Gloria Jansen1,2, Daniel Gebert1,2, Tharini Ravindra Kumar1, Emily Simmons1, Sarah Murphy1 and Felipe Karam Teixeira1,2 1Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom; 2Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom Corresponding author: fk319cam.ac.uk Abstract

Selfish DNA modules like transposable elements (TEs) are particularly active in the germline, the lineage that passes genetic information across generations. New TE insertions can disrupt genes and impair the functionality and viability of germ cells. However, we found that in P–M hybrid dysgenesis in Drosophila, a sterility syndrome triggered by the P-element DNA transposon, germ cells harbor unexpectedly few new TE insertions despite accumulating DNA double-strand breaks (DSBs) and inducing cell cycle arrest. Using an engineered CRISPR–Cas9 system, we show that generating DSBs at silenced P-elements or other noncoding sequences is sufficient to induce germ cell loss independently of gene disruption. Indeed, we demonstrate that both developing and adult mitotic germ cells are sensitive to DSBs in a dosage-dependent manner. Following the mitotic-to-meiotic transition, however, germ cells become more tolerant to DSBs, completing oogenesis regardless of the accumulated genome damage. Our findings establish DNA damage tolerance thresholds as crucial safeguards of genome integrity during germline development.

Received April 11, 2024. Accepted July 5, 2024.