Study of bioengineered zebra fish olfactory receptor 131-2: receptor purification and secondary structure analysis.

How fishes are able to detect trace molecules in large bodies of water is not understood. It is plausible that they use olfactory receptors to detect water-soluble compounds. How the zebra fish Danio Rerio, an organism with only 98 functional olfactory receptors, is able to selectively detect and recognize numerous compounds in water remains a puzzling phenomenon. We are interested in studying the biochemical and molecular mechanisms of olfaction in fish. Here, we report on the study of a bioengineered zebra fish olfactory receptor OR131-2, affinity-purified from a HEK293S tetracycline-inducible system. This receptor was expressed and translocated to the cell plasma membrane as revealed by confocal microscopy. Circular dichroism spectroscopy showed that the purified zebra fish receptor folded into an α-helical structure, as observed for other G-protein coupled receptors (GPCRs). Our study shows that it is possible to produce viable quantities of the zebra fish olfactory receptor. This will not only enable detailed structural and functional analyses, but also aid in the design of biosensor devices in order to detect water-soluble metabolites or its intermediates, which are associated with human health.

Three-dimensional reconstituted extracellular matrix scaffolds for tissue engineering.

The extracellular matrix (ECM) is a rich meshwork of proteins and proteoglycans. Besides assuming a cell adhesive and structural support role, the ECM also helps to sequester and present growth factors to cells. ECM derived from tissues has been used as biological scaffolds for tissue engineering. In contrast, it has been difficult to employ ECM derived from cell lines as scaffolds due to its lack of form and structure. We have developed a mild, aqueous-based method for incorporating cell line derived ECM into biological scaffolds based on polyelectrolyte complexation, using the example of ECM from MC-3T3, a mouse preosteoblast cell line. A DNase step was incorporated in the ECM isolation procedure to further purify it of genetic material. Immunohistochemistry of fibers incorporated with MC-3T3 ECM reveal the presence of the ECM components, collagen type I, collagen type IV, fibronectin and heparan sulfate, on their surface. Reconstituted ECM scaffolds retained the cell-adhesion characteristics of the ECM, as demonstrated by 'reseeding' the ECM-secreting cell on the scaffolds. Human mesenchymal stem cells (hMSCs) were seeded onto the fibrous scaffolds incorporated with MC-3T3 ECM, and implanted subcutaneously into SCID mice. After 4 weeks of implantation, histological evidence showed that the hMSC seeded ECM scaffolds had induced bone formation at the ectopic site.

Porous collagen-apatite nanocomposite foams as bone regeneration scaffolds.

We have created a porous bioresorbable nanocomposite bone scaffold that chemically, structurally and mechanically matched natural bone so that it could be recognized and remodeled by natural bone. Containing collagen fibers and synthetic apatite nanocrystals, our scaffold has high strength for supporting the surrounding tissue. The foam-like scaffold has a similar microstructure as trabecular bone, with nanometer-sized and micron-sized pores. The apatitic phase of the scaffold exhibited similar chemical composition, crystalline phase and grain size as the trabecular bone apatite. The nanocomposite scaffold demonstrated excellent bioactivity for promoting cell attachment and proliferation. It was osteoconductive and successfully healed a non-union fracture in rat femur as well as a critical-sized defect in pig tibia.

Recyclable hydrophilic-hydrophobic micropatterns on glass for microarray applications.

A novel method for fabricating recyclable hydrophilic-hydrophobic micropatterns on glass chips is presented. TiOx patterns (100-2000 microm) were sputtered on glass chips via a through-hole mask. The patterned chips were then vapor-coated with fluoroalkylsilane, for example, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (FTES) to form a hydrophobic coating layer. The fluoroalkyl chain of FTES film on TiOx patterns was photocleaved under UV irradiation, exposing the fresh hydrophilic TiOx patterns. The resulting chip could be used multiple times by repeating the coating and photocleaving processes with negligible deterioration of the hydrophobic FTES film coated on glass. If desired, bare glass patterns could also be generated by removing the TiOx patterns with KOH. The patterned glass chips have been successfully used for microarray fabrication.

Enhanced serotonin response in the hippocampus of Galphaz protein knock-out mice.

The serotonin-1A [5-hydroxytryptamine 1A (5HT1A)] receptor is important for emotional and homeostatic processes in the central nervous system. In the hippocampus, the 5HT1A receptor couples to inhibitory Gi/o proteins to decrease pyramidal cell excitability. Here we investigate the 5HT1A receptor in a mouse deficient in the alpha-subunit of Gz protein (Galphaz knock-out). Behavioural tests showed heightened anxiety and depression-like behaviour in the Galphaz knock-out mice. Whole-cell recording in CA1 pyramidal neurons showed a significantly greater 5HT1A receptor-mediated potassium current in Galphaz knock-out mice. The effect was independent of 5HT4 receptors as the slow after-hyperpolarization was unaffected and a slow depolarization was absent in the Galphaz knock-out mice. Other receptors linked to Gi/o proteins [gamma-aminobutyric acid type B receptor (GABAB), adenosine A1 and muscarinic acetylcholine receptors] were not affected in Galphaz knock-out mice. These results suggest that the 5HT1A receptor may be linked to Galphaz protein, as reported previously in cell culture but shown here in an intact neural network.