ATR is a multifunctional regulator of male mouse meiosis

Meiotic cells undergo genetic exchange between homologous chromosomes through programmed DNA double-strand break (DSB) formation, recombination and synapsis 1, 2 . In mice, the DNA damage-regulated phosphatidylinositol-3-kinase-like kinase (PIKK) ATM regulates all of these processes 3-6 . However, the meiotic functions of another major PIKK, ATR, have remained elusive, because germ line-specific depletion of this kinase is challenging. Using an efficient conditional strategy, we uncover roles for ATR in male mouse prophase I progression. Deletion of ATR causes chromosome axis fragmentation and germ cell elimination at mid pachynema. ATR is required for homologous synapsis, in a manner genetically dissociable from DSB formation. In addition, ATR regulates loading of recombinases RAD51 and DMC1 to DSBs and maintenance of recombination foci on synapsed and asynapsed chromosomes. Mid pachytene spermatocyte elimination in ATR deficient mice cannot be rescued by deletion of ATM and the third DNA damage-regulated PIKK, PRKDC, consistent with the existence of a PIKK-independent surveillance mechanism in the mammalian germ line. Our studies identify ATR as a multifunctional regulator of mouse meiosis.