E2-deficient spermatocytes have unrepaired DSBs that are increased by depletion of E1.

<p>Chromosome spreads from adult WT (a–d), <i>E1+/+E2−/−</i> (e–h), <i>E1+/ΔE2−/−</i> (i–l) and <i>E1Δ/ΔE2−/−</i> spermatocytes (m–o) immunostained for γH2AX (red) and SYCP3 (green). Insets represent the area outlined. (a–d) γH2AX pattern in WT prophase I. (b) γH2AX localizes in the sex chromosomes and as foci in the chromatin adjacent to the SC in autosomes (white arrows). Telomeres in WT diplotene spermatocytes are devoid of γH2AX (d, white inset). (e–h) <i>E1+/+E2−/−</i> spermatocytes; (i–l) <i>E1+/ΔE2−/−</i> spermatocytes. γH2AX persists as foci in autosomes (g,j, white arrows) and in telomeres (g,k white arrows; h,l, blue arrows, insets). (m–o) γH2AX signal is distributed throughout the chromatin in <i>E1Δ/ΔE2−/−</i> early pachytene spermatocytes, primarily in unsynapsed chromosomes and chromosome associations (n, asterisks). The few spermatocytes observed at mid-pachytene displayed telomeric γH2AX foci (o, white inset).