Evolution of filipin-sterol complexes and intramembrane particle distribution during ciliogenesis.

Membrane events during ciliogenesis were studied in the quail oviduct cells. Two membrane domains differentiate during ciliogenesis: the ciliary necklace progressively composed of one to six rows of intramembranous particle (IMPs), and the shaft membrane poor in IMPs but characterized by a high content of sterol. Membrane sterol can be detected by the use of filipin which forms filipin-sterol complexes (f-c complexes) visible in electron microscopy on both freeze fracture replicas and thin sections. During ciliary growth, the necklace IMP rows are progressively organized in an area completely devoid of f-c complexes whereas the membrane of growing shaft shows a high density of f-c complexes except at the ciliary tip.