Dataset Information

LIN-28 balances longevity and germline stem cell number in Caenorhabditis elegans through let-7/AKT/DAF-16 axis.

ABSTRACT: The RNA-binding protein LIN-28 was first found to control developmental timing in Caenorhabditis elegans. Later, it was found to play important roles in pluripotency, metabolism, and cancer in mammals. Here we report that a low dosage of lin-28 enhanced stress tolerance and longevity, and reduced germline stem/progenitor cell number in C. elegans. The germline LIN-28-regulated microRNA let-7 was required for these effects by targeting akt-1/2 and decreasing their protein levels. AKT-1/2 and the downstream DAF-16 transcription factor were both required for the lifespan and germline stem cell effects of lin-28. The pathway also mediated dietary restriction induced lifespan extension and reduction in germline stem cell number. Thus, the LIN-28/let-7/AKT/DAF-16 axis we delineated here is a program that plays an important role in balancing reproduction and somatic maintenance and their response to the environmental energy level-a central dogma of the 'evolutionary optimization' of resource allocation that modulates aging.

SUBMITTER: Wang D

PROVIDER: S-EPMC5242300 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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LIN-28 balances longevity and germline stem cell number in Caenorhabditis elegans through let-7/AKT/DAF-16 axis.

Wang Dan D Hou Lei L Nakamura Shuhei S Su Ming M Li Fang F Chen Weiyang W Yan Yizhen Y Green Christopher D CD Chen Di D Zhang Hong H Antebi Adam A Han Jing-Dong J JJ

Aging cell 20161011 1

The RNA-binding protein LIN-28 was first found to control developmental timing in Caenorhabditis elegans. Later, it was found to play important roles in pluripotency, metabolism, and cancer in mammals. Here we report that a low dosage of lin-28 enhanced stress tolerance and longevity, and reduced germline stem/progenitor cell number in C. elegans. The germline LIN-28-regulated microRNA let-7 was required for these effects by targeting akt-1/2 and decreasing their protein levels. AKT-1/2 and the ...[more]

PMID: 27730721

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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:FoxO transcription factors promote longevity across taxa. How they do so is poorly understood. In the nematode Caenorhabditis elegans, the A- and F-isoforms of the FoxO transcription factor DAF-16 extend life span in the context of reduced DAF-2 insulin-like growth factor receptor (IGFR) signaling. To elucidate the mechanistic basis for DAF-16/FoxO-dependent life span extension, we performed an integrative analysis of isoform-specific daf-16/FoxO mutants. In contrast to previous studies suggesting that DAF-16F plays a more prominent role in life span control than DAF-16A, isoform-specific daf-16/FoxO mutant phenotypes and whole transcriptome profiling revealed a predominant role for DAF-16A over DAF-16F in life span control, stress resistance, and target gene regulation. Integration of these datasets enabled the prioritization of a subset of 92 DAF-16/FoxO target genes for functional interrogation. Among 29 genes tested, two DAF-16A-specific target genes significantly influenced longevity. A loss-of-function mutation in the conserved gene gst-20, which is induced by DAF-16A, reduced life span extension in the context of daf-2/IGFR RNAi without influencing longevity in animals subjected to control RNAi. Therefore, gst-20 promotes DAF-16/FoxO-dependent longevity. Conversely, a loss-of-function mutation in srr-4, a gene encoding a seven-transmembrane-domain receptor family member that is repressed by DAF-16A, extended life span in control animals, indicating that DAF-16/FoxO may extend life span at least in part by reducing srr-4 expression. Our discovery of new longevity genes underscores the efficacy of our integrative strategy while providing a general framework for identifying specific downstream gene regulatory events that contribute substantially to transcription factor functions. As FoxO transcription factors have conserved functions in promoting longevity and may be dysregulated in aging-related diseases, these findings promise to illuminate fundamental principles underlying aging in animals.

Dataset Information

LIN-28 balances longevity and germline stem cell number in Caenorhabditis elegans through let-7/AKT/DAF-16 axis.

Publications

LIN-28 balances longevity and germline stem cell number in Caenorhabditis elegans through let-7/AKT/DAF-16 axis.

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