Genomic structures of the human angiopoietins show polymorphism in angiopoietin-2

The family of human angiopoietins comprises factors with important roles in vascular development and angiogenesis. All angiopoietins bind with similar affinity to the endothelial cell-specific receptor, Tie2. The mechanism by which they contribute to angiogenesis is thought to involve regulation of endothelial cell interactions with supporting perivascular cells. In this study the genomic structures of all three human angiopoietins were characterised by direct sequencing of human genomic DNA from the appropriate P1 artificial chromosome (PAC) clones. The exact positions at the intron/exon boundaries and the lengths of all eight introns were determined. As would be expected from the homology of these three proteins, the positions of the introns in the three genes are highly conserved. The putative RNA transcription start site for each angiopoietin gene was also determined. Intron-specific primers were used to amplify each exon of angiopoietin-1 and angiopoietin-2 from individual genomic DNAs. Although no polymorphism has been detected in the coding region of angiopoietin-1, three independent polymorphisms have been identified for angiopoietin-2.