Myxovirus resistance protein A (MxA) expression in myositides: Sarcoplasmic expression is common in both dermatomyositis and lupus myositis

INTRODUCTION/AIMS

Myxovirus resistance protein A (MxA) is a type I interferon (IFN1) pathway activation marker and MxA sarcoplasmic expression is currently recognized as a highly specific marker for dermatomyositis (DM). However, we have frequently observed endothelial tubuloreticular inclusions (TRI), another surrogate IFN1 activation marker, in a variety of overlap myositides. The aim of this study was to examine MxA expression in those myositides.

METHODS

We retrospectively performed MxA immunostaining on a wide range of myositides.

RESULTS

MxA sarcoplasmic expression was present in DM (94.4%, 17/18), active lupus myositis (LM, 80%,16/20), inactive LM (36%, 4/11), antisynthetase syndrome (ASyS, 20%, 2/10), systemic sclerosis (13%, 2/15), Sjogren's syndrome (7.7%, 1/13), and human immunodeficiency virus (HIV) myositis (5.6%, 1/18) and was absent in immune-mediated necrotizing myopathy (IMNM, 0/16) and hydroxychloroquine myopathy (0/5). The sensitivity and specificity of MxA sarcoplasmic expression for LM and DM combined compared with all other myositides were 84.6% (95% CI: 69.5-94.1) and 92.1 (95% CI: 83.6-97.0), respectively, and superior to TRIs. MxA capillary expression was nonspecific. Histologically, 35% of LM cases demonstrated a unique panfascicular necrotizing myopathy pattern. The remainder of the LM cases had significant morphological overlap with DM/ASyS (20%), IMNM (20%), or polymyositis (15%).

DISCUSSION

MxA sarcoplasmic expression is highly prevalent in LM and DM and is a useful marker in differentiating DM and LM from other myositides. LM can manifest in various pathology patterns that need to be differentiated from DM, IMNM, ASyS, and polymyositis.

Ectopic PLAG1 induces muscular dystrophy in the mouse

Even though various genetic mutations have been identified in muscular dystrophies (MD), there is still a need to understand the biology of MD in the absence of known mutations. Here we reported a new mouse model of MD driven by ectopic expression of PLAG1. This gene encodes a developmentally regulated transcription factor known to be expressed in developing skeletal muscle, and implicated as an oncogene in certain cancers including rhabdomyosarcoma (RMS), an aggressive soft tissue sarcoma composed of myoblast-like cells. By breeding loxP-STOP-loxP-PLAG1 (LSL-PLAG1) mice into the MCK-Cre line, we achieved ectopic PLAG1 expression in cardiac and skeletal muscle. The Cre/PLAG1 mice died before 6 weeks of age with evidence of cardiomyopathy significantly limiting left ventricle fractional shortening. Histology of skeletal muscle revealed dystrophic features, including myofiber necrosis, fiber size variation, frequent centralized nuclei, fatty infiltration, and fibrosis, all of which mimic human MD pathology. QRT-PCR and Western blot revealed modestly decreased Dmd mRNA and dystrophin protein in the dystrophic muscle, and immunofluorescence staining showed decreased dystrophin along the cell membrane. Repression of Dmd by ectopic PLAG1 was confirmed in dystrophic skeletal muscle and various cell culture models. In vitro studies showed that excess IGF2 expression, a transcriptional target of PLAG1, phenocopied PLAG1-mediated down-regulation of dystrophin. In summary, we developed a new mouse model of a lethal MD due to ectopic expression of PLAG1 in heart and skeletal muscle. Our data support the potential contribution of excess IGF2 in this model. Further studying these mice may provide new insights into the pathogenesis of MD and perhaps lead to new treatment strategies.

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.

Molecular markers of brain cholesterol homeostasis are unchanged despite a smaller brain mass in a mouse model of cholesteryl ester storage disease

Lysosomal acid lipase (LAL), encoded by the gene LIPA, facilitates the intracellular processing of lipids by hydrolyzing cholesteryl esters and triacylglycerols present in newly internalized lipoproteins. Loss-of-function mutations in LIPA result in cholesteryl ester storage disease (CESD) or Wolman disease when mutations cause complete loss of LAL activity. Although the phenotype of a mouse CESD model has been extensively characterized, there has not been a focus on the brain at different stages of disease progression. In the current studies, whole-brain mass and the concentrations of cholesterol in both the esterified (EC) and unesterified (UC) fractions were measured in Lal-/- and matching Lal+/+ mice (FVB-N strain) at ages ranging from 14 up to 280 days after birth. Compared to Lal+/+ controls at 50, 68-76, 140-142, and 230-280 days of age, Lal-/- mice had brain weights that averaged approximately 6%, 7%, 18%, and 20% less, respectively. Brain EC levels were higher in the Lal-/- mice at every age, being elevated 27-fold at 230-280 days. Brain UC concentrations did not show a genotypic difference at any age. The elevated brain EC levels in the Lal-/- mice did not reflect EC in residual blood. An mRNA expression analysis for an array of genes involved in the synthesis, catabolism, storage, and transport of cholesterol in the brains of 141-day old mice did not detect any genotypic differences although the relative mRNA levels for several markers of inflammation were moderately elevated in the Lal-/- mice. The possible sites of EC accretion in the central nervous system are discussed.

Using explainable machine learning to identify patients at risk of reattendance at discharge from emergency departments

Short-term reattendances to emergency departments are a key quality of care indicator. Identifying patients at increased risk of early reattendance could help reduce the number of missed critical illnesses and could reduce avoidable utilization of emergency departments by enabling targeted post-discharge intervention. In this manuscript, we present a retrospective, single-centre study where we created and evaluated an extreme gradient boosting decision tree model trained to identify patients at risk of reattendance within 72 h of discharge from an emergency department (University Hospitals Southampton Foundation Trust, UK). Our model was trained using 35,447 attendances by 28,945 patients and evaluated on a hold-out test set featuring 8847 attendances by 7237 patients. The set of attendances from a given patient appeared exclusively in either the training or the test set. Our model was trained using both visit level variables (e.g., vital signs, arrival mode, and chief complaint) and a set of variables available in a patients electronic patient record, such as age and any recorded medical conditions. On the hold-out test set, our highest performing model obtained an AUROC of 0.747 (95% CI 0.722–0.773) and an average precision of 0.233 (95% CI 0.194–0.277). These results demonstrate that machine-learning models can be used to classify patients, with moderate performance, into low and high-risk groups for reattendance. We explained our models predictions using SHAP values, a concept developed from coalitional game theory, capable of explaining predictions at an attendance level. We demonstrated how clustering techniques (the UMAP algorithm) can be used to investigate the different sub-groups of explanations present in our patient cohort.

