Characterization of a novel form of angiopoietin-2 (Ang-2B) and expressionof VEGF and angiopoietin-2 during chicken testicular development and regression

The complex process of angiogenesis is controlled by the vascular endotheli al growth factor (VEGF) and its receptors and by the recently isolated angi opoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) that signal through the trans membrane endothelial receptor tyrosine kinase Tie2. We report here the char acterization of a novel form of Ang-2 (Ang-2B) with a truncated aminotermin al domain resulting from an alternative splicing of the gene. While previou s reports have found the expression of Ang-2 limited to the embryo, female reproductive organs, and tumor tissues, we have observed striking changes i n Ang-2 expression during chicken testicular development and regression. Th e expression of Ang-2 and VEGF is abundant in prepuberal testis and low in quiescent adult testis. Testicular regression is accompanied by high expres sion of Ang-2 and very low expression of VEGF. These observations are in ac cordance with the proposal that Ang-2 induces angiogenesis in the presence of VEGF and vascular regression in its absence. (C) 1999 Academic Press.