Project description:Neural stem cells (NSCs) in the adult mammalian subependymal zone maintain a glial identity and the developmental potential to generate neurons during the lifetime. Production of neurons from these NSCs is not direct but follows an orderly pattern of cell progression which allows the gradual increase in pro-neural factors needed for neuronal fate. Although little is known about how stemness is molecularly balanced with the acquisition of the cell competence for neuronal differentiation along the lineage, regulated translation of existing transcripts is a potential mechanism to avoid the critical challenge posed by genes that encode proteins with conflicting functions, i.e. self-renew or differentiate. Here, we identify MEX3A as a post-transcriptional regulator of a set of stemness-associated transcripts at critical transitions in the subependymal neurogenic lineage. MEX3A regulates a quiescence-related RNA signature in activated NSCs that is needed for the return to quiescence, playing a role in the long-term maintenance of the NSC pool. Furthermore, it is required for the repression of the same program at the onset of neuronal differentiation. Our data indicate that MEX3A acts via a number of downstream targets to function as a pivotal regulator of adult mammalian neurogenesis.
Project description:Mex3a is an RNA binding protein of unknown function. To elucidate the contribution of Mex3a to tumoral heterogeneity, Mex3a KO organoids engineered by CRISPR were sequenced in three different conditions. Live organoids (DAPI negative) were sorted in Control, after 2 days of FOLFIRI and after 5 days of treatment. Two WT organoids (parental and a derived clone) and two KO (KO1 and KO2, two independent clones) were used for this experiment.
Project description:Transcriptomic data related to 4 different subpopulations found in Mex3a Ki/+ Lgr5 Gfp in APCflfl adenomas in untreated animals. Adenomas where induced with 3%DSS and a single shot of 8mg/kg of Tamoxifen. The populations are refered as Mex3a + Lgr5, Mex3a- Lgr5+ Mex3a+ Lgr5- and Mex3a- Lgr5- according to the flow cytometry profile. Cells were isolated using FACsARIA (BD)
Project description:The effort to better understand intestinal stem cell (ISC) identity and regulation remains a challenge. We have been studying the RNA-binding protein MEX3A as a putative ISC marker. In that context, we have generated the first Mex3a knockout (KO) mouse model and show MEX3A is crucial for maintenance of the Lgr5+ ISC pool. As part of a phenotypic characterization pipeline, we have performed transcriptomic profiling (RNA-sequencing) of isolated Mex3a KO small intestinal crypts and compared it against small intestinal crypts isolated from age-matched wild-type controls.
Project description:Mex3a labells a subpopulation of Cancer Stem cells defined by their slow proliferative behaviour. Nevertheless, the precise function of MEX3A is unknown, although it plays a role in chemoresistance. The Mex3a KO adenomas are less chemoresistant compared to their WT controls. We used microarrays to elucidate changes in gene expression in cells with the Mex3a promoter active (tomato expressing cells)
Project description:To demonstrate RIPSeeker program that is developed for RIP-seq analyses, we generated RIP-seq data corresponding to the protein CCNT1 in HEK293 cell line using standard RIP-seq protocols described in Zhao et al., (2010). We performed two in-house RIP-seq experiments both for CCNT1 in human HEK293 cells. Briefly, we generated tagged CCNT1 using a triple tag system that supports lentiviral stable expression and mammalian affinity purification (MAPLE) Mak et al (2010). The HEK293 cells stably expressing tagged CCNT1 was purified by M2 agarose beads, followed by RNA extraction by Trizol. The library synthesis was carried out according to the RIP-seq protocol described in Zhao et al., (2010) except that one of the two experiments was done with non-strand-specific sequencing.
Project description:Epithelial ovarian cancer (OC) is a highly heterogeneous and malignant female cancer with an overall low survival rate. p53 mutation is a predominant genetic factor thought to be responsible for poor clinical outcome. Despite the fact that ovarian clear cell carcinoma (OCCC) shows more severe prognosis, drug resistance, metastasis and recurrence compared to other OC subtypes, mutations in p53 are much less frequent. The underlying mechanisms crucial for tumorigenesis and malignancy of OC harboring wild-type (WT) p53 remain poorly understood. We found that upregulation of MEX3A, which is a dual-function protein containing a RING finger domain and an RNA binding domain, was correlated with poor survival in OC. MEX3A overexpression enhanced tumorigenic activity in RMG-1 and OVISE OCCC cell lines. In contrast, depletion of MEX3A in PA-1 ovarian teratocarcinoma cells and TOV21G OCCC cells reduced cell survival and proliferative ability in cell-based assays, as well as inhibited tumor growth and prolonged survival in orthotopic xenograft models. MEX3A depletion did not alter p53 mRNA level but did increase the protein stability of WT p53. MEX3A-mediated p53 protein degradation was crucial to prevent ferroptosis and enhance tumorigenesis as p53 knockdown reversed the effects of MEX3A depletion. Together, our observations identified MEX3A as an important oncogenic factor promoting tumorigenesis in OC cells harboring WT p53.
Project description:The intestinal epithelium is continuously regenerated by highly proliferative Lgr5+ intestinal stem cells (ISCs). The existence of a population of quiescent ISCs has been suggested yet its identity and features remain controversial. Here we describe that the expression of the RNA-binding protein Mex3a labels a subpopulation of Lgr5+ cells that divide less frequently and contribute to regenerate all intestinal lineages with slow kinetics. Single cell transcriptomic analysis revealed two classes of Lgr5-high cells, one of them defined by the Mex3a-expression program and by low levels of proliferation genes. Lineage tracing experiments show that large fraction of Mex3a+ cell population is continuously recalled into the rapidly dividing self-renewing ISC pool in homeostatic conditions. Chemotherapy and radiation target preferentially rapidly dividing Lgr5+ cells but spare the Mex3a-high/Lgr5+ population, which helps sustain the renewal of the intestinal epithelium during treatment.