Number and brightness studies of the FGFR3 achondroplasia mutant.

Abstract

The oligomer size of membrane proteins controls protein activity and function. Changes in oligomer size due to pathogenic mutations in these proteins can potentially alter protein function and signaling, thereby causing disease. Dysfunction of the fibroblast growth factor receptor-3 has been associated with achondroplasia, a genetic disorder which causes stunted bone development and growth in children. Almost 98% of the cases of achondroplasia are caused by a single site mutation, G380R, in the transmembrane domain of FGFR3. Determining the oligomer size of mutant FGFR3 can shed light on the mechanism behind the pathology in achondroplasia and possibly lead to remedies. We used a fluorescence fluctuations-based technique, Number and Brightness, to determine the apparent molecular brightness, ε, of labeled wildtype and mutant FGFR3 on the basolateral plane and compare it to the monomer control, LAT. Appropriate controls were measured while establishing this method and the oligomer size was determined by calculating the ratio of the measured ε of the receptor to the mean apparent brightness of LAT. By using this technique, we were able to demonstrate that the mutant receptor forms higher order oligomers compared to the wild-type FGFR3. This new knowledge can pave the way for potential drug development in the future.