12 Sep 18. Featured Paper
A new map of more than a billion synapses in the brain helps to shed light on how memories are formed and recalled.
Professor Seth Grant and team have created the first synaptome map of the whole mouse brain, including more than a billion synapses. Their complex series of images is the first to illustrate how these vital connections are organised and could impact on our fundamental understanding of the brain.
Synapses are found in vast numbers in the brain and contain complex proteomes.
We developed genetic labeling and imaging methods to examine synaptic proteins in individual excitatory synapses across all regions of the mouse brain. Synapse catalogs were generated from the molecular and morphological features of a billion synapses. Each synapse subtype showed a unique anatomical distribution, and each brain region showed a distinct signature of synapse subtypes.
The team studied sections of brain tissue engineered to emit light, allowing the scientists to see individual synapses in colour. By tagging distinct types of molecules in each synapse by colour, they were able to detect a vivid pattern of synapses across the brain. Different groups of synapses were active depending on distinct behaviours of the mice – such as feeding, running and jumping. The diversity of synapse types may be key to recalling information, helping the brain to quickly locate memories through patterns of its activity. This finding could help scientists understand more about how memory problems develop.
The study also showed that mice bred to mirror aspects of autism and schizophrenia had altered synaptome maps and did not recall information properly. This could open new avenues towards understanding many different brain diseases and behavioural conditions.