Aldh1a1 is not required for HSC maintenance or function. Irradiated CD45.1⁺ recipient mice were competitively reconstituted with 3 × 10⁵ whole bone marrow cells from 2-month-old, 13-month-old, or 26-month-old Aldh1a1^+/− (black lines) or Aldh1a1^−/− (red lines) CD45.2 donor cells along with a radioprotective dose of 3 × 10⁵ CD45.1⁺ bone marrow cells. Similar levels of long-term multilineage reconstitution were observed at all ages from Aldh1a1^+/− and Aldh1a1^−/− cells. At least 3 independent experiments were performed at each age, from which one representative experiment is shown. Error bars represent SD.