Asymmetric division of stem cells results into two unequal daughter cells, only one of which resembles the parent stem cell. A new study provides genetic evidence in Drosophila melanogaster that the disturbance of this delicately balanced process in neuronal stem cells induces a cancer-like state.
In various organisms, cells divide asymmetrically to produce distinct daughter cells. In the nematode Caenorhabditis elegans, asymmetric division is controlled by the asymmetric activity of a Wnt signaling pathway (the Wnt/beta-catenin asymmetry pathway).
Beta-catenins
In this process, two specialized beta-catenin homologs have crucial roles in the transmission of Wnt signals to the asymmetric activity of a T-cell factor (TCF)-type transcription factor, POP-1, in the daughter cells.
One beta-catenin homolog regulates the distinct nuclear level of POP-1, and the other functions as a coactivator of POP-1.
Both beta-catenins localize asymmetrically in the daughter nuclei using different mechanisms. The recent discovery of reiterative nuclear asymmetries of a highly conserved beta-catenin in an annelid suggests that similar molecular mechanisms might regulate asymmetric cell divisions in other organisms.
References
Mizumoto K, Sawa H. Two betas or not two betas: regulation of asymmetric division by beta-catenin. Trends Cell Biol. 2007 Oct;17(10):465-73. PMID: 17919911
Clevers H. Stem cells, asymmetric division and cancer. Nat Genet. 2005 Oct;37(10):1027-8. PMID: 16195718
Huttner WB, Kosodo Y. Symmetric versus asymmetric cell division during neurogenesis in the developing vertebrate central nervous system. Curr Opin Cell Biol. 2005 Dec;17(6):648-57. PMID: 16243506