This image shows primary cilium (light blue) interacting with a fibrocystin-positive exosome (green). Urinary exosomes from a mouse making epitope-tagged fibrocystin were applied to wild-type ciliated renal epithelial cells. Fibrocystin was detected using 15-nanometer and SV5-Pk gold (yellow).
Microscopic image showing a primary cilium (light blue) interacting with exosome-like vesicles (purple).
In a December 2011 publication, Christopher J. Ward, M.B., Ch.B., Ph.D., and several Mayo Clinic colleagues reported using a knock-in strategy to generate a PKHD1 strain that expresses epitope-tagged fibrocystin.
The mouse with epitope-tagged fibrocystin is phenotypically normal at 14 months and allows western resolution of fibrocystin as a single 500-kilodalton product. Interestingly, the bulk of fibrocystin in its mature cleaved form is secreted in exosome-like vesicles (ELVs) that can attach to cilia.
In summary, tagging of the endogenous PKHD1 facilitates the study of the glycosylation, proteolytic cleavage and shedding of fibrocystin.
Source: Bakeberg JL, et al. Epitope-tagged Pkhd1 tracks the processing, secretion and localization of fibrocystin. Journal of the American Society of Nephrology. 2011;22:2266.