Rat adipocyte fatty acid binding protein 4 (aP2/FABP4) promoter
5' regulatory region of the rat adipocyte fatty acid binding protein 4 (aP2/FABP4) gene, combining a proximal promoter with a fat-specific enhancer to drive high-level transgene or Cre recombinase expression in mature white and brown adipocytes. One of the first adipocyte-specific promoters used to generate fat-restricted transgenic and Cre driver mice.
Length: 3708 bp
Strength: strong
Tissue: Mature white and brown adipocytes; also natively active in adipose-tissue macrophages, unlike the more restricted Adipoq promoter (Makowski et al. 2001)
Expression: constitutive
Origin: Rat Fabp4 (aP2) gene, 5' enhancer/promoter region
Characteristics
A 520 bp fat-specific enhancer located between -4.9 and -5.4 kb upstream of the transcription start is the primary determinant of adipose expression in vivo; proximal sequence alone, containing C/EBP and AP-1/c-Jun binding sites, drives expression in cultured adipocytes but not in the adipose tissue of transgenic mice, so enhancer inclusion is required (Ross et al. 1990). The aP2/FABP4 gene, and the regulatory sequence built from it, is also natively active in macrophages, including adipose-tissue macrophages, not just adipocytes (Makowski et al. 2001).
Applications: Used to generate adipocyte-specific transgenic reporter and Cre driver (aP2-Cre) mouse lines for adipose-restricted transgene expression and conditional gene knockouts (Ross et al. 1990); because the promoter is also active in macrophages, aP2-Cre lines have additionally recombined loxP alleles in adipose-tissue and other tissue-resident macrophages (Makowski et al. 2001).
Limitations: Not adipocyte-restricted - the aP2/FABP4 regulatory region is also natively active in macrophages, including adipose-tissue macrophages, so aP2-Cre lines recombine loxP alleles in macrophages as well as adipocytes (Makowski et al. 2001), unlike the more adipocyte-restricted Adipoq promoter, which shows no detectable Cre activity in adipose-tissue macrophages.
