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The role of emotional health in functional outcomes after orthopaedic surgery: extending the biopsychosocial model to orthopaedics: AOA critical issues

Mon, 03/24/2014 - 11:27am

Orthopaedic surgery successfully restores physical function and relieves pain in millions of Americans each year. In fact, orthopaedic surgery to treat arthritis of the knee and hip and lumbar spine conditions is among the top five surgical procedures by cost and volume in the United States. Despite the overwhelming success of orthopaedic procedures, functional improvement after surgery varies widely. Poor functional outcomes have been correlated with poor emotional health, such as anxiety, depression, poor coping skills, and poor social support1,2. The variation in functional outcomes exists despite state-of-the-art surgical techniques and is independent of postoperative complications. Furthermore, suboptimal functional outcomes associated with poor emotional health have been reported in a variety of orthopaedic specialties, including spine surgery, trauma care and/or fracture repair, rotator cuff repair, sports-related surgery (e.g., anterior cruciate ligament [ACL] reconstruction), total hip replacement, total knee replacement, and hand and upper extremities surgery. It is well established that the emotional health of the patient influences the outcome of many common orthopaedic surgeries.

The patient’s perspective of gout

Mon, 03/24/2014 - 11:27am

This chapter reviews the current literature on patient’s perceptions in reference to gout etiology and management. Lack of knowledge about disease stages, related comorbidities, specific treatment for each state of gout, common side effects of medications and long-term consequences of inadequate care has been demonstrated among patients with gout. These knowledge deficits and the lack of patient self-management training have been associated with poor adherence to recommended therapies, thus leading to recurrent suboptimal care of gout; the most common inflammatory joint disease and the only one for which there is potentially curative therapy. This chapter examines the importance of the patient’s knowledge, cultural beliefs and management preferences of the disease in general, as well as for each specific stage. Recommendations have also been provided to physicians in order to identify concrete ways to improve patient care in terms of patient education and self-management training in an effort to reinforce successful strategies and behaviors towards controlling the condition.

Patient perspectives on achieving treat-to-target goals: a critical examination of patient-reported outcomes

Mon, 03/24/2014 - 11:27am

OBJECTIVE: Treat-to-target (T2T) recommendations suggest that rheumatoid arthritis (RA) patients should strive for remission or low disease activity (LDA). However, it is unclear whether patients experiencing a good response to biologic agents might experience further improvement in patient-reported outcomes (PROs) if they subsequently achieve a lower disease activity state, particularly the T2T goals of LDA or remission.

METHODS: Using the Consortium of Rheumatology Researchers of North America database, we identified RA patients initiating biologic agents. We restricted the analysis to patients with improvement (Clinical Disease Activity Index [CDAI] improvement of >/=10 units) at 3-6 months (baseline visit; n = 1,368) with a followup visit approximately 9 months later (n = 984). Patients in CDAI remission or with a worsened disease activity category were excluded, leaving 562 eligible patients. PROs (global assessment, pain, and fatigue by 0-10 visual analog scales and disability by the modified Health Assessment Questionnaire [M-HAQ]) were examined at these 2 visits. Mean change in PROs compared achievement of a lower disease activity category versus staying in the same disease activity category, adjusting for potential confounders.

RESULTS: Patients who achieved a lower disease activity category (40% of the eligible cohort, 86% of these achieving LDA or remission) had significantly better improvement in patient pain (-14.9; 95% confidence interval [95% CI] -18.4, -11.6), patient global (-17.5; 95% CI -20.8, -14.3), fatigue (-8.5; 95% CI -15.8, -1.3), and M-HAQ score (-0.13; 95% CI -0.18, -0.08) compared to patients who stayed in the same disease activity category. However, even for patients improving, fewer than half exceeded the minimum clinically important difference for each PRO.

CONCLUSION: Achievement of a lower disease activity disease state, especially T2T goals, was associated with further improvement in PROs, albeit modest in magnitude.

Racial and ethnic disparities in disease activity in patients with rheumatoid arthritis

Mon, 03/24/2014 - 11:27am

BACKGROUND: Observational studies of patients with rheumatoid arthritis have suggested that racial and ethnic disparities exist for minority populations. We compared disease activity and clinical outcomes across racial and ethnic groups using data from a large, contemporary US registry.

