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BackgroundGPRC6A is a widely expressed orphan G-protein coupled receptor that senses extracellular amino acids, osteocalcin and divalent cations in vitro. The physiological functions of GPRC6A are unknown.Methods/Principal FindingsIn this study, we created and characterized the phenotype of GPRC6A −/− mice. We observed complex metabolic abnormalities in GPRC6A −/− mice involving multiple organ systems that express GPRC6A, including bone, kidney, testes, and liver. GPRC6A −/− mice exhibited hepatic steatosis, hyperglycemia, glucose intolerance, and insulin resistance. In addition, we observed high expression of GPRC6A in Leydig cells in the testis. Ablation of GPRC6A resulted in feminization of male GPRC6A −/− mice in association with decreased lean body mass, increased fat mass, increased circulating levels of estradiol, and reduced levels of testosterone. GPRC6A was also highly expressed in kidney proximal and distal tubules, and GPRC6A−/− mice exhibited increments in urine Ca/Cr and PO4/Cr ratios as well as low molecular weight proteinuria. Finally, GPRC6A −/− mice exhibited a decrease in bone mineral density (BMD) in association with impaired mineralization of bone.Conclusions/Significance GPRC6A−/− mice have a metabolic syndrome characterized by defective osteoblast-mediated bone mineralization, abnormal renal handling of calcium and phosphorus, fatty liver, glucose intolerance and disordered steroidogenesis. These findings suggest the overall function of GPRC6A may be to coordinate the anabolic responses of multiple tissues through the sensing of extracellular amino acids, osteocalcin and divalent cations.

Purpose: Circular RNAs (circRNAs), a novel class of noncoding RNAs, have recently drawn lots of attention in the pathogenesis of human cancers. However, the role of circRNAs in cancer cells epithelial-mesenchymal transition (EMT) remains unclear. In this study, we aimed to identify novel circRNAs that regulate urothelial carcinoma of the bladder (UCB) cells' EMT and explored their regulatory mechanisms and clinical significance in UCBs. Experimental Design: We first screened circRNA expression profiles using a circRNA microarray in paired UCB and normal tissues, and then studied the clinical significance of an upregulated circRNA, circPRMT5, in a large cohort of patients with UCB. We further investigated the functions and underlying mechanisms of circPRMT5 in UCB cells' EMT. Moreover, we evaluated the regulation effect of circPRMT5 on miR-30c, and its target genes, SNAIL1 and E-cadherin, in two independent cohorts from our institute and The Cancer Genome Atlas (TCGA). Results: We demonstrated that upregulated expression of circPRMT5 was positively associated with advanced clinical stage and worse survival in patients with UCB. We further revealed that circPRMT5 promoted UCB cell's EMT via sponging miR-30c. Clinical analysis from two independent UCB cohorts showed that the circPRMT5/miR-30c/SNAIL1/E-cadherin pathway was essential in supporting UCB progression. Importantly, we identified that circPRMT5 was upregulated in serum and urine exosomes from patients with UCB, and significantly correlated with tumor metastasis. Conclusions: CircPRMT5 exerts critical roles in promoting UCB cells' EMT and/or aggressiveness and is a prognostic biomarker of the disease, suggesting that circPRMT5 may serve as an exploitable therapeutic target for patients with UCB.

Polycystin-1 (PC1) may play an important role in skeletogenesis through regulation of the bone-specific transcription factor Runx2-II. In the current study we found that PC1 co-localizes with the calcium channel polycystin-2 (PC2) in primary cilia of MC3T3-E1 osteoblasts. To establish the role of Runx2-II in mediating PC1 effects on bone, we crossed heterozygous Pkd1 m1Bei and Runx2-II mice to create double heterozygous mice (Pkd1 ؉/m1Bei /Runx2-II ؉/؊ ) deficient in both PC1 and Runx2-II. Pkd1؉/m1Bei /Runx2-II ؉/؊ mice exhibited additive reductions in Runx2-II expression that was associated with impaired endochondral bone development, defective osteoblast-mediated bone formation, and osteopenia. In addition, we found that basal intracellular calcium levels were reduced in homozygous Pkd1 m1Bei osteoblasts. In contrast, overexpression of a PC1 C-tail construct increased intracellular calcium and selectively stimulated Runx2-II P1 promoter activity in osteoblasts through a calcium-dependent mechanism. Site-directed mutagenesis of critical amino acids in the coiled-coil domain of PC1 required for coupling to PC2 abolished PC1-mediated Runx2-II P1 promoter activity. Additional promoter analysis mapped the PC1-responsive region to the "osteoblast-specific" enhancer element between ؊420 and ؊350 bp that contains NFI and AP-1 binding sites. Chromatin immunoprecipitation assays confirmed the calcium-dependent binding of NFI to this region. These findings indicate that PC1 regulates osteoblast function through intracellular calcium-dependent control of Runx2-II expression. The overall function of the primary cilium-polycystin complex may be to sense and transduce environmental clues into signals regulating osteoblast differentiation and bone development.Embryonic bone is formed from mesenchymal stem cells by either direct differentiation of these cells into mineralized matrix-generating osteoblasts (intramembranous bone) or by their condensation and subsequent formation of a cartilage template that is replaced by osteoblast-mediated bone formation (endochondral bone formation) (1-3). Runx2 is a master transcription factor controlling skeletogenesis that regulates the differentiation of mesenchymal precursors into osteoblasts and hypertrophic chondrocytes (4 -10). The total loss of Runx2 in the mouse results in the complete absence of intramembranous and endochondral bone formation. Expression of Runx2 is initiated from the distal P1 and the proximal P2 promoters that, respectively, give rise to N-terminal distinct Runx2-type II (Runx2-II) and Runx2-type I (Runx2-I) isoforms. Selective deletion of the P1 promoter and Runx2-II in mice results in impaired terminal osteoblastic maturation and endochondral bone formation (5, 7, 11). The P2 promoter regulation of Runx2-I is sufficient for early osteoblastogenesis and intramembranous bone formation (11-13). The presence of regulatory sequences in the P1 promoter required for osteoblast-specific expression of Runx2-II have been identified (14), but the developmentally relevant ...