Cortical organization by the septin cytoskeleton is essential for structural and mechanical integrity of mammalian spermatozoa.
Septins are polymerizing GTP binding proteins required for cortical organization during cytokinesis and other cellular processes. A mammalian septin gene Sept4 is expressed mainly in postmitotic neural cells and postmeiotic male germ cells. In mouse and human spermatozoa, SEPT4 and other septins are found in the annulus, a cortical ring which separates the middle and principal pieces. Sept4-/- male mice are sterile due to defective morphology and motility of the sperm flagellum. In Sept4 null spermatozoa, the annulus is replaced by a fragile segment lacking cortical material, beneath which kinesin-mediated intraflagellar transport stalls. The sterility is rescued by injection of sperm into oocytes, demonstrating that each Sept4 null spermatozoon carries an intact haploid genome. The annulus/septin ring is also disorganized in spermatozoa from a subset of human patients with asthenospermia syndrome. Thus, cortical organization based on circular assembly of the septin cytoskeleton is essential for the structural and mechanical integrity of mammalian spermatozoa.
Ihara
Masafumi
M
Biochemistry and Cell Biology Unit, HMRO, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Kinoshita
Ayae
A
Yamada
Shuichi
S
Tanaka
Hiromitsu
H
Tanigaki
Ai
A
Kitano
Ayumi
A
Goto
Motohito
M
Okubo
Kazutoshi
K
Nishiyama
Hiroyuki
H
Ogawa
Osamu
O
Takahashi
Chiaki
C
Itohara
Shigeyoshi
S
Nishimune
Yoshitake
Y
Noda
Makoto
M
Kinoshita
Makoto
M
D000818:Animals; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006801:Humans; D007248:Infertility, Male / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D058112:Septins; D013094:Spermatozoa / Q000378:metabolism / Q000648:ultrastructure*; D013737:Testis / Q000166:cytology / Q000378:metabolism
D003598:Cytoskeletal Proteins; D020558:GTP Phosphohydrolases; C115474:Sept4 protein, mouse; D058112:Septins