B6(SJL)-Plxnb2^{tm1c(EUCOMM)Wtsi}/FrdlJ

Stock number: 036883
Product name: Plexin-B2^fl
Research areas: Cell Biology Research, Developmental Biology Research, Immunology, Inflammation and Autoimmunity Research, Internal/Organ Research, Neurobiology Research, Research Tools

Description

Plexin-B2^fl/fl floxed mice have loxP sites flanking coding exons 7-9 of the Plxnb2 gene. These mice are useful for studying growth, migration, survival, and regeneration during neuronal development, as well as wound healing and cellular responses to damage.

Detailed description

Plexin-B2^fl/fl floxed mice have loxP sites flanking coding exons 7-9 of the plexin B2 (Plxnb2) gene. Plxnb2 encodes a member of a family of Semaphorin receptors involved in the regulation of neural development and axon guidance, playing a specific role in the development of cerebellar granule cells. Homozygous floxed mice are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have coding exons 7-9 deleted in the Cre-expressing tissues.

When bred to Nestin^Cre mice (Stock No. 003771), and also bred to Plxnb2 knock-out mice, resulting Nestin^Cre Plxnb2^fl/- mice display cerebellum migratory defects of cerebellar granule cells, with clusters of ectopic granule cells found near the surface of the adult cerebellum, and in the rostral migratory stream defects of olfactory granule cell precursors, with aberrant chains of granule cells present in the olfactory bulb.

When Nestin^Cre Plxnb2^fl/- mice were also bred to Plxnb1 knock-out mice, a thinner size of the cortex is observed.

When bred to Cx3cr1^CreER mice, and also bred to Plxnb2^B lacZ knock-in/knock-out mice, resulting Cx3cr1^CreER Plxnb2^fl/B mice display impaired phagocytic immune cell corralling, leading to diffuse tissue damage, inflammatory spillover, and hampered axon regeneration after spinal cord injury (SCI), with tamoxifen administration every other day. They show significantly worse recovery in walking, hindlimb movement, and hindpaw placement relative to wildtype controls but have no apparent differences in microglia cell survival, morphology, or growth rate.

Development

The L1L2_st1 cassette was inserted at a position on Chromosome 15 upstream of coding exon 7 of the plexin B2 (Plxnb2) gene. The cassette is composed of a frt-flanked lacZ/neomycin cassette, followed by a loxP site. A second loxP site was inserted downstream of coding exon 9. Exon numbering by the International Mouse Phenotyping Consortium (IMPC) includes a 5’ non-coding exon, making their reported targeted exons 8-10. The mutation was generated in C57BL/6N-derived JM8.N4 embryonic stem (ES) cells, and correctly targeted ES cells of clone EPD0051_2_D09 were injected into blastocysts. The resulting chimeric mice were bred to C57BL/6J mice and then subsequently to ACTB:FLPe mice (Stock No. 005703) to remove the frt-flanked lacZ/neomycin cassette. Resulting Plexin-B2^fl mice were bred to C57BL/6J mice for at least 2 generations. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

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 rederived living colony at The Jackson Laboratory Repository. Three of the 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/6N;C57BL/6J genetic background.

Allele

Symbol: Plxnb2^{tm1c(EUCOMM)Wtsi}
Name: targeted mutation 1c, Wellcome Trust Sanger Institute
MGI accession ID: MGI:5706788
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed)
Synonyms: Plexin-B2^fl
Marker symbol: Plxnb2
Marker name: plexin B2
Marker synonyms: 1110007H23Rik; Debt; dJ402G11.3; lncFAL; mKIAA0315; MM1; Nbla00445; PLEXB2
Chromosome: 15
Strain of origin: C57BL/6N
Molecular note: The L1L2_st1 cassette was inserted at position 89047954 of Chromosome 15 upstream of the critical exons 8-10 (coding exons 7-9, Build GRCm39). The cassette is composed of an FRT flanked lacZ/neomycin sequence followed by a loxP site. An additional loxP site is inserted downstream of the targeted exon 8-10 at position 89049222. The critical exons 8-10 are thus flanked by loxP sites. A "conditional ready" (floxed) allele was created by flp recombinase expression in mice carrying this allele. Subsequent cre expression results in a knockout mouse. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml.