Adjudicating Mild Cognitive Impairment Due to Alzheimer's Disease as a Novel Endpoint Event in the TOMMORROW Prevention Clinical Trial

BACKGROUND

The onset of mild cognitive impairment (MCI) is an essential outcome in Alzheimer's disease (AD) prevention trials and a compelling milestone for clinically meaningful change. Determining MCI, however, may be variable and subject to disagreement. Adjudication procedures may improve the reliability of these determinations. We report the performance of an adjudication committee for an AD prevention trial.

METHODS

The TOMMORROW prevention trial selected cognitively normal participants at increased genetic risk for AD and randomized them to low-dose pioglitazone or placebo treatment. When adjudication criteria were triggered, a participant's clinical information was randomly assigned to a three-member panel of a six-member independent adjudication committee. Determination of whether or not a participant reached MCI due to AD or AD dementia proceeded through up to three review stages - independent review, collaborative review, and full committee review - requiring a unanimous decision and ratification by the chair.

RESULTS

Of 3494 participants randomized, the committee adjudicated on 648 cases from 386 participants, resulting in 96 primary endpoint events. Most participants had cases that were adjudicated once (n = 235, 60.9%); the rest had cases that were adjudicated multiple times. Cases were evenly distributed among the eight possible three-member panels. Most adjudicated cases (485/648, 74.8%) were decided within the independent review (stage 1); 14.0% required broader collaborative review (stage 2), and 11.1% needed full committee discussion (stage 3). The primary endpoint event decision rate was 39/485 (8.0%) for stage 1, 29/91 (31.9%) for stage 2, and 28/72 (38.9%) for stage 3. Agreement between the primary event outcomes supported by investigators' clinical diagnoses and the decisions of the adjudication committee increased from 50% to approximately 93% (after around 100 cases) before settling at 80-90% for the remainder of the study.

CONCLUSIONS

The adjudication process was designed to provide independent, consistent determinations of the trial endpoints. These outcomes demonstrated the extent of uncertainty among trial investigators and agreement between adjudicators when the transition to MCI due to AD was prospectively assessed. These methods may inform clinical endpoint determination in future AD secondary prevention studies. Reliable, accurate assessment of clinical events is critical for prevention trials and may mean the difference between success and failure.

Performance of the ESC 0/1-hour algorithm for diagnosis of myocardial infarction: systematic review and meta-analysis

Background

The European Society of Cardiology (ESC) 0/1-hour algorithm has been recommended for early rule-out and rule-in of non ST-segment elevation acute coronary syndromes. This algorithm has primarily been validated in Europe, America, and Australasia, with less knowledge of its performance outside of these settings.

Purpose

We aim to conduct a systematic review and meta-analysis to evaluate the performance of the ESC 0/1-hour algorithm across different contexts.

Methods

We searched PubMed, Embase, Scopus, Web of Science, and the Cochrane Central Register of Controlled Trials for relevant studies published between 1 January 2008 and 31 May 2019. The primary outcome was index myocardial infarction and the secondary outcome was major adverse cardiac event or mortality. A bivariate random-effects meta-analysis was used to derive the pooled estimate of each outcome.

Results

A total of 11,014 patients from 10 cohorts were included in this meta-analysis. The algorithm based on hs-cTnT (Roche), hs-cTnI (Abbott), and hs-cTnI (Siemens) had pooled sensitivity of 98.4% [95% CI=95.1%-99.5%], 98.1% [95% CI=94.6%-99.3%], and 98.7% [95% CI=97.3%-99.3%], respectively. The algorithm based on hs-cTnT (Roche) and hs-cTnI (Siemens) had pooled specificity of 91.2% [95% CI=86.0%-94.6%] and 95.9% [95% CI=94.1%-97.2%], respectively. Among patients in the rule-out category, the pooled mortality rate at 30 days and at 1 year was 0.1% [95% CI=0.0%-0.4%] and 0.8% [95% CI=0.5%-1.2%], respectively. Among patients in the observation zone, the pooled mortality rate was 0.7% [95% CI=0.3%-1.2%] at 30-days but increased to 8.1% [95% CI=6.1%-10.4%] at 1-year, comparable to the mortality rate in the rule-in group.