A CADM3 variant causes Charcot-Marie-Tooth disease with marked upper limb involvement

The CADM family of proteins consists of four neuronal specific adhesion molecules (CADM1, CADM2, CADM3 and CADM4) that mediate the direct contact and interaction between axons and glia. In the peripheral nerve, axon-Schwann cell interaction is essential for the structural organization of myelinated fibres and is primarily mediated by the binding of CADM3, expressed in axons, to CADM4, expressed by myelinating Schwann cells. We have identified-by whole exome sequencing-three unrelated families, including one de novo patient, with axonal Charcot-Marie-Tooth disease (CMT2) sharing the same private variant in CADM3, Tyr172Cys. This variant is absent in 230 000 control chromosomes from gnomAD and predicted to be pathogenic. Most CADM3 patients share a similar phenotype consisting of autosomal dominant CMT2 with marked upper limb involvement. High resolution mass spectrometry analysis detected a newly created disulphide bond in the mutant CADM3 potentially modifying the native protein conformation. Our data support a retention of the mutant protein in the endoplasmic reticulum and reduced cell surface expression in vitro. Stochastic optical reconstruction microscopy imaging revealed decreased co-localization of the mutant with CADM4 at intercellular contact sites. Mice carrying the corresponding human mutation (Cadm3Y170C) showed reduced expression of the mutant protein in axons. Cadm3Y170C mice showed normal nerve conduction and myelin morphology, but exhibited abnormal axonal organization, including abnormal distribution of Kv1.2 channels and Caspr along myelinated axons. Our findings indicate the involvement of abnormal axon-glia interaction as a disease-causing mechanism in CMT patients with CADM3 mutations.

Distinct tissue injury patterns in juvenile dermatomyositis auto-antibody subgroups

INTRODUCTION

Juvenile dermatomyositis (JDM) can be classified into clinical serological subgroups by distinct myositis-specific antibodies (MSAs). It is incompletely understood whether different MSAs are associated with distinct pathological characteristics, clinical disease activities, or response to treatment.

METHODS

We retrospectively reviewed clinicopathological data from consecutive JDM patients followed in the pediatric rheumatology clinic at a single center between October 2016 and November 2018. Demographics, clinical data, and laboratory data were collected and analyzed. Detailed muscle biopsy evaluation of four domains (inflammation, myofiber, vessels, and connective tissue) was performed, followed by statistical analysis.

RESULTS

Of 43 subjects included in the study, 26 (60.5%) had a detectable MSA. The most common MSAs were anti-NXP-2 (13, 30.2%), anti-Mi-2 (7, 16.3%), and anti-MDA-5 (5, 11.6%). High titer anti-Mi-2 positively correlated with serum CK > 10,000 at initial visit (r = 0.96, p = 0.002). Muscle biopsied from subjects with high titer anti-Mi-2 had prominent perifascicular myofiber necrosis and perimysial connective tissue damage that resembled perifascicular necrotizing myopathy, but very little capillary C5b-9 deposition. Conversely, there was no positive correlation between the levels of the anti-NXP-2 titer and serum CK (r = - 0.21, p = 0.49). Muscle biopsies from patients with anti-NXP-2 showed prominent capillary C5b-9 deposition; but limited myofiber necrosis. Only one patient had anti-TIF1γ autoantibody, whose muscle pathology was similar as those with anti-NXP2. All patients with anti-MDA-5 had normal CK and near normal muscle histology.

CONCLUSIONS

Muscle biopsy from JDM patients had MSA specific tissue injury patterns. These findings may help improve muscle biopsy diagnosis accuracy and inform personalized treatment of JDM.

ASCL1 regulates neurodevelopmental transcription factors and cell cycle genes in brain tumors of glioma mouse models

Glioblastomas (GBMs) are incurable brain tumors with a high degree of cellular heterogeneity and genetic mutations. Transcription factors that normally regulate neural progenitors and glial development are aberrantly coexpressed in GBM, conferring cancer stem‐like properties to drive tumor progression and therapeutic resistance. However, the functional role of individual transcription factors in GBMs in vivo remains elusive. Here, we demonstrate that the basic‐helix–loop–helix transcription factor ASCL1 regulates transcriptional targets that are central to GBM development, including neural stem cell and glial transcription factors, oncogenic signaling molecules, chromatin modifying genes, and cell cycle and mitotic genes. We also show that the loss of ASCL1 significantly reduces the proliferation of GBMs induced in the brain of a genetically relevant glioma mouse model, resulting in extended survival times. RNA‐seq analysis of mouse GBM tumors reveal that the loss of ASCL1 is associated with downregulation of cell cycle genes, illustrating an important role for ASCL1 in controlling the proliferation of GBM.

Distinct Expression Patterns of Carbonic Anhydrase IX in Clear Cell, Microcystic, and Angiomatous Meningiomas

Clear cell, microcytic, and angiomatous meningiomas are 3 vasculature-rich variants with overlapping morphological features but different prognostic and treatment implications. Distinction between them is not always straightforward. We compared the expression patterns of the hypoxia marker carbonic anhydrase IX (CA-IX) in meningiomas with predominant clear cell (n = 15), microcystic (n = 9), or angiomatous (n = 11) morphologies, as well as 117 cases of other World Health Organization recognized histological meningioma variants. Immunostaining for SMARCE1 protein, whose loss-of-function has been associated with clear cell meningiomas, was performed on all clear cell meningiomas, and selected variants of meningiomas as controls. All clear cell meningiomas showed absence of CA-IX expression and loss of nuclear SMARCE1 expression. All microcystic and angiomatous meningiomas showed diffuse CA-IX immunoreactivity and retained nuclear SMARCE1 expression. In other meningioma variants, CA-IX was expressed in a hypoxia-restricted pattern and was highly associated with atypical features such as necrosis, small cell change, and focal clear cell change. In conclusion, CA-IX may serve as a useful diagnostic marker in differentiating clear cell, microcystic, and angiomatous meningiomas.

Cell-of-origin susceptibility to glioblastoma formation declines with neural lineage restriction

The contribution of lineage identity and differentiation state to malignant transformation is controversial. We have previously shown that adult neural stem and early progenitor cells give origin to glioblastoma. Here we systematically assessed the tumor-initiating potential of adult neural populations at various stages of lineage progression. Cell type-specific tamoxifen-inducible Cre recombinase transgenes were used to target glioblastoma-relevant tumor suppressors Nf1, Trp53 and Pten in late-stage neuronal progenitors, neuroblasts and differentiated neurons. Mutant mice showed cellular and molecular defects demonstrating the impact of tumor suppressor loss, with mutant neurons being the most resistant to early changes associated with tumor development. However, we observed no evidence of glioma formation. These studies show that increasing lineage restriction is accompanied by decreasing susceptibility to malignant transformation, indicating a glioblastoma cell-of-origin hierarchy in which stem cells sit at the apex and differentiated cell types are least susceptible to tumorigenesis.

