The PiggyBAC Transposon: Generating Transgenic Mice with Consistent Expression

Описание: In the last video which you can find right here, (   • The Basics of Transgenic Mice: Pronuclear ...  ) we talked about what transgenic mice are and how they are developed by scientists using a traditional pronuclear injection. However, there are some limitations to using the pronuclear injection method to create a transgenic animal.

In order to obtain transgenic mice scientists must inject many zygotes with the transgene before implanting them into a surrogate mother. Although the majority of them will die, each one of them possesses the potential to turn into its own transgenic mouse. In a Traditional pronuclear injection, each of these zygotes will undergo a totally random integration of the transgene. This will lead to great varieties in the expression level of the offspring.


This is great right? We should have a high expression of the transgene in individuals because so many copies have been integrated. Well not exactly. At some loci, These tandem repeats may increase the expression of the target gene, while at others, the tandem integration silences the expression of the gene itself.
The different locations that the transgene may integrate into on the chromosome may play a part in explaining the variability of the gene expression as well. Just like random integration means random number of copies, it means random location as well. If the dna integrates into an area of closed chromatin this will lead to a lower frequency of expression than if other, ore open sites on the chromosome.

For this reason, scientists have used the Piggyback transposon for over a decade as a way to generate Transgenic mice with single copy integration into areas of open chromatin. In the traditional approach used to generate transgenic mice, tandem integration often leads to variable levels of gene expression. Some individuals have medium expression and some have none at all. Using piggyback to generate transgenic mice leads to high and consistent expression of the transgene across all F1 individuals.

Watch this video to learn about how it leads to a higher, more consistent expression by discovering what it means to integrate into open TTAA site, chromatin.

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In most experiments, scientists will try to minimize the amount of independent variables so as not to confuse the results of an experiment. Unless the level of gene expression is the variable that the scientist hopes to study, using the offspring from a transgenic mouse created via traditional pronuclear injection may not be the best option.


Some images in this video were created with Biorender.

Sources:

Handler, A. M., McCombs, S. D., Fraser, M. J., & Saul, S. H. (jun 1998). The lepidopteran transposon vector, piggyBac, mediates germ-line transformation in the Mediterranean fruit fly. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.95.13.7520
Lantz, N. (Director). (2018, October 11). Introduction to Transposons [Video file]. Retrieved February 5, 2021, from    • Introduction to Transposons  
PiggyBac transgenic mice. (n.d.). Retrieved February 09, 2021, from https://www.cyagen.com/us/en/service/...
Piggybac transposon system. (2020, February 24). Retrieved February 09, 2021, from https://www.herabiolabs.com/piggybac-...
Rülicke, T., & Hübscher, U. (2004, May 05). Germ line transformation of mammals by PRONUCLEAR MICROINJECTION. Retrieved February 09, 2021, from https://physoc.onlinelibrary.wiley.co...
Woodard, L. (Director). (2019, December 4). PiggyBac Transposons to Cut and Paste DNA [Video file]. Retrieved February 5, 2021, from https://www.youtube.com/watch?reload=...
Zhao, S., Jiang, E., Chen, S., Gu, Y., Shangguan, A. J., Lv, T., . . . Yu, Z. (2016). PiggyBac transposon vectors: The tools of the human gene encoding. Translational Lung Cancer Research, 120-125. doi:10.3978/j.issn.2218-6751.2016.01.05




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