Adeno-Associated Virus Tet Inducible Gene Expression Vector
VectorBuilder’s adeno-associated virus (AAV) Tet inducible gene expression vector combines the highly versatile AAV vector system and the Tet inducible gene expression system to help you achieve AAV-mediated in vitro and in vivo delivery of tetracycline-inducible gene expression cassettes.
The Tet-On inducible system is a powerful tool to control the timing of expression of the gene(s) of interest (GOI) in mammalian cells. Our Tet-On inducible gene expression vectors are designed to achieve nearly complete silencing of a GOI in the absence of tetracycline and its analogs (e.g. doxycycline), and strong, rapid expression in response to the addition of tetracycline or one of its analogs (e.g. doxycycline). This is achieved through a multicomponent system which incorporates active silencing by the tTS protein in the absence of tetracycline and strong activation by the rtTA protein in the presence of tetracycline. In the absence of tetracycline, the tTS protein derived from the fusion of TetR (Tet repressor protein) and KRAB-AB (the transcriptional repressor domain of Kid-1 protein) binds to the tetracycline responsive-element (TRE) promoter, leading to the active suppression of gene transcription. The rtTA protein, on the other hand, derived from the fusion of a mutant Tet repressor and VP16 (the transcription activator domain of virion protein 16 of herpes simplex virus), binds to the TRE promoter to activate gene transcription only in the presence of tetracycline.
While our AAV Tet inducible gene expression vector includes an inducible gene expression cassette consisting of the TRE promoter driving the user-selected GOI, the TRE binding regulatory proteins tTS and rtTA have to be provided using a separate helper vector to achieve tetracycline induced gene expression in the presence of tetracycline, while minimizing leaky expression in the absence of tetracycline. Users have the option to select between either the 2nd generation (TRE) or the 3rd generation (TRE3G) promoter to drive the expression of their GOI.
The AAV Tet inducible gene expression vector is first constructed as a plasmid in E. coli. It is then transfected into packaging cells along with helper plasmids, where the region of the vector between the two inverted terminal repeats (ITRs) is packaged into live virus. The tetracycline inducible gene expression cassette consisting of the TRE promoter driving the user-selected GOI is placed in-between the two ITRs, which is introduced into target cells along with the rest of viral genome. Gene expression can then be turned on in the presence of the rtTA regulatory protein and tetracycline.
AAV is effective in transducing many mammalian cell types, and, unlike adenovirus, has very low immunogenicity, being almost entirely nonpathogenic in vivo. This makes the AAV inducible gene expression vector the ideal viral vector system for achieving inducible gene expression in vivo.
The wild-type AAV genome is a linear single-stranded DNA (ssDNA) with two ITRs forming a hairpin structure on each end. It is therefore also known as ssAAV. In order to express genes on ssAAV vectors in host cells, the ssDNA genome needs to first be converted to double-stranded DNA (dsDNA) through two pathways: 1) synthesis of second-strand DNA by the DNA polymerase machinery of host cells using the existing ssDNA genome as the template and the 3' ITR as the priming site; 2) formation of intermolecular dsDNA between the plus- and minus-strand ssAAV genomes. The former pathway is the dominant one.
AAV genomic DNA forms episomal concatemers in the host cell nucleus. In non-dividing cells, these concatemers can remain for the life of the host cells. In dividing cells, AAV DNA is lost through the dilution effect of cell division, because the episomal DNA does not replicate alongside host cell DNA. Random integration of AAV DNA into the host genome can occur but is extremely rare. The lack of integration is desirable in many gene therapy settings where the potential oncogenic effect of vector integration can pose a significant concern.
A major practical advantage of AAV is that in most cases AAV can be handled in biosafety level 1 (BSL1) facilities. This is due to AAV being inherently replication-deficient, producing little or no inflammation, and causing no known human disease.
Many strains of AAV have been identified in nature. They are divided into different serotypes based on different antigenicity of the capsid protein on the viral surface. Different serotypes can render the virus with different tissue tropism (i.e. tissue specificity of infection). When our AAV vectors are packaged into virus, different serotypes can be conferred to the virus by using different capsid proteins for the packaging. The table below lists different AAV serotypes and their tissue tropism.
||Smooth muscle, CNS, brain, lung, retina, inner ear, pancreas, heart, liver
||Smooth muscle, CNS, brain, liver, pancreas, kidney, retina, inner ear, testes
||Smooth muscle, liver, lung
||CNS, retina, lung, kidney, heart
||Smooth muscle, CNS, brain, lung, retina, heart
||Smooth muscle, heart, lung, pancreas, adipose, liver
||Lung, liver, inner ear
||Smooth muscle, retina, CNS, brain, liver
||Smooth muscle, CNS, brain, retina, inner ear, liver, pancreas, heart, kidney, adipose
||Smooth muscle, lung, liver, heart, pancreas, CNS, retina, inner ear, testes, kidney, adipose
||Smooth muscle, lung, liver, heart, pancreas, CNS, retina, kidney
||Liver, heart, kidney, spleen
||Liver, brain, spleen, kidney
||Retina, inner ear
||Recommended AAV serotypes
||AAV1, AAV2, AAV3, AAV5, AAV6, AAV7, AAV8, AAV9, AAVrh10
||AAV1, AAV2, AAV4, AAV5, AAV7, AAV8, AAV9, AAVrh10, AAV-PHP.eB
||AAV1, AAV2, AAV5, AAV7, AAV8, AAV-DJ/8
||AAV1, AAV2, AAV4, AAV5, AAV7, AAV8, AAV9, AAVrh10, AAV2.7m8
||AAV1, AAV2, AAV6.2, AAV8, AAV9, AAV2.7m8
||AAV1, AAV3, AAV4, AAV5, AAV6, AAV6.2, AAV9, AAVrh10
||AAV1, AAV2, AAV3, AAV6, AAV6.2, AAV7, AAV8, AAV9, AAVrh10, AAV-DJ, AAV-DJ/8
||AAV1, AAV2, AAV6, AAV8, AAV9, AAVrh10
||AAV1,AAV4, AAV5, AAV6, AAV8, AAV9, AAVrh10, AAV-DJ
||AAV2, AAV4, AAV8, AAV9, AAVrh10, AAV-DJ, AAV-DJ/8
||AAV6, AAV8, AAV9
For further information about this vector system, please refer to the papers below.