Research

My research interest is centered around the functional dissection of sensory-to-motor transformation, combining developmental and evolutionary perspectives. Below is a brief description of my current/past projects.

Evolution of olfactory circuits in drosophilids

Neuroscientists strive to learn the “general principles” on how the brain works, but how do we know if a given feature of the nervous system is unique to its host species (to meet their ecological niches) or is more general across species? I believe that comparative, cross-species approaches to elucidate how nervous systems adapt to confer animals with unique behaviors will be an effective complementary way to extract general principles of brain organization and function.

In this project, I study the central olfactory circuts in Drosophila sechellia, a fly species endemic to the Seychelles archipelago. Drosophila sechellia is specialized to Morinda citrifolia, or noni fruit, which emits a pungent odor that is attractive for this species but not for its cousin species Drosophila melanogaster. Taking advantage of the shifted behavioral output despite the similarity of their nervous sytems, I compare the central olfactory circuits to elucidate how neuronal circuits evolve to enable behavioral adaptation and to understand the general principle of sensory processing.

 

Wiring and miswiring of sensorimotor circuits in Drosophila larvae

Adaptive behavior of an animal is underpinned by the complex yet precise connectivity of its nervous system. The connectivity of a neuron within the network is established through precise neurite guidance and synapse formation mechanisms, which give rise to the unique shape of individual neurons. How does this “shape” impact behavior?

In this project, I study the molecular mechanisms underlying the segment-specific axon guidance of Wave neurons (see below) and the effect of their manipulation on behavioral regulation. We found that manipulation of one gene in Wave neurons suffices to rewire the tactile circuit and induce different behavior in response to tactile inputs. 

For details, see the following preprint:

Takagi S, Takano S, Morise S, Zeng X, Nose A. Segment-Specific Axon Guidance by Wnt/Fz Signaling Diversifies Motor Commands in Drosophila Larvae. Available at SSRN: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3990386

Segment-specific sensorimotor processing in Drosophila larvae

Sensory inputs of the same modality often elicit distinct behaviors depending on the location thereof. For instance, many animal species perform backward movement in response to head touch but perform forward movement to tail touch. How is the location-specificity realized in the brain? We showed that, in fruit fly Drosophila larvae, a class of segmentally-repeated interneurons (named Wave neurons) match their tactile receptive fields to appropriate motor programs by participating in different circuits in different segments. 

For details, see the following publication:

Takagi S, Cocanougher BT, Niki S, Miyamoto D, Kohsaka H, Kazama H, Fetter RD, Truman JW, Zlatic M, Cardona A, Nose A. Divergent Connectivity of Homologous Command-like Neurons Mediates Segment-Specific Touch Responses in Drosophila. Neuron. 2017 Dec 20;96(6):1373-1387.e6. doi: 10.1016/j.neuron.2017.10.030. Epub 2017 Nov 30. PMID: 29198754.