👤 C Y Clement

The discovery of zinc fingers and homeoboxes (ZHX) transcriptional factors and the upregulation of hyposialylated angiopoietin-like 4 (ANGPTL4) in podocytes have been crucial in explaining the cardinal manifestations of human minimal change nephrotic syndrome (MCNS). Recently, uncovered genomic defects upstream of Show less

Zinc fingers and homeoboxes (ZHX) proteins are heterodimeric transcriptional factors largely expressed at the cell membrane in podocytes in vivo. We found ZHX2-based heterodimers in podocytes, with ZHX2-ZHX1 predominantly at the cell membrane of the podocyte cell body, and ZHX2-ZHX3 at the slit diaphragm. In addition to changes in overall ZHX2 expression, there was increased podocyte nuclear ZHX3 and ZHX2 in patients with focal segmental glomerulosclerosis, and increased podocyte nuclear ZHX1 in patients with minimal change disease. Zhx2 deficient mice had increased podocyte ZHX1 and ZHX3 expression. Zhx2 deficient mice and podocyte specific Zhx2 overexpressing transgenic rats develop worse experimental focal segmental glomerulosclerosis than controls, with increased nuclear ZHX3 and ZHX2, respectively. By contrast, podocyte specific Zhx2 overexpressing transgenic rats develop lesser proteinuria during experimental minimal change disease due to peripheral sequestration of ZHX1 by ZHX2. Using co-immunoprecipitation, the interaction of ZHX2 with aminopeptidase A in the podocyte body cell membrane, and EPHRIN B1 in the slit diaphragm were noted to be central to upstream events in animal models of minimal change disease and focal segmental glomerulosclerosis, respectively. Mice deficient in Enpep, the gene for aminopeptidase A, and Efnb1, the gene for ephrin B1 developed worse albuminuria in glomerular disease models. Targeting aminopeptidase A in Zhx2 deficient mice with monoclonal antibodies induced albuminuria and upregulation of the minimal change disease mediator angiopoietin-like 4 through nuclear entry of ZHX1. Thus, podocyte ZHX2 imbalance is a critical factor in human glomerular disease, with minimal change disease disparities mediated mostly through ZHX1, and focal segmental glomerulosclerosis deviations through ZHX3 and ZHX2. Show less

We describe the novel anatomical distribution of exostoses in patients with hereditary multiple exostoses according to their gender and genotype. A prospective database of 143 patients from 65 families with hereditary multiple exostoses was compiled. Patient demographics, genotype and number of exostoses according to anatomical site were recorded. The hand was affected by the greatest proportion of exostoses for both EXT1 (19%) and EXT2 (14%) genotypes and was the most prevalent site for exostoses in patients with an EXT1 genotype (92%). Patients with an EXT1 genotype had a significantly greater number of exostoses compared to those with an EXT2 genotype (2680 vs. 1828, p = 0.006); however, this was only significantly different for 10 of the 19 anatomical regions examined. Male patients with an EXT1 genotype had a significantly (p < 0.05) greater number of exostoses affecting their hands, distal radius, proximal humerus, scapular and ribs compared to female patients with the same genotype and males with an EXT2 genotype. The anatomical distribution of exostoses varies according to genotype and gender; however, the reason for this difference is not clear and may relate to different biochemical pathways. Show less

Hereditary multiple exostoses (HME) is a commonly inherited musculoskeletal condition and is associated with a diminished stature. We demonstrated that adults with HME were significantly shorter when compared with a control group (P<0.001); preadolescents, however, were significantly taller than predicted (P=0.01). This was reflected by their height centile; 58% of the adults were under the 25th centile, whereas 53% of the preadolescence group were above the 75th centile. Stature was more severely affected in patients with an EXT1 mutation (P=0.008). This study illustrates a novel age-related growth pattern associated with HME, which is also affected by genotype. Show less

