Temporally controlled targeted somatic mutagenesis in skeletal muscles of the mouse

Abstract

To generate temporally controlled targeted somatic mutations selectively and efficiently in skeletal muscles, we established a transgenic HSA-Cre-ER(T2) mouse line in which the expression of the tamoxifen-dependent Cre-ER(T2) recombinase is under the control of a large genomic DNA segment of the human skeletal muscle alpha-actin gene, contained in a P1-derived artificial chromosome. In this transgenic line Cre-ER(T2) is selectively expressed in skeletal muscles, and Cre-ER(T2)-mediated alteration of LoxP flanked (floxed) target genes is skeletal muscle-specific and strictly tamoxifen-dependent. HSA-Cre-ER(T2) mice should be of great value to analyze gene function in skeletal muscles, and to establish animal models of human skeletal muscle disorders.

Muscle-specific 4E-BP1 signaling activation improves metabolic parameters during aging and obesity

“…While we cannot rule out a model whereby brown fat levels are enhanced due to secondary effects of reduced subcutaneous white fat to maintain body temperature, this seems unlikely since inactivation of Rptor in skeletal muscle also leads to white adipose tissue atrophy, without an increase in brown fat or any changes in body temperature regulation (17). Instead, we favor a model whereby (a) a myokine signal is transmitted from the skeletal muscle of Tg-4EBP1mt-muscle mice to brown fat or (b) mice with HSA-Cre-ER T2 mice (64) to generate an inducible 4E-BP1 transgenic mouse model, Tg-4EBP1mt-ER, for adult skeletal muscle-specific activation. We induced transgenic 4E-BP1 expression at 2 months of age by daily injection of tamoxifen for 5 days, which activated HSA-Cre-ER T2 to excise the loxP-flanked STOP codon cassette of the 4E-BP1 transgenic allele ( Figure 7A), and monitored body weight, lean mass, and metabolic rate at 4, 6, and 9 months of age.…”

Reducing dynamin 2 expression rescues X-linked centronuclear myopathy

“…We crossed Mtm1 -/y mice with Dnm2 +/-mice under the HSA-Cre ER T2 system to allow excision of DNM2 after birth in muscle, induced by tamoxifen injection (37). Importantly, tamoxifen injections were performed when mice were 3 weeks old, after the onset of muscle atrophy ( Figure 2) and centralized nuclei (15).…”

“…Mice bred and analyzed were 129pas strain (CMV promoter). HSA-Cre C57BL/6 and HSA Cre-ER T2 mice were a kind gift from Daniel Metzger (IGBMC) (37,38) and were used to produce mice with musclespecific reduction of DNM2.…”

RNase H-mediated degradation of toxic RNA in myotonic dystrophy type 1

“…The EpA960 transgene contains the human DMPK exon 15 including 960 interrupted CTG repeats. To inducibly express the transgene specifically in skeletal muscle, EpA960 mice are crossed with HSA-CreERT2 mice (19) and bitransgenic animals were mated to generate double homozygous EpA960/HSA-Cre mice. Mice 2-3 mo of age were injected with tamoxifen to induce expression of the mRNA containing 960 CUG repeats.…”