERK1/2 signaling pathway is responsible for the expression of MIH, which controls the molt cycle. We have identified the stage-specific expression of Gas7 (approximately 48 kDa) in the X-organ sinus gland complex of eyestalk which is involved in the downstream signaling of the ERK1/2 pathway regulating the expression of MIH during the molt cycle of the white shrimp, F. indicus. These are the first data showing an association between the Gas7 signal-transduction process and regulation of the molt cycle and provides an alternative molecular intervention mechanism to the traditional eyestalk ablation in crustaceans.

Human Gas7 isoforms homologous to mouse transcripts differentially induce neurite outgrowth

Gas7, a growth-arrest-specific protein, is expressed preferentially in the brain and is required for neurite outgrowth in cultured cerebellar and peripheral murine neurons. Gas7 interacts with F-actin and colocalizes with the terminal part of actin microfilament in cells in which membrane outgrowth is present. Gas7 isoforms were discovered in murine brain by alternative splicing. This work reports the identification of two human Gas7 cDNA: hGas7-a with 2,427 nucleotides, which encodes 330 amino acids, and hGas7-b with 2,610 nucleotides, which encodes 412 amino acids according to predicted open-reading-frames. The predicted hGas7-b protein is 97% homologous to murine homologues, whereas the hGas7-a is homologous to the mouse Gas7-cb form that is expressed preferentially in cerebellum. Alignment analysis of the Gas7 protein sequences revealed a high homology to that in humans: 99% for the monkey, 97% in murine, and around 75% for the puffer fish and chicken. The hGas7-b protein comprises a WW domain, which often associates with other domains that are typically present in proteins in signal transduction processes, and an FCH domain, which participates in rearranging the cytoskeleton. The hGas7-a comprises only the FCH domain. Analysis of the human Gas7 sequences using the DNA database revealed that the two forms resulted from the canonical alternative splicing of a Gas7 genomic sequence. The abundance of both hGas7 mRNA levels, determined by quantitative PCR in tissues including brain, breast cancer, placenta, and head-neck cancer, revealed that the level of hGas7-a was 14 times that of hGas7-b in these tissues. Transfection of cells with hGas7-a or hGas7-b cDNA yielded the predicted 38-kDa or 50-kDa protein, respectively. The ectopic expression of hGas7 caused neurite-like cell processes in both mouse Neuro-2a and human SH-SY5Y neuroblastoma cells. Interestingly, the hGas7-a preferentially elicited the small lamellipodia, whereas the hGas7-b elicited the small filopodia phenotype. These findings reveal the evolutionary conservation of the structure and function of Gas7. They also suggest that the FCH domain in Gas7 may participate in the development of lamellipodia, and the WW domain may participate in the fine-tuning of the filopodia.

The gas7 protein potentiates NGF-mediated differentiation of PC12 cells

The growth-arrest-specific protein gas7 is required for morphological differentiation of cultured mouse cerebellar neurons and PC12 cells. Moreover, its overexpression in various cell types induces neurite-like outgrowth. The role of gas7 in neuronal differentiation was further characterized by adenovirus-mediated overexpression in PC12 cells and quantification of the expression of various neuronal markers, in the absence and presence of different concentrations of nerve growth factor (NGF). The potential neuroprotective activity of gas7 against various neurotoxic insults was also assessed. In addition to promoting the formation of neurite-like extensions, overexpression of gas7 potentiated NGF-mediated neuronal differentiation of PC12 cells, as shown by the enhanced expression of the neuronal proteins betaIII-tubulin, synaptotagmin, alpha7 subunit of the acetylcholine receptor, and dihydropyrimidinase related protein-3. This effect was exerted independently of cell cycle progression, as gas7 did not affect proliferation of PC12 cells. While some differentiation enhancers protect PC12 cells against lethal insults, gas7 overexpression in PC12 cells did not protect against oxygen-glucose deprivation, the calcium ionophore A23187, or the nitric oxide donor sodium nitroprusside, suggesting that gas7 is not neuroprotective. The ability of gas7 to potentiate neuronal differentiation makes it a potential therapeutic target to promote re-establishment of neuronal connections in the injured or diseased brain, such as following stroke.