Conclusion

Our results support the use of the 0/1-hour algorithm to triage patients with suspected non-ST segment elevation acute coronary syndromes. However, the algorithm may not be sufficiently safe if the 1% miss-rate for myocardial infarction is desired. Patients in the observation zone have a poor prognosis and management strategies for these patients are urgently needed.

Performance of the 0/1-hour algorithm

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Ministry of Science and Technology, R.O.C

Performance of the ESC 0/3-hour algorithm for rapid triage of myocardial infarction: systematic review and meta-analysis

Objective

The European Society of Cardiology (ESC) 0/3-hour algorithm is one of the most widely strategies used for rule-out or rule-in of acute myocardial infarction (AMI). However, a systematic evaluation of its performance has not been conducted. Furthermore, recent studies showed that the 0/3-hour algorithm is non-superior to the 0/1-hour algorithm.

Purpose

This study aims to summarize the safety and efficacy of the 0/3-hour algorithm and its comparative performance with the 0/1-hour algorithm.

Methods

We conducted literature search on PubMed, Embase, Scopus, Web of Science, and the Cochrane Central Register of Controlled Trials for studies published between 1 January 2008 and 31 May 2019. A bivariate random-effects meta-analysis was used to estimate the primary and secondary outcomes, defined as index myocardial infarction and triage efficacy, major adverse cardiac event (MACE) or mortality at 30 days, respectively.

Results

A total of 10,832 patients from 9 studies with a pooled AMI prevalence of 16% were analyzed. The 0/3-hour algorithm ruled out 69% of the patients with a pooled sensitivity of 94.2% [95% CI: 87.6%–97.4%] and negative predictive value of 98.6% [95% CI: 97.0%–99.4%]; 17% of the patients were ruled in with a pooled specificity of 94.9% [95% CI: 88.6%–97.8%] and positive predictive value of 72.9% [95% CI: 54.6%–85.7%]. The 30-day mortality and 30-day MACE for patients that were ruled out were 0.0% [95% CI: 0.0%–0.0%] and 1.4% [95% CI: 0.9%–2.0%], respectively. In a pooled analysis of 3 cohorts, the 0/3-hour algorithm had a non-superior sensitivity compared with the 0/1-hour algorithm (94.4% [95% CI: 87.0%–97.7%] vs. 98.4% [95% CI: 95.4%–99.7%]). The 0/3-hour algorithm also had a similar rule-out efficacy compared with the 0/1-hour algorithm (52% [95% CI: 39%–65%] vs. 53% [95% CI: 42%–64%]).

Conclusion

The widely used 0/3-hour algorithm has sensitivity substantially below the consensus goal of 99% and may not be sufficiently safe for triage of myocardial infarction. Furthermore, the 0/3-hour algorithm is not superior to the 0/1-hour algorithm despite the additional triage time.

Performance of ESC 0/3-hour algorithm

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Taiwan National Ministry of Science and Technology Grants

Insight into the Etiology of Undifferentiated Soft Tissue Sarcomas from a Novel Mouse Model

Aberrant activation of the Hedgehog signaling pathway has been linked to the formation of numerous cancer types, including the myogenic soft tissue sarcoma, embryonal rhabdomyosarcoma (eRMS). Here, we report PCG2, a novel mouse model in which human GLI2A, a constitutive activator of Hedgehog signaling, induced undifferentiated sarcomas that were phenotypically divergent from eRMS. Rather, sarcomas arising in PCG2 mice featured some characteristics that were reminiscent of Ewing sarcoma. Even though it is widely understood that Ewing sarcoma formation is driven by EWS-ETS gene fusions, a genetically defined mouse model is not well-established. While EWS-ETS gene fusions were not present in PCG2 sarcomas, precluding their designation as Ewing sarcoma, we did find that GLI2A induced expression of known EWS-ETS gene targets essential to Ewing pathogenesis, most notably, Nkx2.2. Moreover, we found that naïve mesenchymal progenitors originate tumors in PCG2 mice. Altogether, our work provides a novel genetic mouse model, which directly connects oncogenic Hedgehog activity to the etiology of undifferentiated soft tissue sarcomas for the first time. IMPLICATIONS: The finding that activation of Gli2 transcription factor is sufficient to induce Ewing-like sarcomas provides a direct transformative role of the Hedgehog signaling pathway in undifferentiated soft tissue sarcoma.

