PhysiologyI

Toshiki Kameyama

  (亀山 俊樹)

Profile Information

Affiliation
Associate Professor, Department of Physiology, School of Medicine, Fujita Health University
Degree
博士(理学)(名古屋大学)

Researcher number
60298544
ORCID ID
 https://orcid.org/0000-0002-7348-7572
J-GLOBAL ID
200901005394038415
researchmap Member ID
1000226784

External link

神経細胞の分化機構を研究しています。

 


Committee Memberships

 1

Papers

 28
  • Miho Kawata, Yu Kodani, Mahito Ohkuma, Ei-Ichi Miyachi, Yoko S Kaneko, Akira Nakashima, Hidetaka Suga, Toshiki Kameyama, Kanako Saito, Hiroshi Nagasaki
    PloS one, 17(11) e0276694, Nov, 2022  Peer-reviewed
    The hypothalamus is comprised of heterogenous cell populations and includes highly complex neural circuits that regulate the autonomic nerve system. Its dysfunction therefore results in severe endocrine disorders. Although recent experiments have been conducted for in vitro organogenesis of hypothalamic neurons from embryonic stem (ES) or induced pluripotent stem (iPS) cells, whether these stem cell-derived hypothalamic neurons can be useful for regenerative medicine remains unclear. We therefore performed orthotopic transplantation of mouse ES cell (mESC)-derived hypothalamic neurons into adult mouse brains. We generated electrophysiologically functional hypothalamic neurons from mESCs and transplanted them into the supraoptic nucleus of mice. Grafts extended their axons along hypothalamic nerve bundles in host brain, and some of them even projected into the posterior pituitary (PPit), which consists of distal axons of the magnocellular neurons located in hypothalamic supraoptic and paraventricular nuclei. The axonal projections to the PPit were not observed when the mESC-derived hypothalamic neurons were ectopically transplanted into the substantia nigra reticular part. These findings suggest that our stem cell-based orthotopic transplantation approach might contribute to the establishment of regenerative medicine for hypothalamic and pituitary disorders.
  • Yu Kodani, Miho Kawata, Hidetaka Suga, Takatoshi Kasai, Chikafumi Ozone, Mayu Sakakibara, Atsushi Kuwahara, Shiori Taga, Hiroshi Arima, Toshiki Kameyama, Kanako Saito, Akira Nakashima, Hiroshi Nagasaki
    Frontiers in Endocrinology, 13 941166-941166, Jul 12, 2022  Peer-reviewed
    Human stem cell-derived organoid culture enables the in vitro analysis of the cellular function in three-dimensional aggregates mimicking native organs, and also provides a valuable source of specific cell types in the human body. We previously established organoid models of the hypothalamic-pituitary (HP) complex using human pluripotent stem cells. Although the models are suitable for investigating developmental and functional HP interactions, we consider that isolated pituitary cells are also useful for basic and translational research on the pituitary gland, such as stem cell biology and regenerative medicine. To develop a method for the purification of pituitary cells in HP organoids, we performed surface marker profiling of organoid cells derived from human induced pluripotent stem cells (iPSCs). Screening of 332 human cell surface markers and a subsequent immunohistochemical analysis identified epithelial cell adhesion molecule (EpCAM) as a surface marker of anterior pituitary cells, as well as their ectodermal precursors. EpCAM was not expressed on hypothalamic lineages; thus, anterior pituitary cells were successfully enriched by magnetic separation of EpCAM+ cells from iPSC-derived HP organoids. The enriched pituitary population contained functional corticotrophs and their progenitors; the former responded normally to a corticotropin-releasing hormone stimulus. Our findings would extend the applicability of organoid culture as a novel source of human anterior pituitary cells, including stem/progenitor cells and their endocrine descendants.
  • Yu Kodani, Miho Kawata, Hidetaka Suga, Yoko S Kaneko, Akira Nakashima, Toshiki Kameyama, Kanako Saito, Hiroshi Nagasaki
    eNeuro, Apr 18, 2022  Peer-reviewed
    Hypothalamic melanin-concentrating hormone (MCH) neurons are important regulators of multiple physiological processes, such as sleep, feeding, and memory. Despite the increasing interest in their neuronal functions, the molecular mechanism underlying MCH neuron development remains poorly understood. We report that a three-dimensional culture of mouse embryonic stem cells (mESCs) can generate hypothalamic-like tissues containing MCH-positive neurons, which reproduce morphologic maturation, neuronal connectivity, and neuropeptide/neurotransmitter phenotype of native MCH neurons. Using this in vitro system, we demonstrate that Hedgehog (Hh) signaling serves to produce major neurochemical subtypes of MCH neurons characterized by the presence or absence of cocaine- and amphetamine-regulated transcript (CART). Without exogenous Hh signals, mESCs initially differentiated into dorsal hypothalamic/prethalamic progenitors and finally into MCH+CART+ neurons through a specific intermediate