Intergenomic consensus in multifactorial inheritance loci: the case of multiple sclerosis

Genetic linkage and association studies define chromosomal regions, quantitative trait loci (QTLs), which influence the phenotype of polygenic diseases. Here, we describe a global approach to determine intergenomic consensus of those regions in order to fine map QTLs and select particularly promising candidate genes for disease susceptibility or other polygenic traits. Exemplarily, human multiple sclerosis (MS) susceptibility regions were compared for sequence similarity with mouse and rat QTLs in its animal model experimental allergic encephalomyelitis (EAE). The number of intergenomic MS/EAE consensus genes (295) is significantly higher than expected if the animal model was unrelated to the human disease. Hence, this approach contributes to the empirical evaluation of animal models for their applicability to the study of human diseases.

Using peripheral blood mononuclear cells to determine a gene expression profile of acute ischemic stroke: a pilot investigation

BACKGROUND

Direct brain biopsy is rarely indicated during acute stroke. This study uses peripheral blood mononuclear cells (PBMCs) to determine whether a systemic gene expression profile could be demonstrated in patients with acute ischemic stroke.

METHODS AND RESULTS

Using oligonucleotide microarrays, we compared the gene expression profile of an index cohort of 20 patients with confirmed ischemic stroke on neuroimaging studies with that of 20 referent subjects. Validation studies used quantitative real-time polymerase chain reaction to measure the levels of 9 upregulated genes in the index cohort, and an independent cohort of 9 patients and 10 referent subjects was prospectively studied to determine the accuracy of the Prediction Analysis for Microarrays list to classify stroke. After correction for multiple comparisons with the Bonferroni technique, 190 genes were significantly different between the stroke and referent groups. Broad classes of genes included white blood cell activation and differentiation (approximately 60%), genes associated with hypoxia and vascular repair, and genes potentially associated with an altered cerebral microenvironment. Real-time polymerase chain reaction confirmed increased mRNA expression in 9 of 9 upregulated stroke-associated genes in the index cohort. A panel of 22 genes derived from the Prediction Analysis for Microarrays algorithm in the index cohort classified stroke in the validation cohort with a sensitivity of 78% and a specificity of 80%. Control for the Framingham stroke risk score revealed only a partial dependence of the stroke gene expression profile in PBMCs on vascular risk.

CONCLUSIONS

This study demonstrated an altered gene expression profile in PBMCs during acute ischemic stroke. Some genes with altered expression were consistent with an adaptive response to central nervous system ischemia.

Identification of rat Gas7 isoforms differentially expressed in brain and regulated following kainate-induced neuronal injury

The growth arrest-specific gene 7 (Gas7) is expressed primarily in the brain and is necessary for the formation of neurite in cultured cerebellar preneurons. The endogenous rat Gas7 (rGas7) is transiently elevated before nerve growth factor-promoted neurite outgrowths emerge in cultured PC12 cells. We report three Gas7 isoforms (a, b, and c) in rat tissues. Peptide microsequencing identified two Gas7 forms, rGas7-a (38 kDa) and rGas7-b (47 kDa). rGas7-c can be predicted from a transcription variant by alternative splicing. Although two open reading frames were predicted, a cloned rGas7 cDNA encoded mostly rGas7-a in mammalian cells. The overexpression of the rGas7 cDNA in PC12 cells sufficed to promote small lamellipodia- and filopodia-like cell processes that resemble the initial stages of neurite formation. Three rGas7 isoforms were differentially expressed in all of the brain subregions. Only rGas7-a was detected in rat cerebellum, as in mouse cerebellum. Kainate injury did not affect the level of rGas7-b, but the level of isoform c was substantially suppressed in the hippocampus. Immunohistochemistry reveals that Gas7 was expressed primarily in the pyramidal neurons of the hippocampus and was quickly attenuated before recovery in the CA3 area after kainate was administered. These results suggest that differential expression and unique regulation of Gas7 isoforms in brain subregions may be important in specialized brain functions. Conservation of Gas7 isoforms by alternative splicing in mammals is also considered.

