Differential activation of the DNA replication checkpoint contributes to asynchrony of cell division in C. elegans embryos.
BACKGROUND
Acquisition of lineage-specific cell cycle duration is a central feature of metazoan development. The mechanisms by which this is achieved during early embryogenesis are poorly understood. In the nematode Caenorhabditis elegans, differential cell cycle duration is apparent starting at the two-cell stage, when the larger anterior blastomere AB divides before the smaller posterior blastomere P(1). How anterior-posterior (A-P) polarity cues control this asynchrony remains to be elucidated.


RESULTS
We establish that early C. elegans embryos possess a hitherto unrecognized DNA replication checkpoint that relies on the PI-3-like kinase atl-1 and the kinase chk-1. We demonstrate that preferential activation of this checkpoint in the P(1) blastomere contributes to asynchrony of cell division in two-cell-stage wild-type embryos. Furthermore, we show that preferential checkpoint activation is largely abrogated in embryos that undergo equal first cleavage following inactivation of Galpha signaling.


CONCLUSIONS
Our findings establish that differential checkpoint activation contributes to acquisition of distinct cell cycle duration in two-cell-stage C. elegans embryos and suggest a novel mechanism coupling asymmetric division to acquisition of distinct cell cycle duration during development.
ISREC (Swiss Institute for Experimental Cancer Research), 155, ch. des Boveresses, CH-1066 Epalinges/Lausanne, Switzerland.
Michael
M
Brauchle
Karine
K
Baumer
Pierre
P
Gönczy
D000818:Animals; D030801:Animals, Genetically Modified; D064007:Ataxia Telangiectasia Mutated Proteins; D001757:Blastomeres / Q000502:physiology; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology* / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D016764:Cell Polarity / Q000235:genetics; D000071877:Checkpoint Kinase 1; D020090:Chromosome Segregation / Q000187:drug effects / Q000502:physiology; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D006918:Hydroxyurea / Q000494:pharmacology; D008853:Microscopy / Q000379:methods; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000502:physiology; D010770:Phosphotransferases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D015398:Signal Transduction
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D044385:GTP-Binding Protein alpha Subunits; C576885:Atl-1 protein, C elegans; D010770:Phosphotransferases; D011494:Protein Kinases; D064007:Ataxia Telangiectasia Mutated Proteins; D000071877:Checkpoint Kinase 1; C000605876:chk-1 protein, C elegans; D006918:Hydroxyurea