Figure 1.

Expression of TERT in human hippocampus and in cultured neurons and glia. A, Images showing immunohistochemical and immunofluorescent labeling of TERT in human hippocampus. Top, TERT (brown) and hematoxylin (blue) labeled neurons in the CA1 and CA3 regions of the hippocampus. Right, Immunofluorescence image shows secondary antibody only control (green). Arrows indicate neuronal nuclei. *Autofluorescence of a blood vessel. Second panel, TERT (green) is detected in the cytoplasm of neurons, which are identified using the neuronal marker NeuroTrace (red) and nuclear counterstain (DAPI; blue). Third panel, TERT (red) is expressed by microglial cells, as determined using antibodies against the microglial marker, CD68 (green). Bottom, TERT (red) specific staining was absent in astrocytes, as determined by double-labeling with astrocyte marker, GFAP (green). B, Images showing immunofluorescent labeling of TERT (red) in cultured embryonic mouse neurons and glia. The cell-specific markers βIII-tubulin, CD68, and GFAP identify neurons, microglia, and astrocytes, respectively (green). Top, Neurons express TERT protein in the cytoplasm of the soma and dendrites, but not in the nucleus. Second panel, Activated microglia show high expression of TERT protein in the cytoplasm. Third panel, Astrocytes in culture do not show fluorescent staining of TERT protein. Bottom, Neurons derived from TERT^−/− mice do not label with the anti-TERT antibody. C, An additional antibody recognizing TERT (Rockland) also labels the cytoplasm of human neurons. D, TERT antibody (Abcam) specificity is demonstrated in MRC5 and MRC5-hTERT overexpressing fibroblasts. Top, MRC5 fibroblasts show an absence of TERT staining. Bottom, Intense labeling of TERT (red) in the nucleus of MRC5-hTERT overexpressing fibroblasts. E, Telomerase activity is downregulated in embryonic mouse neurons in culture. Data are mean ± SEM. Scale bars, 50 μm.