Long-lasting redundant gnrh1/3 expression in GnRH neurons enabled apparent switching of paralog usage during evolution
Chika Fujimori,
Kohei Sugimoto,
Mio Ishida,
Christopher Yang,
Daichi Kayo,
Soma Tomihara,
Kaori Sano,
Yasuhisa Akazome,
Yoshitaka Oka,
Shinji Kanda
Affiliations
Chika Fujimori
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan; Optics and Imaging Facility, National Institute for Basic Biology, Okazaki, Aichi, Japan
Kohei Sugimoto
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan; Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
Mio Ishida
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
Christopher Yang
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
Daichi Kayo
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan
Soma Tomihara
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan; Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan
Kaori Sano
Department of Chemistry, Faculty of Science, Josai University, Sakado, Saitama, Japan
Yasuhisa Akazome
Department of Anatomy, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan
Yoshitaka Oka
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
Shinji Kanda
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan; Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Corresponding author
Summary: Expressed subtype of paralogous genes in functionally homologous cells sometimes show differences across species, the reasons for which have not been explained. The present study examined hypophysiotropic gonadotropin-releasing hormone (GnRH) neurons in vertebrates to investigate this mechanism. These neurons express either gnrh1 or gnrh3 paralogs, depending on the species, and apparent switching of the expressed paralogs in them occurred at least four times in vertebrate evolution. First, we found redundant expression of gnrh1 and gnrh3 in a single neuron in piranha and hypothesized that it may represent an ancestral GnRH system. Moreover, the gnrh1/gnrh3 enhancer of piranha induced reporter RFP/GFP co-expression in a single hypophysiotropic GnRH neuron in both zebrafish and medaka, whose GnRH neurons only express either gnrh3 or gnrh1. Thus, we propose that redundant expression of gnrh1/3 of relatively recent common ancestors may be the key to apparent switching of the paralog usage among present-day species.
