Boosting neuregulin 1 type-III expression hastens SMA motor axon maturation

Intercellular communication between axons and Schwann cells is critical for attaining the complex morphological steps necessary for axon maturation. In the early onset motor neuron disease spinal muscular atrophy (SMA), many motor axons are not ensheathed by Schwann cells nor grow sufficiently in radial diameter to become myelinated. These developmentally arrested motor axons are dysfunctional and vulnerable to rapid degeneration, limiting efficacy of current SMA therapeutics. We hypothesized that accelerating SMA motor axon maturation would improve their function and reduce disease features. A principle regulator of peripheral axon development is neuregulin 1 type III (NRG1-III). Expressed on axon surfaces, it interacts with Schwann cell receptors to mediate axon ensheathment and myelination. We examined NRG1 mRNA and protein expression levels in human and mouse SMA tissues and observed reduced expression in SMA spinal cord and in ventral, but not dorsal root axons. To determine the impact of neuronal NRG1-III overexpression on SMA motor axon development, we bred NRG1-III overexpressing mice to SMA∆7 mice. Neonatally, elevated NRG1-III expression increased SMA ventral root size as well as axon segregation, diameter, and myelination resulting in improved motor axon conduction velocities. NRG1-III was not able to prevent distal axonal degeneration nor improve axon electrophysiology, motor behavior, or survival of older mice. Together these findings demonstrate that early SMA motor axon developmental impairments can be ameliorated by a molecular strategy independent of SMN replacement providing hope for future SMA combinatorial therapeutic approaches.

p53-dependent c-Fos expression is a marker but not executor for motor neuron death in spinal muscular atrophy mouse models

The activation of the p53 pathway has been associated with neuronal degeneration in different neurological disorders, including spinal muscular atrophy (SMA) where aberrant expression of p53 drives selective death of motor neurons destined to degenerate. Since direct p53 inhibition is an unsound therapeutic approach due carcinogenic effects, we investigated the expression of the cell death-associated p53 downstream targets c-fos, perp and fas in vulnerable motor neurons of SMA mice. Fluorescence in situ hybridization (FISH) of SMA motor neurons revealed c-fos RNA as a promising candidate. Accordingly, we identified p53-dependent nuclear upregulation of c-Fos protein in degenerating motor neurons from the severe SMNΔ7 and intermediate Smn2B/– SMA mouse models. Although motor neuron-specific c-fos genetic deletion in SMA mice did not improve motor neuron survival or motor behavior, p53-dependent c-Fos upregulation marks vulnerable motor neurons in different mouse models. Thus, nuclear c-Fos accumulation may serve as a readout for therapeutic approaches targeting neuronal death in SMA and possibly other p53-dependent neurodegenerative diseases.

Laser microscopy acquisition and analysis of premotor synapses in the murine spinal cord

Loss of synapses on spinal motor neurons is a major feature of several neurodegenerative diseases; however, analyzing these premotor synapses is challenging because of their small size and high density. This protocol describes confocal and Stimulated Emission Depletion (STED) imaging of murine spinal premotor synapses and their segment-specific quantification by confocal microscopy. We detail the preparation of spinal cord segments, followed by image acquisition and analysis. This protocol enables in-depth analysis of pathological changes in spinal premotor synapses during neurodegeneration.

For complete details on the use and execution of this protocol, please refer to Buettner et al. (2021).

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Dissection and sectioning of identified murine spinal cord segments

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Fluorescent labeling of spinal premotor synapses and motor neurons

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Confocal and super-resolution acquisition of individual premotor synapses

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Quantification of premotor synapses onto motor neurons

Communicating With Diverse Patients About Participating in a Biobank: A Randomized Multisite Study Comparing Electronic and Face-to-Face Informed Consent Processes

Some individuals' understanding of informed consent (IC) information may improve with electronic delivery, but others may benefit from face-to-face (F2F). This randomized, multisite study explores how individuals from diverse backgrounds understand electronic IC documents versus F2F, their confidence in understanding, and enrollment in research. A total of 501 patients at two U.S. biobanks with diverse populations participated. There were no overall differences between electronic and F2F understanding, but F2F predicted higher confidence in understanding and enrollment. Ethnicity and a higher educational level predicted higher understanding and confidence. Study findings suggest that electronic consent may lead to better understanding for non-Hispanic patients of higher socioeconomic status. F2F processes may lead to better understanding and higher enrollment of patients from Hispanic and lower socioeconomic levels. Researchers should carefully consider how they implement electronic IC processes and whether to maintain an F2F process to better address the needs and limitations of some populations.

