This week, the Human Protein Atlas is highlighting a new atlas recently released in HPA 14, The Mouse Brain Atlas. This image from The Mouse Brain Atlas was brought to us by Nadya Petseva, a team member on the project. I know what you're thinking, what's a mouse doing in the "human" protein atlas?!

Though we typically deal with human cells and tissues in the HPA, it is not currently possible to image full human brain at the cellular level, whereas using a mouse brain we can gain key insights into how proteins in the brain function in situ. This makes mice an attractive "model organism" as their brains actually consist of very similar regions to those found in humans. Using this mouse model gives us a larger overview of the different brain regions where proteins are located and what parts of those cells it is localized to.

The protein labeled in Fig 1. is an image of the antibody Glutamate Decarboxylase 1 (GAD1) in mouse brain. GAD1 catalyzes the conversion of glutamic acid to gamma-aminobutyric acid (GABA) which is the major inhibitory neurotransmitter in the central nervous system (Pinal & Tobin 1998). This mechanism is used in nearly all inhibitory synapses (connections) in brains (human and mouse) to regulate the neuronal interactions. Neurons that produce GABA are called "GABAergic".

As the major regulator for inhibitory neurotransmission, it is no surprise that GAD1 is key for proper brain function. Among other diseases, GAD1 is believed to play a key role in Parkinson's disease (Zhang, Chammas, & Soghomonian 2015)

The inserts in Fig 1 show higher magnification images of GAD1 distribution in 5 brain regions. The somatosensory cortex (SS) is responsible for sense of touch and shows pyramidal neurons in the cortical layers. The cingulate cortex (Cg) is involved in memory and emotions and shows strong immunoreactivity in GABAergic synapses and also interneuron perikarya. The globus pallidus (GPe) and suprachiasmatic nucleus (SCH) which modulate movements and circadian rhythm respectively show immunoreactivity in a dense network of GABAergic axons. Lastly, the thalamic reticular nucleus (RT) regulates thalamocortical communication and shows a moderate labelling of the GABAergic synapses passing through it.

More data on GAD1 will be available in the next release of the protein atlas. In the meantime, to get a full appreciation of The Mouse Brain atlas, check out SLC2A1, another member of the membrane protein class highlighted in last week's blog.

We would like to again thank Nadya Petseva and all the team members of The Mouse Brain Atlas for their hard work on this exciting project!

Devin Sullivan