November 15, 2006
In 2003, a team of researchers published an article that described in a large Middle Eastern family a unique genetic syndrome that they later named Cranio-Lenticulo-Sutural dysplasia, or CLSD. Children born with CLDS have skull bones that fuse slowly and abnormally over many years, sometimes as late at their teens. The children also typically have pointed chins, scoliosis, cataracts, unusually wide set eyes, and developmental delays. In the October issue of the journal Nature Genetics, a team of investigators led by the NIDCR grantee Dr. Simeon Boyadjiev, report they have isolated the gene that, when altered during development, causes this striking, largely craniofacial phenotype, or manifestation of traits. The gene encodes a protein called SEC23A that helps to form a bubble-like compartment within our cells called “a COPII-coated vesicle.” These vesicles shuttle needed secretory proteins from the endoplasmic reticulum to the Golgi complex for further processing. Because of a slight gene alteration that causes a single amino acid substitution in the SEC23A protein, the needed vesicles malfunction, secretory proteins build up on the endoplasmic reticulum, and the various clinical features of CLSD arise. “Although the endoplasmic-reticulum-to-Golgi trafficking has been extremely well characterized by both genetic and biochemical methods, very few human disorders have been attributed to defects in individual components,” concluded the authors. “The functional redundancy of the COPII pathway is likely to lead to non-lethal phenotypes that have escaped classification. A systematic survey of tissues from similar bone morphogenesis developmental diseases may uncover other previously unknown mutant alleles of the COPII machinery.”