Organization of the cross-filaments in intestinal microvilli.
We studied the arrangement of the cross-filaments in intestinal microvilli to understand how microfilaments interact with the membrane. Observations on thin-sectioned or negatively stained microvilli with the electron microscope demonstrate that the cross-filaments on the core bundle lie opposite to one another and are spaced 32.5 nm apart. In sections grazing through the membranes, the cross-filaments appear as transverse stripes in a barber-polelike arrangement. The cross-filaments point away from the microvillus tip. This subfragments S1 or HMM. The cross filaments are associated not only with the microfilaments but also with electron-dense patches on the inside surface of the membrane. These results suggest the cross-filaments are arranged as a double helix around the core bundle. Furthermore, the cross-filaments can serve as in situ markers for microvillar polarity. Lastly, the cross-filaments interact not only with specific portions on the actin filaments but also with dense patches on the membrane. These observations are summarized in a model of the microvillus cytoskeleton.
D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure*; D002645:Chickens; D003599:Cytoskeleton / Q000648:ultrastructure*; D005260:Female; D007422:Intestines / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008871:Microvilli / Q000648:ultrastructure*; D008954:Models, Biological; D013194:Staining and Labeling