Comparative microarray analyses between the rat superior olivary complex and the brain

To investigate the participation of deafness genes in the genetic program of the superior olivary complex (SOC), a prominent auditory brainstem center, we performed a comparative genome-wide microarray based gene expression analysis of the rat SOC and the rat brain at postnatal days (P) P4 and P25. Data were validated by qRT-PCR. Statistical analyses revealed 912 oligos up-regulated in the SOC at P4 and 1609 at P25. A total of 453 oligos were up-regulated in the SOC at both developmental stages. Subsequently, a list of 138 transcripts associated with hearing-impairment was extracted from publically available databases and literature. 26 of these transcripts were present in SOC-related gene signature lists, whereas only 11 were present in brain-related gene signature lists. Furthermore, in all 3 SOC-related gene signature lists, transcripts associated with hearing impairment were significantly enriched. Finally, there was a tendency of the SOC-related genes to map to human deafness loci with unknown etiology. Altogether, our study identified a tight genetic link between the SOC-related genetic program and deafness genes. The genome wide expression during the postnatal development of the SOC and the brain was investigated at two different time points: at postnatal (P) day 4 (before hearing onset) and at P25 (after hearing onset). Samples were hybridized onto two color platforms. At least 6 up to nine biological replicates per sample were performed.