Comparative analysis of spatial expression patterns of ectopic olfactory receptors

Background: The oral mucosa comprises anatomically and functionally distinct regions that differ in their degree of keratinization and barrier properties. Ectopic olfactory receptors (OR) have been detected in the oral mucosa. However, their expression patterns and potential roles remain poorly understood. Objective: This study aimed to characterize the molecular features and regional differences of structurally and functionally distinct oral mucosal tissues through unbiased transcriptomic analysis, and to explore the potential involvement of ectopic ORs as chemosensory components within this context. Methods: Gingival, buccal, and palatal mucosal tissues were collected by full-thickness excision from 8-week-old adult mice. Total RNA was extracted and sequenced. Differentially expressed genes (DEGs) and expression patterns were analyzed via bioinformatic approaches, and selected genes were validated by RT-qPCR. Results: Buccal, gingival, and palatal epithelia exhibited distinct transcriptional profiles, with gingiva and palate showing higher mutual correlation compared with buccal mucosa. Buccal tissue was enriched for genes associated with muscle activity and cytoskeletal organization, whereas genes related to keratinization and epithelial differentiation related genes were relatively underrepresented. Pairwise differential expression analysis indicated greater molecular divergence between buccal and masticatory mucosa than between gingiva and palate. Pattern-based transcriptomic analysis defined a global expression topology across oral mucosal tissues, in which ectopic ORs and associated genes were nonrandomly distributed. Several ORs displayed tissue-biased expression patterns linked to keratinization, calcium signaling, and GPCR-related pathways. Conclusion: These findings demonstrate that buccal, gingival, and palatal epithelia constitute transcriptionally and functionally distinct compartments of the oral mucosa. The regional embedding of ectopic ORs within tissue-specific expression architecture suggests a potential role for chemosensory mechanisms in shaping site-specific physiological responses, providing a molecular framework for understanding chemical sensing in the oral mucosa.