Expression of G-protein Alpha Subunit Genes in the Vestibular Periphery of Rattus norvegieus and their Chromosomal Mapping

Abstract

Objective—Heterotrimeric G-proteins play an important role in mediating signals transduced across the cell membrane by membrane-bound receptors. The precise role of G-proteins and their coupled receptors in the physiology of the vestibular neuroepithelium is not well understood. The purpose of this study was to better define the role of these proteins by examining their expression in the rat vestibular periphery and characterizing their chromosomal location.

Material and Methods—To characterize G-protein α subunit gene expression in the target tissue of interest, we performed polymerase chain reaction (PCR) using degenerate G-protein primers corresponding to conserved regions in the G-protein α subunit coding sequence on a normalized rat vestibular cDNA library. PCR amplicons were cloned and 50 clones were randomly selected and sequenced. Radiation hybrid (RH) mapping was used to determine the chromosomal location of Gα_olf and two previously identified G-protein α subunits—Gα_i2 and Gα_i2(vest)—in the rat genome.

Results—The following G-protein α subunits were identified in the normalized cDNA library: Gα_olf, Gα_s, Gα_o and Gα_s2. Gα_olf maps to chromosome 18 between markers D18Mit17b and D18Mgh2. Gα_i2 maps to chromosome 8 between markers D8Rat65 and D8Mgh2. Gα_i2(vest) maps to chromosome 1 between markers D1Rat132 and D1Rat202. These chromosomal locations in the rat genome are syntenic to chromosomal regions in which the homologous G-protein α subunit genes have been localized in the human and mouse genomes, further validating RH mapping as an effective and accurate tool. We were unable to RH map the location of Gα_o due to its extensive homology with the hamster gene.

Conclusion—The characterization of G-protein alpha subunit gene expression in the vestibular periphery and the chromosomal localization of these genes in the rat revealed that a diverse group of these second messengers are expressed.

Key words:

• efferent vestibular system
• G-protein
• radiation hybrid mapping
• receptor
• vestibular