Difference Between Transgenic and Knockout Mice

The key difference between transgenic and knockout mice is that transgenic mice have foreign genes inserted into its genome while knockout mice have a functionally inactivated gene of interest.

Genetic engineering is the field of genetics in which the genetic makeup of an organism is modified or manipulated by recombinant DNA technology. Transgenic organisms are made by introducing foreign genes (transgenes) into organisms using biotechnology. They are also called genetically modified organisms. Transgenic organisms are valuable research tools. They are important in exploring a gene’s function and in gene therapy and agriculture. Mice are used as laboratory animal models since they are more closely related to humans. Transgenic mice and knockout mice are two types of genetically modified animals. In transgenic mice, the host’s DNA at a locus is replaced with a different version of the same gene or a completely different gene. In knockout mice, the host gene is simply deleted or functionally inactivated.

CONTENTS

1. Overview and Key Difference
2. What is Transgenic Mice
3. What is Knockout Mice
4. Similarities Between Transgenic and Knockout Mice
5. Side by Side Comparison – Transgenic vs Knockout Mice in Tabular Form
6. Summary

What are Transgenic Mice?

Transgenic mice are genetically modified mice which have a genetically modified genome via genetic engineering techniques. Foreign DNA can be introduced into the mice in three ways in transgenic mouse technology. These three methods are involving DNA delivery by retroviral infection of mouse embryos at different developing stages, direct microinjection of foreign DNA into the pronuclei of fertilized one-cell mouse embryos and targeted manipulation of mouse embryonic stem (ES) cells at desired loci by introducing loss or gain of function mutations. There are two types of transgenic mice based on the loss or gain of function. They are knockout mice (loss of function) and knockin mice (gain of function).

What are Knockout Mice?

Knockout mice are one of the two types of transgenic mice. In knockout mice, a gene is depleted or silenced to cause a loss of gene function. Therefore, knockout mice are genetically modified organisms. Knockout of a gene can be done replacing it or by inserting an artificial piece of DNA to inactivate it. There are many different types of knockout mice. Knockout mice provide valuable information about the function of the gene. They are used in research in order to study different types of cancers and diseases such as obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, ageing and Parkinson’s disease, etc. In cancer therapy, the target gene inactivation suppresses tumour development.

There are two knockout models as constitutive and conditional. In the constitutive knockout model, the target gene is permanently inactivated in the whole animal while in the conditional knockout model, inducible inactivation of gene expression takes place as tissue-specific or temporal manner.

What are the Similarities Between Transgenic and Knockout Mice?

• Both transgenic and knockout mice are genetically modified animals.
• They have an altered genome.
• They are important research tools.

What is the Difference Between Transgenic and Knockout Mice?

Transgenic mice are genetically modified mice that have foreign DNA introduced to them. Knockout mice are a type of transgenic mice that have a gene deleted or silenced in order to inactivate it functionally. So, this is the key difference between transgenic and knockout mice.

Summary – Transgenic vs Knockout Mice

Transgenic mice have foreign genes inserted into their genome. Knockout mice have a gene that is depleted or silenced to cause a loss of gene function. Knockout mice are a type of transgenic or genetically modified organisms. Both transgenic and knockout mice are used extensively in research as models of human disease. Thus, this summarizes the difference between transgenic and knockout mice.

Reference:

1. Kumar, T Rajendra, et al. “Transgenic Mouse Technology: Principles and Methods.” Methods in Molecular Biology (Clifton, N.J.), U.S. National Library of Medicine, 2009, Available here.
2. “8.8: Transgenic Organisms.” Biology LibreTexts, Libretexts, 13 Sept. 2020, Available here.

Image Courtesy:

1. “Knockout Mice5006-300” By – Ingrid Moen, Charlotte Jevne, Jian Wang, Karl-Henning Kalland, Martha Chekenya, Lars A Akslen, Linda Sleire, Per Ø Enger, Rolf K Reed, Anne M Øyan and Linda EB Stuhr: Gene expression in tumor cells and stroma in dsRed 4T1 tumors in eGFP-expressing mice with and without enhanced oxygenation. In: BMC Cancer. 2012, 12:21. doi:10.1186/1471-2407-12-21 PDF (CC BY 2.0) via Commons Wikimedia

2. “GFP Mice 01” By Maggie Bartlett, NHGRI. –  (Public Domain) via Commons Wikimedia