CD8 cytotoxic T-cell infiltrates and cellular damage in the hypothalamus in human obesity

Rare cases of paraneoplastic obesity in children suggest sporadic obesity might also arise from an adaptive immune cell-mediated mechanism. Since the hypothalamus is a central regulator of feeding behavior and energy expenditure, we quantified lymphocytic inflammation in this region in a cohort of obese and non-obese human post-mortem brains. We report that CD8-positive cytotoxic T-cells are increased in hypothalamic median eminence/arcuate nucleus (ME/Arc) and bed nucleus of the stria terminalis in 40% of obese compared to non-obese patients, but not in other hypothalamic nuclei or brain regions. CD8 T-cells were most abundant in individuals with concurrent obesity and diabetes. Markers of cytotoxic T-cell induced damage, activated caspase 3 and poly-ADP ribose, were also elevated in the ME/Arc of obese patients. To provoke CD8 cytotoxic T-cell infiltrates in ventromedial region of hypothalamus in mice we performed stereotactic injections of an adeno-associated virus expressing immunogenic green fluorescent protein or saline. AAV but not saline injections triggered hypothalamic CD8 T-cell infiltrates associated with a rapid weight gain in mice recapitulating the findings in human obesity. This is the first description of the neuropathology of human obesity and when combined with its reconstitution in a mouse model suggests adaptive immunity may drive as much as 40% of the human condition.

Fatal Post COVID mRNA-Vaccine Associated Cerebral Ischemia

Background

Venous thromboses have been linked to several COVID-19 vaccines, but there is limited information on the Moderna vaccine's effect on the risk of arterial thrombosis. Here we describe a case of post-Moderna COVID-19 vaccination arterial infarct with vaccine-associated diffuse cortical edema that was complicated by refractory intracranial hypertension.

Case Summary

24 hrs after receiving her first dose of the Moderna COVID-19 vaccine, a 30-year-old female developed severe headache. Three weeks later she was admitted with subacute headache and confusion. Imaging initially showed scattered cortical thrombosis with an elevated opening pressure on lumbar puncture. An external ventricular drain was placed, but she continued to have elevated intracranial pressure. Ultimately, she required a hemicraniectomy, but intractable cerebral edema resulted in her death. Pathology was consistent with thrombosis and associated inflammatory response.

Conclusion

Though correlational, her medical team surmised that the mRNA vaccine may have contributed to this presentation. The side effects of COVID-19 infection and vaccination are still incompletely understood. Though complications are rare, clinicians should be aware of presentations like this one.

UBE3A and transsynaptic complex NRXN1-CBLN1-GluD1 in a hypothalamic VMHvl-arcuate feedback circuit regulates aggression

The circuit origins of aggression in autism spectrum disorder remain undefined. Here we report Tac1-expressing glutamatergic neurons in ventrolateral division of ventromedial hypothalamus (VMHvl) drive intermale aggression. Aggression is increased due to increases of Ube3a gene dosage in the VMHvl neurons when modeling autism due to maternal 15q11-13 triplication. Targeted deletion of increased Ube3a copies in VMHvl reverses the elevated aggression adult mice. VMHvl neurons form excitatory synapses onto hypothalamic arcuate nucleus AgRP/NPY neurons through a NRXN1-CBLN1-GluD1 transsynaptic complex and UBE3A impairs this synapse by decreasing Cbln1 gene expression. Exciting AgRP/NPY arcuate neurons leads to feedback inhibition of VMHvl neurons and inhibits aggression. Asymptomatic increases of UBE3A synergize with a heterozygous deficiency of presynaptic Nrxn1 or postsynaptic Grid1 (both ASD genes) to increase aggression. Targeted deletions of Grid1 in arcuate AgRP neurons impairs the VMHvl to AgRP/NPY neuron excitatory synapses while increasing aggression. Chemogenetic/optogenetic activation of arcuate AgRP/NPY neurons inhibits VMHvl neurons and represses aggression. These data reveal that multiple autism genes converge to regulate the VMHvl-arcuate AgRP/NPY glutamatergic synapse. The hypothalamic circuitry implicated by these data suggest impaired excitation of AgRP/NPY feedback inhibitory neurons may explain the increased aggression behavior found in genetic forms of autism.

