Abstract
Caenorhabditis briggsae has emerged as a model for comparative biology against model organism C. elegans. Most of its cell fate specifications are completed during embryogenesis whereas its cell growth is achieved mainly in larval stages. The molecular mechanism underlying the drastic developmental changes is poorly understood. To gain insights into the molecular changes between the two stages, we compared the proteomes between the two stages using iTRAQ. We identified a total of 2,791 proteins in the C. briggsae embryos and larvae, 247 of which undergo up- or down-regulation between the two stages. The proteins that are upregulated in the larval stages are enriched in the Gene Ontology categories of energy production, protein translation, and cytoskeleton; whereas those upregulated in the embryonic stage are enriched in the categories of chromatin dynamics and posttranslational modification, suggesting a more active chromatin modification in the embryos than in the larva. Perturbation of a subset of chromatin modifiers followed by cell lineage analysis suggests their roles in controlling cell division pace. Taken together, we demonstrate a general molecular switch from chromatin modification to metabolism during the transition from C. briggsae embryonic to its larval stages using iTRAQ approach. The switch might be conserved across metazoans.
Highlights
Regulation of protein expression is a fundamental biological process during metazoan development in which a single-cell zygote undergoes a series of divisions followed by cell fate differentiation, enabling formation of a functional organism
As C. elegans, C. briggsae develops from an embryo into adulthood through four larval stages, i.e., L1, L2, L3 and L4 that are punctuated by each molting event
C. briggsae using Isobaric Tags for Relative and Absolute Quantitation (iTRAQ)-based quantitative proteomic approach, with a focus on identification of regulatory proteins involved in C. briggsae embryogenesis and larval development
Summary
Protein identification and characterization of DEPs (Differentially Expressed Proteins) between embryos and larvae. Given a higher level of a subset of proteins in the embryos than in the larvae which are known to be involved in chromatin dynamics (Figs 3 and 4, Table S5), we set to investigate their global roles in regulating asymmetry of division timing during the proliferative stage of C. briggsae embryogenesis This was achieved using RNAi followed by automated cell lineaging analysis[17] which allows for systematic measurement of cell division timings and identification of cell identities. A total of seven proteins that showed a higher level of expression in the embryos were chosen for the lineage analysis, including five proteins required for chromatin structure and dynamics (cbr-lin-53, cbr-lin-40, cbr-let-418, cbr-swsn-6, cbr-isw-1) and two proteins necessary for posttranslational modification (cbr-sip-1, cbr-smo-1) We chose these genes because depletion of their orthologues in C. elegans all produced defects in division asynchrony during embryogenesis[13]. We collected confocal time-lapse fluorescence micrographs of a developing embryo expressing a Pcbr-his-72:HIS-72::mCherry fusion protein as
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