| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2004: ¥1,900,000 (Direct Cost: ¥1,900,000)
|
|---|
| Research Abstract |
It is well accepted that each olfactory sensory neuron (OSN) expresses only one odorant receptor (OR) gene in a mutually exclusive and monoallelic manner. In situ hybridization (ISH) with OR gene probes has demonstrated that the olfactory epithelium (OE) can be divided into four topographically distinct zones and that OSNs expressing a given OR gene are randomly distributed within one zone. The OR genes of various vertebrate species are classified phylogenetically into two different groups, class I and class II. Class I OR genes, first identified in fish and later found in amphibians, were thought to have water-soluble odorous ligands. Class II ORs, which are terrestrial specific, account for a large share of the mammalian OR repertoire and have been investigated in detail in the mouse olfactory system. Recently, we have found that the expression areas are specific to each class II OR gene and are arranged in an overlapping manner in the OE. In contrast, the expression patterns and projection sites for class I ORs are not fully understood. In the present study, we systematically analyzed mouse class I OR genes (42 subfamilies) to elucidate the expression profiles in the OE and the projection sites of their OSNs in the OB. ISH revealed that most class I OR genes (36 subfamilies) were expressed in the dorso-medial zone (zone 1) of the OE. Furthermore, there appeared to be no significant differences in the distributions of OSNs expressing class I genes within zone 1. These results indicate that there is a clear boundary between zone 1 and non-zone 1 areas in the OE. Some class I ORs are known to possess ligand specificity for aliphatic acids, aldehydes and alcohols. Our ISH analysis has revealed that OSNs expressing the class I ORs in zone 1 tend to converge their axons on a cluster of glomeruli in an antero-dorsal domain that is assumed to be involved in responses to the aliphatic compounds on the OB.
|