Opioid analgesia in necrotizing pancreatitis: Incidence and timing of a hidden crisis

BACKGROUND

Rates of opioid usage during necrotizing pancreatitis (NP) disease course are unknown. We hypothesized that a significant number of NP patients were prescribed opioid analgesics chronically.

METHODS

Single institution IRB-approved retrospective study of 230 NP patients treated between 2015 and 2019.

RESULTS

Data were available for 198/230 (86%) patients. 166/198 (84%) were discharged from their index hospitalization with a prescription for an opioid. At the first clinic visit following hospitalization, 110/182 (60%) were using opioids. Six months after disease onset, 72/163 (44%) continued to require opioids. At disease resolution, 38/144 (26%) patients remained on opioid medications. The rate of active opioid prescriptions at six months after disease onset declined throughout the period studied from 68% in 2015 to 39% in 2019.

CONCLUSIONS

Opioid prescriptions are common in NP. Despite decline over time, 1 in 4 patients remain on opioids at disease resolution. These data identify an opportunity to adjust analgesic prescription practice in NP patients.

Enhanced recovery after cardiac surgery protocol reduces perioperative opioid use

Objective

Enhanced Recovery After Surgery protocols are relatively new in cardiac surgery. Enhanced Recovery After Surgery addresses perioperative analgesia by implementing multimodal pain control regimens that include both opioid and nonopioid components. We investigated the effects of an Enhanced Recovery After Surgery protocol at our institution on postoperative outcomes with particular focus on analgesia.

Methods

Single-center retrospective study comparing perioperative opioid use before and after implementation of an Enhanced Recovery After Surgery protocol at our institution. Subjects were divided into 2 cohorts: Enhanced Recovery After Surgery (study group from year 2020) and pre-Enhanced Recovery After Surgery (control group from year 2018). Baseline and perioperative variables including total opioid use from the day of surgery to postoperative day 5 were collected. Opioid use was calculated as morphine milligram equivalents and compared between the 2 cohorts.

Results

A total of 466 patients were included: 250 in the Enhanced Recovery After Surgery group and 216 in the pre-Enhanced Recovery After Surgery group. Both groups had similar baseline characteristics, but the Enhanced Recovery After Surgery group had significantly more subjects with intravenous drug use history (P < .0001), endocarditis (P < .0001), and liver disease (P = .007) compared with the pre-Enhanced Recovery After Surgery group. Every day from the day of surgery to postoperative day 5, the Enhanced Recovery After Surgery group had significant reduction (57%) in opioid use compared with the pre-Enhanced Recovery After Surgery group. Total opioid use for the entire length of stay was 259 morphine milligram equivalents in the Enhanced Recovery After Surgery group versus 452 morphine milligram equivalents in the pre-Enhanced Recovery After Surgery group (P < .0001). Subgroup analysis of subjects with intravenous drug use history did not demonstrate a significant reduction in opioid use.

Conclusions

Enhanced Recovery After Surgery protocols with an emphasis on multimodal pain management throughout perioperative care are associated with a significant reduction in the postoperative use of opioid analgesics.

Circadian Rhythms and Sleep Are Dependent Upon Expression Levels of Key Ubiquitin Ligase Ube3a

