Fig. 4: Defects in resection and spermatogenesis in mice expressing nuclease-dead MRE11.

a Conditional Mre11-H129N strategy combining Ngn3-Cre with compound heterozygous floxed and missense Mre11 exon 5 alleles. b Normal MRE11 protein levels of whole testis lysates from 5–7 wk old Mre11-cHN mice. Here, the phenotypically wild-type control (wt) was Mre11^wt/flox Ngn3-Cre^– and the heterozygous HN strain (HN-Het) was Mre11^H129N/flox Ngn3-Cre^–. c Exo7/T-seq at the hotspot shown in Fig. 1f. d Genome-average Exo7/T-seq at hotspots (5-wk animals). Top and bottom strand reads were co-oriented, averaged, and smoothed (151-bp Hann window), then internally normalized by setting the height of the resection peak to 1. Normalization facilitates comparison of shapes of resection profiles separate from sample-to-sample variation in read frequencies³⁴. Non-normalized plots are in Supplementary Fig. 4c. n = 2 for wt and Mre11-cHN, n = 1 for HN-Het. e MRE11 accumulation at hotspots in Mre11-cHN. MRE11 ChIP-seq signal was averaged around hotspots for Mre11-cHN (n = 3), wt (n = 2), and Atm^–/– (n = 1). f, g Fewer SPO11-oligo complexes in Mre11-cHN. Autoradiograph of radiolabeled complexes immunoprecipitated from testis extracts (f; signal intensity excluding the non-specific band, relative to wild type, indicated below). Lane profiles (g) depicting fast and slow migrating species as a fraction of total signal are shown. Dashed lines represent the boundary of each species. Asterisk, non-specific labeling. h The bar graph summarizing results from two biological replicates. i Reduced testis sizes (mean ± SD). Results of Student’s t tests (two-sided) are shown. j Seminiferous tubule and epididymis sections (7 wk old; cell type labels as in Fig. 3a). k, l Increased spermatocyte apoptosis in Mre11-cHN mice (7 wk). TUNEL staining (k) and quantification (l) are shown. Error bars in (l) indicate mean and range. Wild type reproduced from Supplementary Fig. 3c. m Sperm counts (mean ± SD; P value from Student’s t test (two-sided)). Control combines wt, HN-het, and cHet. n Mre11-cHN spermatocyte spreads showing either normally synapsed autosomes and normal γH2AX-positive sex body (left) or pachytene-like cells with unpaired or tangled autosomes (middle and right; arrowheads, γH2AX-positive domains). Numbers indicate pachytene(-like) cells observed and SYCP3-positive cells counted. o Spermatocyte stages (mean ± SD). Source data are provided as a Source data file.