Functional redundancy between Sall factors is likely to compensate for the heterozygous loss of Sall2 in the eye (33,34,50), particularly Sall1 which is expressed in the developing eye and can be associated with retinochoroidal coloboma in some cases of Townes-Brocks syndrome (48,51). Here, SALL2 is linked to coloboma of choroid and retina.