Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling.

AIMS AND HYPOTHESIS: Glucose-stimulated insulin secretion from beta-cells is a tightly regulated process that requires calcium flux to trigger exocytosis of insulin-containing vesicles. Regulation of calcium handling in beta-cells remains incompletely understood. Gem, a member of the RGK (Rad/Gem/Kir) family regulates calcium channel handling in other cell types, and Gem over-expression inhibits insulin release in insulin-secreting Min6 cells. The aim of this study was to explore the role of Gem in insulin secretion. We hypothesised that Gem may regulate insulin secretion and thus affect glucose tolerance in vivo. METHODS: Gem-deficient mice were generated and their metabolic phenotype characterised by in vivo testing of glucose tolerance, insulin tolerance and insulin secretion. Calcium flux was measured in isolated islets. RESULTS: Gem-deficient mice were glucose intolerant and had impaired glucose stimulated insulin secretion. Furthermore, the islets of Gem-deficient mice exhibited decreased free calcium responses to glucose and the calcium oscillations seen upon glucose stimulation were smaller in amplitude and had a reduced frequency. CONCLUSIONS: These results suggest that Gem plays an important role in normal beta-cell function by regulation of calcium signalling.

Immune cell transcriptome datasets reveal novel leukocyte subset-specific genes and genes associated with allergic processes.

BACKGROUND: The precise function of various resting and activated leukocyte subsets remains unclear. For instance, mast cells, basophils, and eosinophils play important roles in allergic inflammation but also participate in other immunologic responses. One strategy to understand leukocyte subset function is to define the expression and function of subset-restricted molecules. OBJECTIVE: To use a microarray dataset and bioinformatics strategies to identify novel leukocyte markers as well as genes associated with allergic or innate responses. METHODS: By using Affymetrix microarrays, we generated an immune transcriptome dataset composed of gene profiles from all of the major leukocyte subsets, including rare enigmatic subsets such as mast cells, basophils, and plasma cells. We also assessed whether analysis of genes expressed commonly by certain groups of leukocytes, such as allergic leukocytes, might identify genes associated with particular responses. RESULTS: Transcripts highly restricted to a single leukocyte subset were readily identified (>2000 subset-specific transcripts), many of which have not been associated previously with leukocyte functions. Transcripts expressed exclusively by allergy-related leukocytes revealed well known as well as novel molecules, many of which presumably contribute to allergic responses. Likewise, Nearest Neighbor Analysis of genes coexpressed with Toll-like receptors identified genes of potential relevance for innate immunity. CONCLUSION: Gene profiles from all of the major human leukocyte subsets provide a powerful means to identify genes associated with single leukocyte subsets, or different types of immune response. CLINICAL IMPLICATIONS: A comprehensive dataset of gene expression profiles of human leukocytes should provide new targets or biomarkers for human inflammatory diseases.

Clues to asthma pathogenesis from microarray expression studies.

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR), tissue remodeling, and airflow obstruction. The pathogenesis of asthma is only partly understood, and there is an urgent need for improved therapeutic strategies for this disease. Microarray technology has considerable promise as a tool for discovery of novel asthma therapeutic targets, although the field is still in its infancy. A number of studies have described expression profiles derived from human asthmatic lung tissue, mouse airway tissue, or from key cell types associated with asthma, but to date relatively few studies have exploited these findings to discover new pathways involved in the pathogenesis of asthma. Among the genes to have been identified by array studies and validated by further studies are monokine induced by interferon (IFN)-gamma, fatty acid binding proteins (FABP), and complement factor 5 (C5). Here we provide examples of microarray approaches to the discovery of new molecules associated with asthma. We anticipate that these types of analyses will provide considerable insight into asthma pathogenesis and will provide a wealth of new molecules for downstream analyses such as gene deficient mouse studies, or monoclonal antibody production.