Biology subjects

Hakeda-Suzuki, S.

Publications and source records attributed to Hakeda-Suzuki, S..

4 recordsLinked to original sources

bioRxiv2023

Complex Formation of Immunoglobulin Superfamily Molecules Side-IV and Beat-IIb Regulates Synaptic Specificity in the Drosophila Visual System

Neurons establish specific synapses based on the adhesive properties of cell-surface proteins, while also retaining the ability to form synapses in a relatively non-selective manner. However, the comprehensive understanding of the underlying mechanism reconciling these opposing characteristics remains incomplete. Here, we have identified Side-IV/Beat-IIb, members of the Drosophila immunoglobulin superfamily, as a novel combination of cell-surface recognition molecules inducing synapse formation. The Side-IV/Beat-IIb combination transduces bifurcated signaling with Side-IVs co-receptor, Kirre, and a synaptic scaffold protein, Dsyd-1. Genetic experiments and subcellular protein localization analyses showed the newly characterized Side-IV/Beat-IIb/Kirre/Dsyd-1 complex to have two essential functions. First, it narrows neuronal binding specificity through Side-IV/Beat-IIb extracellular interactions. Second, it recruits synapse formation factors, Kirre and Dsyd-1, to restrict synaptic loci and inhibit miswiring. This dual function explains how the combinations of cell-surface molecules enable the ranking of preferred interactions among neuronal pairs to achieve synaptic specificity in complex circuits in vivo.

neuroscience↗

bioRxiv2023

Drosophila model to clarify the pathological significance of OPA1 in autosomal dominant optic atrophy

Autosomal dominant optic atrophy (DOA) is a progressive form of blindness caused by degeneration of retinal ganglion cells and their axons, mainly caused by mutations in the OPA1 mitochondrial dynamin like GTPase (OPA1) gene. OPA1 encodes a dynamin-like GTPase present in the mitochondrial inner membrane. When associated with OPA1 mutations, DOA can present not only ocular symptoms but also multi-organ symptoms (DOA plus). DOA plus often results from point mutations in the GTPase domain, which are assumed to have dominant negative effects. However, the presence of mutations in the GTPase domain does not always result in DOA plus. Therefore, an experimental system to distinguish between DOA and DOA plus is needed. In this study, we found that loss-of-function mutations of the dOPA1 gene in Drosophila can imitate the pathology of optic nerve degeneration observed in DOA. We successfully rescued this degeneration by expressing the human OPA1 (hOPA1) gene, indicating that hOPA1 is functionally interchangeable with dOPA1 in the fly system. However, mutations previously identified did not ameliorate the dOPA1 deficiency phenotype. By expressing both WT and DOA plus mutant hOPA1 forms in the optic nerve of dOPA1 mutants, we observed that DOA plus mutations suppressed the rescue, facilitating the distinction between loss-of-function and dominant negative mutations in hOPA1. This fly model aids in distinguishing DOA from DOA plus and guides initial hOPA1 mutation treatment strategies.

pathology↗

bioRxiv2021

MeDUsA: A novel system for automated axon quantification to evaluate neuroaxonal degeneration

BackgroundDrosophila is an excellent model organism for studying human neurodegenerative diseases (NDs), and the rough eye phenotype (REP) assay is a convenient experimental system for analysing the toxicity of ectopically expressed human disease genes. However, the association between REP and axonal degeneration, an early sign of ND, remains unclear. To address this question, we developed a method to evaluate axonal degeneration by quantifying the number of retinal R7 axons in Drosophila; however, it requires expertise and is time-consuming. Therefore, there is a need for an easy-to-use software that can automatically quantify the axonal degeneration. ResultWe created MeDUsA (a method for the quantification of degeneration using fly axons), which is a standalone executable computer program based on Python that combines a pre-trained deep-learning masking tool with an axon terminal counting tool. This software automatically quantifies the number of axons from a confocal z-stack image series. Using this software, we have demonstrated for the first time directly that axons degenerate when the causative factors of NDs (Syn, Tau, TDP-43, HTT) were expressed in the Drosophila eye. Furthermore, we compared axonal toxicity of the representative causative genes of NDs and their pathological alleles with REP and found no significant correlation between them. ConclusionsMeDUsA rapidly and accurately quantifies axons in Drosophila eye. By simplifying and automating time-consuming manual efforts requiring significant expertise, it enables large-scale, complex research efforts on axonal degeneration, such as screening to identify genes or drugs that mediate axonal toxicity caused by ND disease proteins.

pathology↗

bioRxiv2020

Glial insulin regulates cooperative or antagonistic Golden goal/Flamingo interactions during photoreceptor axon navigation

Transmembrane protein Golden goal (Gogo) interacts with the atypical cadherin Flamingo to direct R8 photoreceptor axons in the Drosophila visual system. However, the precise mechanisms underlying Gogo regulation during columnar- and layer-specific R8 axon targeting are unknown. Our studies demonstrated that the insulin secreted from surface and cortex glia switches the phosphorylation status of Gogo, thereby regulating its two distinct functions in this process. Nonphosphorylated Gogo mediates the initial recognition of the glial protrusion in the center of the medulla column, whereas phosphorylated Gogo suppresses horizontal filopodia extension by counteracting Flamingo to maintain one axon to one column ratio. Later, Gogo expression ceases during the midpupal developmental stage, thus allowing R8 filopodia to extend vertically into the M3 layer. These results demonstrate that the long- and short-range signaling between the glia and R8 axon growth cones regulates growth cone dynamics in a stepwise manner, and thus shape the entire organization of the visual systems functional neuronal circuit.

neuroscience↗