Exocyst Complex Component 4

Alternative Names

  • EXOC4
  • SEC8, S. Cerevisiae, Homolog of
  • SEC8
  • KIAA1699

Associated Diseases

Meckel Syndrome, Type 1
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OMIM Number

608185

Gene Map Locus
7q33

Description

The EXOC4 gene encodes a protein that forms the exocyst complex along with seven other EXOC proteins.  While not fully characterized in humans, the highly conserved protein complex is believed to play a key role in protein transport by targeting exocytic vesicles to specific docking sites on the plasma membrane. The complex is also associated with the biogenesis of epithelial cell surface polarity. 

Molecular Genetics

Located on the long arm of chromosome 7, the EXOC4 gene spans a length of approximately 813 kb and is made up of 24 exons.  The protein encoded by this gene is 110 kDa in size and consists of 974 amino acids. Two transcriptional splice variants, encoding different isoforms, have been characterized.

Epidemiology in the Arab World

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Other Reports

Saudi Arabia

Shaheen et al. (2013) studied Meckel-Gruber syndrome (MKS) patients from 18 consanguineous Saudi families and identified their underlying gene defects.  Individuals were diagnosed with MKS based on the presence of occipital encephalocele as well as any combination of liver fibrosis, cleft palate, dysplastic kidneys, polydactyly and early lethality.  DNA from both affected and healthy members was obtained and an autozygome guided mutation analysis of known MKS genes was carried out.  However, some families did not have mutations in any of the known MKS genes.  In such cases, an exome sequencing was performed.  Exomes were then searched for compound heterozygous mutations in known MKS genes.  Failing that, all detected variants were filtered for homozygous novel changes within the autozygome.  This resulted in the detection of a novel homozygous mutation c.1733A>G (p.Gln578Arg) in the EXOC4 gene in one of the affected families.  This mutation was not found in dbSNP, 1000 genomes or 200 Saudi controls.  In-silico analysis by PolyPhen predicted this variant to be ‘probably damaging’ while SIFT predicted it to be deleterious.  The authors noted that EXOC4 had not previously been linked to MKS syndrome and that more studies were needed to confirm this association.  

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