SALL1 and Townes-Brocks syndrome: SALL1 regulation and SALL1 protein function are incompletely understood.1,2 Heterozygous early-truncating SALL1 mutations are known to cause autosomal dominant Townes–Brocks syndrome (TBS, MIM #107480), a malformation syndrome without severe central nervous system (CNS) involvement.3,4 Such mutations result in truncated proteins thought to act by dominant negative effects.5,6SALL1 haplo-insufficiency7 and late-truncating mutations which partially undergo nonsense-mediated mRNA decay (NMD) cause mild TBS,5,7,8 suggesting distinct pathophysiological mechanisms of SALL1 mutations.