Somatic stem cells, or adult stem cells, have the ability to replenish tissues throughout the body. Adult stem cells are able to self-renew and differentiate. In particular, stem cells play important roles in tissue maintenance and regeneration. However, the regenerative capacity of somatic stem cells declines dramatically in some diseases and ageing. Recent finding suggests the notion that stem cells spontaneously proliferate and subsequently are depleted in old tissues. As somatic stem cell is only a small percentage of total cell number within the tissue and heterogeneity exists within this population, it is a hurdle to identify and isolate these cell populations from adult tissues. Traditionally, identification of low turnover somatic stem cells relies on the label retention tech...[ Read more ]

Somatic stem cells, or adult stem cells, have the ability to replenish tissues throughout the body. Adult stem cells are able to self-renew and differentiate. In particular, stem cells play important roles in tissue maintenance and regeneration. However, the regenerative capacity of somatic stem cells declines dramatically in some diseases and ageing. Recent finding suggests the notion that stem cells spontaneously proliferate and subsequently are depleted in old tissues. As somatic stem cell is only a small percentage of total cell number within the tissue and heterogeneity exists within this population, it is a hurdle to identify and isolate these cell populations from adult tissues. Traditionally, identification of low turnover somatic stem cells relies on the label retention technique. However, detection of DNA labels requires cell fixation and the purity of somatic stem cells is questionable. Even though fluorescence activated cell sorting (FACS) is a powerful method to separate them from a heterogeneous mixture of biological cells in vitro, it requires known markers and available antibodies for specific stem cell populations. To lineage trace a specific somatic stem cell population in vivo, inducible recombinases and multicolor fluorescent reporters have been extensively used. In this study, we aim to generate a transgenic mouse line that can serve as both a lineage tracer and a cell division counter up to two rounds of cell cycle. Lineage tracing of specific cells along with cell cycle history of the low turnover somatic stem cells will provide a better understanding of how they behave during homeostasis, pathological conditions and ageing.