A novel reporter allele for monitoring expression within the embryonic and adult mouse.

Canonical Notch signaling requires the presence of a membrane bound ligand and a corresponding transmembrane Notch receptor. Receptor engagement induces multiple proteolytic cleavage events culminating in the nuclear accumulation of the Notch intracellular domain and its binding to a transcriptional co-factor to mediate gene expression. Notch signaling networks are essential regulators of vascular patterning and angiogenesis, as well as myriad other biological processes. () encodes the earliest Notch ligand detected in arterial cells, and is enriched in sprouting endothelial tip cells. expression has often been inferred by proxy using a knockin reporter allele. This is problematic, as a single copy of is haploinsufficient. Additionally, Notch activity regulates transcription, making it unclear whether these reporter lines accurately reflect expression. Accordingly, precisely defining expression is essential for determining its role in development and disease. To address these limitations, we generated a novel BAC transgenic allele with a nuclear-localized β-galactosidase reporter (). Through a comparative analysis, we show the BAC line overcomes previous issues of haploinsufficiency, it recapitulates expression , and allows superior visualization and imaging. As such, this novel reporter is an important addition to the growing Notch toolkit.