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視覚 1
Visual System 1

開催日 2014/9/11
時間 15:00 - 16:00
会場 Room G(303)
Chairperson(s) 大澤 五住 / Izumi Ohzawa (大阪大学大学院生命機能研究科 / Graduate School of Frontier Bioscience, Osaka University, Japan)
立花 政夫 / Masao Tachibana (東京大学大学院人文社会系研究科 / Graduate School of Humanities and Sociology, University of Tokyo Faculty of Letters, Japan)

Single cell mapping of the neuronal circuitry for the biological clock in the suprachiasmatic nucleus

  • O1-G-1-3
  • Yi-Ting Chang:1 Chi-Chan Lee:1 Shih-Kuo Chen:1 
  • 1:Department of Life Science, National Taiwan University, Taiwan 

In the mammalian retina, a small subset of retinal ganglion cells which expresses the photopigment melanopsin was discovered recently. This novel photoreceptor known as intrinsically photosensitive retinal ganglion cells (ipRGCs) can receive light signals from both autonomous melanopsin and classical photoreceptors rods/cones. The brain targets of ipRGCs include the suprachiasmatic nuclei (SCN) for circadian photoentrainment and the olivary pretectal nuclei for pupil light reflex. The SCN is the mammalian master clock which coordinate circadian rhythm throughout the body. Based on differential expression of neuropeptides, the SCN can be divided into two subdivisions, the ventro-lateral SCN (vlSCN) and the dorso-medial SCN (dmSCN). Several studies have demonstrated that the ipRGCs fully innervate the whole SCN. Moreover, the input of contralateral and ipsilateral sides of the SCN from ipRGCs is about equal, while the contralateral input of the lateral geniculate nucleus (LGN) from regular retinal ganglion cells (RGCs) for image forming functions is about 90%. The overall projection map of ipRGCs has been extensively studied recent years; however, the detail innervation pattern in a single cell level remain to be determined. Here, we randomly labeled a single ipRGC through a genetic mouse model, and analyzed their dendritic structure in the retina and axonal architecture in the SCN. We showed that ipRGCs, according to the projection patterns in the SCN, can classified into two groups, unilateral and bilateral ipRGCs, and both of them had similar dendritic morphology. Moreover, the bilateral ipRGCs contribute to increase in the projection to ipsilateral side of the SCN; therefore, the input of the SCN is bilateral symmetry. In addition, a single ipRGC preferentially innervated a specific region of the SCN, such as the vlSCN and the dmSCN. These results demonstrate that a single ipRGC innervates to the SCN in a various way and this diverge projection pattern reveals the complexity of the neuronal circuitry to control the circadian rhythm.

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