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社会行動 2
Social Behavior 2

開催日 2014/9/13
時間 16:00 - 17:00
会場 Room H(304)
Chairperson(s) 小川 園子 / Sonoko Ogawa (筑波大学行動神経内分泌学研究室 / Laboratory of Behavioral Neuroendocrinology, University of Tsukuba, Japan)
小出 剛 / Tsuyoshi Koide (国立遺伝学研究所 マウス開発研究室 / Mouse Genomics Resource Laboratory, National Institute of Genetics, Japan)

Evolutionary analysis of brain function using non-mammalized Brn-2/Pou3f2 knock-in mice

  • O3-H-4-2
  • 矢田 紗織 / Saori Yada:1 那須 信 / Makoto Nasu:1 五十嵐 惇 / Atsushi Igarashi:1 須藤 伝悦 / Den'etsu Sutoo:2 秋山 佳代 / Kayo Akiyama:2 伊藤 円 / Meguru Ito:1 吉田 進昭 / Nobuaki Yoshida:3 植田 信太郎 / Shintaroh Ueda:1 
  • 1:東京大学大学院理学系研究科生物科学専攻 / Dept. of Biol. Sci., Grad. Sch. of Sci., The Univ. of Tokyo, Japan 2:筑波大学医学医療系 / Inst. of Medi. Sci., Univ. of Tsukuba, Ibaraki, Japan 3:東京大学医科学研究所システム疾患モデル研究センター / Cent. for Exp. Med. and Syst. Biology, Inst. of Med. Sci., The Univ. of Tokyo, Japan 

Recent progress in DNA sequencing technology has made whole genome sequences available from a wide variety of vertebrates. Genome-wide comparisons have revealed characteristics of the evolutionary change of different aspects of genomes involving chromosomes, genes, regulatory regions, and retrotransposons. Various mutations have occurred during evolution among orthologues, genes in different species that diverged from a common ancestral gene by speciation. A major difference between mammals and other vertebrates is the presence or absence of homopolymeric amino acid repeats (sequences without interruptions in the run of a single amino acid residue), indicating that these repeats were acquired specifically in the mammalian lineage. Transcription factor Brn-2/Pou3f2 is prominently expressed in the neocortex. The neocortex has undergone pronounced expansion and development during evolution, and is considered to be responsible for cognitive function, sensory perception, and consciousness. Mammalian Brn-2 has glycine, glutamine, and proline repeats, whereas most or all of these repeats are absent from Brn-2 orthologues in non-mammalian vertebrates. Here we report the remarkable deterioration of a characteristic mammalian maternal behavior, pup retrieval, in non-mammalized mice, in which the transcription factor Brn-2 was replaced with the Xenopus tropicalis orthologue lacking all of the homopolymeric amino acid repeats of mammalian Brn-2. These mice with a non-mammalized Brn-2 gene show less curiosity towards their pups and drastically decreased pup retrieval behavior that leads to increased pup death. Quantitative immunohistochemical analysis revealed decreases in the rate-limiting enzymes of dopamine and serotonin synthesis in various brain structures. This study indicates that pup retrieval behavior in mammals is thus strongly related to monoamine neurotransmitter levels via the acquisition of homopolymeric amino acid repeats during mammalian evolution.

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