Consolidation and maintenance of Drosophila long-term memory require LIM homeodomain protein Apterous in distinct brain neurons

The LIM-homeodomain (LIM-HD) transcription factor Apterous (Ap) and its cofactor Chip (Chi) form a complex that regulates various developmental events in Drosophila. Although Ap continues to be expressed in the adult brain, the functions of the centrally expressed Ap remain incompletely understood. Here, we show that Ap and Chi in the Drosophila memory center, the mushroom bodies (MBs), are indispensable for long-term memory (LTM) maintenance, whereas Ap in a subset of clock neurons [large ventral-lateral neurons (l-LNvs)] plays a crucial role in memory consolidation in a Chi-independent manner. Ex vivo imaging revealed that Ap, but not Chi, in l-LNvs is essential for the appropriate Cl- responses to GABA. Furthermore, knockdown of GABAA receptor in l-LNvs compensated for the impairment of memory consolidation in ap null mutant flies. Our results indicate that Drosophila Ap functions differently in l-LNvs and MBs, and it contributes to the consolidation and maintenance of LTM.