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SUMMARY:INI-RIMS joint seminar:  Regulatory mechanism for sperm chemotaxis
  and flagellar motility - Kogiku  Shiba  (University of Tsukuba)
DTSTART:20231026T080000Z
DTEND:20231026T090000Z
UID:TALK203749@talks.cam.ac.uk
DESCRIPTION:Eukaryotic flagella and cilia are extremely important organell
 es in cell motility and signal reception\, such as sperm motility and cont
 rol of water flow in the body\, and their structure and function are highl
 y conserved throughout evolution. I aim to elucidate the molecular and cel
 lular biology of the regulation of sperm flagellar motility by using the o
 riginal experimental and analytical systems for the functional analysis of
  fine and fast-moving flagella and cilia. I use the ascidian\,&nbsp\;Ciona
 &nbsp\;sperm as experimental animal.&nbsp\;Ciona&nbsp\;spermatozoa have lo
 ng been used for the analysis of sperm and flagellar motility due to their
  advantages in terms of ease of sample handling\, simplicity of morphology
 \, internal structure and motility [1]. Egg-derived sperm attractants have
  also been identified\, and the dramatic changes in swimming direction and
  flagellar waveform during sperm chemotaxis can be recorded under a micros
 cope [2]. Sperm chemotactic behavior is characterized by a change of direc
 tion when sperm swim away the attractant source. This feature is widely co
 nserved among organisms. The sperm flagellar wave generates propulsion by 
 the alternating propagation of two bends from the base to tip. If the curv
 ature of two bends is equal\, the sperm swim straight ahead. On the other 
 hand\, if the curvature of one bend is larger than another bend\, the sper
 m perform a circular motion. Analysis of the changes in the flagellar wave
 forms of&nbsp\;Cionasperm during chemotaxis revealed that the difference b
 etween the two bends curvature increases significantly when the sperm swim
  away from the attractant source\, leading to a turn movement that changes
  direction\, and then the curvatre of the two bends becomes equal and the 
 sperm swim straight towards the attractant source. The series of changes i
 n the waveforms are repeated and finally the sperm reaches the attractant 
 source. Realtime calcium imaging using fluorescent calcium indicator also 
 showed that a transient increase in the concentration of calcium ions in t
 he flagellum triggers the waveform change [3]. Calcium ions are important 
 second messengers in the signaling pathway of attractant reception and dir
 ectly regulate the molecular motor dynein that drives flagellar movement.\
 n&nbsp\;\nOur goal is understanding how sperm sense the attractant concent
 ration gradient\, drive calcium signaling\, and regulate the flagellar mot
 or. In this talk\, I will introduce our biological experiments and studies
  to reveal the function of the calcium-binding protein calaxin\, which dir
 ectly interact dynein activity\, and the role of ion channels in chemoattr
 actant sensing signaling in flagellar waveform regulation [4-5]. I would a
 lso like to discuss our recent challenge to understand the skillful behavi
 oral strategies of swimming single cells through &ldquo\;Ethological dynam
 ics in diorama environments&rdquo\; [6].\nReferences:\n[1] Brokaw\,&nbsp\;
 J Cell Biol.&nbsp\;114(6):1201-15 (1991)&nbsp\;\n[2] Yoshida et al.\,&nbsp
 \;Proc Natl Acad Sci U S A.&nbsp\;99(23):14831-6 (2002)&nbsp\;\n[3] Shiba 
 et al.\,&nbsp\;Proc Natl Acad Sci U S A.&nbsp\;105(49):19312-7 (2008)&nbsp
 \;\n[4] Shiba et al.\,&nbsp\;Int J Mol Sci.&nbsp\;23(3):1648 (2022)&nbsp\;
 \n[5] Shiba et al.\,&nbsp\;Front Cell Dev Biol.&nbsp\;11:1136404 (2023)&nb
 sp\;\n[6] https://diorama-ethology.jp/eng/
LOCATION:Seminar Room 1\, Newton Institute
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