|Ph.D Student||Baron Shahaf Dana|
|Subject||Identification and Characterization of the Gene Involved|
in Rogers' Syndrome
|Department||Department of Medicine||Supervisors||Professor Ami Aronheim|
|Professor Yehuda Assaraf|
Thiamine-responsive megaloblastic anemia (TRMA), also known as Rogers' syndrome, is an early-onset autosomal recessive disorder defined by the occurrence of megaloblastic anemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment. Previous studies have suggested that loss of function of a high affinity thiamine transporter may cause this disorder. The main objective of the following thesis was to identify and characterize the gene responsible for TRMA locus. Using multiple genetic approaches a novel gene, SLC19A2, encoding a putative transmembrane thiamine transporter. Mutations were found in all affected individuals in all TRMA affected individuals enabling prenatal diagnostic tool for affected families.
Subsequently, two missense mutations in SLC19A2; G172D and D93H were characterized. The expression, post-translational modification, and sub-cellular localization were determined. The mutant G172D failed to undergo a complete glycosylation resulted in lack of plasma membrane targeting and its confinement to the Golgi and endoplasmic reticulum compartment. In contrast, the mutant D93H, was normally expressed and underwent a complete N-glycosylation but didn’t exhibit any thiamine transport activity.
The clinical manifestations of thiamine deficiency are commonly observed in cancer patients; therefore the role of thiamine transporters was examined in cancer patients. Using cDNA dot blot array and real time PCR with DNA derived from tumor and normal tissues from cancer patients, an increase expression level of both THTR1 and THTR2 in colon cancer tissues was found. These results have potential therapeutic implications based on vitamin depletion and the possible design of novel anti-tumor agents that are thiamine analogues.