Mllt11 loss decreased neurite outgrowth and branching complexity in vitro. A, Primary cortical neurons derived from E18.5 brains cultured for 24 h postplating. Neurites identified with MAP2 staining (red). B, C, Twenty-four hours postplating, primary neurite length (B) and total neurite length (C) were significantly decreased in cKO neurons relative to controls (D). The proportion of total primary neurite length was significantly increased in cKO neurons relative to controls. E, Examples of neuronal morphologies with varying numbers of neurites 24 h postplating. F, Quantification of number of neurites per neuron 24 h postplating, where cKO neurons had significantly fewer neurites compared with controls. G–I, Quantification of decreases in total neurite length (G) and branching complexity (I) of cKO relative to control primary cortical neurons cultured for 7 d postplating (H). Student's t test with Welch's correction (B–D, F). Paired t test, for both controls and cKOs N = 150 neurons (50 neurons/individual × three individuals). Data presented as mean ± SD; *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. Scale bar: 20 μm (A, E) and 50 μm (H). HPP, hours postplating; DPP, days postplating.