The emergence of the uniquely human α7 nicotinic acetylcholine receptor gene and its roles in inflammation

The uniquely human CHRFAM7A gene is evolved from the fusion of two partially duplicated genes, ULK4 and CHRNA7. Transcription of CHRFAM7A gene produces a 1256-bp open reading frame (ORF) that encodes duplicate α7-nAChR (dup-α7-nAChR), in which a 27-aminoacid peptide derived from ULK4 gene replaces the 146-aminoacid N-terminal extracellular domain of α7-nAChR, and the rest protein domains are exactly the same as those of α7-nAChR. In vitro, dup-α7-nAChR has been shown to form hetero-pentamer with α7-nAChR and dominant-negatively inhibits the channel functions of the latter. α7-nAChR has been shown to participate in many pathophysiological processes such as cognition, memory, neuronal degenerative disease, psychological disease, and inflammatory diseases, among others, and thus has been extensively exploited as potential therapeutic targets for many diseases. Unfortunately, many lead compounds that showed potent therapeutic effect in preclinical animal models failed clinical trials, suggesting the possibility that the contribution of the uniquely human CHRFAM7A gene may not be accounted for in the preclinical research. Here, we review the emergence of CHRFAM7A gene and its transcriptional regulation, the regulatory roles of CHRFAM7A gene in α7-nAChR-mediated cholinergic anti-inflammatory pathway, and the potential implications of CHRFAM7A gene in translational research and drug discovery.