Remote acoustic sensing as a safety mechanism during exposure of metal implants to alternating magnetic fields

Treatment of prosthetic joint infections often involves multiple surgeries and prolonged antibiotic administration, resulting in a significant burden to patients and the healthcare system. We are exploring a non-invasive method to eradicate biofilm on metal implants utilizing high-frequency alternating magnetic fields (AMF) which can achieve surface induction heating. Although proof-of-concept studies demonstrate the ability of AMF to eradicate biofilm in vitro, there is a legitimate safety concern related to the potential for thermal damage to surrounding tissues when considering heating implanted metal objects. The goal of this study was to explore the feasibility of detecting acoustic emissions associated with boiling at the interface between a metal implant and surrounding soft tissue as a wireless safety sensing mechanism. Acoustic emissions generated during in vitro and in vivo AMF exposures were captured with a hydrophone, and the relationship with surface temperature analyzed. The effect of AMF exposure power, surrounding media composition, implant location within the AMF transmitter, and implant geometry on acoustic detection during AMF therapy was also evaluated. Acoustic emissions were reliably identified in both tissue-mimicking phantom and mouse studies, and their onset coincided with the implant temperature reaching the boiling threshold. The viscosity of the surrounding medium did not impact the production of acoustic emissions; however, emissions were not present when the medium was oil due to the higher boiling point. Results of simulations and in vivo studies suggest that short-duration, high-power AMF exposures combined with acoustic sensing can be used to minimize the amount of thermal damage in surrounding tissues. These studies support the hypothesis that detection of boiling associated acoustic emissions at a metal/tissue interface could serve as a real-time, wireless safety indicator during AMF treatment of biofilm on metallic implants.

Diffuse microvascular C5b-9 deposition is a common feature in muscle and nerve biopsies from diabetic patients

Terminal complement complex deposition in endomysial capillaries detected by a C5b-9 immunostain is considered a diagnostic feature for dermatomyositis. However, we found widespread microvascular C5b-9 reactivity in a substantial subset of muscle biopsies with denervation changes, and in nerve biopsies of peripheral neuropathies, particularly in patients with diabetes. It is unclear whether the presence of C5b-9 deposition signifies active immune-mediated vascular injury that requires immune suppression therapy. We retrospectively identified 63 nerve biopsies in patients with a documented history of diabetes, 26 of which had concomitant muscle biopsies, as well as 54 control nerve biopsies in patients without a documented diabetes history, 18 of which had concomitant muscle biopsies. C5b-9 immunostain was performed on all cases. 87% of the nerve biopsies and 92% of the muscle biopsies from diabetic patients showed microvascular C5b-9 reactivity, compared to 34% and 50% in non-diabetic patients. The differences were statistically significant (p < 0.0001 for nerve and p = 0.002 for muscle). The C5b-9 reactivity was generally proportional to the extent of microvascular sclerosis in diabetic patients, but unrelated to inflammation or vasculitis. C5b-9 deposition in micro-vasculature in both muscle and nerve is therefore a common feature in patients with diabetic neuropathies and may have diagnostic utility. Precaution needs to be taken before using muscle capillary C5b-9 reactivity as evidence of myositis.

Aggressive Behavior in Silent Subtype III Pituitary Adenomas May Depend on Suppression of Local Immune Response: A Whole Transcriptome Analysis

Silent subtype III pituitary adenomas (SS-3) are clinically nonfunctional adenomas that are more aggressive in terms of invasion and risk of recurrence than their conventional null cell counterparts. We previously showed that these tumors can be distinguished by immunohistochemistry based on the identification of a markedly enlarged and fragmented Golgi apparatus. To understand the molecular correlates of differential aggressiveness, we performed whole transcriptome sequencing (RNAseq) on 4 SS-3 and 4 conventional null cell adenomas. The genes that were highly upregulated in all the SS-3 adenomas included 2 secreted proteins involved in the suppression of T-lymphocyte activity, i.e., ARG2 (multiple testing adjusted padj = 1.5 × 10-3) and SEMA3A (padj = 3.3 × 10-3). Highly downregulated genes in all the SS-3 adenomas included HLA-B (padj = 3.3 × 10-6), suggesting reduced antigen presentation by the adenoma to cytotoxic T-cells. Quantitative RT-PCR of these genes performed on the adenoma samples supported the RNAseq results. We also found a relative decrease in the overall concentration of T-lymphocytes in the SS-3 tumors. These results suggest that SS-3 adenomas actively suppress the immune system and raise the possibility that they may be treatable with immune checkpoint inhibitors or nonspecific cancer immunotherapies.

Morin Stain Detects Aluminum-Containing Macrophages in Macrophagic Myofasciitis and Vaccination Granuloma With High Sensitivity and Specificity

Macrophagic myofasciitis (MMF) is an inflammatory condition associated with the intramuscular (i.m.) injection of aluminum adjuvant-containing vaccines. It is clinically characterized by myalgia, weakness, and chronic fatigue and histologically by aggregates of cohesive macrophages with abundant basophilic, periodic acid-Schiff (PAS)-positive, diastase-resistant granules that percolate through the peri- and endomysium without eliciting substantial myofiber damage. The definitive diagnosis of MMF requires demonstration of aluminum within these macrophages. We evaluated the Morin stain, a simple, 2-step histochemical stain for aluminum, as a confirmatory diagnostic tool for MMF. Among 2270 muscle biopsies processed at UTSW between 2010 and 2015, a total of 12 MMF cases and 1 subcutaneous vaccination granuloma case were identified (11 pediatric, 2 adults). With the Morin stain, all 13 cases showed strong granular reactivity within the cytoplasm of macrophages but not in myofibers or connective tissue. Three cases of inflammatory myopathy with abundant macrophages (IMAM), 8 cases of granulomatous inflammation and 23 other deltoid muscle biopsies used as controls were all negative. Morin stain could be used in both formalin-fixed paraffin-embedded and cryostat sections. Thus, Morin stain detects aluminum with high sensitivity and specificity in human muscle and soft tissue and may improve the diagnostic yield of MMF and vaccination granuloma.

Non-Invasive Targeted Peripheral Nerve Ablation Using 3D MR Neurography and MRI-Guided High-Intensity Focused Ultrasound (MR-HIFU): Pilot Study in a Swine Model

PURPOSE

Ultrasound (US)-guided high intensity focused ultrasound (HIFU) has been proposed for noninvasive treatment of neuropathic pain and has been investigated in in-vivo studies. However, ultrasound has important limitations regarding treatment guidance and temperature monitoring. Magnetic resonance (MR)-imaging guidance may overcome these limitations and MR-guided HIFU (MR-HIFU) has been used successfully for other clinical indications. The primary purpose of this study was to evaluate the feasibility of utilizing 3D MR neurography to identify and guide ablation of peripheral nerves using a clinical MR-HIFU system.

METHODS

Volumetric MR-HIFU was used to induce lesions in the peripheral nerves of the lower limbs in three pigs. Diffusion-prep MR neurography and T1-weighted images were utilized to identify the target, plan treatment and immediate post-treatment evaluation. For each treatment, one 8 or 12 mm diameter treatment cell was used (sonication duration 20 s and 36 s, power 160-300 W). Peripheral nerves were extracted < 3 hours after treatment. Ablation dimensions were calculated from thermal maps, post-contrast MRI and macroscopy. Histological analysis included standard H&E staining, Masson's trichrome and toluidine blue staining.

