Proximal promoter of the human ITGAM gene, encoding the CD11b (integrin alpha-M) subunit of the Mac-1/CR3 complement receptor. Drives transgene expression preferentially in myeloid cells — mature monocytes, macrophages, and neutrophils — and is used to target reporter or effector genes to myeloid lineages in transgenic mice.
Length: 1795 bp
Strength: strong
Tissue: Mature monocytes, macrophages, and neutrophils (myeloid-restricted); shorter promoter fragments have shown ectopic activity in lymphocytes in transgenic mice (Back et al. 1995).
Expression: constitutive
Origin: Human ITGAM (CD11b) gene
Characteristics
A ~1.7 kb fragment 5' of the human ITGAM transcription start site drives high-level, sustained reporter expression in mature monocytes, macrophages, and neutrophils in transgenic mice, but not in myeloid precursors (Dziennis et al. 1995). A shorter 1.5 kb fragment of the same promoter produced surface reporter expression in granulocytes as expected, but also ectopic expression in lymphocytes in two of three founder lines, showing that specificity depends on fragment length and chromosomal integration site rather than the promoter sequence alone (Back et al. 1995).
Applications: Used to drive myeloid-lineage-restricted transgene or reporter expression in transgenic mice, including constructs targeting mature monocytes/macrophages and neutrophils for lineage marking and in vivo myeloid-specific gene delivery (Dziennis et al. 1995).
Limitations: Fragment length and genomic integration site both affect fidelity of myeloid restriction — a 1.5 kb CD11b promoter fragment produced ectopic reporter expression in lymphocytes in some transgenic founder lines despite expected granulocyte activity (Back et al. 1995), so myeloid specificity should be confirmed for each construct and integration rather than assumed from the promoter sequence alone.
