Browsing Department of Medicine Faculty: Research and Presentations by Subjects
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Accelerated Growth Plate Mineralization and Foreshortened Proximal Limb Bones in Fetuin-A Knockout MiceThe plasma protein fetuin-A/alpha2-HS-glycoprotein (genetic symbol Ahsg) is a systemic inhibitor of extraskeletal mineralization, which is best underscored by the excessive mineral deposition found in various tissues of fetuin-A deficient mice on the calcification-prone genetic background DBA/2. Fetuin-A is known to accumulate in the bone matrix thus an effect of fetuin-A on skeletal mineralization is expected. We examined the bones of fetuin-A deficient mice maintained on a C57BL/6 genetic background to avoid bone disease secondary to renal calcification. Here, we show that fetuin-A deficient mice display normal trabecular bone mass in the spine, but increased cortical thickness in the femur. Bone material properties, as well as mineral and collagen characteristics of cortical bone were unaffected by the absence of fetuin-A. In contrast, the long bones especially proximal limb bones were severely stunted in fetuin-A deficient mice compared to wildtype littermates, resulting in increased biomechanical stability of fetuin-A deficient femora in three-point-bending tests. Elevated backscattered electron signal intensities reflected an increased mineral content in the growth plates of fetuin-A deficient long bones, corroborating its physiological role as an inhibitor of excessive mineralization in the growth plate cartilage matrix - a site of vigorous physiological mineralization. We show that in the case of fetuin-A deficiency, active mineralization inhibition is a necessity for proper long bone growth.
Association between Genetic Variants in DNA and Histone Methylation and Telomere LengthTelomere length, a biomarker of aging and age-related diseases, exhibits wide variation between individuals. Common genetic variation may explain some of the individual differences in telomere length. To date, however, only a few genetic variants have been identified in the previous genome-wide association studies. As emerging data suggest epigenetic regulation of telomere length, we investigated 72 single nucleotide polymorphisms (SNPs) in 46 genes that involve DNA and histone methylation as well as telomerase and telomere-binding proteins and DNA damage response. Genotyping and quantification of telomere length were performed in blood samples from 989 non-Hispanic white participants of the Sister Study, a prospective cohort of women aged 35–74 years. The association of each SNP with logarithmically-transformed relative telomere length was estimated using multivariate linear regression. Six SNPs were associated with relative telomere length in blood cells with p-values<0.05 (uncorrected for multiple comparisons). The minor alleles of BHMT rs3733890 G>A (p = 0.041), MTRR rs2966952 C>T (p = 0.002) and EHMT2 rs558702 G>A (p = 0.008) were associated with shorter telomeres, while minor alleles of ATM rs1801516 G>A (p = 0.031), MTR rs1805087 A>G (p = 0.038) and PRMT8 rs12299470 G>A (p = 0.019) were associated with longer telomeres. Five of these SNPs are located in genes coding for proteins involved in DNA and histone methylation. Our results are consistent with recent findings that chromatin structure is epigenetically regulated and may influence the genomic integrity of telomeric region and telomere length maintenance. Larger studies with greater coverage of the genes implicated in DNA methylation and histone modifications are warranted to replicate these findings.
Improved Immunodetection of Endogenous Î±-SynucleinÎ±-Synuclein is a key molecule in understanding the pathogenesis of neurodegenerative Î±-synucleinopathies such as Parkinson's disease. Despite extensive research, however, its precise function remains unclear partly because of a difficulty in immunoblotting detection of endogenous Î±-synuclein. This difficulty has largely restricted the progress for Î±-synucleinopathy research. Here, we report that Î±-synuclein monomers tend to easily detach from blotted membranes, resulting in no or very poor detection. To prevent this detachment, a mild fixation of blotted membranes with paraformaldehyde was applied to the immunoblotting method. Amazingly, this fixation led to clear and strong detection of endogenous Î±-synuclein, which has been undetectable by a conventional immunoblotting method. Specifically, we were able to detect endogenous Î±-synuclein in various human cell lines, including SH-SY5Y, HEK293, HL60, HeLa, K562, A375, and Daoy, and a mouse cell line B16 as well as in several mouse tissues such as the spleen and kidney. Moreover, it should be noted that we could clearly detect endogenous Î±-synuclein phosphorylated at Ser-129 in several human cell lines. Thus, in some tissues and cultured cells, endogenous Î±-synuclein becomes easily detectable by simply fixing the blotted membranes. This improved immunoblotting method will allow us to detect previously undetectable endogenous Î±-synuclein, thereby facilitating Î±-synuclein research.
Rac1 Activation Driven by 14-3-3f Dimerization Promotes Prostate Cancer Cell-Matrix Interactions, Motility and Transendothelial Migration14-3-3 proteins are ubiquitously expressed dimeric adaptor proteins that have emerged as key mediators of many cell signaling pathways in multiple cell types. Its effects are mainly mediated by binding to selective phosphoserine/threonine proteins. The importance of 14-3-3 proteins in cancer have only started to become apparent and its exact role in cancer progression as well as the mechanisms by which 14-3-3 proteins mediate cancer cell function remain unknown. While protein 14-3-3s is widely accepted as a tumor suppressor, 14-3-3f, b and c isoforms have been shown to have tumor promoting effects. Despite the importance of 14-3-3 family in mediating various cell processes, the exact role and mechanism of 14-3-3f remain unexplored. In the current study, we investigated the role of protein 14-3-3f in prostate cancer cell motility and transendothelial migration using biochemical, molecular biology and electric cell-substrate impedance sensing approaches as well as cell based functional assays. Our study indicated that expression with wild-type protein 14-3-3f significantly enhanced Rac activity in PC3 cells. In contrast, expression of dimer-resistant mutant of protein 14-3-3f (DM-14-3-3) inhibited Rac activity and associated phosphorylation of p21 activated kinase-1 and 2. Expression with wild-type 14-3-3f or constitutively active Rac1 enhanced extracellular matrix recognition, lamellipodia formation, cell migration and trans-endothelial migration by PC3 cells. In contrast, expression with DM 14-3-3f or DN-Rac1 in PC3 cells significantly inhibited these cell functions. Our results demonstrate for the first time that 14-3-3f enhances prostate cancer cell-matrix interactions, motility and transendothelial migration in vitro via activation of Rac1-GTPase and is an important target for therapeutic interventions for prostate cancer.