Mutation Screening of Elongation Factor 2 in Shwachman-Diamond Syndrome Patients Lacking Mutations in the SBDS Gene

Shwachman-Diamond syndrome is an autosomal recessive disorder characterized by bone marrow failure, pancreatic insufficiency, and skeletal abnormalities. Mutations in SBDS gene explain, by literature, 90% of SDS cases. The Italian experience shows that only the 5% of individuals diagnosed as affected by SDS on clinical and hematological grounds lack mutations in the SBDS gene. It is well established that SBDS protein is essential for the assembly of mature ribosomes. The yeast SBDS ortholog functions within a pathway containing elongation factor-like 1, homologous to human GTPase elongation factor-2, to promote the release and recycling of the nucleolar shuttling factor Tif6 from cytoplasmic pre-60S subunits in a cascade targeted to form the active ribosome. We considered that mutations of genes that disrupt pathways shared by SBDS may result in disease with comparable clinical features. EEF2 was evaluated as a candidate gene by mutation screening in clinically defined SDS which lack mutations in the SBDS gene. To date, no deleterious mutations were found in EEF2 in four Italian patients without SBDS mutations, but with a clinical diagnosis of SDS.