These floxed mutant mice possess loxP sites flanking the single exon of the Ddr1a gene. This strain may be useful for generating conditional mutations for applications related to behavioral responses.
Dr. Susumu Tonegawa, Massachusetts Institute of Technology
The single exon of the mouse Drd1a (dopamine receptor D1A) gene is flanked by loxP sites in this conditional targeted mutant strain. Cre-mediated excision of the floxed region produces a knockout allele.
Animals created from crosses with Camk2a-Cre mice (e.g. Stock No. 005359) to create knockouts in excitatory neurons of the mouse forebrain demonstrate significant fear memory deficits. Animals created from crosses with Pomc-Cre mice (e.g. Stock No. 010714) to create knockouts in the granule cells of the dentate gyrus also demonstrate significant fear memory deficits. They exhibit generalized fear between two similar, but different, contexts. Dentate gyrus c-Fos levels in a familiar home cage are higher in the mutant mice than in control wildtype mice. However, c-fos levels do not increase further upon exposure to a novel context or upon shock delivery as observed in control animals. Evidence suggests that this gene contributes to the formation of distinct contextual representations of novel environments.
Animals homozygous for widespread knockouts of Drd1a receptors are not viable after weaning (~3 weeks of age) unless food access is made easily available (e.g., food paste near animal bedding).
A loxP site was introduced 5' of the targeted gene's single exon and an FRT-loxP-(neo-tk)-FRT-loxP (LFNT) cassette was introduced 3' of the exon. The mutation was created through homologous recombination in B6.Cg-Thy1a-derived Bruce 4 embryonic stem (ES) cells. Transfection with a plasmid carrying Cre recombinase excised the neo cassette, leaving the coding region flanked by loxP sites. Mice were then backcrossed 4-5 generations to C57BL/6 by the donating lab.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 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. Two of the 27 markers throughout the genome were segregating, suggesting an incomplete backcross. Also, 2 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.
|Allele Name||targeted mutation 2.1, Susumu Tonegawa|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Allele Synonym(s)||D1R flx|
|Gene Symbol and Name||Drd1, dopamine receptor D1|
|Strain of Origin||B6.Cg-Thy1a|
|Molecular Note||A loxP site was introduced 5' of the targeted gene's single exon and an FRT-loxP-(neo-tk)-FRT-loxP (LFNT) cassette was introduced 3'. Cre-mediated recombination excised the neo cassette, leaving the coding region flanked by loxP sites.|
Heterozygous and homozygous floxed mice are viable and fertile.
When using the STOCK Drd1tm2.1Stl/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #025700 in your Materials and Methods section.