DIFFERENTIAL SCREENING IDENTIFIES GENETIC-MARKERS OF MONOCYTE TO MACROPHAGE MATURATION

Maturation of cells of the mononuclear phagocyte lineage from bone mar row precursors to tissue macrophages (MAC) via circulating blood monoc ytes (MO) is a multistep process only partially understood, Similarly, MAC differentiation can be observed if MO are cultured in vitro. In a n attempt to further characterize molecular changes occurring during t his process we carried out differential screening of a MO-derived MAC cDNA library using MO and MAC cDNA, After subcloning and confirmation by a second round of screening, partial sequencing of 41 cDNA clones w as performed, In 33 clones the sequences of 7 different previously ide ntified cDNAs were found, The mRNA expression of two of the correspond ing genes (apolipoprotein E, ferritin light chain) is already known to be up-regulated during MAC maturation. For one gene (cathepsin B), a specific up-regulation of mRNA expression could be shown corresponding to previous protein data, For four genes [human cartilage glycoprotei n (HC-gp39), osteopontin, type IV collagenase, and tryptophanyl-tRNA s ynthetase] the specific expression in MAC versus MO was previously unk nown but could be confirmed by the use of Northern blot analysis, Of t hese genes, HC-gp39 is especially interesting because it is only expre ssed during the late stages of MAC differentiation.