RESULTS

All targeted peripheral nerves were identifiable on MR neurography and T1-weighted images and could be accurately ablated with a single exposure of focused ultrasound, with peak temperatures of 60.3 to 85.7°C. The lesion dimensions as measured on MR neurography were similar to the lesion dimensions as measured on CE-T1, thermal dose maps, and macroscopy. Histology indicated major hyperacute peripheral nerve damage, mostly confined to the location targeted for ablation.

CONCLUSION

Our preliminary results indicate that targeted peripheral nerve ablation is feasible with MR-HIFU. Diffusion-prep 3D MR neurography has potential for guiding therapy procedures where either nerve targeting or avoidance is desired, and may also have potential for post-treatment verification of thermal lesions without contrast injection.

The defining pathology of the new clinical and histopathologic entity ACTA2-related cerebrovascular disease

INTRODUCTION

Smooth muscle cell contraction is an essential function of arteries and relies on the integrity of the actin-myosin apparatus. The tissue-specific α2-smooth muscle actin, encoded by ACTA2, is predominantly expressed in vascular smooth muscle cells. ACTA2 mutations predispose to development of aortic aneurysms and early onset coronary and cerebrovascular disease. Based on arteriographic findings, a distinct cerebrovascular disease has been proposed for ACTA2 heterozygous patients carrying the R179H mutation.

RESULTS

We present the first integrated analysis of a severely compromised patient with the R179H mutation and define the arterial pathology of ACTA2-related cerebrovascular disease. Histologically, striking morphological abnormalities were present in cerebral arteries of all sizes. Massive intimal smooth muscle cell proliferation, fragmentation of the elastic laminae and medial fibromuscular proliferation characterized large arteries whereas prominent vessel wall thickening, fibrosis and smooth muscle cell proliferation were unique changes in small arteries. The medial fibrosis and smooth muscle cell proliferation explain the characteristic radiologic appearance of "straight arteries" and suggest impaired function of mutant smooth muscle cells. Actin three-dimensional molecular modeling revealed critical positioning of R179 at the interface between the two strands of filamentous actin and destabilization of inter-strand bundling by the R179H mutation, explaining the severe associated phenotype.

CONCLUSIONS

In conclusion, these characteristic clinical and pathologic findings confirm ACTA2-related cerebrovascular disease as a new cerebrovascular disorder for which new therapeutic strategies need to be designed.

Adult Lineage-Restricted CNS Progenitors Specify Distinct Glioblastoma Subtypes

A central question in glioblastoma multiforme (GBM) research is the identity of the tumor-initiating cell, and its contribution to the malignant phenotype and genomic state. We examine the potential of adult lineage-restricted progenitors to induce fully penetrant GBM using CNS progenitor-specific inducible Cre mice to mutate Nf1, Trp53, and Pten. We identify two phenotypically and molecularly distinct GBM subtypes governed by identical driver mutations. We demonstrate that the two subtypes arise from functionally independent pools of adult CNS progenitors. Despite histologic identity as GBM, these tumor types are separable based on the lineage of the tumor-initiating cell. These studies point to the cell of origin as a major determinant of GBM subtype diversity.

Hepatic entrapment of esterified cholesterol drives continual expansion of whole body sterol pool in lysosomal acid lipase-deficient mice

Cholesteryl ester storage disease (CESD) results from loss-of-function mutations in LIPA, the gene that encodes lysosomal acid lipase (LAL). Hepatomegaly and deposition of esterified cholesterol (EC) in multiple organs ensue. The present studies quantitated rates of synthesis, absorption, and disposition of cholesterol, and whole body cholesterol pool size in a mouse model of CESD. In 50-day-old lal(-/-) and matching lal(+/+) mice fed a low-cholesterol diet, whole animal cholesterol content equalled 210 and 50 mg, respectively, indicating that since birth the lal(-/-) mice sequestered cholesterol at an average rate of 3.2 mg·day(-1)·animal(-1). The proportion of the body sterol pool contained in the liver of the lal(-/-) mice was 64 vs. 6.3% in their lal(+/+) controls. EC concentrations in the liver, spleen, small intestine, and lungs of the lal(-/-) mice were elevated 100-, 35-, 15-, and 6-fold, respectively. In the lal(-/-) mice, whole liver cholesterol synthesis increased 10.2-fold, resulting in a 3.2-fold greater rate of whole animal sterol synthesis compared with their lal(+/+) controls. The rate of cholesterol synthesis in the lal(-/-) mice exceeded that in the lal(+/+) controls by 3.7 mg·day(-1)·animal(-1). Fractional cholesterol absorption and fecal bile acid excretion were unchanged in the lal(-/-) mice, but their rate of neutral sterol excretion was 59% higher than in their lal(+/+) controls. Thus, in this model, the continual expansion of the body sterol pool is driven by the synthesis of excess cholesterol, primarily in the liver. Despite the severity of their disease, the median life span of the lal(-/-) mice was 355 days.

The G protein α subunit Gαs is a tumor suppressor in Sonic hedgehog-driven medulloblastoma

Medulloblastoma, the most common malignant childhood brain tumor, exhibits distinct molecular subtypes and cellular origins. Genetic alterations driving medulloblastoma initiation and progression remain poorly understood. Herein, we identify GNAS, encoding the G-protein Gsα, as a potent tumor suppressor gene that defines a subset of aggressive Sonic Hedgehog (Shh)-driven human medulloblastomas. Ablation of the single Gnas gene in anatomically-distinct progenitors is sufficient to induce Shh-associated medulloblastomas, which recapitulate their human counterparts. Gsα is highly enriched at the primary cilium of granule neuron precursors and suppresses Shh-signaling by regulating both the cAMP-dependent pathway and ciliary trafficking of Hedgehog pathway components. Elevation of a Gsα effector, cAMP, effectively inhibits tumor cell proliferation and progression in Gnas mutants. Thus, our gain- and loss-of-function studies identify a previously unrecognized tumor suppressor function for Gsα that acts as a molecular link across Shh-group medulloblastomas of disparate cellular and anatomical origins, illuminating G-protein modulation as a potential therapeutic avenue.

