HEK 293FT cells were transfected with CBX4 fused to a promiscuous variant of the BirA biotin ligase (CBX4-BirA∗) together with either full length SALL1-2xHA or the truncated form of SALL1826-2xHA, causative of TBS. The gene discussed is SALL1; the disease is Townes-Brocks syndrome.