Question

What is the complications or confounding factors with generating or interpreting results from a ‘knock-out’ mice?

Answer 1

Knock-out mice provides valuable insight regarding functions of genes, which may be correlated to humans.

However there are some limitations in the process:

• About 15% of gene knock outs may be lethal to mice. As a result, genetically altered embryos are unable to grow into adult mice, which limits the study. To avoid such limitations, alternative method was developed by Tsein and co-workers in 1996. This method was referred to as conditional gene knockout. This technique utilizes Cre/loxP mediated recombination system.
• Presence of variability called the flanking genes or the passenger genes also pose a variation in phenotypic observations. During the replacement of the wildtype genes with the desired gene, the linked flanking genes also enter the region giving a different phenotype than expected. Repeated backcrossing may reduce these variable regions.
• Further, to avoid genetic biasness, co-isogenic knockout strains are generated. However, these sub-strains created have poor breeding capabilities.
• Also there is a difference in phenotypical data in terms of behavior, reproductive capabilities, learning, memory, or neurogenetic developments between outbred and inbred strains.
• Comparing to mouse whole genome data, phenotype rescue, alternative embryonic stem cell generation and other techniques are used to resolve such issues.