Study on evolution of sex chromosome and sex determination system in Hokou gecko

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H07279
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Evolutionary biology
• Research Institution: Kwansei Gakuin University
• Principal Investigator: Kazumi Matsubara 関西学院大学, 理工学部, 助教 (90399113)
• Project Period (FY): 2017-08-25 – 2019-03-31
• Keywords: 性染色体の分化 / ヤモリ / 収斂進化 / 性決定遺伝子 / DMRT1

Outline of Final Research Achievements

Hokou gecko exhibits genotypic sex determination with ZZ/ZW sex chromosome. In this study, to infer the evolutionary process of the sex chromosomes, sequences of Z and W homologs of two sex chromosome-linked genes, ACO1 and DMRT1, were analyzed for two populations of Hokou gecko, the populations from Okinawa and Ishigaki islands. The former population has morphologically differentiated ZW chromosomes and the latter has undifferentiated ZW chromosomes. Sequences of ACO1 were differentiated between the Z and W homologs in Okinawa population while those were identical between the Z and W homologs in Ishigaki population. In contrast, sequences of DMRT1 were differentiated between the Z and W homologs in commonly both populations. These results suggest that an initial step of sex chromosome differentiation was allelic differentiation of DMRT1 (a sex determining gene in Vertebrate) in the common ancestor. Then, inversions independently occurred in the W chromosome of Okinawa population.

Free Research Field

細胞遺伝学

Academic Significance and Societal Importance of the Research Achievements

沖縄本島産と石垣島産ミナミヤモリの性染色体の比較解析から、両島の個体群の性染色体は共通祖先に端を発し、各島に個体群が定着した後に独自の構造変化を蓄積したことが示唆された。島嶼など小さな隔離地域に生息する個体群では独自の性決定様式や生物学的特徴を獲得した可能性があり、これら隔離個体群の調査や保護の重要性が示される。ミナミヤモリの性染色体の分化の開始には、脊椎動物の性分化関連遺伝子であるDMRT1の対立遺伝子間での分化が切掛となったことが示唆された。この事は、脊椎動物の性染色体は多様な起源を持ちつつも、その誕生には性分化関連遺伝子の収斂進化といった共通原理があることを支持する。