In vivo expression profile of an endothelial nitric oxide synthase promoter-reporter transgene

Endothelium-derived nitric oxide (NO) is primarily attributable to constitu tive expression of the endothelial nitric oxide synthase (eNOS) gene. Altho ugh a more comprehensive understanding of transcriptional regulation of eNO S is emerging with respect to in vitro regulatory pathways, their relevance in vivo warrants assessment. In this regard, promoter-reporter insertional transgenic murine lines were created containing 5,200 bp of the native mur ine eNOS promoter directing transcription of nuclear-localized beta-galacto sidase. Examination of p-galactosidase expression in heart, lung, kidney, l iver, spleen, and brain of adult mice demonstrated robust signal in large a nd medium-sized blood vessels. Small arterioles, capillaries, and venules o f the microvasculature were notably negative, with the exception of the vas a recta of the medullary circulation of the kidney, which was strongly posi tive. Only in the brain was the reporter expressed in non-endothelial cell types, such as the CA1 region of the hippocampus. Epithelial cells of the b ronchi, bronchioles, and alveoli were scored as negative, as was renal tubu lar epithelium. Cardiac myocytes, skeletal muscle, and smooth muscle of bot h vascular and nonvascular sources failed to demonstrate beta-galactosidase staining. Expression was uniform across multiple founders and was not sign ificantly affected by genomic integration site. These transgenic eNOS promo ter-reporter lines will be a valuable resource for ongoing studies addressi ng the regulated expression of eNOS in vivo in both health and disease.