METHODS: We analyzed data from 2 time periods (2005-2007 and 2010-2012). The Clinical Disease Activity Index was examined as both a continuous measure and a dichotomous measure of disease activity states. Outcomes were compared in a series of cross-sectional and longitudinal multivariable regression models.

RESULTS: For 2005-2007, significant differences of mean disease activity level (P < .001) were observed across racial and ethnic groups. Over the 5-year period, modest improvements in disease activity were observed across all groups, including whites (3.7; 95% confidence interval [CI], 3.2-4.1) compared with African Americans (4.3; 95% CI, 2.7-5.8) and Hispanics (2.7; 95% CI, 1.2-4.3). For 2010-2012, significant differences of mean disease activity level persisted (P < .046) across racial and ethnic groups, ranging from 11.6 (95% CI, 10.4-12.8) in Hispanics to 10.7 (95% CI, 9.6-11.7) in whites. Remission rates remained significantly different across racial/ethnic groups across all models for 2010-2012, ranging from 22.7 (95% CI, 19.5-25.8) in African Americans to 27.4 (95% CI, 24.9-29.8) in whites.

CONCLUSIONS: Despite improvements in disease activity across racial and ethnic groups over a 5-year period, disparities persist in disease activity and clinical outcomes for minority groups versus white patients.

The comparative effectiveness of abatacept versus anti-tumour necrosis factor switching for rheumatoid arthritis patients previously treated with an anti-tumour necrosis factor

Mon, 03/24/2014 - 11:27am

OBJECTIVE: We compared the effectiveness of abatacept (ABA) versus a subsequent anti-tumour necrosis factor inhibitor (anti-TNF) in rheumatoid arthritis (RA) patients with prior anti-TNF use.

METHODS: We identified RA patients from a large observational US cohort (2/1/2000-8/7/2011) who had discontinued at least one anti-TNF and initiated either ABA or a subsequent anti-TNF. Using propensity score (PS) matching (n:1 match), effectiveness was measured at 6 and 12 months after initiation based on mean change in Clinical Disease Activity Index (CDAI), modified American College of Rheumatology (mACR) 20, 50 and 70 responses, modified Health Assessment Questionnaire (mHAQ) and CDAI remission in adjusted regression models.

RESULTS: The PS-matched groups included 431 ABA and 746 anti-TNF users at 6 months and 311 ABA and 493 anti-TNF users at 12 months. In adjusted analyses comparing response following treatment with ABA and anti-TNF, the difference in weighted mean change in CDAI (range 6-8) at 6 months (0.46, 95% CI -0.82 to 1.73) and 12 months was similar (-1.64, 95% CI -3.47 to 0.19). The mACR20 responses were similar at 6 (28-32%, p=0.73) and 12 months (35-37%, p=0.48) as were the mACR50 and mACR70 (12 months: 20-22%, p=0.25 and 10-12%, p=0.49, respectively). Meaningful change in mHAQ was similar at 6 and 12 months (30-33%, p=0.41 and 29-30%, p=0.39, respectively) as was CDAI remission rates (9-10%, p=0.42 and 12-13%, p=0.91, respectively).

CONCLUSIONS: RA patients with prior anti-TNF exposures had similar outcomes if they switched to a new anti-TNF as compared with initiation of ABA.

Comparative cancer risk associated with methotrexate, other non-biologic and biologic disease-modifying anti-rheumatic drugs

Mon, 03/24/2014 - 11:27am

OBJECTIVE: There is little information comparing the potential risk of cancer across conventional and biologic disease-modifying anti-rheumatic drugs (DMARDs) in patients with rheumatoid arthritis (RA). Methotrexate has not been the focus of most contemporary pharmacoepidemiologic studies of cancer.

METHODS: We conducted a comparative effectiveness study with cancer as the outcome. A large observational cohort of RA was followed up from 2001 to 2010. Reports of any cancer prompted a confirmation process that included adjudication of the primary cancer records. We used a propensity score (PS) with relevant covariates and cohort trimming to improve the balance between DMARD cohorts. Cox proportional hazard regression models were constructed to estimate the risk of cancer with various DMARDs, all compared with methotrexate.

