In zebrafish, SALL4 acts downstream of TBX5 and is required for pectoral fin outgrowth; mutations at the SALL4 locus on chromosome 20 resulted in a range of clinically overlapping phenotypes, including Okihiro syndrome, HOS, acro-renal-ocular syndrome, and thalidomide embryopathy (Harvey and Logan, 2006). Here, TBX5 is linked to Holt-Oram syndrome.