Diabetes associated with immune checkpoint inhibition: presentation and management challenges

BACKGROUND

In recent years, immune checkpoint blockade has become a standard therapy for a wide range of cancers. Adverse events including endocrinopathies result from the induction of autoimmunity.

CASE REPORT

We report a case series of nine individuals who presented with immunotherapy-induced type 1 diabetes between 2015-2017.

DISCUSSION

Onset of diabetes occurred within 12 weeks of commencing therapy. Anti- GAD antibodies were present in six people. Retrospective testing of islet antibodies in pre-treatment samples was possible in two people and this revealed anti-GAD seroconversion in the first and high anti-GAD titres pre and post-treatment in the second person. Six people had high risk HLA haplotypes. Clinical and genetic factors are described and compared with previously published cases. This article is protected by copyright. All rights reserved.

Bergmann glial Sonic hedgehog signaling activity is required for proper cerebellar cortical expansion and architecture

Neuronal-glial relationships play a critical role in the maintenance of central nervous system architecture and neuronal specification. A deeper understanding of these relationships can elucidate cellular cross-talk capable of sustaining proper development of neural tissues. In the cerebellum, cerebellar granule neuron precursors (CGNPs) proliferate in response to Purkinje neuron-derived Sonic hedgehog (Shh) before ultimately exiting the cell cycle and migrating radially along Bergmann glial fibers. However, the function of Bergmann glia in CGNP proliferation remains not well defined. Interestingly, the Hh pathway is also activated in Bergmann glia, but the role of Shh signaling in these cells is unknown. In this study, we show that specific ablation of Shh signaling using the tamoxifen-inducible TNC^YFP-CreER line to eliminate Shh pathway activator Smoothened in Bergmann glia is sufficient to cause severe cerebellar hypoplasia and a significant reduction in CGNP proliferation. TNC^YFP-CreER; Smo^F/- (Smo^CKO) mice demonstrate an obvious reduction in cerebellar size within two days of ablation of Shh signaling. Mutant cerebella have severely reduced proliferation and increased differentiation of CGNPs due to a significant decrease in Shh activity and concomitant activation of Wnt signaling in Smo^CKO CGNPs, suggesting that this pathway is involved in cross-talk with the Shh pathway in regulating CGNP proliferation. In addition, Purkinje cells are ectopically located, their dendrites stunted, and the Bergmann glial network disorganized. Collectively, these data demonstrate a previously unappreciated role for Bergmann glial Shh signaling activity in the proliferation of CGNPs and proper maintenance of cerebellar architecture.

BET bromodomain inhibitors suppress EWS-FLI1-dependent transcription and the IGF1 autocrine mechanism in Ewing sarcoma

Ewing sarcoma is driven by characteristic chromosomal translocations between the EWSR1 gene with genes encoding ETS family transcription factors (EWS-ETS), most commonly FLI1. However, direct pharmacological inhibition of transcription factors like EWS-FLI1 remains largely unsuccessful. Active gene transcription requires orchestrated actions of many epigenetic regulators, such as the bromodomain and extra-terminal domain (BET) family proteins. Emerging BET bromodomain inhibitors have exhibited promising antineoplastic activities via suppression of oncogenic transcription factors in various cancers. We reasoned that EWS-FLI1-mediated transcription activation might be susceptible to BET inhibition. In this study, we demonstrated that small molecule BET bromodomain inhibitors repressed EWS-FLI1-driven gene signatures and downregulated important target genes. However, expression of EWS-FLI1 was not significantly affected. Repression of autocrine IGF1 by BET inhibitors led to significant inhibition of the IGF1R/AKT pathway critical to Ewing sarcoma cell proliferation and survival. Consistently, BET inhibitors impaired viability and clonogenic survival of Ewing sarcoma cell lines and blocked EWS-FLI1-induced transformation of mouse NIH3T3 fibroblast cells. Selective depletion of individual BET genes partially phenocopied the actions of BET inhibitors. Finally, the prototypical BET inhibitor, JQ1, significantly repressed Ewing sarcoma xenograft tumor growth. These findings suggest therapeutic potential of BET inhibitors in Ewing sarcoma and highlight an emerging paradigm of using epigenetic agents to treat cancers driven by fusion transcription factors.