Patients with hereditary multiple exostoses (HME) in association with palpable shoulder exostoses are more severely affected by their disease. From a prospective database of 78 families with HME identified, 172 patients were identified. Demographic details, deformity, functional scores, standing height, number of exostoses, site, exostosin genotype (EXT1 and EXT2), surgical excision, and malignant change were recorded. Nonparametric tests were used to compare patients with and without shoulder exostoses (clavicle, scapula, and humerus). There were 5361 palpable exostoses, of which 14% were of the shoulder and were present in 145 patients (84.3%). There was a younger mean age (26.8 vs 37.9 years) and a male predominance in those individuals with shoulder exostoses (P = .0005). Patients with shoulder exostoses had significantly worse disease (P < .05). EXT1 mutations were more commonly observed in those with shoulder exostoses (odds ratio [OR], 20.6; 95% confidence interval [CI], 11.2-28.5; P = .001). The likelihood of surgical excision was greater in those with shoulder exostoses (OR, 2.8) and highest for scapular exostoses (OR, 3.7). Risk factors for surgical excision of shoulder exostoses were younger age (P = .03) and male gender (P < .008). Seven chondrosarcomas occurred, 2 scapular and a proximal humeral. The probability of malignant change of was highest for palpable scapular exostoses relative to any other anatomic site (OR, 12.3; P = .05). Shoulder exostoses have a male predominance, and patients are more likely to have an EXT1 mutation. The presence of shoulder exostoses could serve as a tool to identify those individuals at high probability of malignant change. The existence of shoulder exostoses identifies those individuals with a high probability of having an EXT1 genotype (OR 20.6, 94.4% sensitivity, 84.8% positive predictive value), which is associated with sarcomatous change. Show less

Constitutive activation of the Wnt pathway as a result of APC, AXIN1 or CTNNB1 mutations has been found in most colorectal cancers. For a long time, this aberrant Wnt activation has been thought to be independent of upstream signals. However, recent studies indicate that upstream signals retain their ability to regulate the Wnt pathway even in the presence of downstream mutations. Wnt-2 is well known for its overexpression in colorectal cancer. Galectin-3 (Gal-3), a multifunctional carbohydrate binding protein implicated in a variety of biological functions, has recently been reported to interact with beta-catenin. In this study, we investigated roles of Wnt-2 and Gal-3 in the regulation of canonical Wnt/beta-catenin signaling. We found that siRNA silencing of either Wnt-2 or Gal-3 expression inhibited TCF-reporter activity, decreased cytosolic beta-catenin level and induced apoptosis in human colorectal cancer cells containing downstream mutations. More interestingly, we showed that inhibition of both Wnt-2 and Gal-3 had synergistic effects on suppressing canonical Wnt signaling and inducing apoptosis, suggesting that aberrant canonical Wnt/beta-catenin signaling in colorectal cancer can be regulated at multiple levels. The combined inhibition of Wnt-2 and Gal-3 may be of superior therapeutic advantage to inhibition by either one of them, giving rise to a potential development of novel drugs for the targeted treatment of colorectal cancer. Show less

Beyond their critical role in thrombosis, platelets perform important functions in vascular remodeling, inflammation, and wound repair. Many of these functions are executed by molecules expressed by activated platelets. A novel molecule, activated-platelet protein-1 (APP-1), was identified by a monoclonal antibody against activated rabbit platelets. When platelets were stimulated by thrombin, A23187 or ADP, APP-I was expressed on the platelet surface. APP-1 was also detected in whole cell lysates of platelets, but not on the external surfaces of resting platelets. With maximal activation by thrombin, 15 900 +/- 2800 molecules APP-1 were expressed/platelet. A 2.3-kb cDNA fragment containing a partial coding sequence for APP-1 was isolated from a rabbit bone marrow library by expression cloning with the anti-APP-1 monoclonal antibody. When expressed as a recombinant fusion protein in bacteria, APP-1 bound specifically to poly(A)-Sepharose. The full-length cDNA coding for human APP-1, obtained by DNA hybridization techniques, showed 98.7% amino acid sequence identity with the rabbit protein. Northern analysis with human APP-1 identified a 3.7-kb mRNA transcript in megakaryocytic lines that express transcripts for platelet proteins. Human APP-1 has four ribonucleotide binding domains with ribonucleoprotein 1 and 2 motifs. By virtue of its ribonucleotide binding domains, APP-1 is structurally related to polyadenylate-binding protein, which regulates translation initiation and polyadenylate shortening, and to nucleolysin, a specific effector molecule found in the granules of cytotoxic T lymphocytes. Show less