DISCO Interacting Protein 2 regulates axonal bifurcation and guidance of Drosophila mushroom body neurons

Abstract

Axonal branching is one of the key processes within the enormous complexity of the nervous system to enable a single neuron to send information to multiple targets. However, the molecular mechanisms that control branch formation are poorly understood. In particular, previous studies have rarely addressed the mechanisms underlying axonal bifurcation, in which axons form new branches via splitting of the growth cone. We demonstrate that DISCO Interacting Protein 2 (DIP2) is required for precise axonal bifurcation in Drosophila mushroom body (MB) neurons by suppressing ectopic bifurcation and regulating the guidance of sister axons. We also found that DIP2 localize to the plasma membrane. Domain function analysis revealed that the AMP-synthetase domains of DIP2 are essential for its function, which may involve exerting a catalytic activity that modifies fatty acids. Genetic analysis and subsequent biochemical analysis suggested that DIP2 is involved in the fatty acid metabolization of acyl-CoA. Taken together, our results reveal a function of DIP2 in the developing nervous system and provide a potential functional relationship between fatty acid metabolism and axon morphogenesis.

Functional prediction and characterization of Dip2 gene in mice

“…As the species evolved, three members (DIP2A, B and C) of the DIP protein family emerged in higher animals, for example, in zebrafish, mouse and human. Our results further support a previous report in which acyl-CoA levels were reduced in DIP2 mutant Drosophila (Nitta et al, 2016). However, no any experimental evidence for this has yet been provided.…”

“…These results confirm DIP2A as a member of the AFD Class I superfamily that possess the ability to bind AMP and catalyze ATP-dependent acyl-CoA formation. Our results further support a previous report in which acyl-CoA levels were reduced in DIP2 mutant Drosophila (Nitta et al, 2016). DIP2A is reported as a potential cell membrane receptor for a secreted protein, follistatin-like 1 (FSTL1) (Ouchi et al, 2010;Tanaka et al, 2010).…”

“…The Drosophila melanogaster (fruit fly) homolog, DISCO interacting protein 2 (DIP2) gene, was first cloned in-frame from an embryonic cDNA library by the bait of disconnected (disco) cDNA (Mukhopadhyay et al, 2002). DIP2 is required for acyl-CoA metabolism because the level of acyl-CoA in DIP2 mutant fruit fly is decreased, which disturbed the precise axonal bifurcation in Drosophila mushroom body neurons (Nitta et al, 2016). Drosophila homolog of c-Jun N-terminal kinase (JNK), basket (Bsk), activates DIP2 expression that modulates the direction of axon projection (Nitta and Sugie, 2017).…”

DIP2B Interacts With α-Tubulin to Regulate Axon Outgrowth

“…Recent studies in flies and worms indicate that DIP2 is required for axonal guidance during early developmental stages and regeneration in mature neurons (Nitta et al, 2017;Noblett et al, 2019). To determine the role of DIP2B in neurite outgrowth, we quantified axonal outgrowth and branching in cultured hippocampal neurons.…”

“…In Caenorhabditis elegans, DIP2 is critical to axonal regeneration in mature neurons (Noblett et al, 2019). Moreover, DIP2 regulates axonal bifurcation of mushroom body neurons in Drosophila (Nitta et al, 2017). Mammals express three DIP2 genes (DIP2A, DIP2B, and DIP2C) each of which shares highly conserved functional domains and have similar roles in acetyl-coenzyme (acetyl-CoA) synthesis .…”