Genetic basis of state-dependent courtship sounds in inbred mice

Courtship behaviors consist of two phases, namely the appetitive and consummatory states. Despite the long history of the concept, few studies have been done regarding the genetic contribution on those two different phases. Male mice are known to produce distinct ultrasonic vocalizations (USVs) as they progress through courtship states1-14, and these courtship sounds also show strain-specific differences15-18. Here, we delved into USV syllable patterns emitted during specific courtship actions using inbred mouse strains and their progeny: C57BL/6J (B6) mice, 129S4/SvJae (129) mice, and their second filial generation (F2) offspring of mixed genetic backgrounds. B6, 129, and F2 mice generated similar USV syllables during mounting behavior. In contrast, B6 and 129 mice showed different USV syllable patterns during body and anogenital sniffing behavior, and the USV syllable usage of F2 mice in this courtship state diverged according to the degree of genetic similarity with B6 or 129 mice. From these results, we propose that differential selection pressures19-20 favored diversity in appetitive behavior but conservation in consummatory behaviors.