Index

You are welcome to use any of these images or movies for presentations or website; please just give our laboratory the appropriate credit.  To download the high resolution images Right-Click and choose "Save This Link as..." or "Save Target as...".  On Macintosh, hold down control and click, then choose "Save This Link as...". 

Images of research interests

For more detailed information on the projects in the Eisch Laboratory, please see my research page.  If you have any questions about these images or our research, please don't hesistate to contact me.

Seeing is believing...isn't it?

Back to top

Figure legend: Simplified schematic of the mammalian cell cycle (center) surrounded by images depicting each developmental stage leading to SGZ neurogenesis.  Cell cycle (center schematic): The length of the cell cycle in the SGZ of the young adult male rat is about 25 hours, with 9.5 hours consisting of the DNA synthesis, or S, phase, 4.5 hours consisting of G2 and mitosis (M), and the remainder consisting of G1 phase (Cameron and McKay, 2001).  Systemic injection of BrdU or [3H]thymidine leads to incorporation of these mitotic markers into the DNA of cells in S Phase (note red in newly synthesized strand of DNA).  This cell cycle and the surrounding images emphasize the continuum between the time points of proliferation or cytogenesis (left column), differentiation and migration (center column) and survival or neurogenesis (right column).  Proliferation or cytogenesis (left column): Two hours after injection of BrdU, cells in the SGZ appear on the border of the granule cell layer (GCL), and are small and irregularly-shaped.  BrdU-immunoreactive cells will often appear in dense clusters.  A cluster is defined by any BrdU-immunoreactive cells that make contact.  The top left panel is a light microscopic image depicting two BrdU-positive clusters (arrows).  When examined at high magnification (X100) with continual scanning through the Z-plane of section, these clusters can be identified as containing eleven (top cluster) and three (bottom cluster) individual cells.  The bottom panels depict confocal microscope images of a triple immunohistochemical stain of the SGZ from a rat given the mitotic marker BrdU 2 hours earlier.  Cells are labeled for BrdU (green), the neuronal marker NeuN (red) and the glial marker GFAP (blue).  Arrowheads indicate cells double-labeled with BrdU and GFAP, but not with NeuN.  Merged images of the three labels (last panel) show that all BrdU-positive cells in the SGZ are GFAP-positive (blue-green cells) and NeuN-negative.  Note that in contrast to the neuronal morphology of NeuN-labeled cells in the GCL, BrdU-labeled cells in the SGZ are small, clustered, and irregularly shaped. Differentiation, migration (center images): About four or more hours after injection of BrdU, some cells labeled with BrdU will have reached M phase and will divide.  Some of these cells will reenter the cell cycle (or Go, not depicted); others will exit the cell cycle and begin to express markers of postmitotic, migrating, or differentiating cells.  Two such markers are shown here.  The center left panel is a confocal microscope image of the SGZ depicting staining for Hu (green) and nissl substance (red).  Hu is a member of a family of RNA binding proteins shown to be expressed in neurons around the time of exit from the cell cycle (Marusich et al., 1994).  The center right panel is a confocal microscope image of the SGZ depicting class III b-tubulin immunoreactivity (green).  Class III b-tubulin is a cytoskeletal protein expressed in both postmitotic cells that may become neurons and in mature neurons.  Hu and class III b-tubulin are markers of differentiating and migrating cells, but the fate of these maturing cells is considered malleable at least until the cells express markers of mature neurons, such as calbindin or NeuN.  Survival or neurogenesis (right column): Two to four weeks after injection of BrdU, some BrdU-immunoreactive cells have migrated into the GCL and have achieved a neuronal morphology. The top right panel is a light microscopic image depicting four BrdU-positive cells (arrowheads).  These four cells are round, about 10 mm in diameter, and solitary.  Note that some surviving BrdU-immunoreactive cells are solid (black arrowhead) while others are speckled (blue arrowhead).  Due to the depth of penetration of the BrdU antibody and narrow focal plane at this magnification, an additional speckled cell is out of focus (light blue arrowhead).  The heterogeneous labeling reflects either time spent in S Phase or number of cycles of division, e.g. speckled cells were later in S-phase relative to solid cells when BrdU was injected, or speckled cells have gone through more cycles of division than solid cells (Miller and Nowakowski, 1988).  The bottom panels depict confocal microscope images of a triple immunohistochemical stain of the subgranular zone from a rat given BrdU 4 weeks earlier.  Cells are labeled for BrdU (green), the neuronal marker NeuN (red) and the glial marker GFAP (blue).  Arrows indicate a cell double-labeled with BrdU and NeuN but not with GFAP.  Merged images of the three labels (last panel) show that all BrdU-positive cells in the granule cell layer are NeuN-positive (yellow cell) and GFAP-negative.  Note that in contrast to the neuronal morphology of BrdU-labeled cell in the granule cell layer, BrdU-labeled cells in the hilus are small and irregularly shaped.  From (Eisch et al., 2000).  All confocal images shown here were collected on a confocal microscope at X65 magnification using multitrack scanning.  The images presented are taken from a 1 mm optical section through the Z plane of focus.  GCL, granule cell layer; H, hilus.

For more information on this figure and more about the cytogenesis versus neurogenesis debate, please see my recent review article in Progress in Brain Research (Click here for complete citation).

This combinatorial approach of using exogenous and endogenous markers will enable us to learn about how a cluster of newly-born cells matures over time.

Immunodetection of exogenous mitotic markers such as BrdU or [3H]thymidine is useful for "birthdating" a cell.  However, the immunodetection of endogenous cell cycle markers holds immense promise for characterizing newly-born cells in the adult brain.  Some endogenous cell cycle proteins are relatively restricted to various phases of the cell cycle, allowing us to learn about how a cluster divides. This image depicts triple labeling immunofluorescent histochemistry for BrdU (panel b, red staining) and two endogenous cell cycle proteins.  BrdU was given i.p. two hours earlier.  Some parts of the cluster (large arrow) are labeled with all three colors.  Other parts (small arrows) are labeled with just green and blue, suggesting that this cluster was not in S phase when BrdU was injected.  Still other cells (arrowheads) are only labeled with BrdU and one of the cell cycle markers, suggesting that these cells are in a part of the cell cycle that only expressed one of the cell cycle markers.

These four images are different angle views from a three-dimensional reconstruction of a cluster of proliferating cells in the adult rat hippocampal SGZ.  The green label is BrdU, the red label is GFAP and the blue label is an endogenous cell cycle marker.  Using a 3D reconstruction program, we can rotate and zoom in on the "stack" of optical or Z plane sections we have taken on our confocal microscope.  If you'd like to see a movie of this cluster rotating, click here. If you'd like more information on how we did this reconstruction, click here. Back to Top

A great challenge in the field of adult neurogenesis is to identify the cell surface receptors expressed by newly-born cells.  It has previously been challenging to verify the relationship between nuclear and cell surface markers since they are, by definition, in different regions of the cell.  Typically we utilize confocal microscopy and orthogonal sectioning to infer the relationship between two immuno-labeled structures.  Using confocal microscopy and 3D reconstruction we are also able to visualize the relationship between cell surface receptors and BrdU-labeled nuclei.  Here two BrdU-labeled nuclei (panel a, long arrows) appear to be surrounded by a cell surface receptors (panels b, c).  While confocal microscopy and orthogonal sectioning are still useful, the ability to reconstruct and rotate these images enhances our ability to see the relationship between nuclear and cell surface markers.