The knock-in/knock-out Otx2CreERT2 allele replaces exons 1 and 2 of the orthodenticle homeobox 2 (Otx2) with a tamoxifen-inducible Cre-ERT2 under direction of the endogenous Otx2 promoter. These Otx2CreERT2 mice may be useful in studying neural development, retinal development, cellular proliferation, and medulloblastoma.
Thomas Lamonerie , Université Nice Sophia Antipolis
The transcription factor orthodenticle homeobox 2 (Otx2) plays a role in the development and organization of the central nervous system (CNS) and craniofacial structure, midbrain dopaminergic and serotonergic cell proliferation, and is associated with the formation of medulloblastomas (Di et al. 2005; Vernay et al. 2005). These knock-in/knock-out mice express Cre/ERT2 fusion protein under the direction of the endogenous Otx2 promoter.
CreERT2 fusion gene activity is inducible - observed following tamoxifen administration. As such, when Otx2-cre/ERT2 mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of floxed sequences in Otx2-expressing cells of the double mutant offspring. For example, this strain may be crossed to Otx2flox mice (Stock No. 034474) to generate an inducible self-knockout of Otx2 (Fossat et al. 2006).
The donating investigator reports that Otx2CreERT2 mice have tamoxifen-inducible Cre recombinase activity that recapitulates the endogenous Otx2 expression pattern - observed mainly in the developing CNS, with the most robust expression observed in the retina, posterior cerebellum, and forebrain ventricular zone. The donating investigator reports no CreERT2 activity is observed prior to tamoxifen.
The Otx2CreERT2 allele was created in the laboratory of Dr. Thomas Lamonerie at Ecole Normale Supérieure de Lyon. This knock-in/knock-out allele replaces coding exons 1 and 2 of the endogenous orthodenticle homeobox 2 (Otx2) gene with a Cre/ERT2 fusion gene (Cre-ERT2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain) and a PGK-neo selection cassette directed by the endogenous Otx2 promoter. The plasmid was electroporated into 129/Sv-derived ENS ES cells and recombinant clones were selected. The neo cassette, in opposite orientation, was not removed. Otx2CreERT2 positive ES cells were then injected into recipient blastocysts. Chimeric animals were then bred to C57BL/6N mice for germline transmission. The Otx2CreERT2 strain was subsequently backcrossed more than 25 generations and maintained on the 129S2/SvPas background prior to being donated to The Jackson Laboratory in 2020. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize 129S1/SvImJ oocytes (Stock No. 002448).
Of note, the donating investigator reports that the Y chromosome may not have been fixed to the 129S2/SvPas background during backcrossing.
In 2020, a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. Eight of the 43 markers were segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed 129;C57BL/6N genetic background.
|Allele Name||targeted mutation 2, Thomas Lamonerie|
|Allele Type||Targeted (Recombinase-expressing, Inducible)|
|Allele Synonym(s)||Otx2CreERT2; Otx2tm2(cre/ESR1)Tlam|
|Gene Symbol and Name||Otx2, orthodenticle homeobox 2|
|Strain of Origin||129/Sv|
|Molecular Note||A sequence encoding the tamoxifen-inducible Cre-ERT2 and a neomycin resistance gene replaced the coding region.|
When maintaining a live colony, heterozygous mice may be bred to wildtype mice from the colony. Homozygotes are embryonic lethal.
When using the Otx2CreERT2 mouse strain in a publication, please cite the originating article(s) and include JAX stock #034473 in your Materials and Methods section.