Project description:In the mouse neocortex, neural progenitor cells generate neurons through repeated rounds of asymmetric cell division. How distinct fates are established in their daughter cells is unclear. We show here that the TRIM-NHL protein TRIM32 segregates asymmetrically during progenitor division and induces neuronal differentiation in one of the two daughter cells. TRIM32 is highly expressed in differentiating neurons. In both horizontally and vertically dividing progenitor cells, TRIM32 distribution becomes polarized in mitosis so that the protein is enriched in one of the two daughter cells. While TRIM32 overexpression induces cell cycle exit and neuronal differentiation, TRIM32 RNAi causes both daughter cells to proliferate and prevents the initiation of a neuronal differentiation program . TRIM32 ubiquitinates and degrades the transcription factor c-Myc but also binds Argonaute-1 and thereby increases the activity of specific micro-RNAs. We show that Let-7 is one of the TRIM32 targets and is required and sufficient for neuronal differentiation. Our data suggest that the asymmetric segregation of a micro RNA regulator controls self renewal in the mammalian brain. Experiment Overall Design: small RNA from total mouse brain, Ago-1 and TRIM32 IPs were cloned and sequenced using 454 GS FLX system.
Project description:Asymmetric partitioning of fate-determinants is a mechanism that contributes to T cell differentiation. However, it remained unclear whether the ability of T cells to divide asymmetrically is influenced by their differentiation state, as well as if enforcing asymmetric cell division rates would have an impact on T cell differentiation and memory formation. Using the murine LCMV infection model, we established a correlation between cell stemness and the ability of CD8+ T cells to undergo asymmetric cell division (ACD). Transient mTOR inhibition proved to increase ACD rates in naïve and memory cells, and to install this ability in exhausted CD8+ T cells. Functionally, enforced ACD correlated with increased memory potential, leading to more efficient recall response and viral control upon acute or chronic LCMV infection. Moreover, transient mTOR inhibition also increased ACD rates in human CD8+ T cells. Transcriptional profiling of first daughter cells, obtained by sorting CD8lo and CD8hi cells after in vitro stimulation, revealed that progenies emerging from enforced ACD exhibited more pronounced early memory signatures, which functionally endowed these cells with strengthened memory features.
