Fate map of serotonin transporter-expressing cells in developing mouse heart.

Summary: Serotonin regulates cardiovascular functions during embryogenesis and adulthood. However, the source of serotonin in the cardiovascular system and the role of circulating serotonin and serotonin trans-porter (SERT) in the regulation of cardiovascular func-tions are still unclear. We used a cell fate approach to map the regions of the mouse heart expressing SERT, utilizing a Cre/loxP system driven by SERT gene expres-sion. Cell labelling was first detected at E10.5 and was mapped until E18.5. We found labelling in the outflow tract, part of right ventricle and to a very limited extent in the left ventricle. Interestingly, the distribution pattern of SERT-fated cells was remarkably similar to that obtained with markers of the second heart field lineage. In addition, we observed staining of atrioventricular valves, consistent with valvular abnormalities observed in SERT-/-animals. Overall, our data reveal specific and regionally restricted distribution of SERT-expressing cells in the developing heart of mouse.