| Serotonin neurons populate the vertebrate mid-hindbrain and project throughout the central nervous system. This expansive projection pattern permits the serotonergic modulation of circuit activity and behaviors that underlie affect, motor activity, perception and cognition. Not surprisingly, alterations in serotonergic neurotransmission are associated with the development of several CNS pathologies, including depression, obsessive compulsive disorder, aggression and autism. However, the molecular mechanisms underlying these conditions are just beginning to be investigated. Little is known of the genetic interactions that control the development and maintenance of the serotonin system. Recently, the ETS family transcription factor Pet-1 was demonstrated to be expressed specifically in the CNS in serotonin neurons and be required for the specification of this neurotransmitter system. The work presented in the following chapters describes the isolation of the Pet-1 enhancer elements, located in 40kb of genomic DNA 5 ' of the Pet-1 gene. Reporter gene expression driven by the 40kb fragment was demonstrated to be reproducible and accurate in murine serotonin neurons with no ectopic expression in the CNS and minimal expression in the periphery. The enhancer activity was subsequently shown to be present in 1.8kb of the 40kb fragment, directly 5' of the Pet-1 gene. The utility of the 40kb enhancer fragment for the manipulation of the serotonin system was then confirmed with the expression of cre recombinase and eYFP selectively in serotonin neurons. Finally, the serotonin neuron specific cre recombinase was employed to selectively delete the MAP kinase Erk2, marking the beginning of studies aimed at exploring cell autonomous gene function in the serotonin system. |