Central synaptopathy is the most conserved feature of motor circuit pathology across spinal muscular atrophy mouse models

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by reduced survival motor neuron (SMN) protein. Recently, SMN dysfunction has been linked to individual aspects of motor circuit pathology in a severe SMA mouse model. To determine whether these disease mechanisms are conserved, we directly compared the motor circuit pathology of three SMA mouse models. The severe SMNΔ7 model exhibits vast motor circuit defects, including degeneration of motor neurons, spinal excitatory synapses, and neuromuscular junctions (NMJs). In contrast, the Taiwanese model shows very mild motor neuron pathology, but early central synaptic loss. In the intermediate Smn^2B/- model, strong pathology of central excitatory synapses and NMJs precedes the late onset of p53-dependent motor neuron death. These pathological events correlate with SMN-dependent splicing dysregulation of specific mRNAs. Our study provides a knowledge base for properly tailoring future studies and identifies central excitatory synaptopathy as a key feature of motor circuit pathology in SMA.

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Comparison of detailed motor circuit pathology across three SMA mouse models

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Motor circuit pathology correlates with dysregulation of specific mRNAs

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Motor neuron death in severe and intermediate SMA models is p53-dependent

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Central excitatory synaptopathy is the most conserved feature of SMA pathology

Impaired prenatal motor axon development necessitates early therapeutic intervention in severe SMA

Gene replacement and pre-mRNA splicing modifier therapies represent breakthrough gene targeting treatments for the neuromuscular disease spinal muscular atrophy (SMA), but mechanisms underlying variable efficacy of treatment are incompletely understood. Our examination of severe infantile onset human SMA tissues obtained at expedited autopsy revealed persistence of developmentally immature motor neuron axons, many of which are actively degenerating. We identified similar features in a mouse model of severe SMA, in which impaired radial growth and Schwann cell ensheathment of motor axons began during embryogenesis and resulted in reduced acquisition of myelinated axons that impeded motor axon function neonatally. Axons that failed to ensheath degenerated rapidly postnatally, specifically releasing neurofilament light chain protein into the blood. Genetic restoration of survival motor neuron protein (SMN) expression in mouse motor neurons, but not in Schwann cells or muscle, improved SMA motor axon development and maintenance. Treatment with small-molecule SMN2 splice modifiers beginning immediately after birth in mice increased radial growth of the already myelinated axons, but in utero treatment was required to restore axonal growth and associated maturation, prevent subsequent neonatal axon degeneration, and enhance motor axon function. Together, these data reveal a cellular basis for the fulminant neonatal worsening of patients with infantile onset SMA and identify a temporal window for more effective treatment. These findings suggest that minimizing treatment delay is critical to achieve optimal therapeutic efficacy.

Stasimon Contributes to the Loss of Sensory Synapses and Motor Neuron Death in a Mouse Model of Spinal Muscular Atrophy

Reduced expression of the survival motor neuron (SMN) protein causes the neurodegenerative disease spinal muscular atrophy (SMA). Here, we show that adeno-associated virus serotype 9 (AAV9)-mediated delivery of Stasimon—a gene encoding an endoplasmic reticulum (ER)-resident transmembrane protein regulated by SMN—improves motor function in a mouse model of SMA through multiple mechanisms. In proprioceptive neurons, Stasimon overexpression prevents the loss of afferent synapses on motor neurons and enhances sensory-motor neurotransmission. In motor neurons, Stasimon suppresses neurodegeneration by reducing phosphorylation of the tumor suppressor p53. Moreover, Stasimon deficiency converges on SMA-related mechanisms of p53 upregulation to induce phosphorylation of p53 through activation of p38 mitogen-activated protein kinase (MAPK), and pharmacological inhibition of this kinase prevents motor neuron death in SMA mice. These findings identify Stasimon dysfunction induced by SMN deficiency as an upstream driver of distinct cellular cascades that lead to synaptic loss and motor neuron degeneration, revealing a dual contribution of Stasimon to motor circuit pathology in SMA.

SMN deficiency causes motor circuit dysfunction in SMA. Simon et al. show that Stasimon—an ER-resident protein regulated by SMN—contributes to sensory synaptic loss and motor neuron death in SMA mice through distinct mechanisms. In motor neurons, Stasimon dysfunction induces p38 MAPK-mediated phosphorylation of p53 whose inhibition prevents neurodegeneration.

Dysregulation of Mdm2 and Mdm4 alternative splicing underlies motor neuron death in spinal muscular atrophy

Van Alstyne et al. show that loss of SMN-dependent regulation of Mdm2 and Mdm4 alternative splicing underlies p53-mediated death of motor neurons in SMA, establishing a causal link between snRNP dysfunction and neurodegeneration.