High expression of the stem cell marker nestin is an adverse prognostic factor in WHO grade II-III astrocytomas and oligoastrocytomas

Infiltrating astrocytomas and oligoastrocytomas of low to anaplastic grade (WHO grades II and III), in spite of being associated with a wide range of clinical outcomes, can be difficult to subclassify and grade by the current histopathologic criteria. Unlike oligodendrogliomas and anaplastic oligodendrogliomas that can be identified by the 1p/19q codeletion and the more malignant glioblastomas (WHO grade IV astrocytomas) that can be diagnosed solely based on objective features on routine hematoxylin and eosin sections, no such objective criteria exist for the subclassification of grade II-III astrocytomas and oligoastrocytomas (A+OA II-III). In this study, we evaluated the prognostic and predictive value of the stem cell marker nestin in adult A+OA II-III (n = 50) using immunohistochemistry and computer-assisted analysis on tissue microarrays. In addition, the correlation between nestin mRNA level and total survival was analyzed in the NCI Rembrandt database. The results showed that high nestin expression is a strong adverse prognostic factor for total survival (p = 0.0004). The strength of the correlation was comparable to but independent of the isocitrate dehydrogenase 1/2 (IDH 1/2) mutation status. Histopathological grading and subclassification did not correlate significantly with outcome, although the interpretation of this finding is limited by the fact that grade III tumors were treated more aggressively than grade II tumors. These results suggest that nestin level and IDH 1/2 mutation status are strong prognostic features in A+OA II-III and possibly more helpful for treatment planning than routine histopathological variables such as oligodendroglial component (astrocytoma vs. oligoastrocytoma) and WHO grade (grade II vs. III).

TDP-43, an ALS linked protein, regulates fat deposition and glucose homeostasis

The identification of proteins which determine fat and lean body mass composition is critical to better understanding and treating human obesity. TDP-43 is a well-conserved RNA-binding protein known to regulate alternative splicing and recently implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). While TDP-43 knockout mice show early embryonic lethality, post-natal conditional knockout mice show weight loss, fat depletion, and rapid death, suggesting an important role for TDP-43 in regulating energy metabolism. Here we report, that over-expression of TDP-43 in transgenic mice can result in a phenotype characterized by increased fat deposition and adipocyte hypertrophy. In addition, TDP-43 over-expression in skeletal muscle results in increased steady state levels of Tbc1d1, a RAB-GTPase activating protein involved in Glucose 4 transporter (Glut4) translocation. Skeletal muscle fibers isolated from TDP-43 transgenic mice show altered Glut4 translocation in response to insulin and impaired insulin mediated glucose uptake. These results indicate that levels of TDP-43 regulate body fat composition and glucose homeostasis in vivo.

Progressive leg pain and weakness

A 54-year-old man presented with progressive asymmetric leg pain and weakness. He had a history of invasive squamous cell carcinoma that was fully treated 2 years earlier. His leg symptoms progressed relentlessly during several months. Imaging studies demonstrated enhancement of the cauda equina and leptomeninges of the lower spinal cord. Initial cerebrospinal fluid examination showed an elevated protein concentration and lymphocytic pleocytosis with no malignant cells on cytological analysis. There was short-term improvement in symptoms and cerebrospinal fluid abnormalities with intravenous steroids. Two additional cerebrospinal fluid studies showed normal cytological findings, elevated IgG synthesis, and elevated antibody titers to varicella-zoster virus. Over time, the patient worsened, developed cranial neuropathies, and ultimately died. The pathological diagnosis and the approach to the clinical data are discussed.

Using genetics to enable studies on the prevention of Alzheimer's disease

Curing Alzheimer's disease (AD) remains an elusive goal; indeed, it may even prove to be impossible, given the nature of the disease. Although modulating disease progression is an attractive target and will alleviate the burden of the most severe stages, this strategy will not reduce the prevalence of the disease itself. Preventing or (as described in this article) delaying the onset of cognitive impairment and AD will provide the greatest benefit to individuals and society by pushing the onset of disease into the later years of life. Because of the high variability in the age of onset of the disease, AD prevention studies that do not stratify participants by age-dependent disease risk will be operationally challenging, being large in size and of long duration. We present a composite genetic biomarker to stratify disease risk so as to facilitate clinical studies in high-risk populations. In addition, we discuss the rationale for the use of pioglitazone to delay the onset of AD in individuals at high risk.

A calcium channel mutant mouse model of hypokalemic periodic paralysis

Hypokalemic periodic paralysis (HypoPP) is a familial skeletal muscle disorder that presents with recurrent episodes of severe weakness lasting hours to days associated with reduced serum potassium (K+). HypoPP is genetically heterogeneous, with missense mutations of a calcium channel (Ca(V)1.1) or a sodium channel (Na(V)1.4) accounting for 60% and 20% of cases, respectively. The mechanistic link between Ca(V)1.1 mutations and the ictal loss of muscle excitability during an attack of weakness in HypoPP is unknown. To address this question, we developed a mouse model for HypoPP with a targeted Ca(V)1.1 R528H mutation. The Ca(V)1.1 R528H mice had a HypoPP phenotype for which low K+ challenge produced a paradoxical depolarization of the resting potential, loss of muscle excitability, and weakness. A vacuolar myopathy with dilated transverse tubules and disruption of the triad junctions impaired Ca2+ release and likely contributed to the mild permanent weakness. Fibers from the Ca(V)1.1 R528H mouse had a small anomalous inward current at the resting potential, similar to our observations in the Na(V)1.4 R669H HypoPP mouse model. This "gating pore current" may be a common mechanism for paradoxical depolarization and susceptibility to HypoPP arising from missense mutations in the S4 voltage sensor of either calcium or sodium channels.

Somatic gain-of-function mutations in PIK3CA in patients with macrodactyly

Macrodactyly is a discrete congenital anomaly consisting of enlargement of all tissues localized to the terminal portions of a limb, typically within a ‘nerve territory’. The classic terminology for this condition is ‘lipofibromatous hamartoma of nerve’ or Type I macrodactyly. The peripheral nerve, itself, is enlarged both in circumference and in length. It is not related to neurofibromatosis (NF1), nor is it associated with vascular malformations, such as in the recently reported CLOVES syndrome. The specific nerve pathophysiology in this form of macrodactyly has not been well described and a genetic etiology for this specific form of enlargement is unknown. To identify the genetic cause of macrodactyly, we used whole-exome sequencing to identify somatic mutations present in the affected nerve of a single patient. We confirmed a novel mutation in PIK3CA (R115P) present in the patient's affected nerve tissue but not in blood DNA. Sequencing PIK3CA exons identified gain-of-function mutations (E542K, H1047L or H1047R) in the affected tissue of five additional unrelated patients; mutations were absent in blood DNA available from three patients. Immunocytochemistry confirmed AKT activation in cultured cells from the nerve of a macrodactyly patient. Additionally, we found that the most abnormal structure within the involved nerve in a macrodactylous digit is the perineurium, with additional secondary effects on the axon number and size. Thus, isolated congenital macrodactyly is caused by somatic activation of the PI3K/AKT cell-signaling pathway and is genetically and biochemically related to other overgrowth syndromes.

