Identification of candidate genes involved in somatosensory functions of cranial sensory ganglia.

We have shown that the characteristics of tissue trees obtained by the hierarchical cluster analysis of DNA microarray data suggest the cellular expression patterns of genes in the gene clusters [J. Neurosci. Res. 74 (2003) 818]. We here identified three gene clusters containing 11 genes as a potential pool of candidate genes related to somatosensation in cranial structures such as the face, oral cavity and pharynx. To obtain the cellular expression profiles, eight genes other than three genes analyzed previously were subjected to in situ hybridization analysis. The results show that all of the 11 profiles are roughly similar and suggest that the positive cells are probably somatosensory neurons in two cranial sensory ganglia, the trigeminal and petrosal ganglia. The expression profiles and probable physiological functions of the 6 genes such as trkA, NaN and galanin suggest their direct involvement in specific somatosensory functions such as nociception. The function of another gene, calretinin, is putatively related to mechanosensation and proprioception. The roles of the remaining four genes, including aquaporin 1 and two EST clones, in sensory neurons are unknown, and may provide clues to understand the sensory function in TG and PG.