Aging and its 11 hippocampal genes

Aging is being quite extensively studied these days and here is another advance in the field. Pardo et al. (2017) looked at what happens in the hippocampus of 2-months old (young) and 28-months old (old) female rats. Hippocampus is a seahorse shaped structure no more than 7 cm in length and 4 g in weight situated at the level of your temples, deep in the brain, and absolutely necessary for memory.

First the researchers tested the rats in a classical maze test (Barnes maze) designed to assess their spatial memory performance. Not surprisingly, the old performed worse than the young.

Then, they dissected the hippocampi and looked at neurogenesis and they saw that the young rats had more newborn neurons than the old. Also, the old rats had more reactive microglia, a sign of inflammation. Microglia are small cells in the brain that are not neurons but serve very important functions.

After that, the researchers looked at the hippocampal transcriptome, meaning they looked at what proteins are being expressed there (I know, transcription is not translation, but the general assumption of transcriptome studies is that the amount of protein X corresponds to the amount of the RNA X). They found 210 genes that were differentially expressed in the old, 81 were upregulated and 129 were downregulated. Most of these genes are to be found in human too, 170 to be exact.

But after looking at male versus female data, at human and mouse aging data, the authors came up with 11 genes that are de-regulated (7 up- and 4 down-) in the aging hippocampus, regardless of species or gender. These genes are involved in the immune response to inflammation. More detailed, immune system activates microglia, which stays activated and this “prolonged microglial activation leads to the release of pro-inflammatory cytokines that exacerbate neuroinflammation, contributing to neuronal loss and impairment of cognitive function” (p. 17). Moreover, these 11 genes have been associated with neurodegenerative diseases and brain cancers.

112hc-copy

These are the 11 genes: C3 (up), Cd74  (up), Cd4 (up), Gpr183 (up), Clec7a (up), Gpr34 (down), Gapt (down), Itgam (down), Itgb2 (up), Tyrobp (up), Pld4 (down).”Up” and “down” indicate the direction of deregulation: upregulation or downregulation.

I wish the above sentence was as explicitly stated in the paper as I wrote it so I don’t have to comb through their supplemental Excel files to figure it out. Other than that, good paper, good work. Gets us closer to unraveling and maybe undoing some of the burdens of aging, because, as the actress Bette Davis said, “growing old isn’t for the sissies”.

Reference: Pardo J, Abba MC, Lacunza E, Francelle L, Morel GR, Outeiro TF, Goya RG. (13 Jan 2017, Epub ahead of print). Identification of a conserved gene signature associated with an exacerbated inflammatory environment in the hippocampus of aging rats. Hippocampus, doi: 10.1002/hipo.22703. ARTICLE

By Neuronicus, 25 January 2017

Save

Save

The song of a fly… the courtship of another

Drosophila melanogaster image illustrating sexual dimorphism and mating behavior. Credit: TheAlphaWolf (Wikimedia Commons)
Drosophila melanogaster image illustrating sexual dimorphism and mating behavior. Credit: TheAlphaWolf (Wikimedia Commons)

Did you know that flies sing? True to the dictum that I just made up – ‘where is song, there is lust’ – it turns out not only that flies can sing, but they even have courtship songs! Granted, since they don’t have a larynx, the male flies sing by vibrating their wings in a certain way, which is unique to each fly species, and females listen with the feather-looking bit on top of their antennae, called arista. The behavior has generated enough research that a fairly hefty review about it has been published two years ago in Nature Reviews Neuroscience, pointing to a gene central to the male courtship circuitry and expressed only in the fly’s neurons, the fru gene (I bet it was called that way because when you make mutants you get fru/fru …).

Zhou et al. (2015) used a series of complicated experiments to successively activate or inhibit the neurons which express the fru gene, in order to identify the neural circuitry underlying hearing and processing the courtship songs. This circuitry is different in males and females, which makes sense since the serenading male expects different behaviors from his audience, depending on their sex; the listening males hurry to compete for the intended female and the females slow down and… listen carefully. Mind wondering: if I was the one serenading, wouldn’t I want to drive away the competitors, instead of drawing them in towards the object of my desire? Perhaps I want the competitors to also engage in courtship behavior so I can show off my wing vibrating prowess… Anyway, digression aside, in addition to figuring out which neuron does what, the authors managed to elicit courtship behavior in the listening males by optogenetically stimulating the 3rd and 4th order neurons in the newly identified circuit.

Besides being strangely interesting in itself, the research fills a gap in the understanding how courtship behavior is recognized, at least in fruit flies, which may be very useful information for other species as well, humans included.

Reference: Zhou, C., Franconville, R., Vaughan, A. G., Robinett, C. C., Jayaraman, V., & Baker, B. S. (21 September 2015). Central neural circuitry mediating courtship song perception in male Drosophila. Elife, 4:1-15. doi: 10.7554/eLife.08477. Article + FREE PDF

For the interested specialist, the MATLAB source code for analyzing calcium-imaging data can be found here.

By Neuronicus, 24 September 2015