-245 bp of 5′-flanking region from the human platelet factor 4 gene is sufficient to drive megakaryocyte-specific expression in vivo

Platelet factor 4 (PF4) serves as a lineage-specific marker of megakaryocyte development, We previously identified two positively acting sequences in the human platelet factor 4 (hPF4) gene promoter that synergized to drive high-level luciferase reporter gene expression in vitro, Using portions of the hPF4 5'-flanking region linked to the lacZ reporter gene, we observed in this investigation that constructs with -245 bp of 5'-flanking region were more active than constructs with -2 kb of 5'-flanking region in vitro, We created two independent transgenic mouse lines with a -245-bp hPF4/lacZ construct, Cells from these mice were tested for beta-galactosidase (beta-gal) expression at the mRNA level by Northern blot and semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and at the protein level by immunohistochemistry assay. Mice from one line showed beta-gal expression specifically in all megakaryocytes of all ploidy classes from bone marrow and in platelets. Expression level was comparable to that driven by the 1.1-kb rat PF4 promoter in other transgenic mouse lines, Those in the second line showed no beta-gal expression in megakaryocytes, platelets, or any of the eight organs tested, The -245-bp hPF4 promoter is capable of driving reporter gene expression in a megakaryocyte-specific manner in transgenic mice. The small size of this megakaryocyte-specific promoter is compatible with that required in some viral vectors and may provide a model for targeting gene expression to megakaryocytes. (C) 1998 by The American Society of Hematology.