Citations

There has been a longstanding debate regarding the role of proteolysis in Huntington's disease. The toxic peptide theory posits that N-terminal cleavage fragments of mutant Huntington's disease protein [mutant huntingtin (mhtt)] enter the nucleus to cause transcriptional dysfunction. However, recent data suggest a second model in which proteolysis of full-length mhtt is inhibited. Importantly, the two competing theories differ with respect to subcellular distribution of mhtt at initiation of toxicity: nuclear if cleaved and cytoplasmic in the absence of cleavage. Using quantitative single-cell analysis and time-lapse imaging, we show here that transcriptional dysfunction is “downstream” of cytoplasmic dysfunction. Primary and reversible toxic events involve destabilization of microtubules mediated by full-length mhtt before cleavage. Restoration of microtubule structure by taxol inhibits nuclear entry and increases cell survival.

ABSTRACT The TRUGENE HCV 5′NC genotyping kit (GeneLibrarian modules 3.1.1 and 3.1.2) and VERSANT HCV genotyping assay were compared by using 96 hepatitis C virus (HCV) RNA-positive patient specimens, including HCV genotypes 1, 2, 3, 4, 5, 6, and 10. The TRUGENE HCV 5 ′ NC genotyping kit (GeneLibrarian module 3.1.2) yielded the most accurate genotyping results.

Parthenogenesis is the biological phenomenon by which embryonic development is initiated without male contribution. Whereas parthenogenesis is a common mode of reproduction in lower organisms, the mammalian parthenote fails to produce a successful pregnancy. We herein describe in vitro parthenogenetic development of monkey ( Macaca fascicularis ) eggs to the blastocyst stage, and their use to create a pluripotent line of stem cells. These monkey stem cells (Cyno-1 cells) are positive for telomerase activity and are immunoreactive for alkaline phosphatase, octamer-binding transcription factor 4 (Oct-4), stage-specific embryonic antigen 4 (SSEA-4), tumor rejection antigen 1-60 (TRA 1-60), and tumor rejection antigen 1-81 (TRA 1-81) (traditional markers of human embryonic stem cells). They have a normal chromosome karyotype (40 + 2) and can be maintained in vitro in an undifferentiated state for extended periods of time. Cyno-1 cells can be differentiated in vitro into dopaminergic and serotonergic neurons, contractile cardiomyocyte-like cells, smooth muscle, ciliated epithelia, and adipocytes. When Cyno-1 cells were injected into severe combined immunodeficient mice, teratomas with derivatives from all three embryonic germ layers were obtained. When grown on fibronectin/laminin-coated plates and in neural progenitor medium, Cyno-1 cells assume a neural precursor phenotype (immunoreactive for nestin). However, these cells remain proliferative and express no functional ion channels. When transferred to differentiation conditions, the nestin-positive precursors assume neuronal and epithelial morphologies. Over time, these cells acquire electrophysiological characteristics of functional neurons (appearance of tetrodotoxin-sensitive, voltage-dependent sodium channels). These results suggest that stem cells derived from the parthenogenetically activated nonhuman primate egg provide a potential source for autologous cell therapy in the female and bypass the need for creating a competent embryo.

Amino acid sequence variations in SCN5A are known to affect function of wild-type channels and also those with coexisting mutations; therefore, it is important to know the exact sequence and function of channels most commonly present in human myocardium. SCN5A was analyzed in control panels of human alleles, demonstrating that the existing clones (hH1, hH1a, hH1b) each contained a rare variant and thus none represented the common sequence. Confirming prior work, the H558R polymorphism was present in ≈30% of subjects. Quantitative mRNA analysis from human hearts showed that a shorter 2015 amino acid splice variant lacking glutamine at position 1077 (Q1077del) made up 65% of the transcript in every heart examined. Age, sex, race, or structural heart disease did not affect this proportion of Q1077del. Estimated population frequencies for the four common variants were 25% SCN5A, 10% [H558R], 45% [Q1077del], and 20% [H558R;Q1077del], where the reference sequence SCN5A is GenBank AC137587. When expressed in HEK-293 cells, these common variants had a more positive mid-point of the voltage dependence of inactivation than the standard clone hH1. Also, channels containing Q1077 expressed smaller currents. When H558R was present with Q1077 ([H558R]), current expression was profoundly reduced despite normal trafficking to the cell surface. Thus, four variant sequences for SCN5A are commonly present in human myocardium and they exhibit functional differences among themselves and with the previous standard clone. These results have implications for the choice of background sequence for experiments with heterologous expression systems, and possibly implications for electrophysiological function in vivo.

