Recent Submissions

  • Environmental risk factors for attention‐deficit hyperactivity disorder

    Banerjee, Tania Das; Middleton, Frank; Faraone, Stephen V. (Wiley, 2007-06-15)
    Attention-deficit hyperactivity disorder (ADHD) is the most common cognitive and behavioural disorder diagnosed among school children. It is characterized by deficient attention and problem solving, along with hyperactivity and difficulty withholding incorrect responses. This highly prevalent disorder is estimated to affect 5–10% of children and in many cases, persists into adulthood, leading to 4% prevalence among adults. Converging evidence from epidemiologic, neuropsychology, neuroimaging, genetic and treatment studies shows that ADHD is a valid medical disorder. The majority of studies performed to assess genetic risk factors in ADHD have supported a strong familial nature of this disorder. Family studies have identified a 2- to 8-fold increase in the risk for ADHD in parents and siblings of children with ADHD. Various twin and adoption studies have also highlighted the highly genetic nature of ADHD. In fact the mean heritability of ADHD was shown to be 0.77, which is comparable to other neuropsychiatric disorders such as schizophrenia or bipolar disorder. However, several biological and environmental factors have also been proposed as risk factors for ADHD, including food additives/diet, lead contamination, cigarette and alcohol exposure, maternal smoking during pregnancy, and low birth weight. Many recent studies have specifically examined the relationships between ADHD and these extraneous factors. This review describes some of these possible risk factors.
  • Long-term outcome of pediatric obsessive-compulsive disorder: a meta-analysis and qualitative review of the literature

    Stewart, S. E.; Geller, D. A.; Jenike, M.; Pauls, D.; Shaw, D.; Mullin, B.; Faraone, S. V. (Wiley, 2004-07)
    Objective: To review the extant literature on the long-term outcome of child/adolescent-onset obsessive–compulsive disorder (OCD). Method: Medline and Psychlit databases were systematically searched for articles regarding long-term outcomes of child/adolescent-onset OCD. Meta-analysis regression was applied to evaluate predictors and persistence of OCD. Results: Sixteen study samples (n ¼ 6–132; total ¼ 521 participants) in 22 studies had follow-up periods ranging between 1 and 15.6 years. Pooled mean persistence rates were 41% for full OCD and 60% for full or subthreshold OCD. Earlier age of OCD onset (z ¼ )3.26, P ¼ 0.001), increased OCD duration (z ¼ 2.22, P ¼ 0.027) and inpatient vs. out-patient status (z ¼ 2.94, P ¼ 0.003) predicted greater persistence. Comorbid psychiatric illness and poor initial treatment response were poor prognostic factors. Although psychosocial function was frequently compromised, most studies lacked comprehensive outcome measures. Conclusion: Long-term persistence of pediatric OCD may be lower than believed. Future studies should include broader measures of outcome including symptomatic persistence and functional impairment in multiple domains.
  • Stability of executive function deficits into young adult years: a prospective longitudinal follow-up study of grown up males with ADHD

    Biederman, J.; Petty, C. R.; Fried, R.; Doyle, A. E.; Spencer, T.; Seidman, L. J.; Gross, L.; Poetzl, K.; Faraone, S. V. (Wiley, 2007-08)
    Objective: Although individuals with attention deficit‐hyperactivity disorder (ADHD) commonly exhibit deficits in executive functions that greatly increase the morbidity of the disorder, all available information on the subject is cross sectional. Method: Males (n = 85) 9–22 years with ADHD followed over 7 years into young adulthood were assessed on measures of sustained attention/vigilance, planning and organization, response inhibition, set shifting and categorization, selective attention and visual scanning, verbal and visual learning, and memory. A binary definition of executive function deficits (EFDs) was defined based on a subject manifesting at least two abnormal tests 1.5 standard deviations from controls. Results: The majority of subjects maintained EFDs over time (kappa: 0.41, P < 0.001; sensitivity: 55%, specificity: 85%, positive predictive value: 69%, and negative predictive value: 75%). Conclusion: Considering the morbidity of EFDs, these findings stress the importance of their early recognition for prevention and early intervention strategies. EFDs are stable over time.
  • Linkage of chromosome 13q32 to schizophrenia in a large veterans affairs cooperative study sample