Long-term weight-change slope, weight fluctuation and risk of type 2 diabetes mellitus in middle-aged Japanese men and women: findings of Aichi Workers' Cohort Study

OBJECTIVE

This study aims to investigate the association of long-term weight-change slopes, weight fluctuation and the risk of type 2 diabetes mellitus (T2DM) in middle-aged Japanese men and women.

METHODS

A total of 4234 participants of Aichi Workers' Cohort Study who were aged 35-66 years and free of diabetes in 2002 were followed through 2014. Past body weights at the ages of 20, 25, 30, 40 years, and 5 years before baseline as well as measured body weight at baseline were regressed on the ages. Slope and root-mean-square-error of the regression line were obtained and used to represent the weight changes and the weight fluctuation, respectively. The associations of the weight-change slopes and the weight fluctuation with incident T2DM were estimated by Cox proportional hazards models.

RESULTS

During the median follow-up of 12.2 years, 400 incident cases of T2DM were documented. After adjustment for baseline overweight and other lifestyle covariates, the weight-change slopes were significantly associated with higher incidence of T2DM (hazard ratio (HR): 1.80, 95% confident interval (CI): 1.17-2.77 for men; and HR: 2.78, 95% CI: 1.07-7.23 for women), while the weight fluctuation was not (HR: 1.08, 95% CI: 1.00-1.18 for men and HR: 1.02, 95% CI: 0.84-1.25 for women).

CONCLUSIONS

Regardless of the presence of overweight, the long-term weight-change slopes were significantly associated with the increased risk of T2DM; however, the weight fluctuation was not associated with the risk of T2DM in middle-aged Japanese men and women.

Consensus Paper: Cerebellar Development

The development of the mammalian cerebellum is orchestrated by both cell-autonomous programs and inductive environmental influences. Here, we describe the main processes of cerebellar ontogenesis, highlighting the neurogenic strategies used by developing progenitors, the genetic programs involved in cell fate specification, the progressive changes of structural organization, and some of the better-known abnormalities associated with developmental disorders of the cerebellum.

The Purkinje neuron: A central orchestrator of cerebellar neurogenesis

Within the cyto-architecture of the brain is an often complex, but balanced, neuronal circuitry, the successful construction of which relies on the coordinated generation of functionally opposed neurons. Indeed, deregulated production of excitatory/inhibitory interneurons can greatly disrupt the integrity of excitatory/inhibitory neuronal transmission, which is a hallmark of neurodevelopmental disorders such as autism. Recent work has demonstrated that the Purkinje neuron, the central integrator of signaling within the cerebellar system, acts during development to ensure that neurogenesis occurring in spatially opposed domains reaches completion by transmitting the Sonic hedgehog ligand bi-directionally. In addition to a classic role in driving granule cell precursor proliferation, we now know that Purkinje neuron-derived Sonic hedgehog is simultaneously disseminated to the neonatal white matter. Within this neurogenic niche a lineage of Shh-responding stem and progenitor cells expand pools of GABAergic interneuron and astrocyte precursors. These recent findings advance our understanding of how Purkinje neurons function dynamically to oversee completion of a balanced cerebellar circuit.

Controlling COR competence: BCL-6 regulates neurogenesis and tumor suppression

In this issue of Cancer Cell, Tiberi and colleagues describe a tumor-suppressor role for BCL6. In the cerebellum, BCL6 is required for the transition from proliferative precursor cell to a more differentiated immature neuron through repressing the expression of Hedgehog effectors, thus controlling a pathway that is aberrantly activated in medulloblastoma.

Testosterone levels increase in association with recovery from acute fracture in men

In this longitudinal case-control study, acute fracture was associated with low serum testosterone, which was transient in 43% of men. While assessment of gonadal status is part of the assessment of bone fragility, measurement of testosterone in the early period after fracture may overestimate the prevalence of androgen deficiency.

INTRODUCTION

Measurement of circulating testosterone is recommended in the evaluation of bone fragility in men. Since acute illness can transiently decrease circulating testosterone, we quantified the association of acute fracture and serum testosterone levels.

