Mechanism of meiosis in triploid planarian- Different chromosome elimination between sex.

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K06352
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45010:Genetics-related
• Research Institution: Keio University
• Principal Investigator: Matsumoto Midori 慶應義塾大学, 理工学部(矢上), 准教授 (00211574)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 有性生殖 / 減数分裂 / ３倍体 / プラナリア / 染色体削減

Outline of Final Research Achievements

In sexual planarian, germ cells are formed from somatic pluripotent stem cell neoblasts. In triploid planarian capable of sexual reproduction, the sperm are monoploid, whereas the female germ line is maintained triploid until metaphase I of meiotic division.
FACS examination of the nuclear phase of the testicular germ cells of triploid sexual worms revealed that only 4n cells were present, indicating that the cells were reduced by one set during differentiation from neoblasts to spermatogonia and became diploid. Observation of spindle dynamics and chromosome behavior in the mitotic apparatus revealed that in female meiosis I, two out of three sets of chromosomes are incorporated into the mitotic apparatus and are paired and distributed, while unpaired monovalent chromosomes are disconnected from the mitotic apparatus but associated with microtubules.

Free Research Field

発生生殖学

Academic Significance and Societal Importance of the Research Achievements

真核生物には２倍体のものが多いが、異数体も存在する。３倍体個体は減数分裂対合時に異常が発生して正常な２価染色体が出きないために正常な配偶子ができず、有性生殖できないというのが生物学の常識である。
研究代表者はプラナリアでは３倍体個体でも減数分裂を行い、ゲノムの混合を伴う有性生殖を行うことを発見した。本課題では、生物学の常識を覆し、３倍体プラナリアの雌性生殖細胞が行う減数分裂を分子レベルで明らかにすることができた。これは学術的意義が十分に高い成果であると研究代表者は考えている。