Persistence of multiple tumor-specific T-cell clones is associated with complete tumor regression in a melanoma patient receiving adoptive cell transfer therapy

The authors recently reported that adoptive immunotherapy with autologous tumor-reactive tumor infiltrating lymphocytes (TILs) immediately following a conditioning nonmyeloablative chemotherapy regimen resulted in an enhanced clinical response rate in patients with metastatic melanoma. These observations led to the current studies, which are focused on a detailed analysis of the T-cell antigen reactivity as well as the in vivo persistence of T cells in melanoma patient 2098, who experienced a complete regression of all metastatic lesions in lungs and soft tissues following therapy. Screening of an autologous tumor cell cDNA library using transferred TILs resulted in the identification of novel mutated growth arrest-specific gene 7 (GAS7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene transcripts. Direct sequence analysis of the expressed T-cell receptor beta chain variable regions showed that the transferred TILs contained multiple T-cell clonotypes, at least six of which persisted in peripheral blood for a month or more following transfer. The persistent T cells recognized both the mutated GAS7 and GAPDH. These persistent tumor-reactive T-cell clones were detected in tumor cell samples obtained from the patient following adoptive cell transfer and appeared to be represented at higher levels in the tumor sample obtained 1 month following transfer than in the peripheral blood obtained at the same time. Overall, these results indicate that multiple tumor-reactive T cells can persist in the peripheral blood and at the tumor site for prolonged times following adoptive transfer and thus may be responsible for the complete tumor regression in this patient.

Human T lymphotropic virus type-1 p30II alters cellular gene expression to selectively enhance signaling pathways that activate T lymphocytes

Background

Human T-lymphotropic virus type-1 (HTLV-1) is a deltaretrovirus that causes adult T-cell leukemia/lymphoma and is implicated in a variety of lymphocyte-mediated disorders. HTLV-1 contains both regulatory and accessory genes in four pX open reading frames. pX ORF-II encodes two proteins, p13^II and p30^II, which are incompletely defined in the virus life cycle or HTLV-1 pathogenesis. Proviral clones of the virus with pX ORF-II mutations diminish the ability of the virus to maintain viral loads in vivo. Exogenous expression of p30^II differentially modulates CREB and Tax-responsive element-mediated transcription through its interaction with CREB-binding protein/p300 and represses tax/rex RNA nuclear export.

Results

Herein, we further characterized the role of p30^II in regulation of cellular gene expression, using stable p30^II expression system employing lentiviral vectors to test cellular gene expression with Affymetrix U133A arrays, representing ~33,000 human genes. Reporter assays in Jurkat T cells and RT-PCR in Jurkat and primary CD4+ T-lymphocytes were used to confirm selected gene expression patterns. Our data reveals alterations of interrelated pathways of cell proliferation, T-cell signaling, apoptosis and cell cycle in p30^II expressing Jurkat T cells. In all categories, p30^II appeared to be an overall repressor of cellular gene expression, while selectively increasing the expression of certain key regulatory genes.

Conclusions

We are the first to demonstrate that p30^II, while repressing the expression of many genes, selectively activates key gene pathways involved in T-cell signaling/activation. Collectively, our data suggests that this complex retrovirus, associated with lymphoproliferative diseases, relies upon accessory gene products to modify cellular environment to promote clonal expansion of the virus genome and thus maintain proviral loads in vivo.

Gene expression profiling of hairy cell leukemia reveals a phenotype related to memory B cells with altered expression of chemokine and adhesion receptors

