Tomohiro Ishii

Mutually exclusive expression of odorant receptor transgenes.

To study the mutually exclusive expression of odorant receptor (OR) genes, we generated transgenic mice that carried the murine OR gene MOR28. Expression of the transgene and the endogenous MOR28 was distinguished by using two different markers, β-galactosidase and green fluorescent protein (GFP), respectively. Double staining of the olfactory epithelium revealed that the two genes were rarely expressed simultaneously in individual olfactory neurons. A similar exclusion was also observed between differently tagged but identical transgenes integrated into the same locus of one particular chromosome. Although allelic inactivation has been reported for the choice between the maternal and paternal alleles, this is the first demonstration of mutually exclusive activation among non-allelic OR gene members with identical coding and regulatory sequences. Such an unusual mode of gene expression, monoallelic and mutually exclusive, has previously been shown only for the antigen-receptor genes of the immune system.

Expression of Nonclassical Class I Major Histocompatibility Genes Defines a Tripartite Organization of the Mouse Vomeronasal System

The epithelium of the mouse vomeronasal organ (VNO) consists of apical and basal layers of neuronal cell bodies. Vomeronasal sensory neurons (VSNs) with cell bodies in the basal layer express the G-protein subunit Gαo and members of the V2R superfamily of vomeronasal receptor genes and project their axons to the posterior accessory bulb (AOB). V2R+ VSNs also express particular patterns of a family of nine nonclassical class I major histocompatibility Mhc genes, the H2-Mv genes. The function of H2-Mv molecules remains unknown. H2-Mv molecules have been reported to be associated with V2R molecules and have been proposed to participate in pheromone detection. Here, we find that a substantial fraction of V2R+ VSNs does not express these nine H2-Mv genes. The cell bodies of H2-Mv+ and H2-Mv− VSNs reside in the lower and upper sublayers of the basal layer, respectively. This spatial segregation is maintained at the level of the AOB: H2-Mv+ and H2-Mv− VSNs project their axons to the posterior and anterior subdomains of the posterior AOB, respectively. By generating a C-terminal green fluorescent protein fusion protein with M10.2 in gene-targeted mice, we observe subcellular localization of M10.2 not only in dendrites but also in axons of VSNs. Our results reveal a tripartite organization of the VNO and AOB, question the generality of the requirement of these nine H2-Mv molecules for V2R surface expression, and suggest that H2-Mvs can function in both dendrites and axons.

Monoallelic expresion of the odourant receptor gene and axonal projection of olfactory sensory neurones

We have previously generated transgenic mice carrying the murine odourant receptor gene, MOR28, tagged with lacZ. In this animal, the endogenous MOR28 is differently tagged with GFP. It was found that the transgenic and endogenous MOR28 genes are expressed in a mutually exclusive manner and that the two sets of olfactory sensory neurones (OSNs), each expressing either the transgenic or the endogenous MOR28, project their axons to separate glomeruli.

Axonal projection of olfactory sensory neurons during the developmental and regeneration processes

We have studied the projection of olfactory sensory neurons (OSNs), during the developmental and regeneration processes, using the transgenic mouse carrying the differently tagged odorant receptor genes, MOR28. We have found that the axon terminals of the two sets of MOR28-positive OSNs, one expressing the lacZ tag and the other expressing the green fluorescent protein gene, are dispersed and intermingled at early developmental or regeneration stages. Projection areas become more distinct and separated at later stages, however, two sets of axon fibers are not typically bundled or segregated during pathfinding. It appears that segregation of axons mainly occurs when they target at the olfactory bulb to form the glomerular structure.

Study on dynamic characteristics of gyroscopic power generator

To solve energy supply problems for ubiquitous equipment, dynamic analysis of a gyroscopic power generator that uses the kinetic energy developed from human movement is proposed. In the generator, a rotor increases its spinning velocity by precession and friction caused by input vibration. This paper first presents an analytical method of rotor movement. The equations of motion are derived by using Eulers equation and their approximate solution is obtained by assuming the spinning velocity is constant. Then the output power of the prototype generator is estimated by using the solution. The output power of the ideal generator was shown to be 0.11 W and 0.85 W during walking and running, respectively.

Steady State Analysis of Gyroscopic power Generator

Supplying electric power to information and communication devices is a critical issue for both current mobile networks and coming ubiquitous systems. To achieve this, we focus on dynamic energy conversion systems that utilize human vibrations in daily life. The gyroscopic power generator has a rotor, which moves three dimensionally and spins at a high speed from low frequency vibrations, such as human movements. In this paper, simple equations that indicate the relationships among input vibration, rotor movement, impedance of the output circuit, and the critical conditions for stable rotation are derived. Next, by measuring the phase difference between input vibration and rotor precession angle, and critical conditions for stability using prototype generators, validity of the theory is verified.

Study on dynamics characteristics of gyroscopic power generator

In order to solve the energy supply problem for ubiquitous equipments, a gyroscopic power generator is proposed which utilizes kinetic energy of human movement. In the generator, a rotor increases spinning velocity by the precession and friction caused by input vibration. In this paper, first, an analytical method of the rotor movement is presented. Then the output energy of the prototype generator is estimated by using the analysis.

Subpopulations of vomeronasal sensory neurons with coordinated coexpression of type 2 vomeronasal receptor genes are differentially dependent on Vmn2r1

The mouse vomeronasal organ is specialized in the detection of pheromones. Vomeronasal sensory neurons (VSNs) express chemosensory receptors of two large gene repertoires, V1R and V2R, which encode G‐protein‐coupled receptors. Phylogenetically, four families of V2R genes can be discerned as follows: A, B, C, and D. VSNs located in the basal layer of the vomeronasal epithelium coordinately coexpress V2R genes from two families: Approximately half of basal VSNs coexpress Vmn2r1 of family C with a single V2R gene of family A8‐10, B, or D (‘C1 type of V2Rs’), and the other half coexpress Vmn2r2 through Vmn2r7 of family C with a single V2R gene of family A1‐6 (‘C2 type V2Rs’). The regulatory mechanisms of the coordinated coexpression of V2Rs from two families remain poorly understood. Here, we have generated two mouse strains carrying a knockout mutation in Vmn2r1 by gene targeting in embryonic stem cells. These mutations cause a differential decrease in the numbers of VSNs expressing a given C1 type of V2R. There is no compensatory expression of Vmn2r2 through Vmn2r7. VSN axons coalesce into glomeruli in the appropriate region of the accessory olfactory bulb in the absence of Vmn2r1. Gene expression profiling by NanoString reveals a differential and graded decrease in the expression levels across C1 type of V2Rs. There is no change in the expression levels of C2 type of V2Rs, with two exceptions that we reclassified as C1 type. Thus, there appears to be a fixed probability of gene choice for a given C2 type of V2R.

Studies on the expression of olfactory receptor genes by GFP tagging

The perception and processing of pheromones are suggested to be carried out by the vomeronasal system. In this study, to reveal the expression pattern and localization of pheromone receptor proteins, we produced two kinds of polyclonal antibodies against two sets of oligo peptides, which were designed to match the partial sequences of putative pheromone receptor (Dulac & Axel, Cell, 83: 195-206, 1995). The sensory epithelium of the vomeronasal organ, which is receptor organ of vomeronasal system, was examined immunocytochemically in adult rats using these antibodies with electronmicroscope. Both antibodies stained 46% knobs of sensory cells specifically as well as their microvilli. However, the knobs and microvilli of supporting cells were not stained. In addition, after the vomeronasal nerve transections, immunoreactivity disappeared completely in the vomeronasal sensory epithelium. Supported by CREST of JST.