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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:INI-RIMS joint seminar:  Regulatory mechanism for 
 sperm chemotaxis and flagellar motility - Kogiku  
 Shiba  (University of Tsukuba)
DTSTART;TZID=Europe/London:20231026T090000
DTEND;TZID=Europe/London:20231026T100000
UID:TALK203749AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/203749
DESCRIPTION:Eukaryotic flagella and cilia are extremely import
 ant organelles in cell motility and signal recepti
 on\, such as sperm motility and control of water f
 low in the body\, and their structure and function
  are highly conserved throughout evolution. I aim 
 to elucidate the molecular and cellular biology of
  the regulation of sperm flagellar motility by usi
 ng the original experimental and analytical system
 s for the functional analysis of fine and fast-mov
 ing flagella and cilia. I use the ascidian\,&nbsp\
 ;Ciona&nbsp\;sperm as experimental animal.&nbsp\;C
 iona&nbsp\;spermatozoa have long been used for the
  analysis of sperm and flagellar motility due to t
 heir advantages in terms of ease of sample handlin
 g\, simplicity of morphology\, internal structure 
 and motility [1]. Egg-derived sperm attractants ha
 ve also been identified\, and the dramatic changes
  in swimming direction and flagellar waveform duri
 ng sperm chemotaxis can be recorded under a micros
 cope [2]. Sperm chemotactic behavior is characteri
 zed by a change of direction when sperm swim away 
 the attractant source. This feature is widely cons
 erved among organisms. The sperm flagellar wave ge
 nerates propulsion by the alternating propagation 
 of two bends from the base to tip. If the curvatur
 e 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 sperm perf
 orm a circular motion. Analysis of the changes in 
 the flagellar waveforms of&nbsp\;Cionasperm during
  chemotaxis revealed that the difference between t
 he two bends curvature increases significantly whe
 n 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 attr
 actant source. The series of changes in the wavefo
 rms 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 the flagellum triggers the waveform chang
 e [3]. Calcium ions are important second messenger
 s in the signaling pathway of attractant reception
  and directly regulate the molecular motor dynein 
 that drives flagellar movement.\n&nbsp\;\nOur goal
  is understanding how sperm sense the attractant c
 oncentration gradient\, drive calcium signaling\, 
 and regulate the flagellar motor. In this talk\, I
  will introduce our biological experiments and stu
 dies to reveal the function of the calcium-binding
  protein calaxin\, which directly interact dynein 
 activity\, and the role of ion channels in chemoat
 tractant sensing signaling in flagellar waveform r
 egulation [4-5]. I would also like to discuss our 
 recent challenge to understand the skillful behavi
 oral strategies of swimming single cells through &
 ldquo\;Ethological dynamics in diorama environment
 s&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 a
 l.\,&nbsp\;Proc Natl Acad Sci U S A.&nbsp\;105(49)
 :19312-7 (2008)&nbsp\;\n[4] Shiba et al.\,&nbsp\;I
 nt J Mol Sci.&nbsp\;23(3):1648 (2022)&nbsp\;\n[5] 
 Shiba et al.\,&nbsp\;Front Cell Dev Biol.&nbsp\;11
 :1136404 (2023)&nbsp\;\n[6] https://diorama-etholo
 gy.jp/eng/
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:
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