A novel mouse model reveals that polycystin-1 deficiency in ependyma and choroid plexus results in dysfunctional cilia and hydrocephalus.
Polycystin-1 (PC-1), the product of the PKD1 gene, mutated in the majority of cases of Autosomal Dominant Polycystic Kidney Disease (ADPKD), is a very large (approximately 520 kDa) plasma membrane receptor localized in several subcellular compartments including cell-cell/matrix junctions as well as cilia. While heterologous over-expression systems have allowed identification of several of the potential biological roles of this receptor, its precise function remains largely elusive. Studying PC-1 in vivo has been a challenging task due to its complexity and low expression levels. To overcome these limitations and facilitate the study of endogenous PC-1, we have inserted HA- or Myc-tag sequences into the Pkd1 locus by homologous recombination. Here, we show that our approach was successful in generating a fully functional and easily detectable endogenous PC-1. Characterization of PC-1 distribution in vivo showed that it is expressed ubiquitously and is developmentally-regulated in most tissues. Furthermore, our novel tool allowed us to investigate the role of PC-1 in brain, where the protein is abundantly expressed. Subcellular localization of PC-1 revealed strong and specific staining in ciliated ependymal and choroid plexus cells. Consistent with this distribution, we observed hydrocephalus formation both in the ubiquitous knock-out embryos and in newborn mice with conditional inactivation of the Pkd1 gene in the brain. Both choroid plexus and ependymal cilia were morphologically normal in these mice, suggesting a role for PC-1 in ciliary function or signalling in this compartment, rather than in ciliogenesis. We propose that the role of PC-1 in the brain cilia might be to prevent hydrocephalus, a previously unrecognized role for this receptor and one that might have important implications for other genetic or sporadic diseases.
Dulbecco Telethon Institute (DTI) at Dibit, San Raffaele Scientific Institute, Milan, Italy.
Claas
C
Wodarczyk
Isaline
I
Rowe
Marco
M
Chiaravalli
Monika
M
Pema
Feng
F
Qian
Alessandra
A
Boletta
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002831:Choroid Plexus / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism*; D004805:Ependyma / Q000378:metabolism*; D000939:Epitopes / Q000737:chemistry; D006579:Heterozygote; D006849:Hydrocephalus / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D017434:Protein Structure, Tertiary; D050396:TRPP Cation Channels / Q000172:deficiency* / Q000235:genetics*
D000939:Epitopes; D050396:TRPP Cation Channels