Normal neurodevelopment requires precise expression of the key ubiquitin ligase gene Ube3a. Comparing newly generated mouse models for Ube3a downregulation (models of Angelman syndrome) vs. Ube3a upregulation (models for autism), we find reciprocal effects of Ube3a gene dosage on phenotypes associated with circadian rhythmicity, including the amount of locomotor activity. Consistent with results from neurons in general, we find that Ube3a is imprinted in neurons of the suprachiasmatic nuclei (SCN), the pacemaking circadian brain locus, despite other claims that SCN neurons were somehow exceptional to these imprinting rules. In addition, Ube3a-deficient mice lack the typical drop in wake late in the dark period and have blunted responses to sleep deprivation. Suppression of physical activity by light in Ube3a-deficient mice is not due to anxiety as measured by behavioral tests and stress hormones; quantification of stress hormones may provide a mechanistic link to sleep alteration and memory deficits caused by Ube3a deficiency, and serve as an easily measurable biomarker for evaluating potential therapeutic treatments for Angelman syndrome. We conclude that reduced Ube3a gene dosage affects not only neurodevelopment but also sleep patterns and circadian rhythms.

Tumor-Derived Cell Culture Model for the Investigation of Meningioma Biology

Meningioma is the most common primary central nervous system tumor. Although mostly nonmalignant, meningioma can cause serious complications by mass effect and vasogenic edema. While surgery and radiation improve outcomes, not all cases can be treated due to eloquent location. Presently no medical treatment is available to slow meningioma growth owing to incomplete understanding of the underlying pathology, which in turn is due to the lack of high-fidelity tissue culture and animal models. We propose a simple and rapid method for the establishment of meningioma tumor-derived primary cultures. These cells can be maintained in culture for a limited time in serum-free media as spheres and form adherent cultures in the presence of 4% fetal calf serum. Many of the tissue samples show expression of the lineage marker PDG2S, which is typically retained in matched cultured cells, suggesting the presence of cells of arachnoid origin. Furthermore, nonarachnoid cells including vascular endothelial cells are also present in the cultures in addition to arachnoid cells, potentially providing a more accurate tumor cell microenvironment, and thus making the model more relevant for meningioma research and high-throughput drug screening.

Optimal Timing of Administration of Direct-acting Antivirals for Patients With Hepatitis C-associated Hepatocellular Carcinoma Undergoing Liver Transplantation

OBJECTIVE

To investigate the optimal timing of direct acting antiviral (DAA) administration in patients with hepatitis C-associated hepatocellular carcinoma (HCC) undergoing liver transplantation (LT).

SUMMARY OF BACKGROUND DATA

In patients with hepatitis C (HCV) associated HCC undergoing LT, the optimal timing of direct-acting antivirals (DAA) administration to achieve sustained virologic response (SVR) and improved oncologic outcomes remains a topic of much debate.

METHODS

The United States HCC LT Consortium (2015-2019) was reviewed for patients with primary HCV-associated HCC who underwent LT and received DAA therapy at 20 institutions. Primary outcomes were SVR and HCC recurrence-free survival (RFS).

RESULTS

Of 857 patients, 725 were within Milan criteria. SVR was associated with improved 5-year RFS (92% vs 77%, P < 0.01). Patients who received DAAs pre-LT, 0-3 months post-LT, and ≥3 months post-LT had SVR rates of 91%, 92%, and 82%, and 5-year RFS of 93%, 94%, and 87%, respectively. Among 427 HCV treatment-naïve patients (no previous interferon therapy), patients who achieved SVR with DAAs had improved 5-year RFS (93% vs 76%, P < 0.01). Patients who received DAAs pre-LT, 0-3 months post-LT, and ≥3 months post-LT had SVR rates of 91%, 93%, and 78% (P < 0.01) and 5-year RFS of 93%, 100%, and 83% (P = 0.01).

CONCLUSIONS

The optimal timing of DAA therapy appears to be 0 to 3 months after LT for HCV-associated HCC, given increased rates of SVR and improved RFS. Delayed administration after transplant should be avoided. A prospective randomized controlled trial is warranted to validate these results.

Autism BrainNet: A Collaboration Between Medical Examiners, Pathologists, Researchers, and Families to Advance the Understanding and Treatment of Autism Spectrum Disorder

CONTEXT.—

Autism spectrum disorder is a neurodevelopmental condition that affects over 1% of the population worldwide. Developing effective preventions and treatments for autism will depend on understanding the neuropathology of the disorder. While evidence from magnetic resonance imaging indicates altered development of the autistic brain, it lacks the resolution needed to identify the cellular and molecular underpinnings of the disorder. Postmortem studies of human brain tissue currently represent the only viable option to pursuing these critical studies. Historically, the availability of autism brain tissue has been extremely limited.

