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Shaping and timing embryonic development

De­velopment from an al­most iso­tropic ferti­lized egg into an adult with proper body axes is a for­mida­ble task for the small and fairly simple nema­tode Cae­norhabditis ele­gans: Cells need to be posi­tioned at the right places to even­tually create a head and a tail, and the multi­tude of cell divi­sions dur­ing em­bry­onic de­velopment need to be properly timed to allow for this posi­tion­ing. Em­bryos solve this task by self-organiza­tion prin­ciples that rely on basic geo­metric and physi­cal measures.

Physics as conductor of embryogenesis

The em­bry­onic de­velopment of the trans­parent worm Caenorhabdi­tis ele­gans is re­mark­ably robust - virtu­ally all adult ani­mals end up with the same num­ber of cells that have un­der­gone the same migra­tion and dif­feren­tiation path­ways. This al­most de­ter­minis­tic and invar­iant de­velopmen­tal pat­tern sug­gests that not just genet­ics and mo­lecu­lar biolo­gy are set­ting the scene but that also basic phys­ics takes part in con­duct­ing this com­plex play.

Based on previ­ous work, which had re­vealed that cells push each other within the em­bry­o-en­gulf­ing egg­shell, mem­bers of the Elite Grad­uate Pro­gram „Biological Physics“ have shown now with light-sheet fluo­rescence mi­cros­copy that cell vol­umes and cell cycle times are anti-correlated through­out em­bryo­gene­sis. Moreover, exper­imental cycle times were seen to fol­low an Ar­rheni­us scal­ing, i.e., their loga­rithm changes with the in­verse ambi­ent tem­pera­ture. These exper­imental data are fully in line with an ac­com­pany­ing theo­retical model based on a limit­ing com­po­nent and an onset of pro­tein syn­thesis only at the stage of gas­trula­tion. Alto­geth­er, the new data show that basic physi­cal prin­ciples gov­ern ro­bust­ness-related fea­tures of the em­bryo­gene­sis of C. ele­gans.

Text: Elite Graduate Program "Biological Physics“