Hairy cell leukemia (HCL) is a chronic B cell malignancy characterized by the diffuse infiltration of bone marrow and spleen by cells displaying a typical "hairy" morphology. However, the nature of the HCL phenotype and its relationship to normal B cells and to other lymphoma subtypes remains unclear. Using gene expression profiling, we show here that HCL displays a homogeneous pattern of gene expression, which is clearly distinct from that of other B cell non-Hodgkin lymphomas. Comparison with the gene expression profiles of purified normal B cell subpopulations, including germinal center (GC), pre-GC (naive), and post-GC (memory) B cells, shows that HCL cells are more related to memory cells, suggesting a derivation from this B cell population. Notably, when compared with memory cells, HCL cells displayed a remarkable conservation in proliferation, apoptosis, and DNA metabolism programs, whereas they appeared significantly altered in the expression of genes controlling cell adhesion and response to chemokines. Finally, these analyses have identified several genes that are specifically expressed in HCL and whose expression was confirmed at the protein level by immunocytochemical analysis of primary HCL cases. These results have biological implications relevant to the pathogenesis of this malignancy as well as clinical implications for its diagnosis and therapy.

Involvement of Gas7 in nerve growth factor-independent and dependent cell processes in PC12 cells

Gas7, a growth arrest-specific gene originally isolated from serum-starved mouse fibroblast cells, is expressed in vivo predominantly in the brain and is required for neurite formation in cultured mouse cerebellar neurons (Ju et al. [1998] Proc. Natl. Acad. Sci. USA 95: 11423-11428). Here we report that Gas7 plays a key role in the morphological differentiation of PC12 preneuronal rat pheochromocytoma cells (PC12 cells). We found that overexpression of murine Gas7 in PC12 cells leads to an expanded cell morphology and promotes spike-like cell processes that resemble the early stages of neurite formation. These processes undergo elongation upon addition of nerve growth factor (NGF). We also found that the addition of NGF induces the production of endogenous rat-Gas7 (rGas7), which is transiently elevated prior to the appearance of NGF-promoted neurite outgrowths. Furthermore, inhibition of endogenous rGas7 production by antisense nucleotides complimentary to the translation initiation region of a rGas7 cDNA (AJ131902) reduces the NGF-promoted neurite outgrowths. Our results demonstrate that Gas7 by itself influences early cell morphological development and likely functions as an early-stage intermediary in NGF-induced neuronal differentiation of PC12 culture cells.

Inflammation, degeneration and regeneration in the injured spinal cord: insights from DNA microarrays

GeneChip microarrays have recently been introduced to the field of neurobiology to identify and monitor the expression levels of thousands of genes simultaneously. This powerful technique is now used for studying the pathophysiology of CNS injuries including spinal cord lesions. Early stages after injury are characterized by the strong upregulation of genes involved in transcription and inflammation and a general downregulation of structural proteins and proteins involved in neurotransmission. Later, an increase in the expression of growth factors, axonal guidance factors, extracellular matrix molecules and angiogenic factors reflects the attempts for repair, while upregulation of stress genes and proteases and downregulation of cytoskeletal and synaptic mRNA reflect the struggle of the tissue to survive. DNA microarrays have the potential to aid discovery of new targets for neuroprotective or restorative therapeutic approaches

Dimerization contributes to oncogenic activation of MLL chimeras in acute leukemias

MLL is a histone methyltransferase that can be converted into an oncoprotein by acquisition of transcriptional effector domains following heterologous protein fusions with a variety of nuclear transcription factors, cofactors, or chromatin remodeling proteins in acute leukemias. Here we demonstrate an alternative mechanism for activation of MLL following fusions with proteins (AF1p/Eps15 and GAS7) that normally reside in the cytoplasm. The coiled-coil oligomerization domains of these proteins are necessary and sufficient for leukemogenic transformation induced by the respective MLL fusion proteins. Furthermore, homodimerization of MLL by synthetic dimerization modules mimics bona fide MLL fusion proteins resulting in Hox gene activation and enhanced self-renewal of hematopoietic progenitors. Our studies support an oligomerization-dependent mechanism for oncogenic conversion of MLL, presumably in part by recruitment of accessory factors through the dimerized MLL moiety of the chimeric protein.

Congruence of tissue expression profiles from Gene Expression Atlas, SAGEmap and TissueInfo databases

BACKGROUND

Extracting biological knowledge from large amounts of gene expression information deposited in public databases is a major challenge of the postgenomic era. Additional insights may be derived by data integration and cross-platform comparisons of expression profiles. However, database meta-analysis is complicated by differences in experimental technologies, data post-processing, database formats, and inconsistent gene and sample annotation.