METHODS

A case-control study was conducted involving 240 men with a radiologically confirmed minimal trauma fracture presenting to a tertiary referral hospital and 89 age-matched men without a history of minimal trauma fracture serving as controls. Follow-up testosterone levels 6 months after baseline were available for 98 cases and 27 controls. Results were expressed as the median and interquartile (IQR) range.

RESULTS

Compared to controls, cases had lower total testosterone [TT, 7.2 (3.5, 10.8) vs 13.6 (10.9, 17.1) nmol/L, p < 0.001]. The 143 cases treated as inpatients had lower testosterone levels than the 97 cases treated as outpatients [TT 4.7 (2.3, 8.1) vs 10.3 (7.5, 12.7) nmol/L, p < 0.001]. Group differences in calculated free testosterone (cFT) were comparable to the group differences in TT. At follow-up, in 98 cases, median TT increased from 6.5 nmol/L (3.2, 8.5) to 9.6 nmol/L (6.9, 12.0) p < 0.0001, and SHBG remained unchanged. Of cases with low testosterone, 43% with TT <10 nmol/L and/or cFT <230 pmol/L at presentation were reclassified as androgen sufficient at follow-up. TT was unchanged in the controls.

CONCLUSIONS

Low testosterone levels in men presenting with an acute fracture may, at least in part, be due to an acute, fracture-associated, stress response. To avoid over diagnosis, evaluation for testosterone deficiency should be deferred until recovery from the acute event.

Extracellular ATP decreases trophoblast invasion, spiral artery remodeling and immune cells in the mesometrial triangle in pregnant rats

INTRODUCTION

Preeclampsia is characterized by deficient trophoblast invasion and spiral artery remodeling, a process governed by inflammatory cells. High levels of the danger signal extracellular adenosine triphosphate (ATP) have been found in women with preeclampsia and infusion of ATP in pregnant rats induced preeclampsia-like symptoms such as albuminuria and placental ischemia. We hypothesized that ATP inhibits trophoblast invasion and spiral artery remodeling and affects macrophages and natural killer (NK) cells present in the rat mesometrial triangle.

METHODS

Pregnant rats were infused with ATP or saline (control) on day 14 of pregnancy. Rats were sacrificed on day 15, 17 or 20 of pregnancy and placentas with mesometrial triangle were collected. Sections were stained for trophoblast cells, α-smooth muscle actin (spiral artery remodeling), NK cells and various macrophage populations. Expression of various cytokines in the mesometrial triangle was analyzed using real-time RT-PCR.

RESULTS

ATP infusion decreased interstitial trophoblast invasion on day 17 and spiral artery remodeling on day 17 and 20, increased activated tartrate resistant acid phosphatase (TRAP)-positive macrophages on day 15, decreased NK cells on day 17 and 20, and decreased inducible nitric oxide synthase (iNOS)-positive and CD206-positive macrophages and TNF-α and IL-33 expression at the end of pregnancy (day 20).

DISCUSSION

Interstitial trophoblast invasion and spiral artery remodeling in the rat mesometrial triangle were decreased by infusion of ATP. These ATP-induced modifications were preceded by an increase in activated TRAP-positive macrophages and coincided with NK cell numbers, suggesting that they are involved.

CONCLUSION

Trophoblast invasion and spiral artery remodeling may be inhibited by ATP-induced activated macrophages and decreased NK cells in the mesometrial triangle in rat pregnancy.

The Purkinje neuron acts as a central regulator of spatially and functionally distinct cerebellar precursors

The prospective white matter (PWM) in the nascent cerebellum contains a transient germinal compartment that produces all postnatally born GABAergic inhibitory interneurons and astrocytes. However, little is known about the molecular identity and developmental potential of resident progenitors or key regulatory niche signals. Here, we show that neural stem-cell-like primary progenitors (Tnc(YFP-low) CD133(+)) generate intermediate astrocyte (Tnc(YFP-low) CD15(+)) precursors and GABAergic transient amplifying (Ptf1a(+)) cells. Interestingly, these lineally related but functionally divergent progenitors commonly respond to Sonic hedgehog (Shh), and blockade of reception in TNC(YFP-low) cells attenuates proliferation in the PWM, reducing both intermediate progenitor classes. Furthermore, we show that Shh produced from distant Purkinje neurons maintains the PWM niche independently of its classical role in regulating granule cell precursor proliferation. Our results indicate that Purkinje neurons maintain a bidirectional signaling axis, driving the production of spatially and functionally opposed inhibitory and excitatory interneurons important for motor learning and cognition.

