Abstract
We report the existence of lipophilic structures (LS's) associated with demembranated sperm nuclei which together act as a pronuclear envelope organizing center. These structures can be visualized as objects which stain with lipophilic dyes but are resistant to solubilization in 0.1% of the non-ionic detergent Triton X (TX)-100. The structures, located at the acrosomal and centriolar poles of the sea urchin sperm nucleus, initiate ATP-dependent membrane vesicle binding in a fertilized egg extract. The lipophilic material in LS's is incorporated into the nuclear envelope during GTP-induced membrane fusion. Removal of the LS's from sperm nuclei with 1% TX-100 abolishes membrane vesicle binding to the nuclei. LS's recovered from supernatants of extracted nuclei can be reconstituted to their original locations on the stripped nuclei. Rebinding of isolated LS's occurs preferentially at the acrosomal pole. Such re-constituted nuclei direct membrane vesicle binding only to the acrosomal pole region and result in incomplete nuclear envelope assembly following membrane fusion. Binding of LS's and subsequently membrane vesicles to both nuclear poles allows complete nuclear envelope formation.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have