Angiopoietin-1 (Ang-l) prevents endothelial cell apoptosis and promotes blood vessel stability, while angiopoietin-2 (Ang-a), a natural antagonist of Ang-l, disrupts blood vessel structure and induces apoptosis. We have sequenced the chicken angiopoietin-2 gene that spans about 46 kb of DNA and is split in 9 exons by 8 introns. Alternative splicing of the gene gives rise to three different species of Ang-2 mRNAs: Ang-2A Ang-2B, and Ang-2C. The three mRNA isoforms, also present in humans, codify for proteins with an identical fibrinogen-like C-terminal domain and a different coiled-coil N-terminal domain. Ang-2A and particularly Ang-2C are expressed in immature testis and regressed adult testis undergoing vascular remodeling, while their expression is barely detectable in quiescent adult testis. Conversely, Ang-2B is only detectable in adult testis. The new isoforms with truncated amino-terminal domains may modulate the Tie2 receptor during vascular angiogenesis and regression,