Fig. 4.

Tek-Cre, but not Slco1c1-CreERT2, is expressed in fenestrated capillaries of circumventricular organs. Representative confocal images of co-localization of TdTomato (TdT, red) and Cd31 (green) in Tek-TdT animals (a–c, n = 4) confirms co-expression in parenchymal endothelium (filled arrowheads) and fenestrated capillaries (filled arrowheads with asterisk) in the organum vasculosum lamina terminalis (OVLT, a), subfornical organ (SFO, b), arcuate nucleus/median eminence (ARC/ME, c), and choroid plexus (ChP, d). Reporter expression is also seen in microglia in each of these regions (open arrowheads in a–d). Co-labeling of TdT (red) and Cd31(green) in Slco1c1-TdT animals (e–h, n = 4) shows Cre activity in all parenchymal endothelium (filled arrowheads), but not fenestrated capillaries (open arrowheads with asterisk). Reporter expression is also seen in other cells that do not express Cd31, particularly the cuboidal cells of the choroid plexus (open arrowheads in e–h). Higher magnification of the boxed regions in d and h (d′ and h′) demonstrate that ChP fenestrated capillaries express TdT in Tek-Cre but not Slco1c1-CreERT2 animals (filled and open arrowheads with asterisk, respectively). Scale bars: a–h 50 μm; d′ and h′ 10 μm