Mechanisms for Structural Variation in the Human Genome

It has been known for several decades that genetic variation involving changes to chromosomal structure (i.e., structural variants) can contribute to disease; however this relationship has been brought into acute focus in recent years largely based on innovative new genomics approaches and technology. Structural variants (SVs) arise from improperly repaired DNA double-strand breaks (DSB). DSBs are a frequent occurrence in all cells and two major pathways are involved in their repair: homologous recombination and non-homologous end joining. Errors during these repair mechanisms can result in SVs that involve losses, gains and rearrangements ranging from a few nucleotides to entire chromosomal arms. Factors such as rearrangements, hotspots and induced DSBs are implicated in the formation of SVs. While de novo SVs are often associated with disease, some SVs are conserved within human subpopulations and may have had a meaningful influence on primate evolution. As the ability to sequence the whole human genome rapidly evolves, the diversity of SVs is illuminated, including very complex rearrangements involving multiple DSBs in a process recently designated as "chromothripsis". Elucidating mechanisms involved in the etiology of SVs informs disease pathogenesis as well as the dynamic function associated with the biology and evolution of human genomes.

Sonic hedgehog signaling directly targets Hyaluronic Acid Synthase 2, an essential regulator of phalangeal joint patterning

Sonic hedgehog (Shh) signal, mediated by the Gli family of transcription factors, plays an essential role in the growth and patterning of the limb. Through analysis of the early limb bud transcriptome, we identified a posteriorly-enriched gene, Hyaluronic Acid Synthase 2 (Has2), which encodes a key enzyme for the synthesis of hyaluronan (HA), as a direct target of Gli transcriptional regulation during early mouse limb development. Has2 expression in the limb bud is lost in Shh null and expanded anteriorly in Gli3 mutants. We identified an ∼3kb Has2 promoter fragment that contains two strong Gli-binding consensus sequences, and mutation of either site abrogated the ability of Gli1 to activate Has2 promoter in a cell-based assay. Additionally, this promoter fragment is sufficient to direct expression of a reporter gene in the posterior limb mesenchyme. Chromatin immunoprecipitation of DNA-Gli3 protein complexes from limb buds indicated that Gli3 strongly binds to the Has2 promoter region, suggesting that Has2 is a direct transcriptional target of the Shh signaling pathway. We also showed that Has2 conditional mutant (Has2cko) hindlimbs display digit-specific patterning defects with longitudinally shifted phalangeal joints and impaired chondrogenesis. Has2cko limbs show less capacity for mesenchymal condensation with mislocalized distributions of chondroitin sulfate proteoglycans (CSPGs), aggrecan and link protein. Has2cko limb phenotype displays striking resemblance to mutants with defective chondroitin sulfation suggesting tight developmental control of HA on CSPG function. Together, our study identifies Has2 as a novel downstream target of Shh signaling required for joint patterning and chondrogenesis.

Characterization of the E-box binding affinity to snag-zinc finger proteins

Members of the Snail/Gfi-1 domain family of zinc finger proteins are known to recognize the E-box sequence CANNTG, such as that found in the promoter of E-cadherin, however, no studies have shown that the internal "NN" dinucleotides can play a role in different binding affinities. We show via gel shift assays that only the sequences CACCTG and CAGGTG can be recognized more strongly by the SNAG-ZFP members such as Slug, Smuc, Snail, and Scratch while the other combinations of the internal nucleotides were bound weakly. All 16 possible dinucleotide combinations were tested by competition EMSAs to determine their relative binding affinities. The Kd value for the best-binding sequences was approximately 1.25 x 10(-6) M, while the other interactions were less effective. Our study has shown for the first time how different internal dinucleotide combinations of the E-box can be recognized differently by different transcription factors and also sheds light into how this transcription factor binding site may participate in DNA-protein interactions.

