Now that I have something to show for it, let this be a formal announcement that I’ve returned to Toronto to join Paul Frankland’s lab (and therefore the larger Josselyn-Frankland group). I’ve always liked their work and one of the techniques I’m excited to learn is the use of viruses to alter gene expression in neurons. BECAUSE THIS WILL ALLOW ME TO TAKE PRETTY PICTURES!!! I will also say that this will be a short (but hopefully sweet) stay as I’ll be leaving at the end of the year to start my own lab in the Psychology Department at the University of British Columbia (!).
Now, on with the pictures! As always, I recommend high-res viewing (click on the image to view it, bigger, on Flickr).
Using a retrovirus, which infects dividing cells, I made the amazing discovery of four adult-born cells which all had the exact same shape and were located right next to each other!
One trick on the confocal microscope is to use a larger pinhole so that a greater thickness of the section is captured in the image. Images acquired this way are comparable to a bunch of thin sections that are then merged into a “z-stack” except that some of the tissue is out of focus, giving rise to the blurry “rushing water” look that you see here.
Update: The poster is now available at Nature Precedings.
Still acquiring histological images for my SfN poster. My recurring problem is that I end up taking pictures of things because they’re pretty and not because they have anything to do with the task at hand. Today’s case in point:
Well, this does relate to my SfN poster a little bit. Red shows cell nuclei, most of which are dentate gyrus granule neurons. And white is GFAP immunostaining, which largely labels astrocytes but in this part of the brain also labels radial glia, the stem cells (or to be less controversial, “precursor” cells) of the hippocampus. Radial glia can be identified by the long process (almost like a dendrite) that they extend through the granule cell layer. There are a few in the above picture. Continue reading
Everybody knows what the hippocampus is for: memory. And…maybe something about anxiety or depression? Yes – over the last 10 years or so many studies have been published showing that the hippocampus has these two roles and that the mnemonic and emotional functions of the hippocampus are associated with its septal (dorsal) and temporal (ventral) ends, respectively. This new knowledge means that we’ve had to reorient our perspective. What we see when we consider the septal hippocampus may not be the same if we only consider its temporal end. My goal here is not to provide a review of the memory vs. emotional functions of the hippocampus (btw this dichotomy is a vast oversimplification). Instead, I’d like to talk about how people have differentiated these two ends of the hippocampus in their analyses. I’m also happy to showcase a bunch of pretty anatomical images that will probably never be published in a traditional journal article. Continue reading
And now for a journey outside (rostral, to be precise) of my comfort zone. These three pictures show new neurons in the mouse olfactory bulb at successively greater magnifications. Probably inspired by the science magazine I read as a kid that would show high mag photos of everyday objects (with corresponding low mag photos as the answers).
With a 10x objective I could capture nearly the entire bulb (saggital section) in a single field. You can see newborn BrdU+ cells (green) scattered throughout, most co-labeled with doublecortin (red). In the bottom left area you can see about a dozen glomeruli – groups of neurons that represent different odors, located just one synapse upstream of the nasal epithelium. Whereas the majority of adult-born olfactory neurons are inhibitory interneurons, a smaller number of new neurons surrounding the glomeruli (periglomerular neurons) are dopaminergic. (click on the images for full sized versions – 2048 x 2048 pixels)
It’s fun to zoom out and get the big picture sometimes. This is one such picture I took long ago when I wanted to see if staining for zinc transporter 3 effectively labels the mossy fiber axons of the dentate gyrus. You can see by the perfect overlap with calbindin that it does the job, though the staining wasn’t quite as bright and obvious as calbindin. The abundance of zinc in mossy fiber axons is one of the peculiarities of the DG and it underlies numerous synaptic properties of DG neurons.
I think the goal was to build on previous work by Lipp, Ramirez-Amaya, and Routtenberg showing that spatial learning causes “sprouting” of mossy fibers, though when I found out that this phenomenon does not occur in mice the project was aborted.
But what else can you see in this picture?
- clear differential expression of calbindin: DG (lots) > CA1 > CA3 (none), and a scattering of strongly-positive interneurons (e.g. 5 cells where CA3 and CA1 meet)
- in CA1 you can see calbindin is expressed only in the lower band of cells (see hi res photo if needed; there is a ref for this, somewhere)
- a thin band of calbindin-positive fibers crossing the corpus callosum (CC)
- A small group of cells that are not contacted by the calbindin-positive mossy fiber axons (i.e. beyond CA3) yet do not express somatic calbindin (as seen in CA1). I’m guessing this may be mysterious and ambiguous field CA2.