Project description:Whole L1 larvae were collected from GC1459 [naSi2 [pGC550 (mex-5p::mCherry::H2B::nos-2 3'UTR +unc-119(+))] II; unc-119(ed3) III ?; daf-18(ok480) IV] and GC1171 [naSi2 [pGC550 (mex-5p::mCherry::H2B::nos-2 3'UTR +unc-119(+))] II; unc-119(ed3) III] strains up to two hours after hatching without food.
Project description:This experiment was designed to identify early targets of daf-16/FoxO during L1 starvation in C. elegans. Previous work (Baugh et al 2009) examined temporal dynamics of gene expression in fed and starved L1 larvae using the same platform and methods. Here, a single time point was analyzed (~3 hr after hatching) in fed and starved larvae also comparing wild-type and a daf-16 null mutant. Statistical analysis includes pairwise comparisons between the four conditions as well as a two-factor analysis to explicitly identify genes affected by nutrient availability in daf-16-dependent fashion.
Project description:Embryos of wild type N2, daf-16(mu86), daf-18(ok480) and daf-16(mu86); daf-18(ok480) were collected by hypochlorite-treat gravid adult worms and were put in virgin S-basal with 0.1% EtOH at 20 °C. After hatching, those embryos entered L1 arrest. Arrested L1s were collected 16 hr post hypochlorite treatment (about 4 hr of starvation).
Project description:Post-embryonic development of the nematode C. elegans is governed by nutrient availability. L1-stage larvae remain in a state of developmental arrest after hatching until they feed. This “L1 arrest” (or "L1 diapause") is associated with increased stress resistance, supporting starvation survival. Loss of the transcription factor daf-16/FOXO, an effector of insulin/IGF signaling, results in arrest-defective and starvation-sensitive phenotypes. We show that daf-16/FOXO regulates L1 arrest cell-nonautonomously, suggesting that insulin/IGF signaling regulates at least one additional signaling pathway. We used mRNA-seq to identify candidate signaling molecules affected by daf-16/FOXO during L1 arrest. daf-16/FOXO had overlapping but distinct effects on gene expression in L1 arrest compared to daf-2/InsR adults. Notably, dbl-1/TGF-β, a ligand for the Sma/Mab pathway, and daf-36, which encodes an upstream component of the daf-12/NHR steroid hormone signaling pathway, were up-regulated during L1 arrest in a daf-16/FOXO mutant. Using genetic epistasis analysis, we show that dbl-1/TGF-β and daf-12/NHR steroid hormone signaling pathways are required for the daf-16/FOXO arrest-defective phenotype, suggesting that daf-16/FOXO represses dbl-1/TGF-β and daf-36. The dbl-1/TGF-β and daf-12/NHR pathways have not previously been shown to affect L1 development, but we found that disruption of these pathways delayed L1 development in fed larvae, consistent with these pathways promoting development in starved daf-16/FOXO mutants. Though the dbl-1/TGF-β and daf-12/NHR pathways are epistatic to daf-16/FOXO for the arrest-defective phenotype, disruption of these pathways does not suppress starvation sensitivity of daf-16/FOXO mutants. This observation uncouples starvation survival from developmental arrest, indicating that DAF-16/FOXO targets distinct effectors for each phenotype, and revealing that inappropriate development during starvation does not cause the early demise of daf-16/FOXO mutants. Overall, this study shows that daf-16/FOXO promotes developmental arrest cell-nonautonomously by repressing pathways that promote larval development.
Project description:Whole starved L1 larvae from four genotypes (N2, daf-2(e1370), irld-39(duk1);irld-52(duk17), and daf-2(e1370); irld-39(duk1); irld-52(duk17)) were collected after 12 hours of starvation
Project description:hrde-1(tm1200) animals were bleached and embryos were plated on empty vector, daf-2, or pitr-1 RNAi (HT115). Animals were allowed to develop for 72 hr, after which embryos were released via bleaching and allowed to hatch in the absence of food. Arrested L1 larvae were snap frozen in liquid nitrogen ~24 hr after bleaching.
Project description:Many tissue-specific stem cells maintain the ability to produce multiple cell types during long periods of non-division, or quiescence. FOXO transcription factors promote quiescence and stem cell maintenance, but the mechanisms by which FOXO proteins promote multipotency during quiescence are still emerging. The single FOXO ortholog in C. elegans, daf-16, promotes entry into a quiescent and stress-resistant larval stage called dauer in response to adverse environmental cues. During dauer, stem and progenitor cells maintain or re-establish multipotency to allow normal development to resume after dauer. We find that during dauer, daf-16/FOXO prevents epidermal stem cells (seam cells) from prematurely adopting differentiated, adult characteristics. In particular, dauer larvae that lack daf-16 misexpress collagens that are normally adult-enriched. Using col-19p::gfp as an adult cell fate marker, we find that all major daf-16 isoforms contribute to opposing col-19p::gfp expression during dauer. By contrast, daf-16(0) larvae that undergo non-dauer development do not misexpress col-19p::gfp. Adult cell fate and the timing of col-19p::gfp expression are regulated by the heterochronic gene network, including lin-41 and lin-29. lin-41 encodes an RNA-binding protein orthologous to LIN41/TRIM71 in mammals, and lin-29 encodes a conserved zinc finger transcription factor. In non-dauer development lin-41 opposes adult cell fate by inhibiting the translation of lin-29, which directly activates col-19 transcription and promotes adult cell fate. We find that during dauer, lin-41 blocks col-19p::gfp expression, but surprisingly, lin-29 is not required in this context. Additionally, daf-16 promotes the expression of lin-41 in dauer larvae. The col-19p::gfp misexpression phenotype observed in dauer larvae with reduced daf-16 requires the downregulation of lin-41, but does not require lin-29. Taken together, this work demonstrates a novel role for daf-16/FOXO as a heterochronic gene that promotes expression of lin-41/TRIM71 to contribute to multipotent cell fate in a quiescent stem cell model.
Project description:We characterized the effects of early-life starvation and reduced insulin/insulin-like signaling (IIS) during larval development on adult gene expression using mRNA-seq of whole worms. In our two-factor design, 'starved' worms were cultured without food (E. coli) in L1 arrest for eight days, and 'control' worms were starved overnight for synchronization. Both populations of worms were fed ad libitum with either empty vector (EV; negative control) or daf-2/InsR RNAi food (reduced IIS). RNAi was used rather than a daf-2 mutant so that the results would not be confounded by daf-2 function during L1 arrest, instead disrupting daf-2 only after starvation in fed, developing larvae. Upon reaching adulthood, animals were collected for transcript profiling.