Effects of Genetic Mutation Sites in ADR Genes on Modern Chickens Produced and Domesticated by Artificial Selection

SIMPLE SUMMARY: Nine types of complete adrenergic receptor (ADR) gene sequences were analyzed, wherein twenty-four specific mutation sites were found as a result of the artificial selection of Shaver Brown and Shamo chickens. From the analysis, Shamo- and Shaver Brown-specific mutations, and those common to both breeds, could be separated into three groups. The results confirmed that eight mutation sites may be affected by artificial selection. Furthermore, the evolutionary analysis revealed that the identified mutations were not ancestral. These results confirmed that the eight mutations at these sites were artificially selected by domestication and breed specificity. N(ST) population analysis confirmed that there is a difference in the degree of genetic differentiation between the two populations. In particular, the N(ST) rate of ADRA1D (0.064) was most affected by artificial selection. This suggests that these mutations may exert different effects on vasoconstriction, smooth muscles, and the action of the digestive system relevant to the breed’s specific characteristics. ABSTRACT: Associations between neurotransmitters, adrenergic receptor (ADR) mutations, and behaviors in chickens produced and domesticated by artificial selection remain unclear. This study investigates the association of neurotransmitters and ADR mutations with egg laying and cockfighting—behaviors associated with significantly different breeding backgrounds—in Shaver Brown and Shamo chickens. Accordingly, the whole sequences of nine ADR genes were determined, and nine amino acid-specific mutation sites from five genes (ADRα1A: S365G, ADRα1D: T440N, ADRα2A: D273E, ADRβ1: N443S, S445N, ADRβ3: R342C, Q404L, and P406S) were extracted. Evolutionary analysis showed that these mutations were not ancestrally derived. These results confirm that the mutations at these sites were artificially selected for domestication and are breed specific. N(ST) population analysis confirmed a difference in the degree of genetic differentiation between the two populations in seven genes. The results further confirm differences in the degree of genetic differentiation between the two populations in Shaver Brown (ADRA1B and ADRA1D) and Shamo (ADRA1A and ADRA2B) chickens, indicating that the ADR gene differs between the two breeds. The effects of artificial selection, guided by the human-driven selection of desirable traits, are reflected in adrenaline gene mutations. Furthermore, certain gene mutations may affect domestication, while others may affect other traits in populations or individuals.