RESULTS: We identified 6806 DMARD courses for analysis (1566 methotrexate; 904 nbDMARDs; 3761 TNF antagonists; 408 abatacept; and 167 rituximab). Non-biologic DMARDs (HR 0.17, 95% CI 0.05-0.65) and TNF antagonists (HR 0.29, 95% CI 0.05-0.65) were associated with a reduced adjusted risk of cancer compared with methotrexate. Abatacept (HR 1.55, 95% CI 0.40-5.97) and rituximab (HR 0.42, 95% CI 0.07-2.60) were similar in risk of cancer with methotrexate. These results were robust to sensitivity analyses. After controlling for DMARD exposures, risk factors for cancer included male gender, age, and alcohol consumption.

CONCLUSIONS: Cancer risk was elevated for methotrexate users compared with nbDMARDs and TNF antagonists.

Chromatin-mediated Candida albicans virulence

Fri, 03/21/2014 - 11:09am

Candida albicans is the most prevalent human fungal pathogen. To successfully propagate an infection, this organism relies on the ability to change morphology, express virulence-associated genes and resist DNA damage caused by the host immune system. Many of these events involve chromatin alterations that are crucial for virulence. This review will focus on the studies that have been conducted on how chromatin function affects pathogenicity of C. albicans and other fungi. This article is part of a Special Issue entitled: Histone chaperones and Chromatin assembly.

Activated wnt signaling in stroma contributes to development of pancreatic mucinous cystic neoplasms

Fri, 03/21/2014 - 11:09am

BACKGROUND and AIMS: Pancreatic mucinous cystic neoplasm (MCN), a cystic tumor of the pancreas that develops most frequently in women, is a potential precursor to pancreatic ductal adenocarcinoma. MCNs develop primarily in the body and tail of the pancreas and are characterized by the presence of a mucinous epithelium and ovarian-like subepithelial stroma. We investigated the involvement of Wnt signaling in KRAS-mediated pancreatic tumorigenesis and development of MCN in mice, and Wnt activation in human MCN samples.

METHODS: LSL-Kras(G12D), Ptf1a-cre mice were crossed with elastase-tva mice to allow for introduction of genes encoded by the replication-competent avian sarcoma-leukosis virus long-terminal repeat with splice acceptor viruses to pancreatic acinar cells and acinar cell progenitors, postnatally and sporadically. Repeat with splice acceptor viruses that expressed Wnt1 were delivered to the pancreatic epithelium of these mice; pancreatic lesions were analyzed by histopathology and immunohistochemical analyses. We analyzed levels of factors in Wnt signaling pathways in 19 MCN samples from patients.

RESULTS: Expression of Wnt1 in the pancreatic acinar cells and acinar cell progenitors of female mice led to development of unilocular or multilocular epithelial cysts in the pancreas body and tail, similar to MCN. The cystic lesions resembled the estrogen receptor- and progesterone receptor-positive ovarian-like stroma of MCN, but lacked the typical mucinous epithelium. Activated Wnt signaling, based on nuclear localization of beta-catenin, was detected in the stroma but not cyst epithelium. Wnt signaling to beta-catenin was found to be activated in MCN samples from patients, within the ovarian-like stroma, consistent with the findings in mice.

CONCLUSIONS: Based on studies of mice and pancreatic MCN samples from patients, the canonical Wnt signaling pathway becomes activated and promotes development of the ovarian-like stroma to contribute to formation of MCNs.

