In line with the suggested role of HTT in axonal growth and synaptogenesis (Capizzi et al., 2022; McKinstry et al., 2014), human HD neurons show synaptic dysfunctions (Dinamarca et al., 2022; HD iPSC Consortium, 2012) and defective neuronal branching (Guo et al., 2013; Mehta et al., 2018), with branching progressively decreasing in correlation with increased CAG repeats (Mehta et al., 2018). The gene discussed is HTT; the disease is Huntington disease.