FL-HSCs of <i>Atm</i>-knockout mice were pulse-treated with etoposide for 4 h <i>in vitro</i>; metaphase spreads were generated 24 h after pulse treatment.

<p>(A) Representative metaphase spreads. Arrows indicate chromosomal or chromatid breaks. (B) Number of chromosomal breaks and chromatid breaks, shown as a table. (C) Sequence electropherogram of <i>Kmt2a</i>-<i>Ptp4a2</i> fusion mRNA.