progenitor state. Conversely, activation of the Hh pathway specified ventral hypothalamic progenitors that generate both MCH+CART- and MCH+CART+ neurons. These results suggest that in vivo MCH neurons may originate from multiple cell lineages that arise through early dorsoventral patterning of the hypothalamus. Additionally, we found that Hh signaling supports the differentiation of mESCs into orexin/hypocretin neurons, a well-defined cell group intermingled with MCH neurons in the lateral hypothalamic area (LHA). The present study highlights and improves the utility of mESC culture in the analysis of the developmental programs of specific hypothalamic cell types.Significance StatementA growing body of literature has revealed the importance of hypothalamic melanin-concentrating hormone (MCH) neurons in energy homeostasis and the cognitive function, but their developmental biology remains relatively unknown. To establish a new approach for addressing this issue, we tested the ability of an in vitro differentiation system of mouse embryonic stem cells (mESCs) to recapitulate the development of MCH neurons. The mESC culture robustly generated MCH-positive neurons resembling native neurons in several aspects and provided evidence that Hedgehog (Hh) signaling is a key factor to produce neurochemical subtypes of MCH neurons. Our results demonstrate the suitability of mESC culture as a platform to study the molecular mechanisms underlying the development of MCH neurons and possibly of other hypothalamic cell types.
  • Huey-Huey Chua, Toshiki Kameyama, Akila Mayeda, Te-Huei Yeh
    International journal of molecular sciences, 23(5), Feb 24, 2022  Peer-reviewed
    Tumor viruses gain control of cellular functions when they infect and transform host cells. Alternative splicing is one of the cellular processes exploited by tumor viruses to benefit viral replication and support oncogenesis. Epstein-Barr virus (EBV) participates in a number of cancers, as reported mostly in nasopharyngeal carcinoma (NPC) and Burkitt lymphoma (BL). Using RT-nested-PCR and Northern blot analysis in NPC and BL cells, here we demonstrate that EBV promotes specific alternative splicing of TSG101 pre-mRNA, which generates the TSG101∆154-1054 variant though the agency of its viral proteins, such as EBNA-1, Zta and Rta. The level of TSG101∆154-1054 is particularly enhanced upon EBV entry into the lytic cycle, increasing protein stability of TSG101 and causing the cumulative synthesis of EBV late lytic proteins, such as VCA and gp350/220. TSG101∆154-1054-mediated production of VCA and gp350/220 is blocked by the overexpression of a translational mutant of TSG101∆154-1054 or by the depletion of full-length TSG101, which is consistent with the known role of the TSG101∆154-1054 protein in stabilizing the TSG101 protein. NPC patients whose tumor tissues express TSG101∆154-1054 have high serum levels of anti-VCA antibodies and high levels of viral DNA in their tumors. Our findings highlight the functional importance of TSG101∆154-1054 in allowing full completion of the EBV lytic cycle to produce viral particles. We propose that targeting EBV-induced TSG101 alternative splicing has broad potential as a therapeutic to treat EBV-associated malignancies.
  • Otani, Yuta, Fujita, Ken-ichi, Kameyama, Toshiki, Mayeda, Akila
    International Journal of Molecular Sciences, 22(12) 6519, Jun, 2021  Peer-reviewedCorresponding author
    <title>Abstract</title>Using the TSG101 pre-mRNA, we previously discovered cancer-specific re-splicing of mature mRNA that generates aberrant transcripts/proteins. The fact that mRNA is aberrantly re-spliced in various cancer cells implies there must be an important mechanism to prevent deleterious re-splicing on the spliced mRNA in normal cells. We thus postulated that the mRNA re-splicing is controlled by specific repressors and we searched for repressor candidates by siRNA-based screening for mRNA re-splicing activity. We found that knock-down of EIF4A3, which is a core component of the exon junction complex (EJC), significantly promoted mRNA re-splicing. Remarkably, we could recapitulate cancer-specific mRNA re-splicing in normal cells by knock-down of any of the core EJC proteins, EIF4A3, MAGOH or RBM8A (Y14), implicating the EJC core as the repressor of mRNA re-splicing often observed in cancer cells. We propose that the EJC core is a critical mRNA quality control factor to prevent over-splicing of mature mRNA.

Misc.

 26

Books and Other Publications

 2

Presentations

 15

Teaching Experience

 15
  • Apr, 2024 - Present
    Medical Physiology Seminar  (Fujita Health University Graduate school school of Health Research, Fujita Health University)
  • Apr, 2024 - Present
    人体機能学概論  (藤田医科大学大学院医学研究科博士前期課程)
  • Apr, 2022 - Present
    遺伝学  (中京学院大学看護学部)
  • Apr, 2022 - Present
    医学教育入門  (藤田医科大学医学部医学科)
  • Apr, 2021 - Present
    Human Biology  (Fujita Health University)

Research Projects

 18

Academic Activities

 3

Media Coverage

 1

Other

 3