Ubiquitous deficiency in the survival motor neuron (SMN) protein causes death of motor neurons—a hallmark of the neurodegenerative disease spinal muscular atrophy (SMA)—through poorly understood mechanisms. Here, we show that the function of SMN in the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs) regulates alternative splicing of Mdm2 and Mdm4, two nonredundant repressors of p53. Decreased inclusion of critical Mdm2 and Mdm4 exons is most prominent in SMA motor neurons and correlates with both snRNP reduction and p53 activation in vivo. Importantly, increased skipping of Mdm2 and Mdm4 exons regulated by SMN is necessary and sufficient to synergistically elicit robust p53 activation in wild-type mice. Conversely, restoration of full-length Mdm2 and Mdm4 suppresses p53 induction and motor neuron degeneration in SMA mice. These findings reveal that loss of SMN-dependent regulation of Mdm2 and Mdm4 alternative splicing underlies p53-mediated death of motor neurons in SMA, establishing a causal link between snRNP dysfunction and neurodegeneration.

Perspectives on Electronic Informed Consent From Patients Underrepresented in Research in the United States: A Focus Group Study

Digital informed consent may better inform individuals about health research and increase participation. In the United States and elsewhere, minorities and rural populations are underrepresented in health research and may benefit from well-designed electronic informed consent (eIC). Seven focus groups were conducted with 50 Caucasian, African American, and rural patients in the United States. Participants were asked their preferences for a paper versus electronic informed consent document. Participants found the e-version easier to use, more interesting, and better for understanding. Minority participants emphasized limited access, computer literacy, and trust barriers to eIC. Rural participants were concerned about accessibility, connectivity, privacy, and confidentiality. People see value in electronic consenting. Researchers should consider barriers to eIC among underrepresented populations before recruitment.

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

Behavioral deficits in neurodegenerative diseases are often attributed to the selective dysfunction of vulnerable neurons via cell-autonomous mechanisms. Although vulnerable neurons are embedded in neuronal circuits, the contribution of their synaptic partners to the disease process is largely unknown. Here, we show that in a mouse model of spinal muscular atrophy (SMA), a reduction in proprioceptive synaptic drive leads to motor neuron dysfunction and motor behavior impairments. In SMA mice or after the blockade of proprioceptive synaptic transmission we observed a decrease in the motor neuron firing which could be explained by the reduction in the expression of the potassium channel Kv2.1 at the surface of motor neurons. Increasing neuronal activity pharmacologically by chronic exposure in vivo led to a normalization of Kv2.1 expression and an improvement in motor function. Our results demonstrate a key role of excitatory synaptic drive in shaping the function of motor neurons during development and the contribution of its disruption to a neurodegenerative disease.

ALS-Associated Endoplasmic Reticulum Proteins in Denervated Skeletal Muscle: Implications for Motor Neuron Disease Pathology

Alpha-motoneurons and muscle fibres are structurally and functionally interdependent. Both cell types particularly rely on endoplasmic reticulum (ER/SR) functions. Mutations of the ER proteins VAPB, SigR1 and HSP27 lead to hereditary motor neuron diseases (MNDs). Here, we determined the expression profile and localization of these ER proteins/chaperons by immunohistochemistry and immunoblotting in biopsy and autopsy muscle tissue of patients with amyotrophic lateral sclerosis (ALS) and other neurogenic muscular atrophies (NMAs) and compared these patterns to mouse models of neurogenic muscular atrophy. Postsynaptic neuromuscular junction staining for VAPB was intense in normal human and mouse muscle and decreased in denervated Nmd^2J mouse muscle fibres. In contrast, VAPB levels together with other chaperones and autophagy markers were increased in extrasynaptic regions of denervated muscle fibres of patients with MNDs and other NMAs, especially at sites of focal myofibrillar disintegration (targets). These findings did not differ between NMAs due to ALS and other causes. G93A-SOD1 mouse muscle fibres showed a similar pattern of protein level increases in denervated muscle fibres. In addition, they showed globular VAPB-immunoreactive structures together with misfolded SOD1 protein accumulations, suggesting a primary myopathic change. Our findings indicate that altered expression and localization of these ER proteins and autophagy markers are part of the dynamic response of muscle fibres to denervation. The ER is particularly prominent and vulnerable in both muscle fibres and alpha-motoneurons. Thus, ER pathology could contribute to the selective build-up of degenerative changes in the neuromuscular axis in MNDs.

A Stem Cell Model of the Motor Circuit Uncouples Motor Neuron Death from Hyperexcitability Induced by SMN Deficiency

In spinal muscular atrophy, a neurodegenerative disease caused by ubiquitous deficiency in the survival motor neuron (SMN) protein, sensory-motor synaptic dysfunction and increased excitability precede motor neuron (MN) loss. Whether central synaptic dysfunction and MN hyperexcitability are cell-autonomous events or they contribute to MN death is unknown. We addressed these issues using a stem-cell-based model of the motor circuit consisting of MNs and both excitatory and inhibitory interneurons (INs) in which SMN protein levels are selectively depleted. We show that SMN deficiency induces selective MN death through cell-autonomous mechanisms, while hyperexcitability is a non-cell-autonomous response of MNs to defects in pre-motor INs, leading to loss of glutamatergic synapses and reduced excitation. Findings from our in vitro model suggest that dysfunction and loss of MNs result from differential effects of SMN deficiency in distinct neurons of the motor circuit and that hyperexcitability does not trigger MN death.

