Tom Freeman

Fulminant Jejuno-Ileitis following Ablation of Enteric Glia in Adult Transgenic Mice

To investigate the roles of astroglial cells, we targeted their ablation genetically. Transgenic mice were generated expressing herpes simplex virus thymidine kinase from the mouse glial fibrillary acidic protein (GFAP) promoter. In adult transgenic mice, 2 weeks of subcutaneous treatment with the antiviral agent ganciclovir preferentially ablated transgene-expressing, GFAP-positive glia from the jejunum and ileum, causing a fulminating and fatal jejuno-ileitis. This pathology was independent of bacterial overgrowth and was characterized by increased myeloperoxidase activity, moderate degeneration of myenteric neurons, and intraluminal hemorrhage. These findings demonstrate that enteric glia play an essential role in maintaining the integrity of the bowel and suggest that their loss or dysfunction may contribute to the cellular mechanisms of inflammatory bowel disease.

The chemokine TECK is expressed by thymic and intestinal epithelial cells and attracts double- and single-positive thymocytes expressing the TECK receptor CCR9

Chemokines are key regulators of migration in lymphoid tissues. In the thymus, maturing thymocytes move from the outer capsule to the inner medulla and thereby interact with different types of stromal cells that control their maturation and selection. In the process of searching for molecules specifically expressed at different stages of mouse thymic differentiation, we have characterized the cDNA coding for the thymus‐expressed chemokine (TECK) and its receptor CCR9. The TECK receptor gene was isolated and shown to be localized on the mouse chromosome 9F1‐F4. Thymic dendritic cells have been initially thought to be a prevalent source of TECK. In contrast, our results indicate that thymic epithelial cells constitute the predominant source of TECK. Consistent with the latter distribution, the TECK receptor is highly expressed by double‐positive thymocytes, and TECK can chemoattract both double‐positive and single‐positive thymocytes. The TECK transcript is also abundantly expressed in the epithelial cells lining the small intestine. In conclusion, the interplay of TECK and its receptor CCR9 is likely to have a significant role in the recruitment of developing thymocytes to discrete compartments of the thymus.

Correlating physiology with gene expression in striatal cholinergic neurones.

Abstract: The expression of 34 transmitter‐related genes has been examined in the cholinergic neurones of rat striatal brain slices, with the aim of correlating gene expression with functional activity. The mRNAs encoding types I, II/IIA, and III α subunits of the voltage‐sensitive sodium channels were detected, suggesting the presence of these three types of sodium channel. Similarly, mRNAs encoding all four α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionate (AMPA)‐type glutamate receptor subunits and the NR1 and NR2A, 2B, and 2D subunits of the NMDA‐type glutamate receptors were detected, suggesting that various combinations of these subunits mediate the cellular response to synaptically released glutamate. Other mRNAs detected included the NK1 and NK3 tachykinin receptors, all four known adenosine receptors, and the GABA‐synthesising enzyme glutamate decarboxylase. Subpopulations of these cholinergic neurones have been identified on the basis of the expression of the NK3 tachykinin receptor in 5% and the trkC neurotrophin receptor in 12% of the cells investigated.

Relationship between the tissue-specificity of mouse gene expression and the evolutionary origin and function of the proteins

BackgroundThe combination of complete genome sequence information with expression data enables us to characterize the relationship between a proteins evolutionary origin or functional category and its expression pattern. In this study, mouse proteins were assigned into functional and phyletic groups and the gene expression patterns of the different protein groupings were examined by microarray analysis in various mouse tissues.ResultsOur results suggest that the proteins that are universally distributed in all tissues are predominantly enzymes and transporters. In contrast, the tissue-specific set is dominated by regulatory proteins (signal transduction and transcription factors). An increased tendency to tissue-specificity is observed for metazoan-specific proteins. As the composition of the phyletic groups highly correlates with that of the functional groups, the data were tested in order to determine which of the two factors - function or phyletic age - is dominant in shaping the expression profile of a protein. The observed differences in expression patterns of genes between functional groups were found mainly to reflect their different phyletic origin. The connection between tissue specificity and phyletic age cannot be explained by the recent rate of evolution. Finally, although metazoan-specific proteins tend to be tissue-specific compared with phyletically conserved proteins present in all domains of life, many such universal proteins are also tissue-specific.ConclusionThe minimal cellular transcriptome of the metazoan cell differs from that of the ancestral unicellular eukaryote: new functions were added (metazoan-specific proteins), whilst other functions became specialized and no longer took place in all cells (tissue-specific pre-metazoan proteins).

