A Non-Cell-Autonomous Role of BEC-1/BECN1/Beclin1 in Coordinating Cell-Cycle Progression and Stem Cell Proliferation during Germline Development

The decision of stem cells to proliferate and differentiate is finely controlled. The Caenorhabditis elegans germline provides a tractable system for studying the mechanisms that control stem cell proliferation and homeostasis [1-4]. Autophagy is a conserved cellular recycling process crucial for cellular homeostasis in many different contexts [5], but its function in germline stem cell proliferation remains poorly understood. Here, we describe a function for autophagy in germline stem cell proliferation. We found that autophagy genes such as bec-1/BECN1/Beclin1, atg-16.2/ATG16L, atg-18/WIPI1/2, and atg-7/ATG7 are required for the late larval expansion of germline stem cell progenitors in the C. elegans gonad. We further show that BEC-1/BECN1/Beclin1 acts independently of the GLP-1/Notch or DAF-7/TGF-β pathways but together with the DAF-2/insulin IGF-1 receptor (IIR) signaling pathway to promote germline stem cell proliferation. Similar to DAF-2/IIR, BEC-1/BECN1/Beclin1, ATG-18/WIPI1/2, and ATG-16.2/ATG16L all promote cell-cycle progression and are negatively regulated by the phosphatase and tensin homolog DAF-18/PTEN. However, whereas BEC-1/BECN1/Beclin1 acts through the transcriptional regulator SKN-1/Nrf1, ATG-18/WIPI1/2 and ATG-16.2/ATG16L exert their function through the DAF-16/FOXO transcription factor. In contrast, ATG-7 functions in concert with the DAF-7/TGF-β pathway to promote germline proliferation and is not required for cell-cycle progression. Finally, we report that BEC-1/BECN1/Beclin1 functions non-cell-autonomously to facilitate cell-cycle progression and stem cell proliferation. Our findings demonstrate a novel non-autonomous role for BEC-1/BECN1/Beclin1 in the control of stem cell proliferation and cell-cycle progression, which may have implications for the understanding and development of therapies against malignant cell growth in the future.

[1]  K. Oegema,et al.  A complex containing the Sm protein CAR-1 and the RNA helicase CGH-1 is required for embryonic cytokinesis in Caenorhabditis elegans , 2005, The Journal of cell biology.

[2]  E. Hubbard,et al.  Physiological control of germline development. , 2013, Advances in experimental medicine and biology.

[3]  A. Rougvie,et al.  C. elegans DAF-18/PTEN Mediates Nutrient-Dependent Arrest of Cell Cycle and Growth in the Germline , 2006, Current Biology.

[4]  Hilla Peretz,et al.  Ju n 20 03 Schrödinger ’ s Cat : The rules of engagement , 2003 .

[5]  D. Rubinsztein,et al.  Autophagy regulates Notch degradation and modulates stem cell development and neurogenesis , 2016, Nature Communications.

[6]  Titia Sijen,et al.  On the Role of RNA Amplification in dsRNA-Triggered Gene Silencing , 2001, Cell.

[7]  A. Ernst,et al.  Cargo recognition and trafficking in selective autophagy , 2014, Nature Cell Biology.

[8]  Erika Hartwieg,et al.  The Caenorhabditis elegans mucolipin-like gene cup-5 is essential for viability and regulates lysosomes in multiple cell types , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[9]  T. P. Neufeld,et al.  The cell biology of autophagy in metazoans: a developing story , 2008, Development.

[10]  D. Michaelson,et al.  Sensory Regulation of the C. elegans Germline through TGF-β-Dependent Signaling in the Niche , 2012, Current Biology.

[11]  D. Killian,et al.  Caenorhabditis elegans germline patterning requires coordinated development of the somatic gonadal sheath and the germ line. , 2005, Developmental biology.

[12]  E. Hafen,et al.  The lack of autophagy triggers precocious activation of Notch signaling during Drosophila oogenesis , 2012, BMC Developmental Biology.

[13]  E Jane Albert Hubbard,et al.  Caenorhabditis elegans germ line: a model for stem cell biology. , 2007, Developmental dynamics : an official publication of the American Association of Anatomists.

