| Summary: | The G protein‐coupled receptor family C, group 6, member A (GPCR6A) and the calcium‐sensing receptor (CaSR) belong to the GPCRs family C and play a crucial role in sensing amino acids in the mammalian gastrointestinal (GI)‐tract. These receptors, located in the enteroendocrine cells facing the GI‐tract lumen, are activated by dietary amino acids, which stimulate the release of gut hormones leading to the regulation of diverse physiological functions, including digestion, absorption, allocation of substrates for growth, feed intake, etc. While it is established that these receptors play a key role in amino acid sensing in mammals, there is little information in teleosts, including Atlantic salmon ( Salmo salar L.). The Atlantic salmon is a key commercial species in global aquaculture and provides an excellent model to study the fate of duplicated genes due to the salmonid‐specific 4 th round of whole genome duplication. In the Atlantic salmon genome database we have identified at least three gpcr6a genes, named here gpcr6a‐like 1, ‐like 2 and –like 3 . While GPCR6A‐like 1 and ‐like 2 share 93% of similarity at the amino acid level, both only share 46% of similarity with GPCR6A‐like 3. The Atlantic salmon gpcr6a exon‐intron diverges significantly from the mammalian homologue gene, however the 2D topology is well‐conserved. Regarding the Atlantic salmon CaSR, one casr gene in the chromosome (chr) ssa11 was identified and it shared a high similarity (78 %) with the human homologue. In addition, several other casr genes were found in Atlantic salmon, located in unplaced scaffolds and in the chr ssa9 and chr ssa20, which suggests that tandem duplication of casr have occurred in these chromosomes. Further, we have started to investigate the spatial mRNA expression profile for all the salmon gpcr6a transcripts and the casr transcript in chr ssa11 in several tissues, including different regions of the GI‐tract. Preliminary results indicate that these receptors are present in the oropharyngeal area, and, even though in ...
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