Molecular characterization of axonemal dyneins of sperm flagella in the Ascidian <em>Ciona intestinalis</em> — ASN Events
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  2. Poster Session 1-Spermatology
  3. Molecular characterization of axonemal dyneins of sperm flagella in the Ascidian Ciona intestinalis

Molecular characterization of axonemal dyneins of sperm flagella in the Ascidian Ciona intestinalis (#119)

Kazuo Inaba 1 , Osamu Kutomi 1 , Katsutoshi Mizuno 2 , Keiko Hirose 3 , Kogiku Shiba 1 , Lixy Yamada 4 , Hitoshi Sawada 4
  1. Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan
  2. Department of Biological Sciences, Dartmouth College, NH, USA
  3. National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
  4. Sugashima Marine Biological Laboratory, Nagoya University, Mie, Japan

    Axonemal dyneins are molecular motors that drive flagellar motility in spermatozoa. They are observed as “arms” in a corss-sectioned image of the axoneme. From their positions on each outer doublet microtubules, they are called as outer and inner arms. The outer or inner arms are known to play roles in increasing flagellar beat frequency or regulating flagellar bend formation and propagation, respectively. The outer arm dyneins are composed of ~10 subunit including heavy, intermediate and light chains, representing a single molecular species in the axonemes [1, 2]. In contrast, the inner arm dyneins represent diverse molecular species; at least seven inner arm dyneins are known in flagella, as revealed in flagella of the green algae Chlamydomonas [3].

     The outer arm dynein in sperm flagella has two heavy chains, representing two-headed dynein, unlike the case of three-headed in Chlamydomonas flagella. Sperm outer arm dynein has a unique intermediate chain with thioredoxin and nucleoside diphosphate kinase domains (TNDK) and a Ca2+ sensor protein calaxin, both of which are not found in Chlamydomonas flagella [2, 4-6]. In contrast, inner arm dyneins have not been well characterized in sperm flagella. We have recently isolated a two-headed inner arm dynein from Ciona sperm flagella. The two-headed dyneins, termed Ciona-f/I1, show molecular composition closely similar to f/I1 dynein of Chlamydomonas flagella, but a ~32 kDa unique component (p32) with one BLUF domain was identified to be associated with Ciona f/I1. Immunoblotting with anti-p32 antibody revealed that it is also present in Chlamydomonas flagella, suggesting that p32 is also a component of Chlamydomonas f/I1but is dissociated from f/I1 during purification. Thus the outer arm dynein is considered in particular to be specialized in sperm flagella for fertilization.

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2. Inaba K (2011) Mol Hum Reprod 17: 524-538

3. Kamiya R (2002) Int Rev Cytol 219: 115-155

4. Inaba K (2007) Ann N Y Acad Sci 1101: 506-526

5. Mohri et al (2012) Proc Jpn Acad Ser B Phys Biol Sci 88: 397-415

6. Mizuno et al (2012) Proc Natl Acad Sci USA 109: 20497-20502