Voltage-gated potassium channel EAG2 controls mitotic entry and tumor growth in medulloblastoma via regulating cell volume dynamics

Medulloblastoma (MB) is the most common pediatric CNS malignancy. We identify EAG2 as an overexpressed potassium channel in MBs across different molecular and histological subgroups. EAG2 knockdown not only impairs MB cell growth in vitro, but also reduces tumor burden in vivo and enhances survival in xenograft studies. Mechanistically, we demonstrate that EAG2 protein is confined intracellularly during interphase but is enriched in the plasma membrane during late G2 phase and mitosis. Disruption of EAG2 expression results in G2 arrest and mitotic catastrophe associated with failure of premitotic cytoplasmic condensation. While the tumor suppression function of EAG2 knockdown is independent of p53 activation, DNA damage checkpoint activation, or changes in the AKT pathway, this defective cell volume control is specifically associated with hyperactivation of the p38 MAPK pathway. Inhibition of the p38 pathway significantly rescues the growth defect and G2 arrest. Strikingly, ectopic membrane expression of EAG2 in cells at interphase results in cell volume reduction and mitotic-like morphology. Our study establishes the functional significance of EAG2 in promoting MB tumor progression via regulating cell volume dynamics, the perturbation of which activates the tumor suppressor p38 MAPK pathway, and provides clinical relevance for targeting this ion channel in human MBs.

Widespread contribution of Gdf7 lineage to cerebellar cell types and implications for hedgehog-driven medulloblastoma formation

The roof plate is a specialized embryonic midline tissue of the central nervous system that functions as a signaling center regulating dorsal neural patterning. In the developing hindbrain, roof plate cells express Gdf7 and previous genetic fate mapping studies showed that these cells contribute mostly to non-neural choroid plexus epithelium. We demonstrate here that constitutive activation of the Sonic hedgehog signaling pathway in the Gdf7 lineage invariably leads to medulloblastoma. Lineage tracing analysis reveals that Gdf7-lineage cells not only are a source of choroid plexus epithelial cells, but are also present in the cerebellar rhombic lip and contribute to a subset of cerebellar granule neuron precursors, the presumed cell-of-origin for Sonic hedgehog-driven medulloblastoma. We further show that Gdf7-lineage cells also contribute to multiple neuronal and glial cell types in the cerebellum, including glutamatergic granule neurons, unipolar brush cells, Purkinje neurons, GABAergic interneurons, Bergmann glial cells, and white matter astrocytes. These findings establish hindbrain roof plate as a novel source of diverse neural cell types in the cerebellum that is also susceptible to oncogenic transformation by deregulated Sonic hedgehog signaling.

Hedgehog secretion and signal transduction in vertebrates

Signaling by the Hedgehog (Hh) family of secreted proteins is essential for proper embryonic patterning and development. Dysregulation of Hh signaling is associated with a variety of human diseases ranging from developmental disorders such as holoprosencephaly to certain forms of cancer, including medulloblastoma and basal cell carcinoma. Genetic studies in flies and mice have shaped our understanding of Hh signaling and revealed that nearly all core components of the pathway are highly conserved. Although many aspects of the Drosophila Hh pathway are conserved in vertebrates, mechanistic differences between the two species have begun to emerge. Perhaps the most striking divergence in vertebrate Hh signaling is its dependence on the primary cilium, a vestigial organelle that is largely absent in flies. This minireview will provide an overview of Hh signaling and present recent insights into vertebrate Hh secretion, receptor binding, and signal transduction.

