Cell cycle features of C. elegans germline stem/progenitor cells vary temporally and spatially

• Published in: Developmental biology Vol. 409; no. 1; pp. 261 - 271
• Main Authors: Roy, Debasmita, Michaelson, David, Hochman, Tsivia, Santella, Anthony, Bao, Zhirong, Goldberg, Judith D., Hubbard, E. Jane Albert
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2016
• Subjects: Adult reproductive diapause; adulthood; adults; Aging - physiology; Animals; Caenorhabditis elegans - cytology; Caenorhabditis elegans - metabolism; Cell Cycle; Cell fate; Cell Lineage; Cell Proliferation; DNA; DNA - metabolism; germ cells; Germ Cells - cytology; homeostasis; Insulin; interphase; Irises; Larva - cytology; larvae; latitude; mitosis; Mitotic Index; mutants; Mutation - genetics; Notch; nutritional status; Regeneration; S6 Kinase; stem cells; Stem Cells - cytology; Stem Cells - metabolism; Time Factors; Irises; Cell fate; Adult reproductive diapause; Insulin; S6 Kinase; Notch
• ISSN: 0012-1606; 1095-564X; 1095-564X
• DOI: 10.1016/j.ydbio.2015.10.031

Many organisms accumulate a pool of germline stem cells during development that is maintained in later life. The dynamics of establishment, expansion and homeostatic maintenance of this pool are subject to both developmental and physiological influences including the availability of a suitable niche microenvironment, nutritional status, and age. Here, we investigated the dynamics of germline proliferation during stages of expansion and homeostasis, using the C. elegans germ line as a model. The vast majority of germ cells in the proliferative zone are in interphase stages of mitosis (G1, S, G2) rather than in the active mitotic (M) phase. We examined mitotic index and DNA content, comparing different life stages, mutants, and physiological conditions. We found that germ cells in larval stages cycle faster than in adult stages, but that this difference could not be attributed to sexual fate of the germ cells. We also found that larval germ cells exhibit a lower average DNA content compared to adult germ cells. We extended our analysis to consider the effects of distance from the niche and further found that the spatial pattern of DNA content differs between larval and adult stages in the wild type and among mutants in pathways that interfere with cell cycle progression, cell fate, or both. Finally, we characterized expansion of the proliferative pool of germ cells during adulthood, using a regeneration paradigm (ARD recovery) in which animals are starved and re-fed. We compared adult stage regeneration and larval stage expansion, and found that the adult germ line is capable of rapid accumulation but does not sustain a larval-level mitotic index nor does it recapitulate the larval pattern of DNA content. The regenerated germ line does not reach the number of proliferative zone nuclei seen in the continuously fed adult. Taken together, our results suggest that cell cycle dynamics are under multiple influences including distance from the niche, age and/or maturation of the germ line, nutrition and, possibly, latitude for physical expansion. •Higher mitotic index in larval vs adult germline is not due to sperm vs oocyte fate.•Average DNA content is lower in larval vs adult proliferative germ cells.•In wild-type adults, average DNA content increases with distance from the niche.•DNA content is influenced by mutations that affect cell cycle and/or cell fate.•Some, but not all, features are shared between post-ARD adult and larval germ cells.