    Faraone, Stephen V.; Skol, Andrew D.; Tsuang, Debby W.; Bingham, Stephen; Young, Keith A.; Prabhudesai, Sarita; Haverstock, Susan L.; Mena, Felicitas; Menon, Aerath Sri Kumar; Bisset, Darren; et al. (Wiley, 2002-07-29)
    Several prior reports have suggested that chromosomal region 13q32 may harbor a schizophrenia susceptibility gene. In an attempt to replicate this finding, we assessed linkage between chromosome 13 markers and schizophrenia in 166 families, each with two or more affected members. The families, assembled from multiple centers by the Department of Veterans Affairs Cooperative Studies Program, included 392 sampled affected subjects and 216 affected sib pairs. By DSM-III-R criteria, 360 subjects (91.8%) had a diagnosis of schizophrenia and 32 (8.2%) were classified as schizoaffective disorder, depressed. The families had mixed ethnic backgrounds. The majority were northern European-American families (n = 62, 37%), but a substantial proportion were African-American kindreds (n = 60, 36%). Chromosome 13 markers, spaced at intervals of approximately 10 cM over the entire chromosome and 2-5 cM for the 13q32 region were genotyped and the data analyzed using semi-parametric affected only linkage analysis. For the combined sample (with race broadly defined and schizophrenia narrowly defined) the maximum LOD score was 1.43 (Z-score of 2.57; P = 0.01) at 79.0 cM between markers D13S1241 (76.3 cM) and D13S159 (79.5 cM). Both ethnic groups showed a peak in this region. The peak is within 3 cM of the peak reported by Brzustowicz et al.
  • Investigation of parent-of-origin effects in ADHD candidate genes

    Kim, Jang Woo; Waldman, Irwin D.; Faraone, Stephen V.; Biederman, Joseph; Doyle, Alysa E.; Purcell, Shaun; Arbeitman, Lori; Fagerness, Jesen; Sklar, Pamela; Smoller, Jordan W. (Wiley, 2007)
  • The new neuropsychiatric genetics

    Faraone, S.V.; Smoller, J.W.; Pato, C.N.; Sullivan, P.; Tsuang, M.T. (Wiley, 2008-01-05)
  • Pediatric mania: a developmental subtype of bipolar disorder?

    Biederman, Joseph; Mick, Eric; Faraone, Stephen V; Spencer, Thomas; Wilens, Timothy E; Wozniak, Janet (Elsevier BV, 2000-09)
  • Agonal factors distort gene-expression patterns in human postmortem brains

    Dai, Jiacheng; Chen, Yu; Chen, Chao; Liu, Chunyu (Cold Spring Harbor Laboratory, 2020-07-12)
    Agonal factors, the conditions that occur just prior to death, can impact the molecular quality of postmortem brains, influencing gene expression results. Nevertheless, study designs using postmortem brain tissue rarely, if ever, account for these factors, and previous studies had not documented nor adjusted for agonal factors. Our study used gene expression data of 262 samples from ROSMAP with the following terminal states recorded for each donor: surgery, fever, infection, unconsciousness, difficulty breathing, and mechanical ventilation. Performed differential gene expression and weighted gene co-expression network analyses (WGCNA), fever and infection were the primary contributors to brain gene expression changes. Fever and infection also contributed to brain cell-type specific gene expression and cell proportion changes. Furthermore, the gene expression patterns implicated in fever and infection were unique to other agonal factors. We also found that previous studies of gene expression in postmortem brains were confounded by variables of hypoxia or oxygen level pathways. Therefore, correction for agonal factors through probabilistic estimation of expression residuals (PEER) or surrogate variable analysis (SVA) is recommended to control for unknown agonal factors. Our analyses revealed fever and infection contributing to gene expression changes in postmortem brains and emphasized the necessity of study designs that document and account for agonal factors.
  • Risk variants and polygenic architecture of disruptive behavior disorders in the context of attention-deficit/hyperactivity disorder

