Epitope-based labeling for improved live-imaging of endogenous proteins in C. elegans

Visualizing protein expression dynamics with high temporal resolution is essential for understanding how cells acquire specific fates and functions during development, where key decisions can occur within minutes. Conventional direct fluorescent tagging often fails to capture these rapid changes in protein expression due to the relatively slow fluorophore maturation time. Indirect epitope-based labeling strategies offer a promising alternative, yet only a limited number of these systems have been developed and used in the context of multicellular organisms. Here, we evaluate and combine four epitope-based indirect labeling systems for live-imaging of proteins in C. elegans: the SunTag, Frankenbody, MoonTag and AlfaTag systems. Each system uses a fluorescently labeled high-affinity single-chain antibody or nanobody to recognize short peptide epitopes fused to a protein of interest, enabling immediate visualization of newly synthesized proteins. We demonstrate that all four systems specifically label epitope-tagged endogenous proteins and show no detectable cross-reactivity when used in dual-color combinations, enabling simultaneous visualization of distinct proteins within the same embryo. In addition, we show that the SunTag system offers three major advantages over direct labeling: earlier detection of proteins, enhanced sensitivity through signal amplification (as illustrated by CAM-1) and less impact on the function (as demonstrated for ERM-1). Together, this expanded toolkit of epitope-based labeling systems offers many new opportunities for visualizing rapid protein dynamics and for dissecting how their dynamics drive cell fate decisions during development. SUMMARYThe development of epitope-labeling systems has improved live-imaging quality of proteins. Unfortunately, limited systems exist for multicellular organisms to study protein expression in the context of development. Here, we expand the epitope-labeling toolbox for C. elegans by combining SunTag or Frankenbody with MoonTag or AlfaTag. Our data indicates that these systems simultaneously visualize different endogenous proteins without cross-reactivity. Moreover, the SunTag system shows advantages over direct labeling: earlier detection, enhanced sensitivity through signal amplification and less impact on protein function. This expanded epitope-labeling toolbox in C. elegans provides opportunities for accurate visualization of different proteins that drive cell fate decisions. O_FIG O_LINKSMALLFIG WIDTH=155 HEIGHT=200 SRC="FIGDIR/small/703904v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@449fe0org.highwire.dtl.DTLVardef@15c68cforg.highwire.dtl.DTLVardef@1e51ff8org.highwire.dtl.DTLVardef@196114d_HPS_FORMAT_FIGEXP M_FIG C_FIG