Activity Regulates the Incidence of Heteronymous Sensory-Motor Connections

The construction of spinal sensory-motor circuits involves the selection of appropriate synaptic partners and the allocation of precise synaptic input densities. Many aspects of spinal sensory-motor selectivity appear to be preserved when peripheral sensory activation is blocked, which has led to a view that sensory-motor circuits are assembled in an activity-independent manner. Yet it remains unclear whether activity-dependent refinement has a role in the establishment of connections between sensory afferents and those motor pools that have synergistic biomechanical functions. We show here that genetically abolishing central sensory-motor neurotransmission leads to a selective enhancement in the number and density of such "heteronymous" connections, whereas other aspects of sensory-motor connectivity are preserved. Spike-timing-dependent synaptic refinement represents one possible mechanism for the changes in connectivity observed after activity blockade. Our findings therefore reveal that sensory activity does have a limited and selective role in the establishment of patterned monosynaptic sensory-motor connections.

Interactive multimedia consent for biobanking: a randomized trial

Purpose

Interactive multimedia’s potential to improve biobank informed consent has yet to be investigated. The aim of this study was to test the separate effectiveness of interactivity and multimedia at improving participant understanding and confidence of understanding of informed consent, compared to a standard, face-to-face (F2F) biobank consent process.

Methods

A 2 (F2F versus multimedia) × 2 (standard versus enhanced interactivity) experimental design was used with 200 patients randomly assigned to receive informed consent. All patients received the same information provided in the Biobank’s 9-page consent document.

Results

Interactivity (F(1,196)=7.56, p=0.007, partial η²=0.037) and Media (F(1,196)=4.27, p=0.04, partial η²=0.021) independently improved participants’ understanding of the Biobank consent. Interactivity (F(1,196) = 6.793, p = 0.01, partial η²=0.033), but not Media (F(1,196) = 0.455, n.s.), resulted in increased participant confidence in their understanding of the Biobank’s consent. Patients took more time to complete the multimedia (M=18.2 min.) than the F2F (M=12.6 min.) conditions.

Conclusion

This study demonstrated that interactivity and multimedia each can be effective at promoting individuals’ understanding and confidence in understanding of a biobank consent, albeit with additional time investment. Researchers should not assume that multimedia is inherently interactive, but rather separate the two constructs when studying electronic consent.

Public perspectives on biospecimen procurement: what biorepositories should consider

PURPOSE

Human biospecimens are central to biobanking efforts, yet how members of the public think about biobank procurement strategies is not well understood. This study aimed to explore public perspectives toward the procurement of residual clinical material versus "direct" procurement strategies such as the drawing of blood.

METHODS

Members of the public residing in and beyond the biobank catchment area of the University of Iowa Hospitals and Clinics were randomly selected to participate in focus groups and a telephone survey.

RESULTS

The majority of survey participants (75%, n=559) found both residual and direct procurement strategies equally workable. Small proportions preferred either residual (15%; n=117) or direct (5%; n=40) procurement. Focus group participants (n=48) could identify benefits to both procurement strategies, but raised concerns about possible donor inconvenience/discomfort and reduced biospecimen accrual in the case of direct procurement. Residual procurement raised concerns about lower-quality samples being procured without full donor awareness.

CONCLUSION

Biobanks should consider that members of the public in their research programs may be willing to make specimen donations regardless of whether a residual or direct procurement strategy is employed. Limiting patient discomfort and inconvenience may make direct procurement strategies more acceptable to some members of the public. Ensuring donor awareness through effective informed consent may allay public concerns about the indirectness of donating clinical biospecimens.

'Information is information': a public perspective on incidental findings in clinical and research genome-based testing

The potential for genomic incidental findings is increasing with the use of genome-based testing. At the same time approaches to clinical decision making are shifting to shared decision-making models involving both the healthcare community and the public. The public's voice has been nearly absent in discussions on managing incidental findings. We conducted nine focus groups and nine interviews (n = 63) with a broad cross-section of lay public groups to elucidate public viewpoints on incidental findings that could occur as a result of genome-based testing in clinical and research situations. Data were analyzed using qualitative content analysis. Participants wanted incidental findings disclosed to them whether or not these were clinical or research findings. Participants used different terms to define and describe incidental findings; they wanted to know that incidental findings are possible and be given a choice to learn about them. Personal utility was an important reason for disclosure, and participants believed that managing information is a shared responsibility between professionals and themselves. Broad public input is needed in order to understand and incorporate the public's perspective on management of incidental findings as disclosure guidelines, and policies are developed in clinical and research settings.

