Improved Generation of Rat Gene Knockouts by Target-selected Mutagenesis in Mismatch Repair-deficient Animals
Overview
Authors
Affiliations
Background: The laboratory rat (Rattus norvegicus) is one of the preferred model organisms in physiological and pharmacological research, although the availability of specific genetic models, especially gene knockouts, is limited. N-ethyl-N-nitrosourea (ENU)-driven target-selected mutagenesis is currently the most successful method in rats, although it is still very laborious and expensive.
Results: As ENU-induced DNA damage is normally recognized by the mismatch repair (MMR) system, we hypothesized that the effectiveness of the target-selected mutagenesis approach could be improved by using a MMR-deficient genetic background. Indeed, Msh6 knockout rats were found to be more sensitive to ENU treatment and the germ line mutation rate was boosted more than two-fold to 1 mutation per 585 kb. In addition, the molecular mutation spectrum was found to be changed in favor of generating knockout-type alleles by approximately 20%, resulting in an overall increase in efficiency of approximately 2.5 fold. The improved effectiveness was demonstrated by high throughput mutation discovery in 70 Mb of sequence in a set of only 310 mutant F1 rats. This resulted in the identification of 89 mutations of which four introduced a premature stopcodon and 64 resulted in amino acid changes.
Conclusion: Taken together, we show that the use of a MMR-deficient background considerably improves ENU-driven target-selected mutagenesis in the rat, thereby reducing animal use as well as screening costs. The use of a mismatch repair-deficient genetic background for improving mutagenesis and target-selected knockout efficiency is in principle applicable to any organism of interest.
Sheardown E, Mech A, Petrazzini M, Leggieri A, Gidziela A, Hosseinian S Neurosci Biobehav Rev. 2022; 135:104559.
PMID: 35124155 PMC: 9016269. DOI: 10.1016/j.neubiorev.2022.104559.
Leaman R, Wei C, Allot A, Lu Z PLoS Biol. 2020; 18(6):e3000716.
PMID: 32479517 PMC: 7289435. DOI: 10.1371/journal.pbio.3000716.
Gallego-Llamas J, Timms A, Pitstick R, Peters J, Carlson G, Beier D PLoS One. 2016; 11(7):e0159377.
PMID: 27441645 PMC: 4956170. DOI: 10.1371/journal.pone.0159377.
Lack of major genome instability in tumors of p53 null rats.
Hermsen R, Toonen P, Kuijk E, Youssef S, Kuiper R, van Heesch S PLoS One. 2015; 10(3):e0122066.
PMID: 25811670 PMC: 4374866. DOI: 10.1371/journal.pone.0122066.
Advances on genetic rat models of epilepsy.
Serikawa T, Mashimo T, Kuramoro T, Voigt B, Ohno Y, Sasa M Exp Anim. 2014; 64(1):1-7.
PMID: 25312505 PMC: 4329510. DOI: 10.1538/expanim.14-0066.