Figure 3. The distinctive molecular signatures of the six dopamine neuron subtypes.

The normalized expression profile of the six dopamine (DA) neuron subtypes is illustrated using 18 key genes. Plotting cells on the four extracted components of the principal component analysis allow to differentiate most DA subtypes. (a) DA^1A is the only subtype with high expression of Aldh1a1. Sox6, Ndnf and low/absent expression of Foxa2 and Lmx1a. (b) DA^1B depicts an expression profile similar to DA^1A, but lacks Aldh1a1 expression. (c) DA^2A is characterized by the high expression of Slc32a1, but low expression of Satb1, Gsg1l, and Clstn2. (d) DA^2B is defined by the unique co-expression of Lpl, Adcyap1, Otx2 and Aldh1a1. (e) No distinctive marker could be identified for subtype DA^2C, which also possesses some similarity with DA^1B, if it was not for high levels of Calb1, Cck and Slc17a6. (f) DA^2D can be identified by the unique expression of Vip, combined with low expression of Snca, Chrna4, and Ntf3.