Human skeletal muscle alpha-actin 1 (ACTA1) promoter

Human ACTA1 (skeletal muscle alpha-actin) gene promoter, driving transcription almost exclusively in differentiated skeletal myofibers. The 5'-flanking region contains at least three synergistic regulatory subdomains and produces high-level expression in myotubes while remaining inactive in nonmuscle cell lines, giving strong skeletal-muscle-restricted expression for gene delivery constructs.

Length: 2162 bp

Strength: strong

Tissue: Differentiated skeletal myofibers (myotubes); inactive in nonmuscle cell lines and confirmed non-recombining in cardiac muscle in vivo

Expression: constitutive

Origin: Human ACTA1 gene 5'-flanking regulatory region

Characteristics

In transient transfection assays, a 1,300 bp proximal subregion of the 5'-flanking DNA directs high-level expression selectively in differentiated myotubes and is inactive in nonmuscle and undifferentiated myoblast cell lines; deletion analysis identified at least three synergistic regulatory subdomains within this region (a distal domain, a proximal domain, and a basal/TATA-proximal domain).

Applications: Drives skeletal-muscle-restricted transgene and Cre recombinase expression in mouse models, including HSA-Cre lines used to study muscle-specific gene function in glucose homeostasis; Cre-mediated recombination is confirmed restricted to limb and craniofacial skeletal muscle after tamoxifen induction, without unintended cardiac recombination.

Limitations: Active only in differentiated, post-fusion myofibers, not in proliferating myoblasts or nonmuscle tissue, so temporal control requires pairing with an inducible system such as tamoxifen-responsive CreERT2. HSA-Cre transgenic mice show a mild intrinsic glycemic phenotype independent of any floxed allele, requiring HSA-Cre-only controls in metabolic studies.

Sequence

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References

Al Batran et al. (2018). Skeletal muscle-specific Cre recombinase expression, controlled by the human α-skeletal actin promoter, improves glucose tolerance in mice fed a high-fat diet. Diabetologia - Al Batran 2018 HSA-Cre Specificity