Fig. 4. Inv::GFP localization during cilium formation. Primary fibroblasts established from Inv/Inv, Inv::GFP transgenic mice were cultured until they were subconfluent and were then subjected to double staining with antibodies to GFP (red) and antibodies to -tubulin (green). A low-magnification view is shown in A and higher magnification views of centrosomal regions are shown in B-D. Several distinct patterns of Inv::GFP staining were detected. (B) Inv::GFP is localized to one of the centrioles, the mother centriole, even before extension of a cilium becomes obvious (arrowhead). (C) Inv::GFP is restricted to the extension of a mother centriole as it begins to form a cilium. (D) Inv::GFP is present along the entire length of a fully developed cilium. Scale bar: 2.5 µm.