FOXG1 and Down syndrome: For example, LMX1B regulatory loss of function results in limb anomalies rather than full nail–patella syndrome (Haro et al., 2021), SOX10 regulatory loss of function results in isolated Hirschsprung's disease rather than Waardenburg syndrome (Lecerf et al., 2014), and FOXG1 regulatory loss of function results in isolated strabismus rather than FOXG1 syndrome (Ye et al., 2022).