Adult expression of the cell adhesion protein Fasciclin 3 is required for the maintenance of adult olfactory interneurons

The proper functioning of the nervous system is dependent on the establishment and maintenance of intricate networks of neurons that form functional neural circuits. Once neural circuits are assembled during development, a distinct set of molecular programs is likely required to maintain their connectivity throughout the lifetime of the organism. Here, we demonstrate that Fasciclin 3 (Fas3), an axon guidance cell adhesion protein, is necessary for the maintenance of the olfactory circuit in adult Drosophila. We utilized the TARGET system to spatiotemporally knockdown Fas3 in selected populations of adult neurons. Our findings show that Fas3 knockdown results in the death of olfactory circuit neurons and reduced survival of adults. We also demonstrated that Fas3 knockdown activates caspase-3 mediated cell death in olfactory local interneurons, which can be rescued by overexpressing p35, an anti-apoptotic protein. This work adds to the growing set of evidence indicating a critical role for axon guidance proteins in the maintenance of neuronal circuits in adults. SUMMARY STATEMENTLittle is known about the maintenance of adult neural circuits. We show that the continuous expression of Fasciclin 3, a cell adhesion protein involved in axon guidance, is required for neuronal survival in the adult olfactory circuit.