Whether Lrp6 is required for ductal stem cell activity remains to be determined, as does the role of Lrp6-mediated Wnt signaling in the mammary fat pad. Development of conditional mouse models for Lrp6 and Lrp5 deletion will aid in the understanding of the specific roles of these proteins in mammary gland development and tumorigenesis. This is particularly important because Wnt/b-catenin signaling is often activated in human breast cancer. In conclusion, our study demonstrated that Rab21 is transiently associated with macropinocytosis at an intermediate stage partially overlapping both the Rab5-acting stage and the Rab7-acting stage, and probably functions in macropinosome maturation rather than macropinosome formation. The impact of previous immunity to both replication competent and replication GANT61 deficient vaccinia virus has been investigated in several studies and is suggested to reduce the effectiveness of subsequent vaccinations. The second MVAVP2 vaccination in this study was found to boost VP2 specific antibody titres, despite a pre-existing antibody response to the MVA vector, although the third vaccination did not increase the VNAb response any further. Therefore, it may be necessary to investigate methods to enhance immune responses generated against the AHSV antigens. The use of DNA priming prior to vaccination with recombinant MVA has been used successfully in several studies and could be applied to future work with the recombinant MVA AHSV vaccines. In summary, the ability of recombinant MVA viruses encoding AHSV proteins to induce AHSV antigenspecific antibody responses was investigated. The midgestational lethality of constitutive c-myc and N-myc KO mice may also be caused in part by stem cell defects. The stem cell-related functions of myc have in addition been postulated to contribute to formation of tumors, perhaps through transformation of normal stem cells into tumor stem cells. This theory is supported by recent knockdown and knockout studies demonstrating that Nmyc is essential in neural stem cells and precursors of the cerebellum for medulloblastoma genesis, N-myc plays a key role in blocking the differentiation of cells of origin of medulloblastoma, and cmyc is required for glioma stem cell function. The macropinocytic pathway is coordinately regulated by several Rab GTPases, creating sequential Rabeffector links that mediate the progressive maturation of the organelles. Taken together, it can be hypothesized that these residues might be important for functions such as proton-antiport, rocker-switch mechanism or drug binding and translocation and if replaced, would result in a non-functional protein displaying susceptibility to all the drugs. Medulloblastoma is the most common malignant brain tumor of childhood. While outcomes have improved, there is significant therapy-related morbidity.