Fig. 3. CD44 expression is required for sensing a hyaluronan gradient. (A,B) MDA-MB-468 cells were left untreated, mock transfected, transfected with control siRNA oligonucleotides or transfected with CD44 siRNA oligonucleotides. 72 hours later cells were detached from dishes and CD44 expression and hyaluronan binding assessed by flow cytometry or fluorescence microscopy as described in Fig. 2. In A, black lines represent binding of second antibody alone (CD44) or medium alone (FITC-HA) to untreated cells. (C) MDA-MB-468 cells transfected with CD44 or control siRNA oligonucleotides were assayed for their ability to migrate directionally in a gradient of FBS or umbilical cord hyaluronan as described in Fig. 1. Bar, 50 µm.