OBJECTIVE.—

To overcome this limitation, Autism BrainNet, funded by the Simons Foundation, was formed as a network of brain collection sites that work in a coordinated fashion to develop a library of human postmortem brain tissues for distribution to researchers worldwide. Autism BrainNet has collection sites (or Nodes) in California, Texas, and Massachusetts; affiliated, international Nodes are located in Oxford, England and Montreal, Quebec, Canada.

DATA SOURCES.—

Pubmed, Autism BrainNet.

CONCLUSIONS.—

Because the death of autistic individuals is often because of an accident, drowning, suicide, or sudden unexpected death in epilepsy, they often are seen in a medical examiner's or coroner's office. Yet, autism is rarely considered when evaluating the cause of death. Advances in our understanding of chronic traumatic encephalopathy have occurred because medical examiners and neuropathologists questioned whether a pathologic change might exist in individuals who played contact sports and later developed severe behavioral problems. This article highlights the potential for equally significant breakthroughs in autism arising from the proactive efforts of medical examiners, pathologists, and coroners in partnership with Autism BrainNet.

Postmortem Analyses in a Patient With Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD): II. Histological, Lipid, and Gene Expression Outcomes in Regional Brain Tissue

This study has extended previous metabolic measures in postmortem tissues (frontal and parietal lobes, pons, cerebellum, hippocampus, and cerebral cortex) obtained from a 37-year-old male patient with succinic semialdehyde dehydrogenase deficiency (SSADHD) who expired from SUDEP (sudden unexplained death in epilepsy). Histopathologic characterization of fixed cortex and hippocampus revealed mild to moderate astrogliosis, especially in white matter. Analysis of total phospholipid mass in all sections of the patient revealed a 61% increase in cortex and 51% decrease in hippocampus as compared to (n = 2-4) approximately age-matched controls. Examination of mass and molar composition of major phospholipid classes showed decreases in phospholipids enriched in myelin, such as phosphatidylserine, sphingomyelin, and ethanolamine plasmalogen. Evaluation of gene expression (RT² Profiler PCR Arrays, GABA, glutamate; Qiagen) revealed dysregulation in 14/15 GABA_A receptor subunits in cerebellum, parietal, and frontal lobes with the most significant downregulation in ∊, θ, ρ1, and ρ2 subunits (7.7-9.9-fold). GABA_B receptor subunits were largely unaffected, as were ionotropic glutamate receptors. The metabotropic glutamate receptor 6 was consistently downregulated (maximum 5.9-fold) as was the neurotransmitter transporter (GABA), member 13 (maximum 7.3-fold). For other genes, consistent dysregulation was seen for interleukin 1β (maximum downregulation 9.9-fold) and synuclein α (maximal upregulation 6.5-fold). Our data provide unique insight into SSADHD brain function, confirming astrogliosis and lipid abnormalities previously observed in the null mouse model while highlighting long-term effects on GABAergic/glutamatergic gene expression in this disorder.

Genotype and defects in microtubule-based motility correlate with clinical severity in KIF1A-associated neurological disorder