A restricted cell population propagates glioblastoma growth after chemotherapy

Glioblastoma multiforme is the most common primary malignant brain tumour, with a median survival of about one year. This poor prognosis is due to therapeutic resistance and tumour recurrence after surgical removal. Precisely how recurrence occurs is unknown. Using a genetically engineered mouse model of glioma, here we identify a subset of endogenous tumour cells that are the source of new tumour cells after the drug temozolomide (TMZ) is administered to transiently arrest tumour growth. A nestin-ΔTK-IRES-GFP (Nes-ΔTK-GFP) transgene that labels quiescent subventricular zone adult neural stem cells also labels a subset of endogenous glioma tumour cells. On arrest of tumour cell proliferation with TMZ, pulse-chase experiments demonstrate a tumour re-growth cell hierarchy originating with the Nes-ΔTK-GFP transgene subpopulation. Ablation of the GFP+ cells with chronic ganciclovir administration significantly arrested tumour growth, and combined TMZ and ganciclovir treatment impeded tumour development. Thus, a relatively quiescent subset of endogenous glioma cells, with properties similar to those proposed for cancer stem cells, is responsible for sustaining long-term tumour growth through the production of transient populations of highly proliferative cells.

A sodium channel knockin mutant (NaV1.4-R669H) mouse model of hypokalemic periodic paralysis

Hypokalemic periodic paralysis (HypoPP) is an ion channelopathy of skeletal muscle characterized by attacks of muscle weakness associated with low serum K+. HypoPP results from a transient failure of muscle fiber excitability. Mutations in the genes encoding a calcium channel (CaV1.1) and a sodium channel (NaV1.4) have been identified in HypoPP families. Mutations of NaV1.4 give rise to a heterogeneous group of muscle disorders, with gain-of-function defects causing myotonia or hyperkalemic periodic paralysis. To address the question of specificity for the allele encoding the NaV1.4-R669H variant as a cause of HypoPP and to produce a model system in which to characterize functional defects of the mutant channel and susceptibility to paralysis, we generated knockin mice carrying the ortholog of the gene encoding the NaV1.4-R669H variant (referred to herein as R669H mice). Homozygous R669H mice had a robust HypoPP phenotype, with transient loss of muscle excitability and weakness in low-K+ challenge, insensitivity to high-K+ challenge, dominant inheritance, and absence of myotonia. Recovery was sensitive to the Na+/K+-ATPase pump inhibitor ouabain. Affected fibers had an anomalous inward current at hyperpolarized potentials, consistent with the proposal that a leaky gating pore in R669H channels triggers attacks, whereas a reduction in the amplitude of action potentials implies additional loss-of-function changes for the mutant NaV1.4 channels.

Fetal akinesia deformation sequence and neuroaxonal dystrophy without PLA2G6 mutation

We present autopsy findings of a stillborn female infant at 20 to 21 weeks' gestation with neuroaxonal dystrophy. External examination showed features of fetal akinesia deformation sequence. Internal examination showed hypoplasia of the cerebellum, corpus callosum, and optic nerves, as well as nuclear cataracts. Light and electron microscopic examinations showed widespread axonal spheroids in the central and peripheral nervous systems. Gene sequencing failed to reveal PLA2G6 mutations, indicating that fetal neuroaxonal dystrophy presenting as fetal akinesia deformation sequence is genetically distinct from infantile neuroaxonal dystrophy and related disorders. In addition, placental examination showed α-fetoprotein-positive, eosinophilic, globular inclusions in the cytoplasm of a few villous macrophages. The significance of this novel histologic finding is unclear.

Developing pharmacogenetic evidence throughout clinical development

Genetics as a discipline is fundamental for the pharmaceutical industry; it contributes to all therapeutic areas and has an impact throughout the research and development continuum, right up to and including clinical practice. Pharmacogenetics is seen as a significant contributor to increasing the efficiency and effectiveness of pharmaceutical R&D, and it enhances the growing interest in personalized medicine. This article discusses some contemporary issues that influence drug development and examines the potential of pharmacogenetics to reduce the risk and uncertainty that are inherent in the drug development process.

Weekly cyclodextrin administration normalizes cholesterol metabolism in nearly every organ of the Niemann-Pick type C1 mouse and markedly prolongs life

Niemann-Pick type C1 (NPC1) disease arises from a mutation inactivating NPC1 protein that normally moves unesterified cholesterol from the late endosomal/lysosomal complex of cells to the cytosolic compartment for processing. As a result, cholesterol accumulates in every tissue of the body causing liver, lung, and CNS disease. Treatment of the murine model of this disease, the npc1 mouse, s.c. with β-cyclodextrin (4000 mg/kg) one time each week normalized cellular cholesterol metabolism in the liver and most other organs. At the same time, the hepatic dysfunction seen in the untreated npc1 mouse was prevented. The severity of cerebellar neurodegeneration also was ameliorated, although not entirely prevented, and the median lifespan of the animals was doubled. However, in contrast to these other organs, lung showed progressive macrophage infiltration with development of lipoid pneumonitis. These studies demonstrated that weekly cyclodextrin administration overcomes the lysosomal transport defect associated with the NPC1 mutation, nearly normalizes hepatic and whole animal cholesterol pools, and prevents the development of liver disease. Furthermore, this treatment slows cerebellar neurodegeneration but has little or no effect on the development of progressive pulmonary disease.

Progressive motor weakness in transgenic mice expressing human TDP-43

Familial ALS patients with TDP-43 gene mutations and sporadic ALS patients share common TDP-43 neuronal pathology. To delineate mechanisms underlying TDP-43 proteinopathies, transgenic mice expressing A315T, M337V or wild type human TDP-43 were generated. Multiple TDP-43 founders developed a severe early motor phenotype that correlated with TDP-43 levels in spinal cord. Three A315T TDP-43 lines developed later onset paralysis with cytoplasmic ubiquitin inclusions, gliosis and TDP-43 redistribution and fragmentation. The WT TDP-43 mouse line with highest spinal cord expression levels remains asymptomatic, although these mice show spinal cord pathology. One WT TDP-43 line with high skeletal muscle levels of TDP-43 developed a severe progressive myopathy. Over-expression of TDP-43 in vivo is sufficient to produce progressive motor phenotypes by a toxic gain of function paradigm. Transgenic mouse lines expressing untagged mutant and wild type TDP-43 under the same promoter represent a powerful new model system for studying TDP-43 proteinopathies in vivo.

Dystrophinopathy in girls with limb girdle muscular dystrophy phenotype

OBJECTIVES

Limb girdle muscular dystrophy (LGMD) is a diverse group of myopathic disorders characterized by proximal muscle weakness and hyperCKemia. Mutations encoding sarcoglycans and numerous other proteins have been shown to be responsible for most cases. We report a series of girls with a negative family history for boys with Duchenne muscular dystrophy, demonstrating an LGMD phenotype associated with dystrophinopathy.

METHODS

A retrospective chart review of all girls presenting with the LGMD phenotype to our clinic between January 2001 and September 2007 was conducted. Patients 18 years old or younger with dystrophinopathy proven by muscle biopsy and/or gene mutations and a negative family history for affected boys were included in the review.

RESULTS

Five patients, 4 to 10 years of age at presentation, were included in the series. Four had an LGMD phenotype at presentation. All five patients had hyperCKemia, all five patients had gene mutations, and four patients had muscle biopsy consistent with dystrophinopathy.