    Demontis, Ditte; Walters, Raymond K.; Rajagopal, Veera M.; Waldman, Irwin D.; Grove, Jakob; Als, Thomas D.; Dalsgaard, Søren; Ribasés, Marta; Bybjerg-Grauholm, Jonas; Bækvad-Hansen, Maria; et al. (Springer Science and Business Media LLC, 2021-01-25)
    Attention-Deficit/Hyperactivity Disorder (ADHD) is a childhood psychiatric disorder often comorbid with disruptive behavior disorders (DBDs). Here, we report a GWAS meta-analysis of ADHD comorbid with DBDs (ADHD + DBDs) including 3802 cases and 31,305 controls. We identify three genome-wide significant loci on chromosomes 1, 7, and 11. A meta-analysis including a Chinese cohort supports that the locus on chromosome 11 is a strong risk locus for ADHD + DBDs across European and Chinese ancestries (rs7118422, P = 3.15×10-10, OR = 1.17). We find a higher SNP heritability for ADHD + DBDs (h2SNP = 0.34) when compared to ADHD without DBDs (h2SNP = 0.20), high genetic correlations between ADHD + DBDs and aggressive (rg = 0.81) and anti-social behaviors (rg = 0.82), and an increased burden (polygenic score) of variants associated with ADHD and aggression in ADHD + DBDs compared to ADHD without DBDs. Our results suggest an increased load of common risk variants in ADHD + DBDs compared to ADHD without DBDs, which in part can be explained by variants associated with aggressive behavior.
  • Comorbidity of ADHD and adult bipolar disorder: A systematic review and meta-analysis

    Schiweck, Carmen; Arteaga-Henriquez, Gara; Aichholzer, Mareike; Edwin Thanarajah, Sharmili; Vargas-Cáceres, Sebastian; Matura, Silke; Grimm, Oliver; Haavik, Jan; Kittel-Schneider, Sarah; Ramos-Quiroga, Josep Antoni; et al. (Elsevier BV, 2021-05)
    Attention-deficit / hyperactivity disorder (ADHD) and Bipolar Disorder (BD) are common mental disorders with a high degree of comorbidity. However, no systematic review with meta-analysis has aimed to quantify the degree of comorbidity between both disorders. To this end we performed a systematic search of the literature in October 2020. In a meta-analysis of 71 studies with 646,766 participants from 18 countries, it was found that about one in thirteen adults with ADHD was also diagnosed with BD (7.95 %; 95 % CI: 5.31-11.06), and nearly one in six adults with BD had ADHD (17.11 %; 95 % CI: 13.05-21.59 %). Substantial heterogeneity of comorbidity rates was present, highlighting the importance of contextual factors: Heterogeneity could partially be explained by diagnostic system, sample size and geographical location. Age of BD onset occurred earlier in patients with comorbid ADHD (3.96 years; 95 % CI: 2.65-5.26, p < 0.001). Cultural and methodological differences deserve attention for evaluating diagnostic criteria and clinicians should be aware of the high comorbidity rates to prevent misdiagnosis and provide optimal care for both disorders.
  • DRAMS: A tool to detect and re-align mixed-up samples for integrative studies of multi-omics data

    Jiang, Yi; Giase, Gina; Grennan, Kay; Shieh, Annie W.; Xia, Yan; Han, Lide; Wang, Quan; Wei, Qiang; Chen, Rui; Liu, Sihan; et al. (Public Library of Science (PLoS), 2020-04-13)
  • Role of RPTPzeta/phosphacan in the neural extracellular matrix