[14]  G. Ruvkun,et al.  The C. elegans PTEN homolog, DAF-18, acts in the insulin receptor-like metabolic signaling pathway. , 1998, Molecular cell.

[15]  Kailiang Jia,et al.  Autophagy genes function in apoptotic cell corpse clearance during C. elegans embryonic development , 2013, Autophagy.

[16]  N. Mizushima,et al.  Autophagy: process and function. , 2007, Genes & development.

[17]  M. Hansen,et al.  Guidelines for monitoring autophagy in Caenorhabditis elegans , 2015, Autophagy.

[18]  R. Plasterk,et al.  PPW-1, a PAZ/PIWI Protein Required for Efficient Germline RNAi, Is Defective in a Natural Isolate of C. elegans , 2002, Current Biology.

[19]  G. Ruvkun,et al.  The Fork head transcription factor DAF-16 transduces insulin-like metabolic and longevity signals in C. elegans , 1997, Nature.

[20]  D. Hall,et al.  Autophagy Genes Are Essential for Dauer Development and Life-Span Extension in C. elegans , 2003, Science.

[21]  H. Stenmark,et al.  Cell polarity and migration: emerging role for the endosomal sorting machinery. , 2011, Physiology.

[22]  Dana T Byrd,et al.  Cellular analyses of the mitotic region in the Caenorhabditis elegans adult germ line. , 2006, Molecular biology of the cell.

[23]  Marvin Wickens,et al.  Regulation of the mitosis/meiosis decision in the Caenorhabditis elegans germline. , 2003, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[24]  E. Hubbard,et al.  Soma‐germline interactions that influence germline proliferation in Caenorhabditis elegans , 2010, Developmental dynamics : an official publication of the American Association of Anatomists.

[25]  J. Kimble,et al.  glp-1 Is required in the germ line for regulation of the decision between mitosis and meiosis in C. elegans , 1987, Cell.

[26]  B. Levine,et al.  Cell biology: Autophagy and cancer , 2007, Nature.

[27]  M. Driscoll,et al.  Insulin signaling promotes germline proliferation in C. elegans , 2010, Journal of Cell Science.

[28]  Tim Schedl,et al.  Multi-pathway control of the proliferation versus meiotic development decision in the Caenorhabditis elegans germline. , 2004, Developmental biology.

[29]  Jennifer M. A. Tullet,et al.  Direct Inhibition of the Longevity-Promoting Factor SKN-1 by Insulin-like Signaling in C. elegans , 2008, Cell.

[30]  Zheng Zhou,et al.  Detecting apoptotic cells and monitoring their clearance in the nematode Caenorhabditis elegans. , 2009, Methods in molecular biology.

[31]  Robert Clarke,et al.  Guidelines for the use and interpretation of assays for monitoring autophagy , 2012 .

[32]  N. Munakata.  [Genetics of Caenorhabditis elegans]. , 1989, Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme.

[33]  A. Meléndez,et al.  Autophagy in C. elegans. , 2009, WormBook : the online review of C. elegans biology.

[34]  D. Hall,et al.  The Atg6/Vps30/Beclin 1 ortholog BEC-1 mediates endocytic retrograde transport in addition to autophagy in C. elegans , 2011, Autophagy.

[35]  E Jane Albert Hubbard,et al.  Genetic analysis of Caenorhabditis elegans glp-1 mutants suggests receptor interaction or competition. , 2003, Genetics.

[36]  T. Schedl,et al.  Analysis of the multiple roles of gld-1 in germline development: interactions with the sex determination cascade and the glp-1 signaling pathway. , 1995, Genetics.

[37]  Nayoung Suh,et al.  GLD-3 and Control of the Mitosis/Meiosis Decision in the Germline of Caenorhabditis elegans , 2004, Genetics.

[38]  A. Thorburn.  Autophagy and Its Effects: Making Sense of Double-Edged Swords , 2014, PLoS biology.

[39]  Jongkyeong Chung,et al.  UVRAG is required for organ rotation by regulating Notch endocytosis in Drosophila. , 2011, Developmental biology.

[40]  S. Slaugenhaupt,et al.  Caenorhabditis elegans functional orthologue of human protein h-mucolipin-1 is required for lysosome biogenesis. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[41]  M. Labouesse.  [Caenorhabditis elegans]. , 2003, Medecine sciences : M/S.