第14回 公開セミナー |
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日時:2004年6月17日(木)14時00分~16時30分 |
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野口 立彦 氏 演題:『ショウジョウバエ精子形成における 要旨:当研究室ではアクチン依存的モー タータンパク質の一つである Myosin VI の細胞内機能を明らかにするために、ショウジョウバエ(Drosophila melanogaster)の精子形成 に注目して解析をしている。ショウジョウバエ精子形成においては、一次精子細胞から減数分裂までの分裂が不完全であるため、その後期では64の spermatid がシンシ チウム (シスト) を形成している。Individualizationとよばれる精子形成の最終段階 で、劇的な細胞膜の形態変化を伴って64個の精子への分裂が起こる。 |
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木下 専 氏 要旨: Septins are polymerizing GTP-binding proteins that assemble into rings during cytokinesis in diverse eukaryotes. The septin-based ring structure in yeast serves as a scaffold for checkpoint kinases and enzymes required for cell wall deposition, and as a diffusion barrier for bud-specific cortical proteins. In Drosophila, septins conprise ring canals formed between syncytial germ cells. In mammals, septins are most abundant in terminally differentiated cells, however, septin functions in non-dividing cells remain largely unknown. To shed light on the postmitotic roles of the septin cytoskeleton in vivo, we disrupted a mouse septin gene which is mainly expressed in the brain and testis. The septin-null male mice have normal reproductive organs, but are absolutely sterile. In the wildtype and heterozygotic mouse sperm, the septin protein localizes as an electron-dense cortical ring (annulus), which has been supposed as a structural border and diffusion barrier between the middle piece and tail. The septin-null sperm exhibits total absence of annulus and severe defects in morphology, motility and fertility, despite normal ultrastructure of the head and microtubule-based axonemal 9+2 structure. These data demonstrate that the septin cytoskeleton is the structural basis of the annulus, raising its implication in a subset of human male infertility withterato-asthenospermia. |