In most regions with a temperate climate, four seasons cycle through the year. Since seasonal changes significantly affect environmental conditions, animals living in these regions need to adapt to these changes. To cope with seasonal environmental changes, many animals adapt their physiology and behavior in response to photoperiod. This phenomenon is called photoperiodism. Although photoperiodism has been known for decades, the molecular mechanisms of photoperiodism are not fully understood.
 To further understand the mechanisms of seasonal adaptation in vertebrates, we use Japanese medaka (Oryzias latipes) as a model because of its highly sophisticated seasonal responses. In the previous research, we conducted genome-wide gene expression analysis using time-series samples of brain transitioned from short-day to long-day conditions and found 1,249 transcripts expression were changed by long-day stimulus. Including these transcripts, we found an uncharacterized long non-coding RNA called LDAIR and demonstrated LDAIR regulates seasonal changes in stress responses behaviors (Nakayama et al., Nat Ecol Evol 2019). Furthermore, we found another novel gene whose expression was significantly changed between short-day and long-day conditions. Interestingly, although this gene is conserved in almost vertebrates except for some mammals, its function has not been clarified in any animal. In this presentation, I will introduce our current work on the analysis of this novel gene.