    Matthews, Rick; Eill, Geoffrey (2020)
    The mammalian brain is the most structurally and functionally complex system in biology. In order to carry out diverse functions such as thought and cognition, neurons in the brain must properly differentiate, make millions of functional interconnections, and incredibly be able to maintain those interconnections while retaining plasticity and the ability to learn throughout its lifetime. In order for neurons to carry out these complex functions, they must have an intricate relationshipwith their extracellular environment, which provides numerous molecules, such as growth factors and neurotransmitters, and physical cues to initiate critical downstream signaling cascades. In the central nervous system (CNS), the neural extracellular matrix (ECM) largely organizes this extracellular environment, and as such, is implicated in a multitude of neuronal functions. Not only can it serve as a physical barrier, the neural ECM is shown to regulate neuronal cell differentiation, migration, synaptogenesis, and maintain the mature state by restricting plasticity and neurite outgrowth. Of particular import, a subset of the neural ECM, the perineuronal net (PNN), is implicated to regulate neuronal plasticity in the CNS. PNNs were historically believed to be critical for restricting experience dependent plasticity in the brain but more recently shown to regulate several forms of learning and memory, in addition to multiple neurological diseases. However, despite these implicated functions, PNNs comprise only a fraction of the total ECM in the CNS. A majority of the neural ECM is derived from the diffuse ECM, a structure that is ubiquitously expressed throughout the CNS. As the diffuse ECM is very similar in molecular composition and structure to PNNs, it is difficult to specifically target PNNs for functional and mechanistic studies.As such, a better toolset is needed to differentiate the contributions ivbetween PNNs and the diffuse ECM in regulating plasticity and learning and memory. To develop thistoolset, there is a great need to better understand PNN molecular composition and structure. Therefore, the purpose of this work was to provide critical insight into the molecular composition and structure of PNNs soas to better understand its function in the CNS. In Chapter 2, using multiple ECM genetic knockout models, we show compelling evidence of an additional PNN anchor that importantlylays the groundworkforfuture functional studies. Specifically, we suggestchondroitin sulfate proteoglycan (CSPG) phosphacan, secreted isoform of receptor protein tyrosine phosphatase zeta (RPTPζ), iscritical for PNN structure as it partially anchors PNNs to the neuronal surface through cooperation with tenascin-R. Additionally, as the neural ECM is involved in numerous neurological diseases, in Chapter 3, we investigated the function of major ECM component, RPTPζ, in a group of O-mannosyl related congenital muscular dystrophy with associated brain abnormalities (CMD). Our data suggest a possible role of RPTPζ in proper cortical lamination in a CMD mouse model. Interestingly, we found evidence of a novel O-mannosyl substrate in the developing brain that could critically contribute to the underlying deficits of CMD. In conclusion, the neural ECM, once previously disregarded in the field, is becoming a novel source to understand mature mammalian brain function and disease, but more work is needed to better differentiate the specific roles of its substructures.
  • THE ROLE OF DENGUE VIRUS NON-STRUCTURAL PROTEIN 1 IN DISEASE PATHOGENESIS

    King, Christine; Endy, Timothy; Barbachano-Guerrero, Arturo (2020)
    Dengue virus (DENV) causes an estimated 390 million infections worldwide annually, with severe forms of disease marked by vascular leakage and an over reactive inflammatory response. Endothelial cells (EC) are directly responsible for vascular homeostasis and are highly responsive to circulating mediators but are not commonly infected. Mast cells (MC) are potent cells of the innate immune system that play an important role in EC biology and inflammatory responses. DENV encodes 10 proteins; with only one, the non-structural protein 1 (NS1), secreted from infected cells and accumulating in the blood of patients.NS1 has been implicated in the pathogenesis of vascular permeability, but the mechanism is not completely understood. Using a complementary array of in vitroassays and disease relevant ECs and MCs, we described the possible roles for NS1 in dengue disease pathogenesis. Using microscopy and immunoblotting we observed that ECs internalize NS1 into endosomes, where it accumulates and is degraded overtime. Transcriptome and pathway analysis defined changes in global gene expression in ECs that are associated with cell dysfunction. We observed that NS1 induced an increase in multicellular rearrangements and a decrease in barrier function in ECs. We demonstrated that NS1-dependent activation of the p38 MAPK pathway controls the changes in EC permeability in vitro. Further, we discovered iiithat ECs and MCs respond to NS1 by secreting a specific array of proinflammatory cytokines and chemokines that may contribute to the cytokine storm in dengue disease. Finally, we found that NS1 internalization can mediate the uptake of bound antibodies into ECs. Together, these results suggest a vasoactive and proinflammatory role for DENV NS1 that may participate in the development of severe symptoms in dengue disease. The observed functions of NS1 could lead to the discovery of new therapeutic targets in dengue disease.
  • Expression and Function of Paxillin Genes in Zebrafish: A Role in Skeletal Muscle Development

