March 28, 2017
Tokyo Metropolitan Institute of Medical Science
Bureau of Social Welfare and Public Health
Keio University
Researcher Hironobu Hirai and Associate Principal Investigator Haruo Okado of the Tokyo Metropolitan Institute of Medical Science, in collaboration with Senior Assistant Professor Koji Hotta of the Faculty of Science and Technology, Keio University, have discovered a new function of the AMPA-type glutamate receptor (hereafter, AMPA receptor). The function of the AMPA receptor has been known to play an important role in learning and memory as a mediator of excitatory synaptic transmission in the adult mammalian brain. However, while this receptor is expressed from the early fetal stage, its role during the developmental stage has not been clear. To clarify the role of the AMPA receptor during the developmental stage, experiments that reduce its function are useful, but such experiments have been technically difficult in mammals because they have four types of AMPA receptors. Therefore, in this study, we conducted an analysis using the protochordate ascidian (sea squirt), which is known as an ancestor of vertebrates. We took advantage of the fact that ascidians have only one AMPA receptor and that their developmental process from fertilization to adulthood is easy to observe. As a result, we revealed that the AMPA receptor is essential for the formation of the photoreceptive sensory organ, which corresponds to the pineal gland in mammals, and is also essential for the phenomenon of metamorphosis, a change into an adult form that many organisms undergo. This study is the first to analyze the function of the AMPA receptor at the whole-organism level, and it has succeeded in discovering a new function of the AMPA receptor in development.
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