β2KO mice have a neo cassette replacing exon 1 of the Sntb2 gene. These mice may be useful when studying the dystrophin complex and Duchenne muscular dystrophy.
Stanley C Froehner, University of Washington
β2KO mice have a neo cassette replacing exon 1 of the syntrophin, basic 2 (Sntb2) gene, which encodes half of the first PH domain and the entire PDZ domain. Syntrophins are a family of 58-60 kDa proteins consisting of five isoforms (α, β1, β2, γ1 and γ2) encoded by separate genes. α, β1, and β2 have multiple binding motifs and directly bind to dystrophin, utrophin and dystrobrevin, where they recruit and anchor a variety of signaling proteins. Specifically, β2-Syntrophin encodes a dystrophin associated protein expressed primarily at the neuromuscular junction (NMJ). Dystrophin is a large, rod-like cytoskeletal protein found at the inner surface of muscle fibers. Dystrophin is missing in Duchenne Muscular Dystrophy (DMD) patients and is present in reduced amounts in Becker Muscular Dystrophy patients. Muscular Dystrophy is a genetic disorder characterized by progressive muscle degeneration and weakness due to the alterations of dystrophin that helps keep muscle cells intact. β2KO homozygous mice are viable and fertile, with no overt phenotype, or muscular dystrophy, and form structurally normal NMJs.
When β2KO mice are bred to αKO mice (Stock No. 012940), NMJs from resulting double knock-out (DKO) mice have fewer junctional folds than either parent strain, and the remaining folds are abnormally shaped with few openings to the synaptic space. The levels of acetylcholine receptors are reduced to 23% of wild type in mice lacking both isoforms. Furthermore, the DKO mice run significantly shorter distances on voluntary exercise wheels despite having normal neuromuscular junction transmission as determined by micro-electrode recording of endplate potentials.
β2KO mice were also bred to αKO mice and β1KO mice (Stock No. 035532) to produce triple syntrophin knockout (tKO) mice. tKO mice exhibit diminished function and reduced dystrophin expression in both cardiac and skeletal muscle.
The β2-syn KO targeting vector was designed to replace exon 1 with a neomycin resistance (neo) cassette. The construct was electroporated into 129P2/OlaHsd-derived E14 embryonic stem (ES) cells and correctly targeted ES cells were injected into (C3H x C57BL/6)F1 recipient blastocysts. The resulting β2KO chimeric mice were backcrossed to C57BL/6J mice (Stock No. 000664) for at least 10 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.
|Allele Name||targeted mutation 1, Stanley C Froehner|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||beta2SynKO; Sntb2tm1Maad|
|Gene Symbol and Name||Sntb2, syntrophin, basic 2|
|Strain of Origin||129P2/OlaHsd|
|Molecular Note||A neo replaced exon 1, amino acids 1-173 which encode half of the first PH domain and the entire PDZ domain. Immunoblot confirmed the absence of protein in mutant muscle extracts.|
When maintaining a live colony, homozygous mice may be bred together.
When using the beta2SynKO mouse strain in a publication, please cite the originating article(s) and include JAX stock #035533 in your Materials and Methods section.