Fig. 6: Maternal MET-2 and SET-25 act in the early embryo to regulate monoallelic expression.

a, b show reciprocal crosses generating F1 hybrids that are heterozygous for recessive met-2(cat), with the mutation coming from either the paternal (a) or maternal (b) germ line. met-2(cat) from the paternal germline leads to BAE in F1 heterozygotes (c), whereas met-2cat from the maternal germline leads to aRMAE (d); a 10 micrometer white scale bar is inset in the bottom left of each animal. e Scatterplots of intestine cells from the animals in (c and d). f Boxplots of intrinsic noise values from each cross. Top of boxplot is 75th percentile, bottom of box is 25th percentile, line is median, top and bottom error bars are 90th and 10th percentile, respectively, and dots are 95th and 5th percentile. Heterozygotes that got the met-2(cat) allele from the maternal germline had significantly higher intrinsic noise than animals that got the same allele from the paternal germline; 0.0469 median intrinsic noise for maternal met-2 vs 0.00193 for paternal met-2, P < 0.001, Mann–Whitney Rank Sum Test, two-sided, N = 180 cells per group, three independent experiments. Despite being heterozygous for met-2(cat), animals got the mutant allele via the maternal germline had similar phenotypes to met-2(RNAi) and met-2(null), shown in Figs. 1c and 2a. g, h show reciprocal crosses generating F1 hybrids that are homozygous for met-2cat and heterozygous for set-2(cat), with the set-25(cat) mutation coming from either the paternal (g) or maternal (h) germline; a 10 micrometer white scale bar is inset in the bottom left of each animal. Homozygous met-2(cat) results in aRMAE, however, when the set-25(cat) mutation is passed through the maternal, but not the paternal germline, the result is a BAE phenotype in met-2(cat);set-25(cat) animals (i, j). k shows scatterplots of cells from F1 animals from each reciprocal cross shown. l shows boxplots of intrinsic noise of cells from F1 animals from each reciprocal cross shown. Top of boxplot is 75th percentile, bottom of box is 25th percentile, line is median, top and bottom error bars are 90th and 10th percentile, respectively, and dots are 95th and 5th percentile. The F1 met-2(cat) homozygous, set-25(cat) heterozygous animals that got the set-25(cat) allele from the maternal germline had the same decreased intrinsic noise as homozygous set-25 mutants and RNAi (shown in Figs. 4f and 5e), with a significantly lower intrinsic noise than animals that got the mutant set-25(cat) allele from the paternal germline; 0.00109 median intrinsic noise for maternal mutant set-25 vs. 0.0508 for paternal mutant set-25, P < 0.001, Mann–Whitney Rank Sum Test, two-sided, N = 180 cells per group, three independent experiments.