Lu, W. et al. Comparison of Pkd1-targeted mutants reveals that loss of polycystin-1 causes cystogenesis and bone defects. Hum. Mol. Genet. 10, 2385-2396

Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
Human Molecular Genetics (Impact Factor: 6.39). 11/2001; 10(21):2385-96. DOI: 10.1093/hmg/10.21.2385
Source: PubMed

ABSTRACT

A high level of polycystin-1 expression is detected in kidneys of all patients with autosomal dominant polycystic kidney disease (ADPKD). Mice that overexpress polycystin-1 also develop renal cysts. Whether overexpression of polycystin-1 is necessary for cyst formation is still unclear. Here, we report the generation of a targeted mouse mutant with a null mutation in Pkd1 and its phenotypic characterization in comparison with the del34 mutants that carry a 'truncation mutation' in Pkd1. We show that null homozygotes develop the same, but more aggressive, renal and pancreatic cystic disease as del34/del34. Moreover, we report that both homozygous mutants develop polyhydramnios, hydrops fetalis, spina bifida occulta and osteochondrodysplasia. Heterozygotes also develop adult-onset pancreatic disease. We show further that del34 homozygotes continue to produce mutant polycystin-1, thereby providing a possible explanation for increased immunoreactive polycystin-1 in ADPKD cyst epithelia in the context of the two-hit model. Our data demonstrate for the first time that loss of polycystin-1 leads to cyst formation and defective skeletogenesis, and indicate that polycystin-1 is critical in both epithelium and chondrocyte development.

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Available from: Leighton Pritchard, Feb 22, 2014
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    • "The level of PC1 V expressed is therefore as low as 10%–20% of the total PC1 amount (i.e., PC1 U plus PC1 cFL ) in wild-type controls. The Pkd1 V/V animals are viable with virtually normal appearing kidneys at birth[40], whereas Pkd1 null mice develop very severe cystic kidneys starting at e15.5 and are embryonically lethal424344. One explanation for the hypomorphic nature of the Pkd1 V allele would be that the resulting PC1 V has a partial, but otherwise redundant function of PC1 cFL to allow the animals to get through embryonic development, but is insufficient to prevent cystogenesis in the postnatal period. "
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    ABSTRACT: Polycystin-1 (PC1) plays an essential role in renal tubular morphogenesis, and PC1 dysfunction causes human autosomal dominant polycystic kidney disease. A fundamental characteristic of PC1 is post-translational modification via cleavage at the juxtamembrane GPCR proteolysis site (GPS) motif that is part of the larger GAIN domain. Given the considerable biochemical complexity of PC1 molecules generated in vivo by this process, GPS cleavage has several profound implications on the intracellular trafficking and localization in association with their particular function. The critical nature of GPS cleavage is further emphasized by the increasing numbers of PKD1 mutations that significantly affect this cleavage process. The GAIN domain with the GPS motif therefore represents the key structural element with fundamental importance for PC1 and might be polycystic kidney disease's (PKD) Achilles' heel in a large spectrum of PKD1 missense mutations. We highlight the central roles of PC1 cleavage for the regulation of its biogenesis, intracellular trafficking and function, as well as its significance in polycystic kidney disease.
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    • "Lack of functional PC1 displays much less Ca2+ influx in response to mechanical stimuli [13]. Moreover, PC1-deficient mice exhibit multiple developmental defects, including skeletal and vascular abnormalities [14], [15], [16]. Recent researches show that PC1 plays an important role in bone development through Runx2-dependent signaling cascade [17], [18]. "
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    ABSTRACT: Mechanical regulation of bone formation involves a complex biophysical process, yet the underlying mechanisms remain poorly understood. Polycystin-1 (PC1) is postulated to function as a mechanosensory molecule mediating mechanical signal transduction in renal epithelial cells. To investigate the involvement of PC1 in mechanical strain-induced signaling cascades controlling osteogenesis, PKD1 gene was stably silenced in osteoblastic cell line MC3T3-E1 by using lentivirus-mediated shRNA technology. Here, our findings showed that mechanical tensile strain sufficiently enhanced osteogenic gene expressions and osteoblastic proliferation. However, PC1 deficiency resulted in the loss of the ability to sense external mechanical stimuli thereby promoting osteoblastic osteogenesis and proliferation. The signal pathways implicated in this process were intracellular calcium and Akt/β-catenin pathway. The basal levels of intracellular calcium, phospho-Akt, phospho-GSK-3β and nuclear accumulation of active β-catenin were significantly attenuated in PC1 deficient osteoblasts. In addition, PC1 deficiency impaired mechanical strain-induced potentiation of intracellular calcium, and activation of Akt-dependent and Wnt/β-catenin pathways, which was able to be partially reversed by calcium ionophore A23187 treatment. Furthermore, applications of LiCl or A23187 in PC1 deficient osteoblasts could promote osteoblastic differentiation and proliferation under mechanical strain conditions. Therefore, our results demonstrated that osteoblasts require mechanosensory molecule PC1 to adapt to external mechanical tensile strain thereby inducing osteoblastic mechanoresponse, partially through the potentiation of intracellular calcium and downstream Akt/β-catenin signaling pathway.
    Full-text · Article · Mar 2014 · PLoS ONE
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    • "As a mechanosensory organelle, a primary cilium can sense body fluid movement in all visceral organs (Abdul-Majeed & Nauli, 2011c). These include urine in the renal nephron (Nauli et al., 2006; Xu et al., 2007, 2009), nodal flow in Hensen's node (McGrath, Somlo, Makova, Tian, & Brueckner, 2003), bile in the hepatic biliary system (Masyuk et al., 2006), digestive fluid in the pancreatic duct (Cano, Murcia, Pazour, & Hebrok, 2004; Cano, Sekine, & Hebrok, 2006), dentin in dental pulp (Magloire, Couble, Romeas, & Bleicher, 2004; Thivichon-Prince et al., 2009), lacunocanalicular fluid in bone and cartilage (Hou, Kolpakova-Hart, Fukai, Wu, & Olsen, 2009; Lu et al., 2001; Xiao et al., 2006), blood in vasculature (AbouAlaiwi et al., 2009; Nauli et al., 2008), and cerebral spinal fluid in the nervous system (Fuchs & acTub YFP-PC1 Merge A B C D Figure 1.1 Sensory primary cilium in endothelial and epithelial cells. A primary cilium is a sensory organelle that projects to the extracellular space from the apical membrane of a cell. "
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    ABSTRACT: Primary cilia are sensory organelles that transmit extracellular signals into intracellular biochemical responses. Structural and functional defects in primary cilia are associated with a group of human diseases, known as ciliopathies, with phenotypes ranging from cystic kidney and obesity to blindness and mental retardation. Primary cilia mediate mechano- and chemosensation in many cell types. The mechanosensory function of the primary cilia requires the atypical G-protein-coupled receptor polycystin-1 and the calcium-permeable nonselective cation channel polycystin-2. Mechanical stimulations such as fluid-shear stress of the primary cilia initiate intracellular calcium rise, nitric oxide release, and protein modifications. In this review, we describe a set of protocols for cell culture to promote ciliation, mechanical stimulations of the primary cilia, and measurements of calcium rise and nitric oxide release induced by fluid shear stress.
    Full-text · Article · Mar 2013 · Methods in enzymology
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