Mice are a poor model for retinal defects caused by type I Usher syndrome (USH1) because their photoreceptors have almost no calyceal processes, the structures in which all USH1 proteins are detected in other vertebrates.

The vascular endothelial growth factor is produced by a large variety of human tumors, including melanoma, in which it appears to play an important role in the process of tumor-induced angiogenesis. Little information is available on the role of placenta growth factor, a member of the vascular endothelial growth factor family of cytokines, in tumor angiogenesis, even though placenta growth factor/vascular endothelial growth factor heterodimers have been recently isolated from tumor cells. To investigate the role of placenta growth factor and vascular endothelial growth factor homodimers and heterodimers in melanoma angiogenesis and growth, 19 human melanoma cell lines derived from primary or metastatic tumors were characterized for the expression of these cytokines and their receptors. Release of placenta growth factor and vascular endothelial growth factor polypeptides into the supernatant of human melanoma cells was demonstrated. Reverse transcriptase polymerase chain reaction analysis showed the presence of mRNAs encoding at least three different vascular endothelial growth factor isoforms (VEGF(121), VEGF(165), and VEGF(189)) and transcripts for two placenta growth factor isoforms (PlGF-1 and PlGF-2) in human melanoma cells. In addition, placenta growth factor expression in human melanoma in vivo was detected by immunohistochemical staining of tumor specimens. Both primary and metastatic melanoma cells were found to express the mRNAs encoding for vascular endothelial growth factor and placenta growth factor receptors (KDR, Flt-1, neuropilin-1, and neuropilin-2), and exposure of melanoma cells to these cytokines resulted in a specific proliferative response, supporting the hypothesis of a role of these angiogenic factors in melanoma growth. J Invest Dermatol 115:1000-1007 2000

by antibodies directed against the α5β1 integrin. Moreover, VEGFR-1 promoted endothelial cell migration, and this effect was inhibited by anti-α5β1 antibodies. Direct binding of VEGFR-1 to the α5β1 integrin was also detected. Finally, binding to VEGFR-1 initiated endothelial cell spreading. Altogether these results indicate that the soluble VEGFR-1 secreted by endothelial cells becomes a matrix-associated protein that is able to interact with the α5β1 integrin, suggesting a new role of VEGFR-1 in angiogenesis, in addition to growth factor binding.