Molecular analysis of the mouse S100A9 gene and evidence that the myeloid specific transcription factor C/EBPepsilon is not required for the regulation of the S100A9/A8 gene expression in neutrophils.

The genomic locus of the mouse S100A9 (MRP14) gene, a myeloid expressed gene belonging to the S100 family, is split in three exons and two introns. Insertions of B1 like and LINE elements as well as several sequence repeat structures are scattered over the gene suggesting that this region of the S100 gene cluster has been the subject of a high mutational activity in mouse evolution. The insertions may represent molecular footprints of a recently postulated inversion event, which resulted in a rearrangement of the S100 gene cluster in mouse compared to man. Deletion analysis of the promoter reveals, that a 1200 bp fragment is able to direct a cell type-specific expression of a reporter gene in granulocytic 32D cells. Unexpectedly, the myeloid-specific transcription factor C/EBPepsilon is not needed for the transcriptional upregulation of the S100A9 and S100A8 genes in neutrophils. The data described here provide further insights into the evolution of the S100 gene cluster and into the myeloid-specific regulation of the murine S100A9 gene expression.