Project description:Neoblasts are adult stem cells (ASCs) in planarians which sustain cell replacement during homeostasis and regeneration of any missing tissue. While numerous studies have examined genes underlying neoblast pluripotency, molecular pathways driving the postmitotic fate remain poorly defined. Here we used transcriptional profiling of irradiation-sensitive and -insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny. We identified 32 new markers, which distinguish two epithelial progenitor populations, and a planarian homolog to the MEX3 RNA-binding protein (Smed-mex3-1) as a key regulator of lineage progression. mex3-1 is required for generating progenitors of epithelial, neural, eye, pharyngeal, and protonephridial lineages, and restricting expansion of the stem cell compartment. We also demonstrate the utility of using mex3-1(RNAi) animals to identify additional progenitor markers. These results show that mex3-1 promotes differentiation in multiple, if not all, lineages, and maintains the balance between ASC self-renewal and commitment. Sorted and irradiated animals were collected as previously described (Labbe, et al., 2012) and RNAi conditions were triplicated, RNA was purified independently, then each replicate was pooled in equal amounts for sequencing at the timepoint: 1 feed day 12 for control RNAi and mex3-1 RNAi.
Project description:Neoblasts are adult stem cells (ASCs) in planarians which sustain cell replacement during homeostasis and regeneration of any missing tissue. While numerous studies have examined genes underlying neoblast pluripotency, molecular pathways driving the postmitotic fate remain poorly defined. Here we used transcriptional profiling of irradiation-sensitive and -insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny. We identified 32 new markers, which distinguish two epithelial progenitor populations, and a planarian homolog to the MEX3 RNA-binding protein (Smed-mex3-1) as a key regulator of lineage progression. mex3-1 is required for generating progenitors of epithelial, neural, eye, pharyngeal, and protonephridial lineages, and restricting expansion of the stem cell compartment. We also demonstrate the utility of using mex3-1(RNAi) animals to identify additional progenitor markers. These results show that mex3-1 promotes differentiation in multiple, if not all, lineages, and maintains the balance between ASC self-renewal and commitment.
Project description:The adult brain of the planarian Schmidtea mediterranea (a freshwater flatworm) is a dynamic structure with constant cell turnover as well as the ability to completely regenerate de novo. Despite this, function and pattern is achieved in a reproducible manner from individual to individual in terms of the correct spatial and temporal production of specific neuronal subtypes. Although several signalling molecules have been found to be key to scaling and cell turnover, the mechanisms by which specific neural subtypes are specified remain largely unknown. Here we performed a 6 day RNAseq time course on planarians that were regenerating either 0, 1, or 2 heads in order to identify novel regulators of brain regeneration. Focusing on transcription factors, we identified a TCF/LEF factor, Smed-tcf1, which was required to correctly pattern the dorsal-lateral cell types of the regenerating brain. The most severely affected neurons in Smed-tcf1(RNAi) animals were the dorsal GABAergic neurons, which failed to regenerate, leading to an inability of the animals to phototax away from light. Together, Smed-tcf1 is a critical regulator, required to pattern the dorsal-lateral region of the regenerating planarian brain.
Project description:Transcriptional profiling of Schmidtea mediterranea planarians that have been subjected to 2 weeks of runt-1 or control RNAi, amputated and RNA was directly collected at 5min, 9h, and 24h, or neoblasts (X1) were isolated from 9h wounded animals and subsequently RNA was extracted
Project description:Lipid metabolism is recognized as a key process for stem cell maintenance and differentiation but genetic factors that instruct stem cell function by influencing lipid metabolism remain to be delineated. Here we identify Tnfaip2 as an inhibitor of reprogramming of mouse fibroblasts into induced pluripotent stem cells. Tnfaip2 knockout embryonic stem cells (ESCs) exhibit differentiation failure and knockdown of the planarian orthologue, Smed-exoc3, abrogates in vivo differentiation of somatic stem cells, tissue homeostasis, and regeneration. Tnfaip2 deficient ESCs fail to induce synthesis of cellular triacylglycerol (TAG) and lipid droplets (LD) coinciding with reduced expression of Vimentin (Vim) – a known inducer of LD formation. Knockdown of Vim and Tnfaip2 act epistatically in enhancing cellular reprogramming of mouse fibroblasts. Similarly, planarians devoid of Smed-exoc3 displayed acute loss of TAGs. Supplementation of palmitic acid (PA) and palmitoyl-L-carnitine (a mitochondrial carrier of PA) restores the differentiation capacity of Tnfaip2 deficient ESCs as well as stem cell differentiation and organ maintenance in Smed-exoc3-depleted planarians. Together, these results identify a novel pathway, which is essential for stem cell differentiation and organ maintenance by instructing lipid metabolism.