    Turner, Chris; Amack, Jeffrey; Jacob, Andrew (2017)
    Paxillin is a key component of the Integrin adhesion complex, which regulates cellular signaling events in response to extracellular matrix interactions. Although the roles for Paxillin in cell migration have been extensively studied, less is understood about its role in vertebrate development. Depletion of Paxillin from mouse embryos results in early lethality due to impaired cardiovascular development and function, necessitating the development of alternative vertebrate genetic models for examining the role of Paxillin during embryogenesis. Zebrafish have emerged as an experimental vertebrate model amenable to genetic manipulation. The work compiled herein first characterizes the expression profiles for Paxillin genes in zebrafish, and then describes the embryonic phenotypes observed upon mutation of these genes. The identification of two Paxillin genes in zebrafish, pxnaand pxnb, provided new insight into the evolution of this gene family in the Teleost lineage. Both overlapping and unique expression profiles for these genes during zebrafish embryogenesis were uncovered. While both genes are expressed in developing skeletal muscle, pxnawas restricted to the notochord during earlier stages of embryogenesis and pxnbwas expressed in the developing heart. Targeted mutation of either gene alone did not impair embryonic development, suggesting partial functional redundancy between each gene during embryogenesis. Accordingly, combined mutations in pxnaand pxnbrevealed defects during the development ofseveral embryonic tissues. In particular, skeletal muscle morphogenesis iiiwas perturbed in these double mutant embryos. Further characterization revealed that Paxillin genes in zebrafish serve to regulate embryonic myotome shape and proper extracellular matrix composition during muscle development. The amount of Laminin was reduced, while the abundance of Fibronectin persisted, during myotome morphogenesis in Paxillin double mutant embryos. In addition, a role for cytoskeletal contractility in regulatingsubcellular localization of Paxillin in developing skeletal muscle was established. Defects in the development of the cardiovascular system were also apparent in Paxillin double mutant embryos, and future work will focus on characterizing these in further detail. Altogether, this work provides a new vertebrate model to use for understanding the role of Paxillin during embryonic development, and uncovers an unrecognized role for Paxillin in establishing the extracellular matrix of skeletal muscle.
  • EVALUATION OF THE ROLE OF THE CENTRAL PAIR IN CHLAMYDOMONAS REINHARDTII FLAGELLAR MOTILITY

    Mitchell, David; Brandon, Smith (2013)
    Cilia and flagella are essential for the function of nearly all eukaryotes. This organelle is made up of nine outer doublet microtubules and two central singlet microtubules to form the canonical (9+2) ciliary structure. Cilia and flagella use this structure, as well as several protein complexes, such as the outer and inner dynein arms, the radial spokes, and the proteins that decorate the central pair to propagate the bending that produces motion. Flagellar motion is highly regulated, and each of these structures is necessary to regulate the dynein arms that generate the motile force. The central pair is one of the least understood of these structures. To date there are two major impediments hindering our understanding of the central pair: a lack of understanding as to how distinct central pair structures work in concert, and a general lack of available central pair mutant strains in the model organism Chlamydomonas reinhardtii. In order to further our understanding of how the central pair functions I have used multiple strategies. Firstly I have used previously characterized central pair mutants to study both structural interactions within the central pair and how the double mutant affects motility regulation. Secondly I provide evidence that a potential central pair mutant, H2, is indeed a central pair mutant and affects the C2b projection. Lastly I will attempt to characterize a new Chlamydomonas mutant, 10B5. Together these analyses will demonstrate that double mutants can have an additive effect on the structure of the central pair, and that double central pair mutants do not appear to suppress one another, but are at least ivepistatic to the most severe phenotype. I will also show evidence that 10B5 is not a central pair mutant, but with further study it may offer new insight into motilityregulation.
  • ANTIVIRAL ACTIVITY AND MECHANISM OF ACTION OF A NOVEL URACIL ANALOG FOR VARICELLA-ZOSTER VIRUS

