There are so many different kinds of neurons in the brain and they control all sorts of mechanisms. In C.elegans, several dopamine(a neurotransmitter) -secreting neurons are differentiated from different lineage, but they are all producing dopamine. This has raised an interesting question: are the genes controlling the dopamine synthesis regulated differently or the same way in different dopamine-secreting neurons?
A recent study by Nuria Flames & Oliver Hobert from Columbia University has revealed the latter is true. They made extensive promoter constructs of all the genes involved in dopamine production (which is a good example for those of us who are going to do similar promoter analyses). Their results showed all five genes were regulated by the same regulatory element, presumably by the same transcription factor(s). Therefore, these dopamine synthesis genes are regulated the same way in different dopaminergic neurons. More importantly, they have also found that this regulatory mechanism is conserved in mice!
This is the terminal differentiation we have just discussed. The study has demonstrated that this differentiation circuit is modular and has been incorporated in different types of dopaminergic neurons to carry out the same final function. In other words, the final output function of the gene network is the same while the upstream specification architecture can be quite different.
Reference
Flames N, Hobert O. Gene regulatory logic of dopamine neuron differentiation. Nature. 2009 Apr 16;458(7240):885-9. [PubMed][Nature][Commentary in Nature]