Mother cell inheritance and regulation of SYS-1/β-catenin during Wnt-driven asymmetric cell divisions in C. elegans.

During development, a single fertilized egg gives rise to all the different tissues found in the adult organism. One of the ways cell diversity is achieved is through a process called asymmetric cell division (ACD). During ACDs, the mother cell unequally distributes different cell fate determinants between the two daughters that will allow them to turn on/off different genes, so they become distinct from one another. In addition to expanding cell diversity during development, ACD is needed for adult tissue maintenance. We study this process because when cells fail to divide asymmetrically this can lead to abnormal growth and tumor formation. We can study this process in the nematode Caenorhabditis elegans where many of the ACDs are regulated by a signaling pathway called the Wnt/β-catenin asymmetry pathway. This pathway ensures that the different cell fate determinants are polarized in the mother cell and drive the asymmetric inheritance. However, the inheritance of the key gene expression regulator in the pathway, SYS-1/β-catenin, is unknown. My project focuses on how the mother and daughter cells are regulating SYS-1 and analyzes SYS-1 inheritance from the mother to the daughter cells. We found that mother cell SYS-1 degradation needs to be precisely regulated to prevent its over-inheritance to achieve a successful ACD. Additionally, with a trackable SYS-1, we showed that SYS-1 is inherited in normal conditions and negative regulators of SYS-1 work in both daughter cells. Altogether, our research shows the importance of tight regulation of SYS-1 for proper development and adult tissue maintenance.