RESULTS

We have analysed expression profiles from three public databases: Gene Expression Atlas, SAGEmap and TissueInfo. These are repositories of oligonucleotide microarray, Serial Analysis of Gene Expression and Expressed Sequence Tag human gene expression data respectively. We devised a method, Preferential Expression Measure, to identify genes that are significantly over- or under-expressed in any given tissue. We examined intra- and inter-database consistency of Preferential Expression Measures. There was good correlation between replicate experiments of oligonucleotide microarray data, but there was less coherence in expression profiles as measured by Serial Analysis of Gene Expression and Expressed Sequence Tag counts. We investigated inter-database correlations for six tissue categories, for which data were present in the three databases. Significant positive correlations were found for brain, prostate and vascular endothelium but not for ovary, kidney, and pancreas.

CONCLUSION

We show that data from Gene Expression Atlas, SAGEmap and TissueInfo can be integrated using the UniGene gene index, and that expression profiles correlate relatively well when large numbers of tags are available or when tissue cellular composition is simple. Finally, in the case of brain, we demonstrate that when PEM values show good correlation, predictions of tissue-specific expression based on integrated data are very accurate.

Isolation and properties of Gas8, a growth arrest-specific gene regulated during male gametogenesis to produce a protein associated with the sperm motility apparatus

Growth arrest-specific (Gas) genes are expressed during serum starvation or contact inhibition of cells grown in culture. Here we report the isolation and characterization of Gas8, a novel gene identified on the basis of its growth arrest-specific expression in murine fibroblasts. We show that production of Gas8 mRNA and protein occurs in adult mice predominantly in the testes, where expression is regulated during postmeiotic development of male gametocytes. Whereas a low level of Gas8 mRNA was detected by Northern blotting in testes of murine male neonates and young adolescents, Gas8 mRNA increased rapidly postmeiotically. In adult males, both Gas8 mRNA and protein reached steady state levels in testes that were 10-fold higher than in other tissues. Immunohistochemical analyses showed that Gas8 protein accumulates in gametocytes as they approach the lumen of seminiferous tubules and is localized to the cytoplasm of round spermatids, the tails of elongating spermatids, and mature spermatid tail bundles protruding into the lumen; in epididymal spermatozoa Gas8 protein was present in the flagella. However, premeiotic murine gametocytes lacked detectable Gas8 protein, as did seminiferous tubules in biopsy specimens from seven human males having cytological evidence of non-obstructive azoospermia secondary to Sertoli cell-only syndrome. Our findings, which associate Gas8 production developmentally with the later stages of spermatogenesis and spatially with the sperm motility apparatus, collectively suggest that this growth arrest-specific gene product may have a role in sperm motility. This postulated role for Gas8 is supported by our observation that highly localized production of Gas8 protein occurs also in the cilia of epithelial cells lining pulmonary bronchi and fallopian tubes and by the flagellar association of a Trypanosoma brucei ortholog of Gas8.

Association of the growth-arrest-specific protein Gas7 with F-actin induces reorganization of microfilaments and promotes membrane outgrowth

The growth-arrest-specific gene, Gas7, is required for neurite outgrowth in cerebellar neurons. Here we report that Gas7 can induce the formation of extended cellular processes in NIH3T3 cells by interacting with actin and mediating reorganization of microfilaments. The Gas 7 protein, which increased markedly during growth arrest of NIH3T3 cells and persisted transiently at high levels upon reentry of cells into the cell cycle, localized near the plasma membrane and selectively colocalized with microfilaments in membrane ruffles. Process extensions induced by ectopic overexpression of Gas7 were blocked by the actin-depolymerizing agent cytochalasin D, suggesting that membrane extensions produced by Gas7 require actin polymerization. Association of endogenous Gas7 protein with microfilaments was verified by F-actin affinity chromatography; direct binding of purified His-Gas7 to actin also was demonstrated and shown to be mediated by the Gas7 C-terminal domain. Similarly, localization of Gas7 in membrane ruffles was mediated by the C-terminal domain, although neither this region nor the N-terminal domain was individually sufficient to induce process formation. Biochemical studies and electron microscopy showed that both full-length Gas7 protein and its C-terminal region can promote actin assembly as well as the crosslinking of actin filaments. We propose that Gas7 localized near the plasma membrane induces the assembly of actin and the membrane outgrowth.

