Identification and Characterization of Factors Critical in Regulating the Selective Vulnerability of Distinct Motor neuron Pools in Spinal Muscular Atrophy Models of Mice

Identification and Characterization of Factors Critical in Regulating the Selective Vulnerability of Distinct Motor neuron Pools in Spinal Muscular Atrophy Models of Mice 2013

Figure 1: Variability in neuromuscular junction vulnerability in muscles from the abdomen or neck in SMA mice.
This figure shows neuromuscular junctions with either high or low vulnerability. The red staining represents the part of the neuromuscular junction formed by the muscle. The green represents the part of the neuromuscular junction formed by the neuron. In the examples from the healthy mouse, the green staining very tightly correlates with the red staining implying neuromuscular junctions are intact and functional. In theneck muscles from the SMA mouse, again, neuromuscular junctions appear intact i.e. all the red staining is accompanied by green staining. In the abdominal muscles, there are frequent examples of red staining which has no green staining. This implies that the neuron has been lost and the neuromuscular junction has therefore degenerated. Our work aims to ask why we see these different levels of degeneration within an individual mouse.

Figure 2: Diagram showing methods employed to identify motor neurons in the spinal cord.
This figure demonstrates the procedures we use to identify which motor neurons correspond to the muscles that we are interested in. A red fluorescent dye is injected into the muscle of interest and travels along the motor neuron until it reaches the cell body located in the spinal cord. After euthanizing the mouse, we remove the spinal cord and can identify the motor neurons that we are interested in by looking for the red fluorescence. An example image can be seen on the right. Note that all the motor neurons are marked with a green stain, but only 2 of the 3 also display a red stain. We use this method to identify which cells to dissect out to analyze gene activity

Figure 3: Example of laser capture microdissection.
This figure demonstrates the process we use to isolate motor neurons. The spinal cord is cut into sections that are 10 microns thick. A laser is then fired at the cells we want to dissect. This allows us to cut out only the cells we are interested in and leave the rest of the tissue intact. (Click the image to view a large version)