Midbrain dopamine neurons from hESCs

The Kriks et al. protocol has finally achieved what we believe are genuine midbrain, dopamine neurons. Perrier et al. (2004) described a method to make dopamine neurons that we initially thought were mDA neurons. Later work by developmental biologists, however, discovered additional markers of these neurons that the Perrier cells lacked (e.g., FOXA2/TH). The Perrier protocol used neural rosettes as a patterning intermediate to make dopamine neurons. Later work in vivo demonstrated that rodent mDA neurons are derived from the floor plate, a cell type at the base of the neural tube that is not normally neurogenic – its usual role is to produce SHH that helps pattern the neural tube. Fasano et al. (2010) demonstrated a protocol to make floor plate from hESCs but the protocol was not efficient at making mDA neurons. Floor plate is achieved by very early, pre-rosette exposure to high levels of SHH. The Kriks et al. protocol modified this protocol to include early WNT activation, and this turned out to be the key for driving the progenitors into mature mDA neurons. Importantly, these neurons can be transplanted into the brain and retain the mDA neuron phenotype: something that the Perrier et al. cells could not do.