Telomeres are specialized structures required for the proper protection and replication of the end of linear chromosomes, such as those in eukaryotes. In mammals, telomeres are composed of long tracks of double stranded TTAGGG repeated DNA which can extend up to 10kb and 100kb in human and mice respectively. Telomeric DNA shortens after each round of cell division, leading ultimately to cell cycle arrest. However, stem cells can extend telomere length by the action of the telomerase, a specialized enzyme that adds new telomeric DNA. Telomere length must be properly controlled to ensure normal development, aging and to ensure cellular homeostasis. Interestingly, telomerase is not the only way to maintain telomere length. In about 10-15% of cancer, an alternative mechanism of telomere lengthening takes place. The ALT (Alternative Lengthening of Telomeres) pathway is a recombination based mode of telomere maintenance, which has been so far studied predominantly in cancer cells. How ALT is regulated and initiated is still not known. Previous studies identified a telomerase independent telomere lengthening in early mouse embryos, underlying that an ALT or ALT-like system can be used in a physiological context.
The purpose of this research is to use mouse pre-implantation embryos and other embryonic cellular models to characterize the ALT (or ALT-like) pathway naturally occurring during early embryonic development. The research is organized into three aims: (WP1) developing tools to visualize and track telomere in mouse embryos, (WP2) characterize telomere regulation in mouse genetic models conditionally inactivated for Atrx and Daxx, (WP3) perform biochemical purification of proteins associated to telomeres of Atrx and Daxx conditional KO mouse embryonic stem cells lines. The identified proteins will be tested for their physiological relevance in mouse embryos.
