Several advanced lineage tracing approaches, such as DNA barcode technology and single-cell RNA sequencing (scRNA-seq), have recently emerged to monitor organ formation and tissue damage and regeneration. To date, gene targeting has been widely used in studies of organogenesis, disease models, and susceptibility. It can also be used in the single object at different time points to monitoring different dynamic changes in real time.

Lineage tracing gene targeting owns the advantage of improved accuracy and integrity which reduced the experimental animal number. Gene-targeting technology utilizes homologous recombination such as the Cre-loxp and Dre-rox systems to control the expression of Cre in specific cells to achieve knockout or modification of target gene. More importantly, the tracers could be continuously observed in proliferation cells. With the help of mature genetic engineering technology, stable gene-targeting technologies have been applied for cell lineage tracing, which overcome traditional lineage disadvantage of the short-term and low specificity. However, exogenous markers gradually become diluted as the cell proliferate and cannot effectively label progeny cells. Later, researchers tried to physically inject a variety of dyes and probes into cells and observe the differences in expression between labeled cells and unlabeled cells. Subsequently, Mio succeed observing embryonic development used time-lapse cinematography to monitor the living embryos development which were widely used to study morphogenetic and development changes during the embryonic dynamics. Later, Cheng and Leblond used iron hematoxylin and 3H-thymidine treatment to stain mature enteroendocrine cells to trace differentiation pattern of enteroendocrine cells by electron microscopy however, inaccuracy of the pigmentation differences limited its further application. The principle of lineage tracing is to track and observe physiological and pathological changes in single-cell level by specific exogenous and endogenous cell markers.Ĭonklin found that the early mitotic bulb coloration of sea squirt embryos differed in the early twentieth century which was considered as the very beginning of lineage tracing. Therefore, tracing the fates of specific cells provides important understandings for monitoring organogenesis, physiological, and pathological processes. During embryonic development, every single cell assumes different roles of movement, migration, and differentiation to satisfy special organ or system physiological needs.

Lineage 2 on screen damage display