    Moffat, Jennifer; DE, CHANDRAV (2015)
    The alphaherpesvirus varicella-zoster virus (VZV) is widespread in humans. VZV causes primary and recurrent diseases that are preventable with live vaccines and are treatable with antiviral drugs. New antiviral drugs for varicella-zoster virus (VZV) with increased potency are needed, especially to prevent post-herpetic neuralgia. The purpose of this project was to evaluate β-L-1-[5-(E-2-Bromovinyl)-2-(hydroxymethyl)-1,3-dioxolan-4- yl)] uracil (L-BHDU) and 5′-O-valyl-L-BHDU for efficacy, safety, resistance, and mechanism of action in three models of VZV replication: primary human foreskin fibroblasts (HFFs), skin organ culture (SOC) and in SCID-Hu mice with skin xenografts. We found that L-BHDU and valyl-L-BHDU were safe and effective against VZV in culture and in a mouse model. Herpes simplex virus Type 1 was also sensitive to LBHDU in cultured cells. The mechanism of action of L-BHDU and its effect on drugdrug interactions were not known. Given its similar structure to brivudine (BVdU), we addressed whether L-BHDU, like BVdU, inhibits 5-fluorouracil (5-FU) metabolism. LBHDU did not interfere with 5FU metabolism, indicating that L-BHDU is a safer drug than BVdU. However, L-BHDU antagonized the activity of acyclovir (ACV), BVdU and foscarnet (PFA) in cultured cells, which was due to competition for phosphorylation by VZV thymidine kinase (TK). The mechanism of action of L-BHDU was studied by evaluating its activity against related α-herpesviruses and by analyzing resistant VZV viii strains. VZV strains resistant to L-BHDU (L-BHDUR ) were cross-resistant to ACV and BVdU but not to PFA and cidofovir (CDV). Whole genome sequencing of L-BHDUR strains identified mutations in ATP-binding (G22R) and nucleoside binding (R130Q) domains of VZV TK. The purified L-BHDUR TKs were enzymatically inactive and failed to phosphorylate the drug. In wild type VZV- infected cells, L-BHDU was converted to L-BHDU mono- and diphosphate forms; cells infected with L-BHDUR virus did not phosphorylate the drug. We also investigated whether addition of nucleosides reversed LBHDU inhibition of VZV in dividing and quiescent HFFs. Excess thymidine and uridine, but not purines, in proportion to L-BHDU restored VZV replication only in dividing cells, suggesting that the active form of L-BHDU interfered with pyrimidine biosynthesis. Like other herpesviruses, VZV infection induced thymidine triphosphate (dTTP) in confluent cells while L-BHDU treatment decreased the dTTP pool. Some herpesviruses raise dNTP pools by inducing cellular enzymes. However, VZV infection did not increase cellular thymidylate synthase (TS) expression to facilitate viral replication. Furthermore, the active form of L-BHDU did not interfere with cellular metabolism, suggesting a viral target. Further studies are required to identify the target(s) of L-BHDU active form(s).
  • Biological importance of TIMP-2 phosphorylation on MMP-2 activity

    Bourboulia, Dimitra; Bullard, Renee (2016)
    Matrix metalloproteinases (MMPs) are proteolytic enzymes that are secreted from the cell and play an important role in embryonic development and tissue remodeling. In cancer, MMPs are hyperactive, promoting degradation of the ex-tracellular matrix. Enhancement of MMP proteolytic activity allows tumor cells to migrate and invade surrounding tissues, increasing the chance of metastasis. Tissue inhibitor of metalloproteinases (TIMPs) are also known to act extracellu-larly, and are the endogenous inhibitors of MMPs. To inhibit the protease activi-ty of MMPs, the N-terminus of the TIMP protein binds to the catalytic domain of MMP at a ratio of 1:1. Studies from our lab have found that TIMP-2 is phosphor-ylated on three tyrosine residues, and this phosphorylation increases the inter-action with MMP-2. This is the first time that phosphorylation of TIMP-2 has been reported. Fascinatingly, the proto-oncogene tyrosine kinase c-Src was found to phosphorylate TIMP-2. This is significant in that c-Src has not yet been shown to act extracellularly, and there are no details within the current lit-erature describing how this protein may function outside of the cell. In this the-sis, we usedmammalian cells as a model to decipher whether TIMP-2 phosphor-ylation wasable to occur extracellularly,as well as the effect that phosphoryla-tion of TIMP-2 hadon its functionto both inhibit/activate MMP-2. We found that(1) c-Src is able to phosphorylate TIMP-2 extracellularly in conditioned me-vidia; and (2) phosphorylation of TIMP-2 enhances its function of inhibiting MMP-2 proteolytic activity, as well as assisting in the activation of pro-MMP-2. Our results suggest the presence of anovel mechanismin whichphosphoryla-tion of TIMP-2is able to regulate the extracellular environment through en-hanced interaction with MMP-2. The information gained from this research couldlead to development of novel therapies that use phosphorylated TIMP-2 as a means of decreasing cellular migration and invasion with the overall goal of preventing metastasis.
  • Mechanisms of aseptic loosening in total knee arthroplasty