CONCLUSION

Dystrophinopathy is an important cause of LGMD phenotype in girls and should be considered in the differential diagnosis.

Autoantibody profiles in two patients with non-autoimmune muscle disease implicate a role for gliadin autoreactivity

The objective of this case study was to characterize autoreactivity in two patients with non-autoimmune forms of muscle disease who had positivity for antinuclear antibodies (ANA) and Ro (SSA) autoantibodies. Serum samples from these two patients were applied to an autoantigen protein array with more than 70 specificities and were compared to samples from healthy controls and patients with systemic lupus erythematosus. Both myopathy patients had high levels of gliadin autoreactivity in serum and one patient had an overall autoantibody profile with lupus-like features. The findings suggest that some disorders of muscle that are considered non-autoimmune, may in fact have autoimmune features. Further examination of the role of subclinical gluten autoreactivity in the pathogenesis of myopathy syndromes has the potential to suggest improved approaches to diagnosis and treatment of these conditions.

Abstract C10: Neural stem cells and lineage-restricted progenitors can initiate malignant astrocytoma formation in somatic tumor suppressor mouse models

Malignant astrocytomas are infiltrative and incurable brain tumors. Despite profound therapeutic implications, the identity of the cell (or cells) of origin has not been rigorously determined. We previously reported mouse models based on conditional inactivation of the human astrocytoma-relevant tumor suppressors Nf1, p53, and Pten, wherein through somatic loss of heterozygosity, mutant mice develop tumors with 100% penetrance. In the present study, we show that tumor suppressor inactivation in neural stem cells induces malignant astrocytoma formation. Genetic targeting of lineage-restricted progenitors alone is also sufficient to initiate astrocytomas. We demonstrate in vivo that transformed cells and their progeny undergo infiltration and multi-lineage differentiation in situ during tumor development. Analysis of mutant mice several months prior to advanced disease shows defects in proliferation, differentiation, and migration, suggesting that these are requisite processes prior to tumor formation. Gene expression profiling in pre-symptomatic mutant mice provides insight into the molecular events involved during brain tumor development.

Citation Information: Cancer Res 2009;69(23 Suppl):C10.

Cell of origin and microenvironment contribution for NF1-associated dermal neurofibromas

The tumor predisposition disorder neurofibromatosis type I (NF1) is one of the most common genetic disorders of the nervous system. It is caused by mutations in the Nf1 tumor-suppressor gene, which encodes a GTPase-activating protein (GAP) that negatively regulates p21-RAS. Development of malignant nerve tumors and neurofibromas occurs frequently in NF1. However, little is known about the molecular mechanisms mediating the initiation and progression of these complex tumors, or the identity of the specific cell type that gives rise to dermal or cutaneous neurofibromas. In this study, we identify a population of stem/progenitor cells residing in the dermis termed skin-derived precursors (SKPs) that, through loss of Nf1, form neurofibromas. We propose that SKPs, or their derivatives, are the cell of origin of dermal neurofibroma. We also provide evidence that additional signals from nonneoplastic cells in the tumor microenvironment play essential roles in neurofibromagenesis.

Risk prediction of prevalent diabetes in a Swiss population using a weighted genetic score--the CoLaus Study

AIMS/HYPOTHESIS

Several susceptibility genes for type 2 diabetes have been discovered recently. Individually, these genes increase the disease risk only minimally. The goals of the present study were to determine, at the population level, the risk of diabetes in individuals who carry risk alleles within several susceptibility genes for the disease and the added value of this genetic information over the clinical predictors.

METHODS

We constructed an additive genetic score using the most replicated single-nucleotide polymorphisms (SNPs) within 15 type 2 diabetes-susceptibility genes, weighting each SNP with its reported effect. We tested this score in the extensively phenotyped population-based cross-sectional CoLaus Study in Lausanne, Switzerland (n = 5,360), involving 356 diabetic individuals.

RESULTS

The clinical predictors of prevalent diabetes were age, BMI, family history of diabetes, WHR, and triacylglycerol/HDL-cholesterol ratio. After adjustment for these variables, the risk of diabetes was 2.7 (95% CI 1.8-4.0, p = 0.000006) for individuals with a genetic score within the top quintile, compared with the bottom quintile. Adding the genetic score to the clinical covariates improved the area under the receiver operating characteristic curve slightly (from 0.86 to 0.87), yet significantly (p = 0.002). BMI was similar in these two extreme quintiles.

CONCLUSIONS/INTERPRETATION

In this population, a simple weighted 15 SNP-based genetic score provides additional information over clinical predictors of prevalent diabetes. At this stage, however, the clinical benefit of this genetic information is limited.

Malignant astrocytomas originate from neural stem/progenitor cells in a somatic tumor suppressor mouse model

Malignant astrocytomas are infiltrative and incurable brain tumors. Despite profound therapeutic implications, the identity of the cell (or cells) of origin has not been rigorously determined. We previously reported mouse models based on conditional inactivation of the human astrocytoma-relevant tumor suppressors p53, Nf1, and Pten, wherein through somatic loss of heterozygosity, mutant mice develop tumors with 100% penetrance. In the present study, we show that tumor suppressor inactivation in neural stem/progenitor cells is both necessary and sufficient to induce astrocytoma formation. We demonstrate in vivo that transformed cells and their progeny undergo infiltration and multilineage differentiation during tumorigenesis. Tumor suppressor heterozygous neural stem/progenitor cultures from presymptomatic mice show aberrant growth advantage and altered differentiation, thus identifying a pretumorigenic cell population.

Pten haploinsufficiency accelerates formation of high-grade astrocytomas

We previously reported that central nervous system (CNS) inactivation of Nf1 and p53 tumor suppressor genes in mice results in the development of low-grade to high-grade progressive astrocytomas. When the tumors achieve high grade, they are frequently accompanied by Akt activation, reminiscent of the frequent association of PTEN mutations in human high-grade glioma. In the present study, we introduced CNS heterozygosity of Pten into the Nf1/p53 astrocytoma model. Resulting mice had accelerated morbidity, shortened survival, and full penetrance of high-grade astrocytomas. Haploinsufficiency of Pten accelerated formation of grade 3 astrocytomas, whereas loss of Pten heterozygosity and Akt activation coincided with progression into grade 4 tumors. These data suggest that successive loss of each Pten allele may contribute to de novo formation of high-grade astrocytoma and progression into glioblastoma, respectively, thus providing insight into the etiology of primary glioblastoma. The presence of ectopically migrating neural stem/progenitor lineage cells in presymptomatic Pten-deficient mutant brains supports the notion that these tumors may arise from stem/progenitor cells.

