Limitations of the Pax7-creER(T2) transgene for driving deletion of Nf1 in adult mouse muscle

作者：Summers Matthew A; Mikulec Kathy; Peacock Lauren; Little David G; Schindeler Aaron^*

来源：International Journal of Developmental Biology, 2017, 61(8-9): 531-536.

DOI：10.1387/ijdb.170182as

• neurofibromatosis type 1 (NF1)
• muscle weakness
• myopathy
• Cre-ERT2
• cre/loxP

Neurofibromatosis Type 1 (NF1) is an autosomal dominant genetic disorder that results in a variety of characteristic manifestations. Prior studies have shown reduced muscle size and global skeletal muscle weakness in children with NF1. This associated weakness can lead to significant challenges impacting on quality of life. Pre-clinical studies using a muscle-specific NF1 knockout mouse have linked this weakness to an underlying primary metabolic deficiency in the muscle. However, the neonatal lethality of this strain prevents analysis of the role of NF1 in adult muscle. In this study, we present the characterization of an inducible muscle-specific NF1 knockout strain (Nf1Pax7i(f/f)) produced by cross breeding the Pax7-CreER(T2) strain with the conditional Nf1flox/(flox) line. Tamoxifen dosing of 8-week old Nf1Pax7i(f/f) mice led to recombination of the floxed allele in muscle, as detected by PCR. Detailed phenotypic analysis of treated adult mice over 8 weeks revealed no changes in body weight or muscle weight, no histological signs of myopathy, and no functional evidence of distress or impairment. Subsequent analysis using the Ai9 Cre-dependent td Tomato reporter strain was used to analyse labelling in embryos and in adult mice. Cell tracking studies identified a lower than expected rate of integration of recombined satellite cells into adult muscle. In contrast, a high persistent contribution of embryonic cells that were Pax7+ were found in adult muscle. These findings indicate important caveats with the use of the Pax7-CreER(T2) strain and highlight a need to develop new tools for investigating the function of NF1 in mature muscle.

• 出版日期2017