gene delivery (rus. доставка генов) — process of introducing target genes into the nucleus of a target host cell.

Description

The process consists of the following steps: 1) packaging of genes into a vector; 2) delivery of vectors to target cells; 3) insertion of the genes into the cells; 4) insertion of the genes into the cell nucleus.

The simplest vector for gene delivery is a plasmid created by genetic engineering, a circular DNA of several thousand base pairs in size. The plasmid should contain the target gene and its promoter, as well as various regulatory and signal sequences required for the synthesis of large amounts of mRNA and target protein. The plasmid should also contain DNA sequences for its reproduction in bacterial cells. In gene therapy, plasmid DNA is often called "naked DNA", meaning that the gene is not placed in a protective nanocontainer. The efficiency of naked DNA gene transfer is low, but it does not require use of nanocontainers, whose biological effects are not always predictable.

To improve the efficiency of gene delivery into cells it has been proposed to use viral vectors (adenovirus, lentivirus, etc.), and nonviral vectors (liposomes, dendrimers, DNA-lipid complexes, etc.). Targeted delivery is mediated by specific molecules on the vector surface which are recognised by receptors on the target cells. These molecules include viral capsid proteins recognised by cell surface receptors, integrated into the liposome membrane antibodies to cell surface antigens, and folic acid molecules that are captured by tumour cells. Therapeutic genes can be released into cell cytoplasm, for example, when a liposome fuses with the cytoplasmic membrane. Otherwise, cell membrane is drawn into the cytoplasm (invaginated) at the site of vector attachment and pinched off to form a membrane vesicle (endosome). Endosomes then fuse with other vesicles, but some physical and chemical methods help to release the introduced genes directly into the cytoplasm. These genes penetrate into the nucleus during cell division, when the nuclear membrane disappears and then reforms, and a part of the foreign DNA becomes introduced into the nucleus. Lentivirus vectors have a specific protein that helps to import the viral RNA genome with the inserted therapeutic gene into the nucleus through the nuclear pores. This property allows lentivirus vectors to introduce genes into the nucleus of nondividing or rarely dividing cells, such as neurons, heart muscle cells, and stem cells. The gene must be introduced into the nucleus for its integration into the cell genome and functioning as a part of genome. Carried inside lentivirus RNA genome, it is first converted into DNA with the help of viral and nuclear enzymes. Genes that are not introduced into the genome still have to get into the nucleus, because that is the location of enzyme systems for the synthesis and processing of mRNAs necessary for protein production.

Author

  • Shirinsky Vladimir P.

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