Expression and localization of myosin-1d in the developing nervous system

Myosin-1d is a monomeric actin-based motor found in a wide range of tissues, but highly expressed in the nervous system. Previous microarray studies suggest that myosin-1d is found in oligodendrocytes where transcripts are upregulated during the maturation of these cells. Myosin-1d was also identified as a component of myelin-containing subcellular fractions in proteomic studies and mutations in MYO1D have been linked to autism. Despite the potential implications of these previous studies, there is little information on the expression and localization of myosin-1d in the developing nervous system. Therefore, we analyzed myosin-1d expression patterns in the peripheral and central nervous systems during postnatal development. In mouse sciatic nerve, myosin-1d is expressed along the axon and in the ensheathing myelin compartment. Analysis of mouse cerebellum prior to myelination at day 3 reveals that myosin-1d is present in the Purkinje cell layer, granule cell layer, and region of the cerebellar nuclei. Upon the onset of myelination, myosin-1d enrichment expands along axonal tracts, while still present in the Purkinje and granule cell layers. However, myosin-1d was undetectable in oligodendrocyte progenitor cells at early and late time points. We also show that myosin-1d interacts and is co-expressed with aspartoacylase, an enzyme that plays a key role in fatty acid synthesis throughout the nervous system. Together, these studies provide a foundation for understanding the role of myosin-1d in neurodevelopment and neurological disorders.

Rosiglitazone does not improve cognition or global function when used as adjunctive therapy to AChE inhibitors in mild-to-moderate Alzheimer's disease: two phase 3 studies

INTRODUCTION

Two phase 3 studies evaluated the efficacy and safety of rosiglitazone (RSG), a type 2 diabetes treatment, in an extended release (RSG XR) form as adjunctive therapy to ongoing acetylcholine esterase inhibitor (AChEI) treatment in AD (REFLECT-2, adjunctive to donepezil; REFLECT-3, to any AChEI). An open-label extension study (REFLECT-4) assessed RSG XR long-term safety.

METHODS

In these two double-blind, placebo-controlled studies, subjects with mild-to-moderate probable AD were randomized within 2 apolipoprotein E (APOE) allelic strata (APOE ε4-positive, APOE ε4-negative) to once daily placebo, 2 mg RSG XR, or 8 mg RSG XR for 48 weeks (REFLECT-2, N=1,496; REFLECT-3, N=1,485). Co-primary efficacy endpoints were change from baseline in Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and Clinical Dementia Rating scale - Sum of Boxes (CDR-SB) scores at week 48. Three populations were analyzed: APOE4-negative, all subjects except APOE ε4 homozygotes, and the full intent-to-treat population.

RESULTS

No statistically or clinically relevant differences between treatment groups were observed on the a priori primary endpoints in REFLECT-2 or REFLECT-3. Edema was the most frequent adverse event with RSG in each study (14% and 19%, respectively, at 8 mg RSG XR).

CONCLUSIONS

No evidence of statistically or clinically significant efficacy in cognition or global function was detected for 2 mg or 8 mg RSG XR as adjunctive therapy to ongoing AChEIs. There was no evidence of an interaction between treatment and APOE status. Safety and tolerability of RSG XR was consistent with the known profile of rosiglitazone.

Darinaparsin is a multivalent chemotherapeutic which induces incomplete stress response with disruption of microtubules and Shh signaling

Chemotherapeutics and other pharmaceuticals are common sources of cellular stress. Darinaparsin (ZIO-101) is a novel organic arsenical under evaluation as a cancer chemotherapeutic, but the drug's precise mechanism of action is unclear. Stress granule formation is an important cellular stress response, but the mechanisms of formation, maintenance, and dispersal of RNA-containing granules are not fully understood. During stress, small, diffuse granules initially form throughout the cytoplasm. These granules then coalesce near the nucleus into larger granules that disperse once the cellular stress is removed. Complete stress granule formation is dependent upon microtubules. Human cervical cancer (HeLa) cells, pre-treated with nocodazole for microtubule depolymerization, formed only small, diffuse stress granules upon sodium arsenite treatment. Darinaparsin, as a single agent, also induced the formation of small, diffuse stress granules, an effect similar to that of the combination of nocodazole with sodium arsenite. Darinaparsin inhibited the polymerization of microtubules both in vivo and in vitro. Interestingly, upon removal of darinaparsin, the small, diffuse stress granules completed formation with coalescence in the perinuclear region prior to disassembly. These results indicate that RNA stress granules must complete formation prior to disassembly, and completion of stress granule formation is dependent upon microtubules. Finally, treatment of cells with darinaparsin led to a reduction in Sonic hedgehog (Shh) stimulated activation of Gli1 and a loss of primary cilia. Therefore, darinaparsin represents a unique multivalent chemotherapeutic acting on stress induction, microtubule polymerization, and Shh signaling.