Temporal expression of neuronal connexins during hippocampal ontogeny

Communication through gap junction channels provides a major signaling mechanism during early brain histogenesis, a developmental time during which neural progenitor cells are inexcitable and do not express ligand-gated channel responses to the major CNS neurotransmitters. Expression of different gap junction types during neurogenesis may therefore define intercellular pathways for transmission of developmentally relevant molecules. To better understand the molecular mechanism(s) by which growth and differentiation of neurons are modulated by gap junction channels, we have been examining the developmental effects of a specific set of cytokines on differentiation and gap junction expression in a conditionally immortalized mouse embryonic hippocampal neuronal progenitor cell line (MK31). When multipotent MK31 cells are in an uncommitted state, they uniformly express the neuroepithelial intermediate filament class VI marker, nestin, are strongly coupled by gap junctions composed of connexin43 (Cx43) and express connexin45 (Cx45) at the mRNA level. As these cells undergo neuronal lineage commitment and exit from cell cycle, they begin to express the early neurofilament marker, NF66, and coupling strength and expression of Cx43 begin to decline with concurrent expression of other connexin proteins, including Cx26, Cx33, Cx36, Cx40 and Cx45. Terminal neuronal differentiation is heralded by the expression of more advanced neurofilament proteins, increased morphologic maturation, the elaboration of inward currents and action potentials that possess mature physiological properties, and changing profiles of expression of connexin subtypes, including upregulation of Cx36 expression. These important developmental transitions are regulated by a complex network of cell cycle checkpoints. To begin to examine the precise roles of gap junction proteins in traversing these developmental checkpoints and in thus regulating neurogenesis, we have focused on individual members of two classes of genes involved in these seminal events: ID (inhibitor of differentiation)-1 and GAS (growth arrest-specific gene)5. When MK31 cells were maintained in an uncommitted state, levels of ID-1 mRNA were high and GAS5 transcripts were essentially undetectable. Application of cytokines that promote neuronal lineage commitment and cell cycle exit resulted in down-regulation of ID-1 and upregulation of GAS5 transcripts, whereas additional cytokine paradigms that promoted terminal neuronal differentiation resulted in the delayed down-regulation of GAS5 mRNA. Stable MK31 transfectants were generated for ID-1 and GAS5. In basal conditions, cellular proliferation was enhanced in the ID-1 transfectants and inhibited in the GAS5 transfectants when compared with control MK31 cells. When cytokine-mediated neurogenesis was examined in these transfected cell lines, constitutive expression of ID-1 inhibited and constitutive expression of GAS5 enhanced initial and terminal stages of neuronal differentiation, with evidence that terminal neuronal maturation in both transfectant lines was associated with decreased cellular viability, possibly due to the presence of conflicting cell cycle-associated developmental signals. These experimental reagents will prove to be valuable experimental tools to help define the functional interrelationships between changing profiles of connexin protein expression and cell cycle regulation during neuronal ontogeny in the mammalian brain. The present review summarizes the current state of research involving the temporal expression of such connexin types in differentiating hippocampal neurons and speculates on the possible role of these intercellular channels in the development and plasticity of the nervous system. In addition, we describe the functional properties and expression pattern of the newly discovered neuronal-specific gap junctional protein, Cx36, in the developing mouse fetal hippocampus and in the rat retina and brain.