Pregnancy-associated plasma protein A (PAPP-A) is an IGF-binding protein-4 (IGFBP-4) metalloproteinase that cleaves inhibitory IGFBP-4 to amplify local IGF-I bioavailability in vitro. Thus it has functional implications in injury/repair responses. In this study we determined PAPP-A expression in healing human skin. Wounds were induced with a scalpel on the forearms of three normal subjects and were allowed to heal by first intention. Biopsies obtained on d 0, 2, 8, and 14 were processed for immunohistochemical detection of PAPP-A, IGF-I, and IGFBP-4. In uninjured skin (d 0), strong staining for PAPP-A was present in the epidermis, sweat and sebaceous gland epithelial cells, hair follicles, and blood vessels; no PAPP-A was detected in dermal fibroblasts or with mature collagen bundles. IGF-I localized strongly to epithelial cells of skin glands was weak to moderate in epidermis and blood vessels, and was absent in dermal cells. Weak focal staining for IGFBP-4 was found within uninjured epidermis. During wound healing, PAPP-A expression was induced in dermal granulation tissue within and adjacent to the injury. PAPP-A was present in dermis on d 2 and was increased in intensity and extent on d 8 and 14. PAPP-A expression also increased in the epidermis. PAPP-A expression in cells of granulation tissue colocalized with α-smooth actin staining of myofibroblasts and new blood vessels as well as with CD68 staining of macrophages and was associated with the compact, newly synthesized collagen of the healing wound. IGF-I staining was enhanced in the epidermis localized to the area of the incision and in granulation tissue associated with lymphoid cells. IGFBP-4 staining of the epidermis remained unchanged during wound healing, but was induced in the fibroblastic cells of granulation tissue over time. These data demonstrate localized and regulated expression of PAPP-A in human skin and suggest that PAPP-A may play an important role in an integrated IGF system in wound healing and tissue remodeling in vivo.

Albuminuria increases the risk of cardiovascular events in patients with essential hypertension and diabetic subjects. The heritability (h 2 ) of albuminuria in multiplex hypertensive families is unknown. We calculated the familial aggregation of urine albumin:creatinine ratio (ACR) and performed a genome-wide scan to assess for loci contributing to ACR in participants enrolled in the Hyper tension G enetic E pidemiology N etwork (HyperGEN). To perform the genome scan, we analyzed genotype results from 2589 individuals from 805 families in the Family Blood Pressure Program. ACR and covariates were available in 1727 individuals (mean age, 57.1 years). Estimates of h 2 were obtained by using variance component methodology as implemented in the SOLAR software package. Linkage was tested between 387 markers spanning the genome at an average interval of 9.32 cM, using SOLAR multipoint analysis. The h 2 of log urine ACR was 0.49 ( P <1×10 −7 ) after controlling for significant main and interactive effects of age, gender, race, body mass index, blood pressure, and use of ACE inhibitors or angiotensin-2 receptor blockers. The genome-wide scan revealed a maximum LOD score of 2.73 on chromosome 19 (robust corrected LOD, 2.40; P =0.0009) at marker D19S591 and a LOD score of 2.0 on chromosome 12 (robust corrected LOD, 1.75; P =0.005) at marker PAH. These analyses demonstrate the marked heritability of urine ACR in families enriched for the presence of members with essential hypertension. They suggest that a gene(s) associated with urinary ACR may be present on human chromosomes 19 and 12.

B7‐H1 is a novel B7 family protein attributed to costimulatory and immune regulatory functions. Here we report that human myoblasts cultured from control subjects and patients with inflammatory myopathies as well as TE671 muscle rhabdomyosarcoma cells express high levels of B7‐H1 after stimulation with the inflammatory cytokine IFN‐γ. Coculture experiments of MHC class I/II‐positive myoblasts with CD4 and CD8 T cells in the presence of antigen demonstrated the functional consequences of muscle‐related B7‐H1 expression: production of inflammatory cytokines, IFN‐γ and IL‐2, by CD4 as well CD8 T cells was markedly enhanced in the presence of a neutralizing anti‐B7‐H1 antibody. This observation was paralleled by an augmented expression of the T cell activation markers CD25, ICOS, and CD69, thus showing B7‐H1‐mediated inhibition of T cell activation. Further, we investigated 23 muscle biopsy specimens from patients with polymyositis (PM), inclusion body myositis (IBM), dermatomyositis (DM), and nonmyopathic controls for B7‐H1 expression by immunohistochemistry: B7‐H1 was expressed in PM, IBM, and DM specimens but not in noninflammatory and nonmyopathic controls. Staining was predominantly localized to areas of strong inflammation and to muscle cells as well as mononuclear cells. These data highlight the immune regulatory properties of muscle cells and suggest that B7‐H1 expression represents an inhibitory mechanism induced upon inflammatory stimuli and aimed at protecting muscle fibers from immune aggression.