Or4n4, an olfactory receptor gene, belongs to the G-protein coupled seven-transmembrane-domain receptor supergene family. Initially thought to be only expressed in the olfactory epithelium, recent studies suggest a broader expression pattern. Olfactory receptors are crucial for the detection of volatile odorant molecules by olfactory sensory neurons, and their ectopic expression may imply additional functions in non-olfactory tissues [1].

One study found that Or4n4 showed exclusive expression in testis among the investigated tissues through analyzing mRNA-Seq data from multiple human tissues, which provides a basis for further functional studies [1]. Another study identified Or4n4 as one of the six commonly misregulated genes in a human thyroid epithelial cell line after exposure to high-dose γ-radiation. These genes are involved in apoptosis, the immune response, regulation of transcription, and receptor signaling pathways, indicating a potential role of Or4n4 in radiation-induced thyroid tumors [2]. In Prader-Willi syndrome, a subset of subjects with a larger type I deletion in the 15q11-q13 region had loss of Or4n4 along with other genes, suggesting its possible relation to this genetic disorder [3].

In conclusion, Or4n4, an olfactory receptor gene, has a tissue-specific expression pattern in testis. Its misregulation is associated with radiation-induced thyroid tumors and may be related to Prader-Willi syndrome due to gene deletion. Further functional studies, potentially including gene knockout models, could help to clarify its exact role in these biological processes and disease conditions.

References:

1. Flegel, Caroline, Manteniotis, Stavros, Osthold, Sandra, Hatt, Hanns, Gisselmann, Günter. 2013. Expression profile of ectopic olfactory receptors determined by deep sequencing. In PloS one, 8, e55368. doi:10.1371/journal.pone.0055368. https://pubmed.ncbi.nlm.nih.gov/23405139/

2. Bang, Hyun Soon, Choi, Moo Hyun, Kim, Cha Soon, Choi, Seung Jin. 2016. Gene expression profiling in undifferentiated thyroid carcinoma induced by high-dose radiation. In Journal of radiation research, 57, 238-49. doi:10.1093/jrr/rrw002. https://pubmed.ncbi.nlm.nih.gov/27006382/

3. Butler, Merlin G, Fischer, William, Kibiryeva, Nataliya, Bittel, Douglas C. . Array comparative genomic hybridization (aCGH) analysis in Prader-Willi syndrome. In American journal of medical genetics. Part A, 146A, 854-60. doi:10.1002/ajmg.a.32249. https://pubmed.ncbi.nlm.nih.gov/18266248/