Mammalian nervous systems are composed of diverse neurons, some of which have been identified by one or more properties: specific shape, physiology, or molecular signature. However, a consensus approach to neuronal classification does not exist, and the correlations of different types of neuronal properties with one another and neuronal function have not been systematically examined. Therefore, scientists still don’t know how many different flavors of cellular building blocks comprise even relatively simple mammalian brains such as the mouse brain.

The Molecular Genetics team with the Allen Institute's Brain Science accelerator approaches this question at the molecular level by analyzing transcriptomes and epigenetic landscapes of individual neurons. Through these efforts, they have discovered many specific marker genes and enhancers that can be used to classify these cells into types and that we use to create tools for genetic access to specific cell types. They also collaborate with many teams across the institute to establish multi-modal neuronal phenotyping and classification. In the long run, they hope their studies will reveal how molecular characteristics determine neuronal phenotypes, and how they govern myriads of functions carried out by mammalian brains.