Calcineurin controls the expression of numerous genes in cerebellar granule cells

The Ca(2+)/calmodulin-dependent phosphatase calcineurin plays a crucial role in gene expression in different cell types such as T-lymphocytes, cardiac myocytes, and smooth muscle cells. A possible role for calcineurin in gene expression was recently found in neurons, where calcineurin regulates the expression of several genes involved in Ca(2+) homeostasis. To detect additional genes regulated in a calcineurin-dependent way in neurons we analysed gene expression profiles of cerebellar granule cells cultured in depolarising conditions in the presence or absence of the calcineurin inhibitory agents FK506 and CsA. Using oligonucleotide arrays we identified 34 genes that are differentially expressed between the samples and confirmed the calcineurin-dependent regulation of some of these genes by RT-PCR. Therefore, our results, which are likely not to be comprehensive, suggest that calcineurin plays a fundamental role in neuronal gene expression by either activating or repressing the expression of genes such as receptors, transcription factors, and signalling molecules.

Expression profiling of murine intestinal adenomas reveals early deregulation of multiple matrix metalloproteinase (Mmp) genes

Initiation of intestinal tumours occurs as a consequence of aberrant Wnt signalling. This causes altered expression of a number of genes which provides the mechanistic basis of neoplastic change in normal epithelium. In order to identify these genes, expression profiles of normal intestinal mucosa and intestinal adenomas from multiple intestinal neoplasia (Min) mice were compared. A total of 116 genes were found to show significant changes in expression in adenomas compared with normal mucosa. Functional classification of these genes clearly identified the biological processes of cellular adhesion and matrix remodelling to be profoundly affected. Notably, three members of the matrix metalloproteinase (Mmp) gene family (Mmp10, Mmp13, and Mmp14) were consistently up‐regulated in tumour tissue. To extend these data, expression of 17 Mmp genes was defined using quantitative reverse transcriptase‐polymerase chain reaction (Q‐RT‐PCR). Several Mmp genes were profoundly up‐regulated and every tumour showed overexpression of at least four Mmp genes. These results underscore the probable importance of interactions between the intestinal epithelium and stroma in early tumour development. Furthermore, the inferred role of Mmps at the adenomatous stage of tumourigenesis suggests that this may represent the optimal therapeutic window for the use of Mmp antagonists as anti‐cancer agents. Copyright

Spatial, a new nuclear factor tightly regulated during mouse spermatogenesis.

In order to clarify general mechanisms of T cell development, we used array technology to identify genes differentially expressed between wild type and mutant mice thymuses. This quantitative differential screening leads to the isolation of Spatial, a putative transcription factor, expressed at high level in thymic cortical stromal cells. We report here, by RT-PCR on 48 distinct tissues that Spatial is also highly expressed in testis. Interestingly, the testicular expression is developmentally regulated, since it only appears in adult mice around 7-8 weeks of age. Analysis of purified testicular cell types show that Spatial expression is restricted to haploid round spermatids during spermiogenesis and the expression sites were further localized by in situ hybridization to step 2-10 spermatids. Thus, this recently described nuclear factor constitutes a new marker of the round spermatid stage that may play a key role in the control of male germ cell development.

Corrigendum to “Spatial, a new nuclear factor tightly regulated during mouse spermatogenesis” [Gene Expression Patterns 3 (2003) 135–138]

ERM 206 INSERM, Faculte de Science de Luminy, Universite de Ia Mediterranee, Case 906, Parc Scientifique de Luminy, F-13288 Marseille Cedex 9, 1FR57, France INSERM U435, Universite de Rennes I, Campus de Beaulieu, Avenue du General, Leclerc, 35042 Rennes Cedex, France MRC HGMP, Wellcome Trust Genome Campus, Hinxton CB10 ISB, UK Centre d’Immunologie INSERM-CNRS, Case 906, Parc Scientifique de Luminy, F-13288 Marseille Cedex 9, Faculte de Science de Luminy, Universite de la Mediterranee, IFR57, Marseille, France

Development of a PCR product-based microarray system for expression profiling of rat systems

Development of a PCR product-based microarray system for expression profiling of rat systems