Developmental maturation from fetus to adult is associated with changes in the angiogenic potential of arteries. Importantly, angiogenic response is regulated by a coordinated transcriptional and translational regulation of angiogenesis genes. In the present proposal, we will examine the role of a new class of regulatory RNA molecules known as long non-coding RNAs (lncRNAs) in developmental regulation of angiogenesis in fetus and adult cerebral arteries. Out of more than 180,000 transcripts in mouse, 20,000 are the protein coding genes and majorities of the remaining 160,000 are lncRNA. Most of these lncRNA sequences are poorly conserved and have been regarded as transcriptional noise. However, a subset of lncRNA has its own promoter, and is well conserved in mammals. This group is known as long intergenic non-coding RNA (lincRNA). This group is known for acting as potent molecular switch in cellular differentiation, movement, as well as in reprogramming of cell states by altering gene expression patterns. Identification of lincRNAs with cellular and molecular functions in angiogenesis will provide an exciting opportunity to discover new regulatory pathways that may lead to a better understanding of this vital process. Thus, we propose to identify and characterize the role of lincRNAs in regulating angiogenesis with development. Our specific aims will identify and analyze candidate lincRNAs involved in endothelial activation by a loss or gain of function screen in fetal and adult ovine cerebral arteries. The rationale for our experimental approach is that it will allow a careful, stage-specific dissection of the yet uncharacterized roles of lincRNAs in angiogenesis and changes with maturation. It also has the potential to provide insights into the pathogenesis of hemangioma, cancer, as well as contribute in efforts to realize the potential of regulated angiogenesis for regenerative medicine and tissue engineering.