Neural Activity-Dependent Tool: Tet-on/off System Introduction

AAV Vector (Tet-On/Off)

The tetracycline response element (TRE) and the tetracycline repressor protein (TetR) are essential components of the Dox-induced gene expression mechanism. After years of development, this system has been optimized numerous times. The most frequent TRE consists of seven tetracycline resistance operators (TetO) with a length of 19 amino acids. TRE and the downstream CMV promoter form the tetracycline-dependent promoter (Ptet). The alteration of TetR has resulted in the gradual emergence of a number of Tet regulatory systems, the most common of which are the inhibitory Tet-off and activating Tet-on.

Tet-off

Scientists have modified the TetR of E. coli by fusing the transcriptional activation region of the herpesvirus VP16 protein to the TetR, thereby synthesizing the transcriptional activation protein tTA and altering the nature of the TetR deterrent protein. In the absence of tetracycline, tTA binds to the TRE and VP16 activates Ptet and promotes gene expression, whereas in the presence of tetracycline, tTA binds to tetracycline and represses target gene expression.

Fig.1 The Tet-Off system.¹

Tet-on

The four key amino acid residues of tetR involved in the tetracycline-induced inhibition reaction can cause a reverse reaction after mutation of these amino acid residues, i.e. the target gene can express protein in the presence of tetracycline, but cannot express the target gene in the absence of tetracycline. The new transactivator protein is called rtTA, which is a fusion of rTetR and VP16.

Fig.2 The Tet-On system.¹

Applications in the Neurosciences

The tetracycline (Dox)-inducible gene expression system is commonly used for in vitro gene function, in vitro gene therapy, protein function and mRNA function studies, and is also used for in vivo experimental studies.

The tetracycline-inducible system primarily fulfills the function of gene expression regulation through the collaboration of pTRE and tTA/rtTA. In principle, two types of mice must be established to regulate the expression of a target gene in mice using the tetracycline-inducible system.

First, to establish pTRE mice, the target gene must be inserted downstream of the tetracycline-dependent promoter, thereby enabling the expression of the target gene to be controlled by tetracycline. Secondly, it is necessary to establish tTA or rtTA mice, in which the tTA/rtTA activating factor is driven by a specific promoter, and tTA or rtTA can be expressed in specific cells or tissues or throughout the body.

Advantages

At present, in addition to the tetracycline-induced system, scientists have also developed a variety of conditional gene regulation systems, such as the Cre-loxp system, the Flp-frt system, the Dre-rox system, etc., and the tetracycline-induced gene expression system still has its own unique advantages.

• The highest induction multiple of the Tet-On system can reach 10,000 times.
• The Tet system has high regulatory specificity and is suitable for regulating the expression of a wide range of genes in vivo and in vitro.
• The Tetracycline System is reversible. The system can be shut down after the inducer is removed, or the inducer can be added repeatedly to start the induced reaction multiple times.

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Creative Biolabs' goal is to help our clients accelerate breakthroughs in neuroscience through high-quality research services and innovative technologies. Although we do not offer the Tet-on/off System, our scientists promote the development and launch of more innovative drugs. If you have any needs or questions, please feel free to contact us and we will be happy to serve you!

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Reference

1. Hui, Yuqing, et al. "Strategies for targeting neural circuits: how to manipulate neurons using virus vehicles." Frontiers in Neural Circuits 16 (2022): 882366. Distributed under Open Access license CC BY 4.0, without modification.