[Introduction to Gene Therapy]

After many years of research and numerous setbacks, there are now undeniable success stories of gene therapies, namely the direct modification of genetic information on the DNA or RNA level. Both "ex vivo" strategies, i. e. the genetic manipulation of patient cells in a dish, as well as "in vivo" approaches are being used successfully. In addition to the supplementation of defective genes, the use of the CRISPR-Cas9 system to alter nuclear DNA sequences and the sequence-specific interference with the transcriptional process on the RNA level can be designated as gene therapies in a broad sense.