The disclosure of incidental genomic findings: an "ethically important moment" in pediatric research and practice

Although there are numerous position papers on the issues and challenges surrounding disclosure of incidental genomic findings involving children, there is very little research. To fill this gap, the purpose of this study was to explore the perspectives of multiple professional (N = 103) and public (N = 63) stakeholders using both interviews and focus groups. Using qualitative analysis, we identified one overarching theme, "It's hard for us; it's hard for them," and three subthemes/questions: "What to disclose?," "Who gets the information?," and "What happens later?" Perspectives differed between professional (Institutional Review Board chairs, clinicians, and researchers) and public stakeholders. While professionals focused on the complexities of what to disclose, the lay public stated that parents should have all information laid out for them. Professionals pondered multiple parent and child situations, while the public identified parents as informational gatekeepers who know their children best. Professionals described the potential requirement for follow-up over time as a logistical "nightmare," while the public believed that parents have the responsibility for managing their children's health information over time. However, the parent role as gatekeeper was seen as time limited and in need of professional support and backup. Our findings present a case for needed dialogue around what we propose as an "ethically important moment," with the goal of protecting and respecting the viewpoints of all stakeholders when policies regarding children are developed.

A closer look at the recommended criteria for disclosing genetic results: perspectives of medical genetic specialists, genomic researchers, and institutional review board chairs

Next generation sequencing offers benefit of improved health through knowledge, but comes with challenges, such as inevitable incidental findings (IFs). The applicability of recommended criteria for disclosure of individual results when applied to disclosure of IFs is not well known. The purpose of this study was to examine how medical genetic specialists, genomic researchers, and Institutional Review Board (IRB) chairs perceive the importance of recommended criteria when applied to genetic/genomic IFs. We conducted telephone interviews with medical genetic specialists (genetic counselors, genetic nurses, medical geneticists, laboratory professionals), genomic researchers, and IRB chairs (N = 103). Respondents rated and discussed the importance of nine recommended criteria regarding disclosure of genetic/genomic IFs. Stakeholders agreed the most important criteria for disclosure were: (1) the IF points to a life-threatening condition; (2) there is a treatment; (3) individuals indicate in writing they wanted to be informed of IFs. Criteria rated less important were: analytic validity, high penetrance, association with a young age of onset and relative risk more than 2.0. Respondents indicated that some technical criteria were confusing, and in need of context. Our findings suggest that development of guidelines regarding management of IF include multiple stakeholders' perspectives and be based on a common language.

Genetics specialists' perspectives on disclosure of genomic incidental findings in the clinical setting

OBJECTIVE

Evidence documenting management of incidental findings (IFs) from clinical genomic testing is limited. The aim of this study was to examine genetics specialists' perspectives regarding current and preferred disclosure of clinical genomic IFs.

METHODS

50 genetics specialists, including medical geneticists, laboratory professionals, genetic counselors, and nurses participated in structured telephone interviews. Data were analyzed using qualitative content analysis and descriptive statistics.

RESULTS

Most specialists had encountered IFs, but definitions of IFs varied. They discussed challenges with informing patients about the prospect of IFs and disclosing IFs to patients. Causing psychological harm to patients was a concern. Participants were divided on whether IFs needed to be clinically significant and/or actionable in order to be disclosed to patients. Creating formal disclosure guidelines was considered useful, but only if they were flexible. Additional counseling, more interdisciplinary communication, maintaining contact with patients, and a centralized database to interpret IFs were also proposed.

CONCLUSION

Genetics specialists offer insights into the challenges of defining IFs, knowing when and how to disclose them, and the potential need for flexible disclosure guidelines.

PRACTICE IMPLICATIONS

Further discussion between practicing genetics specialists is needed to develop consensus on the development of best-practice guidelines for IF management.

Informed consent and genomic incidental findings: IRB chair perspectives

It is unclear how genomic incidental finding (GIF) prospects should be addressed in informed consent processes. An exploratory study on this topic was conducted with 34 purposively sampled Chairs of institutional review boards (IRBs) at centers conducting genome-wide association studies. Most Chairs (96%) reported no knowledge of local IRB requirements regarding GIFs and informed consent. Chairs suggested consent processes should address the prospect of, and study disclosure policy on, GIFs; GIF management and follow-up; potential clinical significance of GIFs; potential risks of GIF disclosure; an opportunity for participants to opt out of GIF disclosure; and duration of the researcher's duty to disclose GIFs. Chairs were concerned about participant disclosure preferences changing over time; inherent limitations in determining the scope and accuracy of claims about GIFs; and making consent processes longer and more complex. IRB Chair and other stakeholder perspectives can help advance informed consent efforts to accommodate GIF prospects.

