Zebrafish cardiac myosin light chain 2 (cmlc2/myl7) promoter
Zebrafish cardiac myosin light chain 2 (cmlc2/myl7) gene regulatory region (~1.6 kb, spanning the upstream promoter, first exon, first intron, and part of the second exon), driving expression exclusively in cardiomyocytes from early embryonic cardiac development onward in Danio rerio. The standard heart-specific promoter for cardiac reporter, Cre, and Cas9 transgenic lines in zebrafish.
Origin: Zebrafish cardiac myosin light chain 2 (cmlc2/myl7) gene regulatory region
Characteristics
A 1.6 kb PCR fragment spanning the cmlc2 upstream region, first exon, first intron, and part of the second exon, fused to GFP, gives germline-transmissible, myocardium-restricted green fluorescence in zebrafish, intensely marking cardiomyocytes around the heart chambers and atrioventricular canal from early embryonic development onward. Regulatory elements within the fragment (including the intron) are required for full activity and specificity, not just the upstream promoter alone.
Applications: Cardiomyocyte-restricted reporter expression (e.g. GFP, dsRed2-nuc) and cardiac-restricted Cre or Cas9 expression for heart-specific gene manipulation in transgenic zebrafish lines, including cardiac regeneration and cardiomyocyte ablation studies.
Limitations: Requires the first intron along with the flanking exonic sequence for full activity and specificity - a promoter-only truncation that omits the intron is not established to reproduce the same restricted expression. Validated in zebrafish; cross-species portability of this specific regulatory fragment to other teleosts or mammals is not established.
Sequence
References
- Huang et al. (2003). Germ-line transmission of a myocardium-specific GFP transgene reveals critical regulatory elements in the cardiac myosin light chain 2 promoter of zebrafish. Dev Dyn - Huang 2003 cmlc2 promoter