Figure 1.
PP4 inhibition in the early C. elegans embryo impairs chromosome congression and results in chromosome mis-segregation. (A) Cartoon of C. elegans PP4 (the catalytic subunit is represented by two paralogs) and of the dividing one-cell embryo with the spindle region imaged in this study outlined by dashed lines. (B) Selected images from time-lapse movies of one-cell embryos co-expressing GFP::histone H2B (HIS-58) and GFP::γ-tubulin (TBG-1). Time is relative to NEBD. The number of anaphases with chromatin (chr) bridges, highlighted by the arrow, relative to the total number of anaphases examined is indicated in the last frame. Scale bar, 5 µm. (C) Time-aligned kymographs generated from time-lapse movies such as those shown in B and Video 1. Scale bar, 5 µm. (D) Chromosome span (top) and pole–pole distance (bottom) versus time relative to NEBD, measured in one-cell embryos such as those shown in B, as indicated in the schematics. Values correspond to the mean of n embryos ± SEM, and vertical dashed lines mark the average time of anaphase onset. Conditions are color-coded as in B. (E) Selected images from time-lapse movies of one-cell embryos co-expressing mCherry::histone H2B (HIS-11) and GFP::β-tubulin (TBB-2). Time is relative to anaphase onset (AO). Arrows highlight defective chromosome congression and segregation in PP4-inhibited embryos. The frequency of anaphase chromatin (chr) bridges is indicated as described for B. Scale bar, 5 µm. (F) Chromosome span versus time, measured in one-cell embryos such as those shown in E and plotted as described for D. Conditions are color-coded as in B–E. (G) Selected images from time-lapse movies of one-cell embryos co-expressing mCherry::histone H2B (HIS-11) and GFP::β-tubulin (TBB-2), isolated from control mothers or homozygous mutant mothers before the onset of sterility. Time point corresponds to NEBD. Arrows point to structurally aberrant extra chromosomes in the female pronucleus, which are carried over into the first mitosis from defective meiotic divisions. This meiosis-derived defect is only observed in the two most penetrant PP4 inhibition conditions shown here. Centrosome maturation remains unaffected by penetrant PP4 inhibition (arrowheads). Scale bar, 5 µm.

PP4 inhibition in the early C. elegans embryo impairs chromosome congression and results in chromosome mis-segregation. (A) Cartoon of C. elegans PP4 (the catalytic subunit is represented by two paralogs) and of the dividing one-cell embryo with the spindle region imaged in this study outlined by dashed lines. (B) Selected images from time-lapse movies of one-cell embryos co-expressing GFP::histone H2B (HIS-58) and GFP::γ-tubulin (TBG-1). Time is relative to NEBD. The number of anaphases with chromatin (chr) bridges, highlighted by the arrow, relative to the total number of anaphases examined is indicated in the last frame. Scale bar, 5 µm. (C) Time-aligned kymographs generated from time-lapse movies such as those shown in B and Video 1. Scale bar, 5 µm. (D) Chromosome span (top) and pole–pole distance (bottom) versus time relative to NEBD, measured in one-cell embryos such as those shown in B, as indicated in the schematics. Values correspond to the mean of n embryos ± SEM, and vertical dashed lines mark the average time of anaphase onset. Conditions are color-coded as in B. (E) Selected images from time-lapse movies of one-cell embryos co-expressing mCherry::histone H2B (HIS-11) and GFP::β-tubulin (TBB-2). Time is relative to anaphase onset (AO). Arrows highlight defective chromosome congression and segregation in PP4-inhibited embryos. The frequency of anaphase chromatin (chr) bridges is indicated as described for B. Scale bar, 5 µm. (F) Chromosome span versus time, measured in one-cell embryos such as those shown in E and plotted as described for D. Conditions are color-coded as in B–E. (G) Selected images from time-lapse movies of one-cell embryos co-expressing mCherry::histone H2B (HIS-11) and GFP::β-tubulin (TBB-2), isolated from control mothers or homozygous mutant mothers before the onset of sterility. Time point corresponds to NEBD. Arrows point to structurally aberrant extra chromosomes in the female pronucleus, which are carried over into the first mitosis from defective meiotic divisions. This meiosis-derived defect is only observed in the two most penetrant PP4 inhibition conditions shown here. Centrosome maturation remains unaffected by penetrant PP4 inhibition (arrowheads). Scale bar, 5 µm.

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