Protecting participants, promoting progress: public perspectives on community advisory boards (CABs) in biobanking

Few studies have explored public perspectives on community advisory board (CAB) involvement in biobank-based research. This study held focus groups (n = 7) with 48 individuals residing in the catchment of an emerging comprehensive tissue and DNA biobank in the state of Iowa. Participants recognized benefits of bringing CABs into biobank oversight, including additional levels of protection they could afford research participants. Yet, CAB goals of protecting participants were also seen as potentially antithetical to research and medical progress. Participants expressed uncertainty about the relationship of CABs to IRBs, communities, and industry. Findings suggest members of the public are in principle supportive of CAB involvement in biobanking, yet anticipate a range of problems and concerns. These perceptions will need to be proactively addressed.

Ciliary neurotrophic factor-induced sprouting preserves motor function in a mouse model of mild spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is caused by homozygous loss or mutation of the SMN1 gene on human chromosome 5. Depending on the levels of SMN protein produced from a second SMN gene (SMN2), different forms of the disease are distinguished. In patients with milder forms of the disease, type III or type IV SMA that normally reach adulthood, enlargement of motor units is regularly observed. However, the underlying mechanisms are not understood. Smn(+/-) mice, a mouse model of type III/IV SMA, reveal progressive loss of motor neurons and denervation of motor endplates starting at 4 weeks of age. Loss of spinal motor neurons between 1 month and 12 months reaches 40%, whereas muscle strength is not reduced. In these animals, amplitude of single motor unit action potentials in the gastrocnemic muscle is increased more than 2-fold. Confocal analysis reveals pronounced sprouting of innervating motor axons. As ciliary neurotrophic factor (CNTF) is highly expressed in Schwann cells, we investigated its role for a compensatory sprouting response and maintenance of muscle strength in this mouse model. Genetic ablation of CNTF results in reduced sprouting and decline of muscle strength in Smn(+/-) mice. These findings indicate that CNTF is necessary for a sprouting response and thus enhances the size of motor units in skeletal muscles of Smn(+/-) mice. This compensatory mechanism could guide the way to new therapies for this motor neuron disease.

P90 Ribosomal s6 kinase 2 negatively regulates axon growth in motoneurons

Mutations in Ribosomal s6 kinase 2 (Rsk2) are associated with severe neuronal dysfunction in Coffin-Lowry syndrome (CLS) patients, flies and mice. So far, the mechanisms of how Rsk2 regulates development, maintenance and activity of neurons are not understood. We have investigated the consequences of Rsk2 deficiency in mouse spinal motoneurons. Survival of isolated Rsk2 deficient motoneurons is not reduced, but these cells grow significantly longer neurites. Conversely, overexpression of a constitutively active form of Rsk2 leads to reduced axon growth. Increased axon growth in Rsk2 deficient neurons was accompanied by higher Erk 1/2 phosphorylation, and the knockout phenotype could be rescued by pharmacological inhibition of MAPK/Erk kinase (Mek). These data indicate that Rsk2 negatively regulates axon elongation via the MAPK pathway. Thus, the functional defects observed in the nervous system of CLS patients and animal models with Rsk2 deficiency might be caused by dysregulated neurite growth rather than primary neurodegeneration.

CNS injury biomechanics and experimental models

Traumatic brain injury (TBI) and traumatic spinal cord injury (SCI) are acquired when an external physical insult causes damage to the central nervous system (CNS). Functional disabilities resulting from CNS trauma are dependent upon the mode, severity, and anatomical location of the mechanical impact as well as the mechanical properties of the tissue. Although the biomechanical insult is the initiating factor in the pathophysiology of CNS trauma, the anatomical loading distribution and the resulting cellular responses are currently not well understood. For example, the primary response phase includes events such as increased membrane permeability to ions and other molecules, which may initiate complex signaling cascades that account for the prolonged damage and dysfunction. Correlation of insult parameters with cellular changes and subsequent deficits may lead to refined tolerance criteria and facilitate the development of improved protective gear. In addition, advancements in the understanding of injury biomechanics are essential for the development and interpretation of experimental studies at both the in vitro and in vivo levels and may lead to the development of new treatment approaches by determining injury mechanisms across the temporal spectrum of the injury response. Here we discuss basic concepts relevant to the biomechanics of CNS trauma, injury models used to experimentally simulate TBI and SCI, and novel multilevel approaches for improving the current understanding of primary damage mechanisms.

Interpreter accuracy and informed consent among Spanish-speaking families with cancer

Language interpreters mediate a growing number of health care communication events, including the informed consent process, which underlies the ethical conduct of clinical research. This article explores a key interpretive outcome, accuracy, in 21 Spanish/English informed consent consultations. Discussions were transcribed, translated, and coded according to established techniques. Most (74%) discussion was accurately interpreted (range: 47%-98%; std. deviation: .137). Accuracy was lower in the more technical portions of the discussion when compared with nontechnical portions such as discussion of coping and quality-of-life issues (p = .024). The concept of "randomization" often was poorly communicated and interpreted. These differences may be due in part to the use of long, uninterrupted, and jargon-filled sentences by clinicians explaining research, among other factors. The article concludes that accuracy may be promoted if clinicians used less technical language and shorter sentences, and are more "process driven." Interpreters may need to be better informed about research-related concepts such as randomization. Further research is needed to determine the effects of interpretive accuracy on the informed consent process, the decision to participate in research, and other outcomes.