KIF1A-associated neurological disorder (KAND) encompasses a group of rare neurodegenerative conditions caused by variants in KIF1A, a gene that encodes an anterograde neuronal microtubule (MT) motor protein. Here we characterize the natural history of KAND in 117 individuals using a combination of caregiver or self-reported medical history, a standardized measure of adaptive behavior, clinical records, and neuropathology. We developed a heuristic severity score using a weighted sum of common symptoms to assess disease severity. Focusing on 100 individuals, we compared the average clinical severity score for each variant with in silico predictions of deleteriousness and location in the protein. We found increased severity is strongly associated with variants occurring in protein regions involved with ATP and MT binding: the P loop, switch I, and switch II. For a subset of variants, we generated recombinant proteins, which we used to assess transport in vivo by assessing neurite tip accumulation and to assess MT binding, motor velocity, and processivity using total internal reflection fluorescence microscopy. We find all modeled variants result in defects in protein transport, and we describe three classes of protein dysfunction: reduced MT binding, reduced velocity and processivity, and increased non-motile rigor MT binding. The rigor phenotype is consistently associated with the most severe clinical phenotype, while reduced MT binding is associated with milder clinical phenotypes. Our findings suggest the clinical phenotypic heterogeneity in KAND likely reflects and parallels diverse molecular phenotypes. We propose a different way to describe KAND subtypes to better capture the breadth of disease severity.

T lymphocytes and cytotoxic astrocyte blebs correlate across autism brains

OBJECTIVE

Autism spectrum disorder (ASD) affects 1 in 59 children, yet except for rare genetic causes, the etiology in most ASD remains unknown. In the ASD brain, inflammatory cytokine and transcript profiling shows increased expression of genes encoding mediators of the innate immune response. We evaluated postmortem brain tissue for adaptive immune cells and immune cell-mediated cytotoxic damage that could drive this innate immune response in the ASD brain.

METHODS

Standard neuropathology diagnostic methods including histology and immunohistochemistry were extended with automated image segmentation to quantify identified pathologic features in the postmortem brains.

RESULTS

We report multifocal perivascular lymphocytic cuffs contain increased numbers of lymphocytes in ~65% of ASD compared to control brains in males and females, across all ages, in most brain regions, and in white and gray matter, and leptomeninges. CD3+ T lymphocytes predominate over CD20+ B lymphocytes and CD8+ over CD4+ T lymphocytes in ASD brains. Importantly, the perivascular cuff lymphocyte numbers correlate to the quantity of astrocyte-derived round membranous blebs. Membranous blebs form as a cytotoxic reaction to lymphocyte attack. Consistent with multifocal immune cell-mediated injury at perivascular cerebrospinal fluid (CSF)-brain barriers, a subset of white matter vessels have increased perivascular space (with jagged contours) and collagen in ASD compared to control brains. CSF-brain barrier pathology is also evident at cerebral cortex pial and ventricular ependymal surfaces in ASD.

INTERPRETATION

The findings suggest dysregulated cellular immunity damages astrocytes at foci along the CSF-brain barrier in ASD. ANN NEUROL 2019;86:885-898.

Lymphocytic ganglionitis leading to megacolon in lymphocyte-rich glioblastoma

T-cell immune attack of cancer cells underlies the efficacy of immune checkpoint inhibitors in many cancer subtypes, but is not yet well established in the primary brain cancer glioblastoma. Immune checkpoint inhibitor treatments that disinhibit the immune system to enhance immune clearance of cancer have in rare cases resulted in T-cell attack of peripheral ganglia causing lymphocytic ganglionitis. In glioblastoma, lymphocytic ganglionitis has not been reported and checkpoint inhibitors are not routinely used. Here we report a case of glioblastoma not treated with checkpoint inhibitors in which the primary tumor and peripheral ganglia of the celiac and sympathetic chains, as well as myenteric plexus, are infiltrated by CD8⁺ cytotoxic T-cells. In addition to the marked lymphocytic infiltrates, this case is also notable for an unusually long survival (8 years) after diagnosis with glioblastoma, but an ultimately fatal outcome due to ileus. The findings suggest T-cell immune attack of glioblastoma may prolong survival, but also suggest T-cell autoimmune diseases such as lymphocytic ganglionitis could become a risk with the future use of immune-targeted therapies for glioblastoma.