An improved predictive recognition model for Cys2-His2 zinc finger proteins

Fri, 03/21/2014 - 11:09am

Cys2-His2 zinc finger proteins (ZFPs) are the largest family of transcription factors in higher metazoans. They also represent the most diverse family with regards to the composition of their recognition sequences. Although there are a number of ZFPs with characterized DNA-binding preferences, the specificity of the vast majority of ZFPs is unknown and cannot be directly inferred by homology due to the diversity of recognition residues present within individual fingers. Given the large number of unique zinc fingers and assemblies present across eukaryotes, a comprehensive predictive recognition model that could accurately estimate the DNA-binding specificity of any ZFP based on its amino acid sequence would have great utility. Toward this goal, we have used the DNA-binding specificities of 678 two-finger modules from both natural and artificial sources to construct a random forest-based predictive model for ZFP recognition. We find that our recognition model outperforms previously described determinant-based recognition models for ZFPs, and can successfully estimate the specificity of naturally occurring ZFPs with previously defined specificities.

Mediterranean and Dietary Approaches to Stop Hypertension dietary patterns and risk of sudden cardiac death in postmenopausal women

Thu, 03/20/2014 - 8:54am

BACKGROUND: The Mediterranean and Dietary Approaches to Stop Hypertension (DASH) diets are characterized by higher intake of fruit, vegetables, whole grains, and unsaturated fatty acids. All of these foods and nutrients may affect cholesterol, inflammation, the development of atherosclerosis, and, therefore, risk of cardiac death.

OBJECTIVE: Our objective was to examine the association between the Mediterranean and DASH dietary patterns and risk of sudden cardiac death (SCD) in women. DESIGN: We used a prospective cohort of 93,122 postmenopausal women enrolled in the Women's Health Initiative study between 1993 and 1998 and followed for an average of 10.5 y. Women completed a food-frequency questionnaire (FFQ) twice during follow-up. We scored their diets according to how closely the reported diet resembled each dietary pattern. SCD was defined as death that occurred within 1 h of symptom onset.

RESULTS: A higher Mediterranean diet score was associated with lower risk of SCD (HR: 0.64; 95% CI: 0.43, 0.94) when women in the highest quintile were compared with women in the lowest quintile after adjustment for age, total energy, race, income, smoking, and physical activity. After adjustment for potential mediators, the association was similar (HR: 0.67; 95% CI: 0.46, 0.99). A higher DASH diet score was not associated with risk of SCD. However, sodium intake, which is a crucial component of the DASH dietary pattern, was not well characterized by the FFQ.

CONCLUSION: The Mediterranean dietary pattern may be associated with lower risk of SCD in women.

This trial was registered at clinicaltrials.gov as NCT00000611.

Food preparation supplies predict children's family meal and home-prepared dinner consumption in low-income households

Thu, 03/20/2014 - 8:53am

Frequent family meals and home food preparation are considered important for children's nutritional health and weight maintenance. This cross-sectional study tested whether these parent-driven behaviors are related to the availability of food preparation supplies in low-income urban households. Caregivers of children ages 6-13 provided information on family meal frequency, child consumption of home-prepared dinners, household food insecurity, and attitudes towards cooking. Researchers used a newly developed Food Preparation Checklist (FPC) to assess the availability of 41 food preparation supplies during a physical audit of the home environment. Caregivers and children provided anthropometric measurements and jointly reported on child dietary intake. In ordinal logistic regression models, greater home availability of food preparation supplies was associated with more frequent family meals and child consumption of home-prepared dinners. Associations were independent of household financial strain, food insecurity, caregiver attitudes toward cooking, and sociodemographic characteristics. Fewer food preparation supplies were available in households characterized by greater food insecurity, lower income, and negative caregiver attitudes towards cooking, but did not differ by child or caregiver weight status. As in prior studies, more frequent family meals and consumption of home-prepared dinners were associated with healthier child dietary intake in several areas. We conclude that food preparation supplies are often limited in the most socioeconomically disadvantaged households, and their availability is related to the frequency with which children consume family meals and home-prepared dinners. The potential role of food preparation supplies as contributors to socioeconomic disparities in child nutritional health and obesity deserves further study.

