Sequence of vascular patterning and gene transcription in the chick chorioallantoic membrane (15.1)

Abstract

Introduction: The chick chorioallantoic membrane (CAM) is a well‐established model of both vasculogenesis and angiogenesis; however, little is known about the genetic control of vascular patterning in the CAM.Methods: Using recent advances in chicken genomics, we investigated the relative expression of 84 angiogenesis genes during the growth and remodeling of the CAM microcirculatory network. Chick embryos, cultured ex ovo, were studied during embryonic development days (EDD) 8‐14. UV laser microdissection was used to harvest capillary plexus and 1st, 2nd, and 3rd order conducting vessels for qRT‐PCR analysis.Results: Two transcription peaks were observed between EDD 8 and 14. The first peak occurred prior to EDD 10 and was correlated with maturation of capillary meshwork. The dominant gene expressed during this developmental phase was Epas1. The second peak occurred on EDD 12 and was correlated with growth of the 1st and 2nd order conducting vessels. Dominant transcription peaks were observed in Tgfb3, Timp3, Fn1, F3, Col18a1, Itgb3, Ptk2, Mdk, Sphk1 and Notch1. Nrp2, Mdk, Tgfb3, and Vegfa demonstrated bimodal regulation with peak expression on EDD 9 and 12.Conclusion: We observed bimodal transcriptional activity of the chick CAM during vascular network development. The peaks correlated with the initial maturation of the capillary meshwork followed by expansion of the 1st and 2nd order conducting vessels. These results provide insights into the genetic control of vascular patterning.