Lin9 is a subunit of the DREAM complex, which is crucial for regulating gene expression during the cell cycle. It plays an essential role in the cell mitotic process, and is involved in multiple biological pathways related to cell proliferation, development, and tumorigenesis. Genetic models, such as knockout (KO) mouse models, have been instrumental in studying its functions [1,2].

In KO mouse models, loss of Lin9 abolishes cell proliferation and leads to multiple defects in mitosis and cytokinesis due to the down-regulation of a large set of mitotic genes, such as Plk1, Aurora A, and Kif20a. Lin9-heterozygous mice are more susceptible to lung tumorigenesis induced by oncogenic c-Raf than wild-type mice, suggesting its potential role as a haploinsufficient tumor suppressor [2]. In zebrafish, Lin9-depleted embryonic cells accumulate in mitosis, followed by apoptosis, especially in the developing central nervous system [3].

In conclusion, Lin9 is essential for the proliferation and genome stability of cells by activating genes with important functions in mitosis and cytokinesis. Studies using KO models have revealed its significance in embryonic development, adult mouse survival, and tumor suppression, providing insights into the underlying mechanisms of related diseases [1,2,3].