SALL4

More than 25 mutations in the SALL4 gene have been identified in people with Duane-radial ray syndrome (also known as Okihiro syndrome) or a very similar condition called acro-renal-ocular syndrome. Researchers suspect that Duane-radial ray syndrome and acro-renal-ocular syndrome are part of an overlapping set of syndromes with many possible signs and symptoms.

Most SALL4 gene mutations create a premature stop signal in the instructions for making the SALL4 protein. As a result, cells do not produce any functional protein from one copy of this gene. Researchers are investigating how a reduction in the amount of the SALL4 protein disrupts eye, heart, and limb development in people with Duane-radial ray syndrome and acro-renal-ocular syndrome.

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A least one mutation in the SALL4 gene has been found to cause IVIC syndrome, a condition whose signs and symptoms overlap with those of Duane-radial ray syndrome and acro-renal-ocular syndrome (described above). The acronym IVIC stands for Instituto Venezolano de Investigaciones Cientìficas, the center where the condition was first described. Major features of IVIC syndrome include abnormally formed bones in the arms and hands, hearing loss, and problems with eye movement caused by abnormalities of the muscles that surround the eyes (extraocular muscles).

The SALL4 gene mutation responsible for IVIC syndrome creates a premature stop signal in the instructions for making the SALL4 protein. As a result, cells produce an abnormally short version of the protein from one copy of this gene. It is unclear whether this shortened protein is completely nonfunctional or if it retains some of its function as a transcription factor. Researchers are working to determine how this SALL4 gene mutation disrupts early development and leads to the characteristic features of IVIC syndrome.