Step into my zapatos, doc: understanding and reducing communication disparities in the multicultural informed consent setting

Current informed consent standards are aimed at promoting an equitable and ethical environment for conducting research across diverse patient populations. This paper explores the possible effects of ethnicity and culture on the consent process for pediatric cancer clinical trials. Informed consent discussions were observed, recorded, transcribed, and coded. Question asking by parents and clinician/parent word ratios were used to create an interactivity measure, or "I-score." Visual analog scales were used to rate the clarity of specific explanations. Cases were sorted into two groups on the basis of parents' self-reported ethnicity: Caucasian (n=79, 56%) and minority (predominantly Latino) parents (n=61, 44%). Chi-square and t-tests were used to compare the groups. A series of logistic regression analyses (controlling for ethnicity and SES) were run for variables that showed statistically significant differences (p < 0.05). Our findings suggest that the content and quality of the informed consent process is linked to parental ethnicity, or clinician attitudes toward parental ethnicity. These findings are discussed in terms of current perspectives on culture and "cultural competence" in health care. Further research is needed to understand how cultural factors affect outcomes such as parental understanding, decision making, mutual trust, and satisfaction within the informed consent process.

Comparison of the informed consent process for randomized clinical trials in pediatric and adult oncology

PURPOSE

To compare the informed consent processes for phase III pediatric and adult oncology clinical trials in view of the critical importance of human subjects protection in both pediatric and adult cancer care. Findings are discussed in terms of the opportunities for improving pediatric and adult oncology informed consent.

PATIENTS AND METHODS

A total of 219 subjects are reported on. Adult oncology patients made up 36.1% (n = 79) of the sample. Pediatric surrogates made up the remaining 63.9% (n = 140). Subjects in both studies were observed and audiotaped in conversation with their oncologists, and interviewed afterwards. Comparisons between the adult and pediatric subjects were done using chi(2) statistics and t tests.

RESULTS

Differences between the pediatric and adult informed consent processes were found. Adult oncology decision makers were, on average, more fully informed and more actively engaged by their oncologists. Pediatric decision makers were, however, given more information about survival/cure, randomization, and voluntariness. Comprehension difficulties were more frequent among pediatric decision makers. Suggestions for improvement are made in view of the differences between adult and pediatric oncology research environments.

CONCLUSION

Ongoing efforts to improve the ethical framework of clinical cancer research need to take into account the key differences between pediatric and adult oncology informed consent. More research needs to be done to explore the differences between adult and pediatric informed consent processes in oncology.

An essential role for nuclear receptors SXR/PXR in detoxification of cholestatic bile acids

Hepatic hydroxylation is an essential step in the metabolism and excretion of bile acids and is necessary to avoid pathologic conditions such as cholestasis and liver damage. In this report, we demonstrate that the human xenobiotic receptor SXR (steroid and xenobiotic receptor) and its rodent homolog PXR (pregnane X receptor) serve as functional bile acid receptors in both cultured cells and animals. In particular, the secondary bile acid derivative lithocholic acid (LCA) is highly hepatotoxic and, as we show here, a metabolic substrate for CYP3A hydroxylation. By using combinations of knockout and transgenic animals, we show that activation of SXR/PXR is necessary and sufficient to both induce CYP3A enzymes and confer resistance to toxicity by LCA, as well as other xenotoxicants such as tribromoethanol and zoxazolamine. Therefore, we establish SXR and PXR as bile acid receptors and a role for the xenobiotic response in the detoxification of bile acids.

Reciprocal activation of xenobiotic response genes by nuclear receptors SXR/PXR and CAR

The cytochrome P450 (CYP) gene products such as CYP3A and CYP2B are essential for the metabolism of steroid hormones and xenochemicals including prescription drugs. Nuclear receptor SXR/PXR (steroid and xenobiotic receptor/pregnenolone X receptor) has been shown both biochemically and genetically to activate CYP3A genes, while similar studies have established constitutive androstane receptor (CAR) as a CYP2B regulator. The response elements in these genes are also distinct, furthering the concept of independent regulation. Unexpectedly, we found that SXR can regulate CYP2B, both in cultured cells and in transgenic mice via adaptive recognition of the phenobarbital response element (PBRE). In a type of functional symmetry, orphan receptor CAR was also found to activate CYP3A through previously defined SXR/PXR response elements. These observations not only provide a rational explanation for the activation of multiple CYP gene classes by certain xenobiotics, but also reveal the existence of a metabolic safety net that confers a second layer of protection to the harmful effects of toxic compounds and at the same time increases the propensity for drug-drug interactions.