Severity of Depressive Symptoms and Accuracy of Dietary Reporting among Obese Women with Major Depressive Disorder Seeking Weight Loss Treatment

Thu, 03/20/2014 - 8:53am

An elevation in symptoms of depression has previously been associated with greater accuracy of reported dietary intake, however this association has not been investigated among individuals with a diagnosis of major depressive disorder. The purpose of this study was to investigate reporting accuracy of dietary intake among a group of women with major depressive disorder in order to determine if reporting accuracy is similarly associated with depressive symptoms among depressed women. Reporting accuracy of dietary intake was calculated based on three 24-hour phone-delivered dietary recalls from the baseline phase of a randomized trial of weight loss treatment for 161 obese women with major depressive disorder. Regression models indicated that higher severity of depressive symptoms was associated with greater reporting accuracy, even when controlling for other factors traditionally associated with reporting accuracy (coefficient = 0.01 95% CI = 0.01 - 0.02). Seventeen percent of the sample was classified as low energy reporters. Reporting accuracy of dietary intake increases along with depressive symptoms, even among individuals with major depressive disorder. These results suggest that any study investigating associations between diet quality and depression should also include an index of reporting accuracy of dietary intake as accuracy varies with the severity of depressive symptoms.

The mitosis-to-interphase transition is coordinated by cross talk between the SIN and MOR pathways in Schizosaccharomyces pombe

Tue, 03/18/2014 - 2:05pm

The mechanisms that regulate cytoskeletal remodeling during the transition between mitosis and interphase are poorly understood. In fission yeast the MOR pathway promotes actin polarization to cell tips in interphase, whereas the SIN signaling pathway drives actomyosin ring assembly and cytokinesis. We show that the SIN inhibits MOR signaling in mitosis by interfering with Nak1 kinase-mediated activation of the most downstream MOR component, the NDR family kinase Orb6. Inactivation of the MOR may be a key function of the SIN because attenuation of MOR signaling rescued the cytokinetic defects of SIN mutants and allowed weak SIN signaling to trigger ectopic cytokinesis. Furthermore, failure to inhibit the MOR is toxic when the cell division apparatus is compromised. Together, our results reveal a mutually antagonistic relationship between the SIN and MOR pathways, which is important for completion of cytokinesis and coordination of cytoskeletal remodeling at the mitosis-to-interphase transition.

Crosstalk between casein kinase II and Ste20-related kinase Nak1

Tue, 03/18/2014 - 2:05pm

Although the sterile 20 (Ste20) serine/threonine protein kinase was originally identified as a component of the S. cerevisiae mating pathway, it has homologs in higher eukaryotes and is part of a larger family of Ste20-like kinases. Ste20-like kinases are involved in multiple cellular processes, such as cell growth, morphogenesis, apoptosis and immune response. Carrying out such a diverse array of biological functions requires numerous regulatory inputs and outputs in the form of protein-protein interactions and post-translational modifications. Hence, a thorough knowledge of Ste20-like kinase binding partners and phosphorylation sites will be essential for understanding the various roles of these kinases. Our recent study revealed that Schizosaccharomyces pombe Nak1 (a conserved member of the GC-kinase sub-family of Ste20-like kinases) is in a complex with the leucine-rich repeat-containing protein Sog2. Here, we show a novel and unexpected interaction between the Nak1-Sog2 kinase complex and Casein kinase 2 (Cka1, Ckb1 and Ckb2) using tandem-affinity purification followed by mass spectrometric analysis. In addition, we identify unique phosphosites on Nak1, Sog2 and the catalytic subunit of casein kinase 2, Cka1. Given the conserved nature of these kinases, we expect this work will shed light on the functions of these proteins both in yeast and higher eukaryotes.

Symptom Experience and Treatment Delay during Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Dissertation

