Besides its functions as a negative regulator of the Wnt signalling pathway, APC plays also a role in the organization of microtubues and of cell contacts. In a yeast-two-hybrid screen, we have identified a novel interaction partner of APC, which we have called Amer1 (APC Membrane Recruitment 1). is associated to the plasma membrane through interaction with phosphatidylinositol lipids and recruits APC from the microtubules to the plasma membrane. Conversely, loss of Amer1 by siRNA leads to an increased association of APC to the tips of microtubules. In addition, we have observed loss of cell-cell contacts in epithelial cells when Amer1 is down regulated. It turns out that Amer1 is identical to the tumour suppressor WTX, which is mutated in Wilms tumours and acts as a negative regulator of Wnt signalling. We have recently identified Amer2 and Amer3, which are related proteins albeit with distinct domain organization and we are in the process of analysing their function in normal and cancer cells.