Neuron secrets exposed
Image: Researchers have studied neurons from the cerebellum, a brain region involved in coordinating movement. [Elitsa Stoyanova and Maria V. Moya]
Researchers from the University of Rockefeller, US, have devised a new method to characterise neurons and their gene expression with, they claim, unrivalled precision.
Studies were supported with confocal fluorescence microscopy, with researchers unveiling a stunning image of the neurons from the cerebellum.
Crucially, the latest results suggest that even some of the most well-researched neuron types still hold secrets.
Suspecting that neurons from different species vary in subtle but important ways, Professor Nathaniel Heintz and colleagues set out to determine which genes are expressed in cerebellar neurons from mouse and human brains.
Improving on established techniques, the researchers used cell-specific antibodies to purify nuclei from well-documented neural subtypes - Purkinje cells, granule cells, and basket cells - and to analyse which genes they expressed.
To confirm these results, they also used a technique called ATAC-seq, another way of determining which genes are turned on in a particular cell.
Sliced brain samples were imaged on a Zeiss LSM700 confocal microscope using the same acquisition settings for mouse and human slides.
Brightness and contrast adjustments were made in ImageJ post-acquisition with the same adjustments applied to mouse and human images.
Results revealed that human neurons expressed hundreds of genes that the mouse neurons did not, which Heintz attributes to evolutionary changes affecting gene regulation.
In addition to investigating genetic differences across species, the researchers also looked for changes that might occur over the lifetime of a single individual.
They found that older neurons express genes in different proportions than younger counterparts, but that cells don’t always age at the same rate.
“When we plotted gene expression changes according to age, we observed that the cells of some individuals looked biologically older than their chronologic age,” says Heintz. “And since age is the determining factor for the onset of human degenerative disorders, it is possible that these older-seeming cells are more vulnerable to disease.”
In some brains, the researchers also observed distinct genetic deviations that were caused by some unknown variable, possibly a brain disorder.
The researchers propose that understanding these molecular distinctions could prove useful in identifying cellular abnormalities that underlie brain disease.
More research will be required to establish what might underlie this type of change in gene expression, but Heintz says he is encouraged by the fact that his team was able to observe these changes at all.
“This shows us that we can detect changes at the molecular level that could be important in the context of diseases affecting specific cell types in the brain,” he says.