This review will cover direct modification of the neuronal cell genome to achieve

therapeutic intervention, as well as elucidation of neuronal functions. Targeted

engineering of the mammalian genome can be accomplished using viral vectors,

oligonucleotides, and DNA fragments, as well as proteins, such as recombinases and rare

restriction enzymes, which recognize specific nucleotide sequences. Topics covered

include: adeno-associated virus (AAV) mediated integration of transgenes into the

AAVS1 site; oligonucleotide site-directed gene mutagenesis and correction; homologous

recombination (HR) using small and larger DNA sequences, and use of recombinases,

such as Cre, Flp and the fC31 integrase to insert or delete genes or alter gene structure, so as to turn off or on informative genes. Therapeutic interventions are discussed, such as

replacement and correction of defective genes, as well as introduction of modulating

genes. Elucidation of neuronal functions covers marking of specific neuronal subtypes,

tracing neuronal circuitry and monitoring of neuronal activity. The review is intended to

inform gene therapists as to the multipotential approaches currently available to expand

the ability to understand and treat human disease.