    Cyndari, Karen (2017)
    Introduction: Cemented Total Knee Arthroplasty (TKA) is the gold standard of care for end-stage, multi-etiologic arthritis. While the longevity of these devices may now reach or even surpass 15 years in service, a minority (~10%) will fail prematurely due to a process called aseptic loosening. Historically, this process has been attributed to an inflammatory reaction against wear debris from the TKA polyethylene (PE) insert. However, we have previously estimated supraphysiologic fluid shear stress (FSS) (exceeding 900 Pa) at the cement-bone interface of cemented joint replacements, and examined this as a possible alternative cause of increased osteoclast activity. Methods: We analyzed the cement-bone interlock of tibial and femoral components from en-bloc, postmortem-retrieved, non-revised TKAs to explore the process of loss of fixation, prior to any clinical loosening. For the tibial components, we used a novel protocol wherein whole undecalcified bone+PMMA cement segments from the proximal tibia were embedded in Spurr’s resin and thinly sectioned. Polarized light microscopy was used to identify and quantify co-located PE debris. Using a novel bioreactor developed by our lab called the Multi-Well Fluid Loading (MFL) System, we examined static, subphysiologic, physiologic, and supraphysiologic FSS on RAW 264.7 osteoclast activity and morphology, with and without PE particle treatment. Results: We found no association been the amount or presence of PE debris and the amount or location of loss of interlock in retrieved TKAs. FSS up to 17 Pa increased the ability of osteoclasts to resorb mineral, and FSS up to 4.4 Pa induced the formation of larger osteoclasts. FSS and fluid shear rate interacted together to increase the area of actin rings, while PE treatment increased the number of actin rings and TRAP production. FSS up to 4.4 Pa decreased expression of Ctsk and Il1a, but PE co-treatment abolished this effect. Conclusions: These results indicate there may be alternative factors leading to aseptic loosening apart from PE debris. We demonstrated that osteoclasts are mechanosensitive and able to adjust activity, morphology, and gene expression based on FSS. Further, PE interferes with osteoclast gene downregulation in response to FSS, indicating PE could be a potentiator of osteoclast activity or differentiation.
  • Alternative splicing dysregulation in mental disorders

    Glatt, Stephen; Cohen, Ori S (2014)
    The brain's ability to adapt ultimately depends on the efficiency with which neuronal connections are made, destroyed, or manipulated. This connectivity is largely controlled by synaptic plasticity, which creates, strengthens, or weakens signals that are necessary for appropriate functioning of the organism. This constant rewiring allows an organism to learn, mature, and cope with the ever-changing environment. However, this rewiring is dependent on the ability to make new proteins, which highlights the importance of transcription, translation, and post-translational modification in the process of synaptic plasticity. Among these cellular functions, transcription plays a key role in providing the necessary variability that is required to regulate neurodevelopment and cognitive behaviors. During transcription, alternative splicing regulates the contents of transcriptomic elements by cutting and stitching the transcribed pre-mRNA and adjusting the configuration of the mature mRNA(s) to meet the necessary cellular requirements. Therefore, it is conceivable that alternative splicing abnormalities can result in inappropriate adjustment of the transcriptome and result in pathological adaptation. In this dissertation, I review the evidence of dysfunctional gene splicing in neuropsychiatric disorders. Then I evaluate the extent of alternative splicing in an animal model for social interaction. This model utilizes valproic acid exposure at a critical developmental period to illicit significant and long-lasting changes in social interaction behavior. Next, I explore the abundance and types of alternative-splicing dysregulationin postmortembrain tissue samples from schizophrenia patients as compared to non-psychotic comparison subjects. Finally, I describe the mechanisms by which a schizophrenia-associated polymorphism in a strong candidate gene (DRD2, which encodes the D2 dopamine receptor) disrupts alternative splicing and leads to inappropriate transcription that is associated with cognitive dysfunction. Collectively, these results reinforce the notion that consideration of genetic variants that dysregulate particular mRNA isoforms and understanding the biological consequence of expressing such isoforms is a crucial step in our efforts to understand human behavior and to develop therapeutic interventions for mental disorders.

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