FUNCTIONAL-ANALYSIS OF MOUSE POLYCOMB GROUP GENES

Two groups of genes, the Polycomb group (Pc-G) and trithorax group (tr x-G), have been identified in Drosophila to provide a transcriptional memory mechanism. They ensure the maintenance of transcription pattern s of key regulators such as the Hox genes and thereby the correct exec ution of developmental programmes. Recent data suggest that this memor y mechanism is conserved in vertebrates and plants. Here we discuss cu rrent insights into the role of mouse Pc-G genes, with a particular fo cus on the best-studied Bmi1, Mel18 and M33 genes, as representative e xamples. Common phenotypes observed in knockout mice mutant for each o f these genes indicate an important role for Pc-G genes not only in re gulation of Hox gene expression and axial skeleton development but als o in control of proliferation and survival of haematopoietic cell line ages. Proliferation defects are also observed in other cell lineages d erived from these null-mutant mice, and provide new tools to study the impact of Pc-G deregulation on cell cycle control.