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive regions of Helix aspersa

We used 2',7'-bis(carboxyethyl)-5(6)-carboxyflourescein (BCECF), a pH-sensitive fluorescent dye, to study intracellular pH (pH(i)) regulation in neurons in CO(2) chemoreceptor and nonchemoreceptor regions in the pulmonate, terrestrial snail, Helix aspersa. We studied pH(i) during hypercapnic acidosis, after ammonia prepulse, and during isohydric hypercapnia. In all treatment conditions, pH(i) fell to similar levels in chemoreceptor and nonchemoreceptor regions. However, pH(i) recovery was consistently slower in chemoreceptor regions compared with nonchemoreceptor regions, and pH(i) recovery was slower in all regions when extracellular pH (pH(e)) was also reduced. We also studied the effect of amiloride and DIDS on pH(i) regulation during isohydric hypercapnia. An amiloride-sensitive mechanism was the dominant pH(i) regulatory process during acidosis. We conclude that pH(e) modulates and slows pH(i) regulation in chemoreceptor regions to a greater extent than in nonchemoreceptor regions by inhibiting an amiloride-sensitive Na(+)/H(+) exchanger. Although the phylogenetic distance between vertebrates and invertebrates is large, similar results have been reported in CO(2)-sensitive regions within the rat brain stem.

Humanized xenobiotic response in mice expressing nuclear receptor SXR

The cytochrome CYP3A gene products, expressed in mammalian liver, are essential for the metabolism of lipophilic substrates, including endogenous steroid hormones and prescription drugs. CYP3A enzymes are extremely versatile and are inducible by many of their natural and xenobiotic substrates. Consequently, they form the molecular basis for many clinical drug-drug interactions. The induction of CYP3A enzymes is species-specific, and we have postulated that it involves one or more cellular factors, or receptor-like xeno-sensors. Here we identify one such factor unequivocally as the nuclear receptor pregnenolone X receptor (PXR) and its human homologue, steroid and xenobiotic receptor (SXR). We show that targeted disruption of the mouse PXR gene abolishes induction of CYP3A by prototypic inducers such as dexamethasone or pregnenolone-16alpha-carbonitrile. In transgenic mice, an activated form of SXR causes constitutive upregulation of CYP3A gene expression and enhanced protection against toxic xenobiotic compounds. Furthermore, we show that the species origin of the receptor, rather than the promoter structure of CYP3A genes, dictates the species-specific pattern of CYP3A inducibility. Thus, we can generate 'humanized' transgenic mice that are responsive to human-specific inducers such as the antibiotic rifampicin. We conclude that SXR/PXR genes encode the primary species-specific xeno-sensors that mediate the adaptive hepatic response, and may represent the critical biochemical mechanism of human xenoprotection.

Constitutive activation of transcription and binding of coactivator by estrogen-related receptors 1 and 2

In this report, we demonstrate that, in contrast to most previously characterized nuclear receptors, hERR1 and hERR2 (human estrogen receptor-related protein 1 and -2) are constitutive activators of the classic estrogen response element (ERE) as well as the palindromic thyroid hormone response element (TRE(pal)) but not the glucocorticoid response element (GRE). This intrinsically activated state of hERR1 and hERR2 resides in the ligand-binding domains of the two genes and is transferable to a heterologous receptor. In addition, we show that members of the p160 family of nuclear receptor coactivators, ACTR (activator of thyroid and retinoic acid receptors), GRIP1 (glucocorticoid receptor interacting protein 1), and SRC-1 (steroid receptor coactivator 1), potentiate the transcriptional activity by hERR1 and hERR2 in mammalian cells, and that both orphan receptors bind the coactivators in a ligand-independent manner. Together, these results suggest that hERR1 and hERR2 activate gene transcription through a mechanism different from most of the previously characterized steroid hormone receptors.

Images and image: technology and the social politics of revealing disorder in a North American hospital

In the United States and elsewhere diagnostic activities are now prominently centered on images derived from technologies such as magnetic resonance, computed tomography, and angiography. In this article I examine language, actions, and interactions in a multidisciplinary team of biomedical specialists whose members meet routinely to visually interpret and assess such images. Convened behind the scenes, in a conference room from which patients are excluded, these meetings are examined as privileged performances in which team members exercise their visual faculties and interpretive skills to address issues that include their statuses and reputations, and to politically position themselves and their specialties. Ethnographic data derived from close observation of 23 such diagnostic meetings are presented. I suggest that problems posed by the attempt to synthesize information from diagnostic images serve as vehicles for evaluating or "diagnosing" the professional capabilities and "image" of the participating physicians. Team-based divisions and attempts to reassert challenged autonomies also characterize this socially oriented diagnostic process.