Genetically modified organisms, called GMOs, are organisms whose genetic material (DNA) is altered.
For example, pieces of DNA can be cut out (knock-out), as in the “Apolipoprotein E receptor knock-out mouse”.
In this mouse, the Apolipoprotein E receptorgen is cut out. Due to the absence of this receptor, cholesterol transport is disturbed. Because of this, the animals develop high cholesterol levels in the blood.
Figure 3: Female Apolipoprotein E receptor knock-out mouse with her litter.
In addition, pieces of DNA can also be added (knock-in), as in the “CX3-CR1-eGFP mouse”.
In this mouse, a green fluorescent protein (eGFP) is added to the CX3-CR1 gene, which is present in microglia, a special cell type of the central nervous system. Therefore, these microglia have a green colour when looked at from under a microscope.
Figure 4: Male CX3-CR1-eGFP mouse.
Figure 5: Microscopic photograph of tissue from a CX3-CR1-eGFP mouse. By labeling the DNA of the mouse with a green fluorescent protein (eGFP), the microglia, a specific cell type of the nervous system, have a green color. Additional manual staining was performed to visualize the blood vessels in this photograph with a red fluorescent color.
Even human DNA can be added as in the “APP/PS1 mouse”.
In this case, two human mutations were applied to the DNA of the mouse. These mutations were found in patients diagnosed with Alzheimer’s disease. Therefore, the animals will develop a similar disease process. At a later age, they will encounter memory problems.
Figure 6: Male APP/PS1 mouse.