Induction of abnormal proliferation by nonmyelinating schwann cells triggers neurofibroma formation

Recent evidence suggests that alterations in the self-renewal program of stem/progenitor cells can cause tumorigenesis. By utilizing genetically engineered mouse models of neurofibromatosis type 1 (NF1), we demonstrated that plexiform neurofibroma, the only benign peripheral nerve sheath tumor with potential for malignant transformation, results from Nf1 deficiency in fetal stem/progenitor cells of peripheral nerves. Surprisingly, this did not cause hyperproliferation or tumorigenesis in early postnatal period. Instead, peripheral nerve development appeared largely normal in the absence of Nf1 except for abnormal Remak bundles, the nonmyelinated axon-Schwann cell unit, identified in postnatal mutant nerves. Subsequent degeneration of abnormal Remak bundles was accompanied by initial expansion of nonmyelinating Schwann cells. We suggest abnormally differentiated Remak bundles as a cell of origin for plexiform neurofibroma.

Creation and characterization of E-selectin- and VCAM-1-deficient mice

A variety of adhesion molecules have been identified which mediate the interaction of leukocytes with endothelial cells. In order to define the role of individual molecules in inflammation we have produced lines of mice which are deficient in the synthesis of specific adhesion molecules. Null mutations were introduced into the genes encoding E-selectin or vascular cell adhesion molecule-1 (VCAM-1) in embryonic stem cells and these cells were used to produce lines of mice carrying the mutation. E-selectin-deficient mice were viable and exhibited no developmental defects. The roles of E- and P-selectin in the influx of neutrophils were examined using these mice. The data suggest that the two selectins are functionally redundant in mediating neutrophil emigration in a model of chemically induced peritonitis. VCAM-1-deficient mice are not viable. Analysis of VCAM-1 gene expression in wild-type embryos and phenotypic analysis of VCAM-1 -/- embryos suggests that VCAM-1 is required for development of the extraembryonic circulatory system and the embryonic heart.

Inactivation of NF1 in CNS causes increased glial progenitor proliferation and optic glioma formation

The gene responsible for neurofibromatosis type 1 (NF1) encodes a tumor suppressor that functions as a negative regulator of the Ras proto-oncogene. Individuals with germline mutations in NF1 are predisposed to the development of benign and malignant tumors of the peripheral and central nervous system (CNS). Children with this disease suffer a high incidence of optic gliomas, a benign but potentially debilitating tumor of the optic nerve; and an increased incidence of malignant astrocytoma, reactive astrogliosis and intellectual deficits. In the present study, we have sought insight into the molecular and cellular basis of NF1-associated CNS pathologies. We show that mice genetically engineered to lack NF1 in CNS exhibit a variety of defects in glial cells. Primary among these is a developmental defect resulting in global reactive astrogliosis in the adult brain and increased proliferation of glial progenitor cells leading to enlarged optic nerves. As a consequence, all of the mutant optic nerves develop hyperplastic lesions, some of which progress to optic pathway gliomas. These data point to hyperproliferative glial progenitors as the source of the optic tumors and provide a genetic model for NF1-associated astrogliosis and optic glioma.

The Werner Syndrome Helicase Is a Cofactor for HIV-1 Long Terminal Repeat Transactivation and Retroviral Replication

The Werner syndrome helicase (WRN) participates in DNA replication, double strand break repair, telomere maintenance, and p53 activation. Mutations of wrn cause Werner syndrome (WS), an autosomal recessive premature aging disorder associated with cancer predisposition, atherosclerosis, and other aging related symptoms. Here, we report that WRN is a novel cofactor for HIV-1 replication. Immortalized human WRN(-/-) WS fibroblasts, lacking a functional wrn gene, are impaired for basal and Tat-activated HIV-1 transcription. Overexpression of wild-type WRN transactivates the HIV-1 long terminal repeat (LTR) in the absence of Tat, and WRN cooperates with Tat to promote high-level LTR transactivation. Ectopic WRN induces HIV-1 p24(Gag) production and retroviral replication in HIV-1-infected H9(HIV-1IIIB) lymphocytes. A dominant-negative helicase-minus mutant, WRN(K577M), inhibits LTR transactivation and HIV-1 replication. Inhibition of endogenous WRN, through co-expression of WRN(K577M), diminishes recruitment of p300/CREB-binding protein-associated factor (PCAF) and positive transcription elongation factor b (P-TEFb) to Tat/transactivation response-RNA complexes, and immortalized WRN(-/-) WS fibroblasts exhibit comparable defects in recruitment of PCAF and P-TEFb to the HIV-1 LTR. Our results demonstrate that WRN is a novel cellular cofactor for HIV-1 replication and suggest that the WRN helicase participates in the recruitment of PCAF/P-TEFb-containing transcription complexes. WRN may be a plausible target for antiretroviral therapy.

Neuropathy associated with hyperoxaluria: improvement after combined renal and liver transplantations

Little is known about oxaluria-associated neuropathy, and no effective treatments have been described. We report two patients with clinically severe and progressive sensorimotor polyneuropathy associated with oxaluria. Electrodiagnostic testing and sural nerve histopathology revealed evidence of severe axon loss and demyelination. In addition, birefringent crystalline deposits were identified within endoneurial and perineurial blood vessel walls, axon cylinders, and perimysial blood vessel walls. Electron probe microscopy confirmed that calcium (consistent with calcium oxalate) was a major constituent of the crystals. Both patients had substantial improvement in neuropathic signs and symptoms after kidney and liver transplantations despite no prior improvement with hemodialysis. Our results confirm previous reports of a mixed axonal and demyelinating neuropathy with calcium oxalate deposition in association with oxaluria. In addition, our findings suggest that renal and liver transplantation may be potential treatments for the associated neuropathy.

Neurocytoma-like neoplasm of the thoracic spine in a 15-month-old child presenting with diffuse leptomeningeal dissemination and communicating hydrocephalus. Case report

This unusual mixed glioneuronal neoplasm of the spine resembling central neurocytoma is only the second reported example of a neoplasm of this type involving the spinal cord and is, seemingly, the first to present with diffuse leptomeningeal dissemination and communicating hydrocephalus. This 15-month-old boy presented with somnolence, bilateral sixth nerve palsy, and lower-extremity weakness and was found to harbor a primary neoplasm within the thoracic spine and associated syrinx, widespread leptomeningeal dissemination, and communicating hydrocephalus. The patient underwent cerebrospinal fluid shunt placement, thoracic laminectomy for tumor debulking and biopsy, chemotherapy, and radiation therapy to the neuraxis. Immunohistochemically, the tumor was marked by evidence of mixed glial (glial fibrillary acidic protein-positive) and neuronal (synaptophysin-positive) differentiation. Mitotic activity was inconspicuous. No areas of vascular proliferation, necrosis, or marked nuclear pleomorphism were noted. Mixed glioneuronal neoplasms are a heterogeneous group of tumors whose biological potential remains incompletely defined. The present case illustrates the reality that some of these neoplasms can be clinically aggressive, despite comparatively bland histological features. The authors' goal is to acquaint neurosurgeons with the expanding spectrum of mixed glioneuronal neoplasms and with the potential of some of these lesions to pursue an aggressive clinical course.