What is Gene Editing and Gene Therapy?
A genetic disease is caused, either in whole or part, by mutations in DNA sequences. These mutations can result in the loss or attenuation of protein or RNA products (loss of function) or the gain of a toxic RNA or protein (gain of function). Gene editing and gene therapy hold great promise in treating, or even curing, genetic diseases. Gene therapy works by adding a functional copy of a DNA sequence into a cell or by suppressing harmful activity from a native DNA sequence (i.e., a native DNA sequence that produces a toxic RNA or protein). Gene editing seeks to correct disease-related DNA sequences directly, resulting in permanent fixes. While gene editing and gene therapy each have advantages and drawbacks in their applications, both have strong potential to treat or potentially cure a broad range of diseases.
Gene editing seeks to change DNA sequences within living cells. Gene editing has the potential to correct inherited or acquired genetic errors. To change a DNA sequence, two basic steps are required: first, to locate the DNA sequence of interest, and second, to correct that DNA sequence.
We search for specific DNA sequences using proteins that naturally recognize DNA sequences. Several of these proteins can be reprogrammed to recognize a desired DNA sequence, thereby enabling the location of genes with mutations. Mutated DNA sequences can be corrected in many ways, including introducing a controlled DNA break, the most common form of gene editing. This controlled break, referred to as a DNA double-strand break, enables, in general, four types of changes:
- Targeted mutagenesis. A small number of DNA bases are deleted or added at the site of the DNA double-strand break.
- Targeted deletion. The DNA sequence between two DNA double-strand breaks is deleted.
- Targeted insertion. A user-supplied DNA molecule is inserted at the site of a DNA double-strand break.
- Precise modification. A user-supplied DNA molecule recombines with the sequence adjacent to the DNA double-strand break, resulting in the seamless correction of the DNA sequence.
1. Targeted Mutagenesis
Target DNA sequence (e.g., an aberrant gene)
Modified DNA sequence
2. Targeted Deletion
3. Targeted Insertion
User-supplied therapeutic nucleic acid
4. Precise Repair
User-supplied therapeutic nucleic acid with homology arms
While gene editing seeks to directly change DNA sequences, gene therapy seeks to add a functional copy of a DNA sequence into a cell or suppress harmful activity from a native DNA sequence.