NKX2-5 and hypoplastic left heart syndrome: Although several studies have examined the molecular underpinnings of HLHS, the number of genes associated with this disease is small (e.g. NKX2-5, NOTCH1, ETS1, MYH6, LRP2, and CELSR1), and they are not yet conclusively determined as causal for HLHS (Garg et al., 2005; Ye et al., 2010; Kobayashi et al., 2014; Theis et al., 2015a; Tomita-Mitchell et al., 2016; Theis et al., 2020; Theis, 2021; Theis et al., 2022).