longitudinals lacking (lola) is among the most complex genes in Drosophila melanogaster, encoding up to 20 different protein isoforms and acting as a key transcription factor in axonal pathfinding and neural reprograming. To better characterize Lola function we have generated specific mutations in each isoform using the CRISPR/Cas9 system. Our targeted screen allows us to revisit the previously demonstrated roles for few isoforms, to assign known functions to specific isoforms and to reveal a critical role for a specific variant in the octopaminergic pathway. Thus, our comprehensive study expands the repertoire of Lola functions, and demonstrates that the CRISPR/Cas9 approach is a valuable tool to systematically address the role of complex loci in vivo. Overall design: Embryos were collected for two hours at 25°C and subsequently developed for 20 hours, collected and frozen. Genomic DNA was isolated,RNAseA treated and DpnI digested. DamID adaptors were ligated to DpnI digested DNA followed by DpnII digestion PCR amplification, sonication and removal of DamID adaptors.Libraries were generated using the NebNext Ultra II DNA Library Kit. Libraries were sequenced on a NextSeq 500.