Fig. 9. Dominant-negative KIF3B and Syne-1 fragments block syntaxin localization to the midbody. (A) Enriched mitotic NRK cells were either mock-transfected (a,b) or transfected with myc-tagged full-length KIF3B (c,d), myc-tagged KIF3B tail domain (e,f), or HA-tagged Syne-1 fragment GSSF1 (g,h). Cells were fixed and stained with anti-myc (a,c,e) or anti-HA (g) antibodies to identify transfected cells, and with anti-syntaxin (b,d,f,h). As observed with Syne-1 localization under these conditions (Fig. 7), syntaxin was easily detected at the midbody in mock transfected cells (b, arrows) and in cells transfected with the control full-length KIF3B (d, arrow). However, in cells transfected with KIF3B tail (f, arrow) or GSSF1 (h, arrow), syntaxin was significantly reduced from the midbody region. (B) To quantify these results, examples of mock transfected cells, cells transfected with full-length KIF3B (full-length), KIF3B tail (tail) and GSSF1 were subjected to digital image analysis as described for Fig. 7e (^* indicates statistically significant difference from mock transfected cells by Student's t-test).