Gene expression profiling of the rat superior olivary complex using serial analysis of gene expression

The superior olivary complex (SOC) is an auditory brainstem region that represents a favourable system to study rapid neurotransmission and the maturation of neuronal circuits. Here we performed serial analysis of gene expression (SAGE) on the SOC in 60-day-old Sprague-Dawley rats to identify genes specifically important for its function and to create a transcriptome reference for the subsequent identification of age-related or disease-related changes. Sequencing of 31 035 tags identified 10 473 different transcripts. Fifty-seven per cent of the unique tags with a count greater than four were statistically more highly represented in the SOC than in the hippocampus. Among them were genes encoding proteins involved in energy supply, the glutamate/glutamine shuttle, and myelination. Approximately 80 plasma membrane transporters, receptors, channels, and vesicular transporters were identified, and 25% of them displayed a significantly higher expression level in the SOC than in the hippocampus. Some of the plasma membrane proteins were not previously characterized in the SOC, e.g. the purinergic receptor subunit P2X₆ and the metabotropic GABA receptor Gpr51. Differential gene expression between SOC and hippocampus was confirmed using RNA in situ hybridization or immunohistochemistry. The extensive gene inventory presented here will alleviate the dissection of the molecular mechanisms underlying specific SOC functions and the comparison with other SAGE libraries from brain will ease the identification of promoters to generate region-specific transgenic animals. The analysis will be part of the publicly available database ID-GRAB.