Diffusion barriers in the C. elegans germline syncytium shape long-range diffusion
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Stem cells and their descendants make non-autonomous differentiation decisions
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Expression of Notch is noisy in the distal half of the germline mitotic zone
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Diffusion, barriers, and negative feedback provide robustness against noise in Notch
Summary
Positional information derived from local morphogen concentration plays an important role in patterning. A key question is how morphogen diffusion and gene expression regulation shape positional information into an appropriate profile with suitably low noise. We address this question using a model system—the C. elegans germline—whose regulatory network has been well characterized genetically but whose spatiotemporal dynamics are poorly understood. We show that diffusion within the germline syncytium is a critical control of stem cell differentiation and that semi-permeable diffusion barriers present at key locations make it possible—in combination with a feedback loop in the germline regulatory network—for mitotic zone size to be robust against spatial noise in Notch signaling. Spatial averaging within compartments defined by diffusion barriers is an advantageous patterning strategy, which attenuates noise while still allowing for sharp transitions between compartments. This strategy could apply to other organs.