SMRC-1 promotes genome integrity.

(A) Apoptotic germ cells are identified by CED-1::GFP expression in control and representative fertile and sterile smrc-1;ced-1::gfp adult gonads. Each gonad is oriented with the loop region to the right. Plots show the number of CED-1::GFP positive cells per gonad arm in wildtype, met-2, and fertile smrc-1 mutants; box represents the middle 50% of values, line represents the 50th percentile (median) value, and bars indicate the full range of values. CED-1::GFP is observed throughout sterile smrc-1 and smrc-1 met-2 gonads; these individuals were not quantified because it was difficult to reliably distinguish individual cells. Elevated apoptosis is CEP-1-dependent. ***PS2C Fig for more smrc-1 met-2 images. (B) Reversion of the unc-58(e665) phenotype is enhanced by smrc-1 loss-of-function at 20° and 25°C. Total = number of individuals assayed. (C) The dog-1 poly G/C deletion phenotype is elevated in smrc-1 and met-2 mutants. Data represent the deletion frequency within vab-1 exon 5. Total = number of individuals assayed. Deletion = number of deletions identified. Note that smrc-1 met-2 double mutants were assayed in the M+Z- generation. (D) Antibody S9.6 immunolabeling detects elevated RNA:DNA hybrids throughout the smrc-1 germ line. The proportion of nuclei with S9.6 foci (the S9.6 index) was calculated independently for proliferative, leptotene/ zygotene (transition), and pachytene regions of 25°C wildtype and smrc-1 M-Z- hermaphrodite germ lines. *PPsmrc-1 mutations alter bivalent formation. Images show representative diakinesis-stage nuclei in the -1 oocyte. Wildtype image contains 6 larger DAPI-bright bodies, representing 6 bivalents, and spo-11(ok79) image contains 12 smaller DAPI-bright bodies, representing 12 univalents. Righthand panel shows the number of DAPI-stained bodies per diakinesis nucleus in strains raised at 25°C. smrc-1(om138) and smrc-1(ea8) oocytes contain 4–7 distinct DAPI-bright bodies of variable size; larger bodies often appear to contain chromosomes held together by DNA bridging (arrows). DNA linkages were verified by rotation of confocal microscopy Z-stacks. smrc-1(om138);spo-11(ok79) oocytes contain 5–12 DAPI-bright bodies of variable size.