Mon, 03/17/2014 - 12:20pm

Chronic obstructive pulmonary disease (COPD) is a major health problem in the United States. Acute exacerbations of COPD are primarily responsible for the physical, psychological and economic burden of this disease. Early identification and treatment of exacerbations is important to improve patient and healthcare outcomes. Little is known about how patients with COPD recognize an impending exacerbation and subsequently decide to seek treatment. The purpose of this qualitative descriptive study was to explore and describe symptom recognition and treatment delay in individuals experiencing an acute exacerbation of chronic obstructive pulmonary disease (COPD). Leventhal’s Common Sense Model of illness representation undergirded this study. Using semi-structured interviews, adults hospitalized with an acute exacerbation of COPD were asked to describe their symptom experience and self care behaviors, including treatment seeking, in the days to weeks prior to hospitalization. Data analysis revealed one main theme: Recognizing, responding and reacting to change, and six subthemes: Something’s coming, Here we go again, Seeking urgent treatment, Riding it out, Not in charge anymore and My last day that richly described the COPD exacerbation experience. The study revealed that patients experience an illness prodrome prior to exacerbation and have a recurrent exacerbation symptom pattern that was self-recognized. Treatment seeking was most influenced by the speed and acuity of exacerbation onset, severity of breathlessness, fears of death, nature of patient-provider relationship and the perception of stigmatization during prior healthcare encounters. These findings are important for the development of interventions to improve patient recognition and management of COPD exacerbations in the future.

Chemotherapy-Induced Premature Menopause Among Latina Women With Breast Cancer: An Interpretive Description: A Dissertation

Mon, 03/17/2014 - 12:20pm

The description and interpretation of Latinas’ experience with chemotherapyinduced premature menopause from breast cancer treatment were explored in this study, which utilized an interpretive descriptive method from a feminist lens, and Knobf’s (1998, 2002) “Carrying on” theory. The specific aims of the study and the interview questions were guided by the state of the science literature. Overall, the impact of physiological effects, psychosocial effects, barriers, influencing factors that made their experience easier or harder, and how participants adjusted to a cancer diagnosis, treatment course, and menopause transition were described as bigger than the menopause experience alone. Participants also described a period of uncertainty or “ever-changing landscape” that began at the time of diagnosis and continued through survivorship. The impact of information, access to healthcare, acculturation levels, support, and a sense of control were elucidated as important factors in “working through” the experience. A range of collateral data sources were employed. Study limitations and future implications for practice, research, and health policy were demarcated.

Understanding Regulation of the Cytoskeleton during Cell Cycle Transitions through Examination of Crosstalk between Homologous Fission Yeast Pathways, Septation Initiation Network and Morphogenesis ORB6 Network: A Dissertation

Mon, 03/17/2014 - 11:57am

The fission yeast Schizosaccharomyces pombe has become a powerful model system for studying cytokinesis, a process of cytoplasmic division by which one cell divides into two identical daughter cells. Like mammalian cells, S. pombe divides through the use of an actomyosin contractile ring, which is composed of a set of highly conserved cytoskeletal proteins. Cytokinesis in S. pombe is primarily regulated by the SIN pathway, which is activated in late mitosis and is required for actomyosin contractile ring and septum assembly, and also plays a role in spindle checkpoint inactivation, and telophase nuclear positioning. The various functions of the SIN are carried out by the terminal kinase in the pathway called Sid2. The lack of information in the downstream targets of Sid2 has limited our understanding of the different functions of the SIN. We recently showed that, in addition to its other functions, the SIN promotes cytokinesis through inhibition the MOR signaling pathway, which normally drives cell separation and initiation of polarized growth following completion of cytokinesis (Ray et al, 2010). The molecular details of this inhibition and the physiological significance of inhibiting MOR during cytokinesis was unclear. The results presented in Chapter II describe our approach to identify Sid2 substrates, particularly focusing on Nak1 and Sog2 that function in the MOR signaling cascade. We identified and characterized Sid2 phosphorylation sites on the Nak1 and Sog2 proteins. Chapter III explores how post translational modification of MOR proteins by Sid2 regulates polarized growth during cytokinesis. This includes delineating the effect of Sid2 mediated phosphorylation of Nak1 and Sog2 on protein-protein interactions in the MOR pathway as well as on the regulation of their localization during late mitosis. Finally, results in Chapter IV demonstrate that failure to inhibit MOR signaling is lethal because cells initiate septum degradation/cell separation before completing cytokinesis thereby emphasizing the importance of cross-regulation between the two pathways to prevent initiation of the interphase polarity program during cytokinesis.

