Oral Session

Oral Session 3 一般口演3

O3-1 A novel approach to visualize optogenetics-induced structural changes of axonal fibers; A Opto-DTI study オプトジェネティクスにより誘導された軸索構造変化の新規可視化技術 Abe Yoshifumi（阿部欣史）¹，小牧裕司²，岡野栄之³，田中謙二¹ ¹Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan ²Live Imaging Center, Central Institute for Experimental Animals, Kawasaki, Japan ³Department of Physiology, Keio University School of Medicine, Tokyo, Japan Imaging techniques to visualize a structural change in axonal fibers is limited. Diffusion tensor imaging (DTI) is a suitable imaging tool to visualize the neural structural change over a whole brain. Our hypothesis is that an optogenetics long-term activation is changed to neural structural information about fibers and/or myelin. In this study, we demonstrated a novel technique of “Opto-DTI” to detect the optogenetics-induced structural changes of axonal fibers. Then, the induced structural change was validated by a super-resolution microscopy (SRM). Our target is the striatonigral (SN) tract which consists of unmyelinated axons of striatal medium-spiny neurons (MSNs) and cortical myelinated axons. The one-week optogenetic stimulation was conducted to the dorsal striatum (dStr) of mice which express a ChR2-YFP in MSNs. DTI images were acquired with their fixed brains after stimulation using to calculate a fractional anisotropy (FA) value. The stimulation decreased FA in the ipsilateral dStr as well as substantia nigra reticular (SNr), which indicated structural changes of axonal fibers and/or myelin. A fiver tracking technique of DTI also visualized the decrease in the ipsilateral SN tract. Next, we observed fine structural changes at the dStr and the SNr with the SRM. This microscopy observation showed the decrease in the diameters of YFP positive axons of MSNs. In addition, we detected the decrease in the diameter of myelin proteolipid protein (PLP) positive axons, while we found no change in PLP positive myelin thickness. These results showed that the optogenetics stimulation to MSNs induced the structural changes of their axons and the cortical axons. We proposed Opto-DTI as a novel imaging technique to visualize the structural changes of axonal fibers.		O3-2 CD38 is Required for Dendritic Organization in Visual Cortex and Hippocampus 視覚野および海馬の樹状突起形成におけるCD38の役割 Matsuzaki Hideo（松崎秀夫） Research Center for Child Mental Development, University of Fukui Morphological screening of mouse brains with known behavioral deficits can give great insight into the relationship between brain regions and their behavior. Oxytocin- and CD38-deficient mice have previously been shown to have behavioral phenotypes, such as restrictions in social memory, social interactions, and maternal behavior. CD38 is reported as an autism spectrum disorder (ASD) candidate gene and its behavioral phenotypes may be linked to ASD. To address whether these behavioral phenotypes relate to brain pathology and neuronal morphology, here we investigate the morphological changes in the CD38-deficient mice brains, with focus on the pathology and neuronal morphology of the cortex and hippocampus, using Nissl staining, immunohistochemistry, and Golgi staining. No difference was found in terms of cortical layer thickness. However, we found abnormalities in the number of neurons and neuronal morphology in the visual cortex and dentate gyrus (DG). In particular, there were arborisation differences between CD38-/- and CD38+/+ mice in the apical dendrites of the visual cortex and hippocampal CA1 pyramidal neurons. The data suggest that CD38 is implicated in appropriate development of brain regions important for social behavior.

O3-3 Correlation between organelle dynamics and apical dendrite patterning of neocortical neurons 大脳皮質神経細胞の樹状突起パターニングにおける細胞内小器官の関与 Gonda Yuko（権田裕子）¹，石　龍徳¹，花嶋かりな² ¹Dept Histology and Nuroanatomy, Tokyo Med Univ, Tokyo, Japan ²Lab. Dev. Biol., Waseda University, Tokyo, Japan In the neocortex, neurons of each layer exhibit high diversity in their dendritic patterning. Excitatory neurons, which represent around 80% of neocortical neurons, can be divided into two subtypes according to the morphology of apical dendrites; pyramidal cells and spiny stellate cells. During development, these neurons are born in the ventricular zone and migrate toward the surface of the cortical plate. Upon arrival beneath the marginal zone, neurons terminate their migration and undergo changes in their morphology and establish specific dendritic patterns. Here, we focus on pyramidal neurons, which represent the major class and retain a single apical dendrite with multiple basal dendrites. It has been considered that several molecules are required for their proper differentiation, however, the mechanisms by which a single apical dendritic establish remains unknown. We previously reported that suppression of roundabout (Robo)1, one of the axon guidance molecules expressed in neocortical layers 2/3 neurons, causes extension of multiple apical neurites from the soma during the postnatal week. To investigate the cellular mechanisms underlying these morphological changes, we examined the cytoskeletal dynamics during dendritic establishment. Our results indicate that the establishment of apical dendrite in pyramidal neurons requires a two-step regulation of dendritic Golgi, through the stabilization of Golgi via Cullin5 molecule and extension of Golgi into the primary dendrite mediated by Robo1 signaling.