Rosa26LsLBcorA mice contain Cre-inducible myc-tagged Bcor*A gene expressed from the Gt(ROSA)26Sor locus. This strain is useful for studying X-linked Microphthalmia Syndromic 2 (MCOPS2) disorders.
Vivian J. Bardwell, University of Minnesota
Rosa26LsLBcorA mice contain loxP-flanked STOP cassette (including a neo cassette and 4 polyadenylation signals) and a myc-tagged BCL6 interacting corepressor (Bcor) isoform A (Bcor*A) cDNA, followed by another polyadenylation signal. This targeting vector was inserted into the Gt(ROSA)26Sor locus. BCOR is a transcriptional corepressor that plays a role in embryonic development and tumor development. BCOR mutations cause two rare X-linked Microphthalmia Syndromic 2 (MCOPS2) disorders: Oculofaciocardiodental syndrome (OFCD) and MAA2 associated Lenz microphthalmia. OFCD is only seen in females and is characterized by defects in the craniofacial, skeletal, and cardiovascular systems. Virtually all reported OFCD mutations, which include nonsense, frameshifting insertions/deletions/duplications, splicing mutations, and large deletions, are predicted to reduce BCOR function via gene loss or protein truncation and/or nonsense-mediated decay. Hemizygous OFCD mutations of BCOR in males cause embryonic lethality. MAA2 associated Lenz Microphthalmia presentation is characterized by microphthalmia and clinical anophthalmia, mental retardation, cardiac anomalies, radioulnar synostosis, and other skeletal anomalies, and has been seen in only males and results from a BCOR missense point mutation (P85L).
Of four isoforms, isoform A includes all possible coding sequences of Bcor. Mice that are homozygous for this Gt(ROSA)26Sor targeted insertion are viable and fertile.
In the absence of Cre, myc-tagged Bcor*A gene expression is prevented by the STOP cassette. After removal of the loxP-flanked STOP cassette via cre-mediated recombination, myc-tagged Bcor*A expression is evident where cre recombinase is expressed.
When bred to β-actin Cre mice (Stock No. 033984) mice, overexpression of Bcor*A during development results in complete midgestation lethality by E14.5. The embryos hindbrain is more bulbous, and by E12.5 the snout and mandible are shortened and misshapen. By E12.5 the eyes are misshapen, and by E13.5 they exhibit small and misshapen forelimbs.
The Rosa26LsLBcorA targeting vector was designed with a loxP-flanked STOP cassette (containing a neomycin resistance cassette and 4 polyadenylation signals) and a myc-tagged BCL6 interacting corepressor (Bcor) isoform A (Bcor*A) cDNA, followed by another polyadenylation signal. This targeting vector was inserted into the Gt(ROSA)26Sor locus. The construct was electroporated into 129S1/Sv-Oca2+ Tyr+ Kitl+-derived CJ7 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts and resulting chimeric mice were bred with C57BL/6N mice. Resulting Rosa26LsLBcorA mice were bred to C57BL/6N mice for at least 5 generations by the donating laboratory (see SNP note below). Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6JN oocytes (Stock No. 005304).
In 2021, 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 males sent to The Jackson Laboratory Repository. Six of the 43 markers throughout the genome were segregating with 129. Also, two of the 5 markers that determine C57BL/6J from C57BL/6N, on Chromosomes 1 and 8, were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed genetic background.
|Allele Name||targeted mutation 1, Vivian J Bardwell|
|Allele Type||Targeted (Conditional ready (e.g. floxed), Inserted expressed sequence)|
|Gene Symbol and Name||Gt(ROSA)26Sor, gene trap ROSA 26, Philippe Soriano|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|Molecular Note||A conditional Lox-Stop-Lox myc-tagged Bcor splice version A (mBcorA) expression cassette was inserted into the murine ROSA26 locus. Overexpression can be induced by cre excision of the loxP-flanked stop-cassette (LsL).|
When maintaining a live colony, homozygous mice may be bred together.
When using the Rosa26LsLmBcorA mouse strain in a publication, please cite the originating article(s) and include JAX stock #035714 in your Materials and Methods section.