hox Gene Regulation and Function During Zebrafish Embryogenesis: A Dissertation

Mon, 03/17/2014 - 11:57am

Hox genes encode a conserved family of homeodomain containing transcription factors essential for metazoan development. The establishment of overlapping Hox expression domains specifies tissue identities along the anterior-posterior axis during early embryogenesis and is regulated by chromatin architecture and retinoic acid (RA). Here we present the role nucleosome positioning plays in hox activation during embryogenesis. Using four stages of early embryo development, we map nucleosome positions at 37 zebrafish hox promoters. We find nucleosome arrangement to be progressive, taking place over several stages independent of RA. This progressive change in nucleosome arrangement on invariant sequence suggests that trans-factors play an important role in organizing nucleosomes. To further test the role of trans-factors, we created hoxb1b and hoxb1a mutants to determine if the loss of either protein effected nucleosome positions at the promoter of a known target, hoxb1a. Characterization of these mutations identified hindbrain segmentation defects similar to targeted deletions of mouse orthologs Hoxa1 and Hoxb1 and zebrafish hoxb1b and hoxb1a morpholino (MO) loss-of-function experiments. However, we also identified differences in hindbrain segmentation as well as phenotypes in facial motor neuron migration and reticulospinal neuron formation not previously observed in the MO experiments. Finally, we find that nucleosomes at the hoxb1a promoter are positioned differently in hoxb1b-/- embryos compared to wild-type. Together, our data provides new insight into the roles of hoxb1b and hoxb1a in zebrafish hindbrain segmentation and reticulospinal neuron formation and indicates that nucleosome positioning at hox promoters is dynamic, depending on sequence specific factors such as Hox proteins.

Vpx rescue of HIV-1 from the antiviral state in mature dendritic cells is independent of the intracellular deoxynucleotide concentration

Fri, 03/14/2014 - 10:50am

BACKGROUND: SIVMAC/HIV-2 Vpx recruits the CUL4A-DCAF1 E3 ubiquitin ligase complex to degrade the deoxynucleotide hydrolase SAMHD1. This increases the concentration of deoxynucleotides available for reverse transcription in myeloid cells and resting T cells. Accordingly, transduction of these cells by SIVMAC requires Vpx. Virus-like particles containing SIVMAC Vpx (Vpx-VLPs) also increase the efficiency of HIV-1 transduction in these cells, and rescue transduction by HIV-1, but not SIVMAC, in mature monocyte-derived dendritic cells (MDDCs). Differences in Vpx mechanism noted at that time, along with recent data suggesting that SAMHD1 gains additional restriction capabilities in the presence of type I IFN prompted further examination of the role of Vpx and SAMHD1 in HIV-1 transduction of mature MDDCs.

RESULTS: When challenged with Vpx-VLPs, SAMHD1 was degraded in MDDCs even after cells had been matured with LPS, though there was no increase in deoxynucleotide levels. Steady-state levels of HIV-1 late reverse transcription products in mature MDDCs were increased to the same extent by either Vpx-VLPs or exogenous nucleosides. In contrast, only Vpx-VLPs increased the levels of 2-LTR circles and proviral DNA in myeloid cells. These results demonstrate that exogenous nucleosides and Vpx-VLPs both increase the levels of HIV-1 cDNA in myeloid cells, but only Vpx-VLPs rescue 2-LTR circles and proviral DNA in myeloid cells with a previously established antiviral state. Finally, since trans-acting Vpx-VLPs provide long-lasting rescue of HIV-1 vector transduction in the face of the antiviral state, and exogenous nucleosides do not, exogenous nucleosides were used to achieve efficient transduction of MDDCs by vectors that stably encode Vprs and Vpxs from a collection of primate lentiviruses. Vpr from SIVDEB or SIVMUS, Vpx from SIVMAC251 or HIV-2, but not SIVRCM, degraded endogenous SAMHD1, increased steady-state levels of HIV-1 cDNA, and rescued HIV-1 from the antiviral state in MDDCs.

CONCLUSION: Inhibition of deoxynucleotide hydrolysis by promoting SAMHD1 degradation is not the only mechanism by which Vpx rescues HIV-1 in MDDCs from the antiviral state. Vpx has an additional effect on HIV-1 transduction of these cells that occurs after completion of reverse transcription and acts independently of deoxynucleotide levels.