Bioluminescence Imaging of Vascular Endothelial Growth Factor Promoter Activity in Murine Mammary Tumorigenesis

Vascular endothelial growth factor (VEGF) is a major inducer of angiogenesis. We generated a transgenic reporter mouse, VEGF-GL, in which an enhanced green fluorescent protein-luciferase fusion protein is expressed under the control of a human VEGF-A promoter. The VEGF-GL mouse exhibited intense bioluminescence throughout the body at 1 week of age. The signals rapidly declined to a relatively low level as the mice grew. The adult VEGF-GL mouse showed restricted bioluminescence to the areas undergoing wound healing. In contrast, the VEGF-GL mice, which were crossed with mouse mammary tumor virus-polyoma virus middle T antigen transgenic mammary tumor mice, exhibited prominent bioluminescence in the tumors, correlating with VEGF transcription. Tumor bioluminescence was observed in the bigenic mice as early as 8 weeks, before tumors were palpable, and the signals increased with tumor growth. In conclusion, the VEGF-GL mouse permits longitudinal and quantitative assessment of VEGF promoter activity in vivo. The model should facilitate understanding of the molecular controls and pathways that regulate VEGF transcription in vivo

Vacuolar Protein Sorting Protein 13A, TtVPS13A, Localizes to the Tetrahymena thermophila Phagosome Membrane and Is Required for Efficient Phagocytosis▿†

Vacuolar protein sorting 13 (VPS13) proteins have been studied in a number of organisms, and mutations in VPS13 genes have been implicated in two human genetic disorders, but the function of these proteins is poorly understood. The TtVPS13A protein was previously identified in a mass spectrometry analysis of the Tetrahymena thermophila phagosome proteome (M. E. Jacobs et al., Eukaryot. Cell 5:1990–2000, 2006), suggesting that it is involved in phagocytosis. In this study, we analyzed the structure of the macronuclear TtVPS13A gene, which was found to be composed of 17 exons spanning 12.5 kb and was predicted to encode a protein of 3,475 amino acids (aa). A strain expressing a TtVPS13A-green fluorescent protein (GFP) fusion protein was constructed, and the protein was found to associate with the phagosome membrane during the entire cycle of phagocytosis. In addition, Tetrahymena cells with a TtVPS13A knockout mutation displayed impaired phagocytosis. Specifically, they grew slowly under conditions where phagocytosis is essential, they formed few phagosomes, and the digestion of phagosomal contents was delayed compared to wild-type cells. Overall, these results provide evidence that the TtVPS13A protein is required for efficient phagocytosis