Fig. 5: Heat stress destabilizes MET-2 foci and heterochromatin.

a, Representative images of MET-2::mCherry foci in live WT embryos cultured normally (20 °C) or heat-stressed (HS; 37 °C, 60 min). Scale bar, 5 µm. N = 3. b, RNA-seq comparing the gene expression in RPKM (reads per kilobase million) of HS treatment or met-2Δ relative to WT(20 °C) early embryos. Genes marked in light purple and dark red are upregulated in 37 °C-treated embryos and met-2Δ, respectively, relative to WT(20 °C) (FDR < 0.01; log₂FC > 2). N = 3. c,d, Venn diagram of derepressed genes (c) and correlation between HS-treated and met-2Δ log₂FC in gene expression compared with WT(20 °C) (d). WT 37 °C versus met-2Δ: P < 2.2 × 10⁻¹⁶ by two-sided Fisher’s exact test. Pearson correlation coefficient (r) is displayed. e, Immunofluorescence and quantification of H3K9me2 per nucleus normalized to H4 in WT(20 °C) and 30-min HS-treated embryos. Scale bar, 5 µm. N = 3, n nuclei(embryos): 20 °C = 1,522(51), 37 °C = 1,139(46). Median and quartiles shown. P < 2.0 × 10⁻¹⁶ by two-sided Wilcoxon signed-rank test. f,g, Representative western blots and quantification of H3K9me2 (f) or H3ac (g) normalized to MRG-1 in WT(20 °C) and HS-treated WT embryos. HS: 37 °C, 30 min (f) or 60 min (g). H3K9me2 N = 5, P = 1.1 × 10⁻⁴; pan-H3ac N = 4, P = 0.0012; H3K9ac N = 5, P = 0.025; H3K27ac N = 4, P = 0.018 by two-sided t-test. h, H3K27ac ChIP-seq HS-treated early embryos compared with WT(20 °C). Differentially enriched peaks are highlighted in color (FDR < 0.01). N = 3. i, Venn diagram of H3K27ac differentially enriched peaks in HS treatment versus met-2 mutants shown in Fig. 5h and Fig. 3e relative to WT (20 °C) (FDR < 0.01). WT 37 °C versus met-2Δ: P < 2.2 × 10⁻¹⁶ by two-sided Fisher’s exact test. *P < 0.01, **P < 0.001, ***P < 0.0001, ****P < 0.00001.

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