Detection of leukemia-associated MLL-GAS7 translocation early during chemotherapy with DNA topoisomerase II inhibitors

Leukemias with MLL gene translocations are a complication of primary cancer treatment with DNA topoisomerase II inhibitors. How early translocations appear during primary cancer treatment has not been investigated. We tracked the leukemic clone with an MLL gene translocation during neuroblastoma therapy in a child who developed acute myeloid leukemia. The karyotype of the leukemic clone showed del(11)(q23). We used panhandle PCR-based methods to isolate the breakpoint junction involving MLL and an unknown partner gene. Marrow DNA from neuroblastoma diagnosis and DNA and RNA from serial preleukemic marrows were examined for the translocation. The karyotypic del(11)(q23) was a cryptic t(11;17). GAS7, a growth arrest-specific gene at chromosome band 17p13, was the partner gene of MLL. Two different MLL-GAS7 fusion transcripts were expressed. The translocation was already detectable by 1.5 months after the start of neuroblastoma treatment. The translocation was not detectable in the marrow at neuroblastoma diagnosis or in peripheral blood lymphocyte DNAs of six normal subjects. GAS7 is a new partner gene of MLL in treatment-related acute myeloid leukemia. MLL gene translocations can be present early during anticancer treatment at low cumulative doses of DNA topoisomerase II inhibitors. Although MLL has many partner genes and most have not been characterized, panhandle PCR strategies afford new means for detecting MLL gene translocations early during therapy when the partner gene is unknown.

The Gas7 gene encodes two protein isoforms differentially expressed within the brain

Gas7, a growth arrest-specific gene first isolated from serum-starved NIH3T3 cells, is expressed abundantly in the brain and is essential for the outgrowth of neurites from cultured cerebellar neurons. Here, we report the existence of a Gas7-related cDNA, designated Gas7-cb, isolated from the mouse cerebellum, and we report the finding that Gas7-cb transcripts and protein are expressed at different locations than those of Gas7. Gas7-cb cDNA differs from the Gas7 cDNA only in the 5' region. Its encoded protein shares the same 320 amino acids in its C-terminus with those of Gas7. Analyses of the RNA and protein expression of Gas7-cb and Gas7 by RNase protection assay and Western blot indicated that while Gas7 expression is predominant in the cerebrum and in growth-arrested NIH3T3 fibroblasts, Gas7-cb expression is predominant in the cerebellum. Characterization of Gas7 and Gas7-cb RNAs and of the genomic structure of murine Gas7 cloned in a bacterial artificial chromosome indicated that the Gas7 gene spans more than 60 kb and consists of at least 15 exons. The 5'-terminus of Gas7-cb is located at exon 6a, which is absent in Gas7 transcripts but is retained in its entirety in Gas7-cb transcripts, resulting in the presence of a unique 20-amino-acid sequence at the N-terminus of the Gas7-cb protein. Our results show that the Gas7 gene encodes two Gas7 isoforms, Gas7 and Gas7-cb, whose expression is differentially regulated within mouse brain.

Activating signal cointegrator 1, a novel transcription coactivator of nuclear receptors, and its cytosolic localization under conditions of serum deprivation

Activating signal cointegrator 1 (ASC-1) harbors an autonomous transactivation domain that contains a putative zinc finger motif which provides binding sites for basal transcription factors TBP and TFIIA, transcription integrators steroid receptor coactivator 1 (SRC-1) and CBP-p300, and nuclear receptors, as demonstrated by the glutathione S-transferase pull-down assays and the yeast two-hybrid tests. The ASC-1 binding sites involve the hinge domain but not the C-terminal AF2 core domain of nuclear receptors. Nonetheless, ASC-1 appears to require the AF2-dependent factors to function (i.e., CBP-p300 and SRC-1), as suggested by the ability of ASC-1 to coactivate nuclear receptors, either alone or in cooperation with SRC-1 and p300, as well as its inability to coactivate a mutant receptor lacking the AF2 core domain. By using indirect immunofluorescence, we further show that ASC-1, a nuclear protein, is localized to the cytoplasm under conditions of serum deprivation but is retained in the nucleus when it is serum starved in the presence of ligand or coexpressed CBP or SRC-1. These results suggest that ASC-1 is a novel coactivator molecule of nuclear receptors which functions in conjunction with CBP-p300 and SRC-1 and may play an important role in establishing distinct coactivator complexes under different cellular conditions.