DEPDC5 takes a second hit in familial focal epilepsy

Loss-of-function mutations in a single allele of the gene encoding DEP domain-containing 5 protein (DEPDC5) are commonly linked to familial focal epilepsy with variable foci; however, a subset of patients presents with focal cortical dysplasia that is proposed to result from a second-hit somatic mutation. In this issue of the JCI, Ribierre and colleagues provide several lines of evidence to support second-hit DEPDC5 mutations in this disorder. Moreover, the authors use in vivo, in utero electroporation combined with CRISPR-Cas9 technology to generate a murine model of the disease that recapitulates human manifestations, including cortical dysplasia-like changes, focal seizures, and sudden unexpected death. This study provides important insights into familial focal epilepsy and provides a preclinical model for evaluating potential therapies.

Autism BrainNet: A network of postmortem brain banks established to facilitate autism research

Autism spectrum disorder (ASD or autism) is a neurodevelopmental condition that affects over 1% of the population worldwide. Developing effective preventions and treatments for autism will depend on understanding the genetic perturbations and underlying neuropathology of the disorder. While evidence from magnetic resonance imaging and other noninvasive techniques points to altered development and organization of the autistic brain, these tools lack the resolution for identifying the cellular and molecular underpinnings of the disorder. Postmortem studies of high-quality human brain tissue currently represent the only viable option to pursuing these types of studies. However, the availability of high-quality ASD brain tissue has been extremely limited. Here we describe the establishment of a privately funded tissue bank, Autism BrainNet, a network of brain collection sites that work in a coordinated fashion to develop an adequate library of human postmortem brain tissues. Autism BrainNet was initiated as a collaboration between the Simons Foundation and Autism Speaks, and is currently funded by the Simons Foundation Autism Research Initiative. Autism BrainNet has collection sites (nodes) in California, Texas, New York, and Massachusetts; an affiliated, international node is located in Oxford, England. All donations to this network become part of a consolidated pool of tissue that is distributed to qualified investigators worldwide to carry out autism research. An essential component of this program is a widespread outreach program that highlights the need for postmortem brain donations to families affected by autism, led by the Autism Science Foundation. Challenges include an outreach campaign that deals with a disorder beginning in early childhood, collecting an adequate number of donations to deal with the high level of biologic heterogeneity of autism, and preparing this limited resource for optimal distribution to the greatest number of investigators.

Tanycytic ependymoma of the brain stem, presentations of rare cystic disease variants and review of literature

INTRODUCTION

The aim of this paper was to systematically review the evidence linking Propionibacterium acnes (P. acnes) with the develop Tanycytic ependymoma (tcE) is a rare variant of ependymoma and management guidelines for patients with this disease are not established.

EVIDENCE ACQUISITION

We performed a systematic search on Pubmed complimented by hand-searching citation lists to identify patients with pathologically confirmed tcE. Signs and symptoms, radiological and specific pathological findings as well as reported treatment modalities and outcomes were recorded and analyzed.

EVIDENCE SYNTHESIS

Fifty-one studies involving a total of 77 patients were identified and included in this review. Most cases of tcEs occurred in the spinal cord (50.6%), followed by lesions located in upper intracranial sites (36.4%) and only a few at the cervicomedullary junction (3.9%). Female to male ratio was calculated as about 1:1.5, with a mean age at diagnosis of approximately 36.1±18 years. Complete resection of the tumor without further additional therapy was the treatment of choice in most cases (63.6%), radiotherapy was considered in 10 cases (13.0%). In 18 reported cases of tcE (23.4%), the treatment was not documented. Defined follow-up periods for patients with tcE were only documented in 44 cases (57.1%), the mean follow-up was 22.3 months. 36 cases (46.8%) had no recurrence of tumor after treatment (26 months mean follow-up).

CONCLUSIONS

This comprehensive review on tcEs supports surgery as the initial treatment modality of choice. Radiotherapy can be considered when total gross resection cannot be achieved and allows for prolonged progression-free survival. Given the benign nature of this subtype of ependymoma, aggressive treatment such as chemotherapy is usually not indicated.

Hypersociability in the Angelman syndrome mouse model

Deletions and reciprocal triplications of the human chromosomal 15q11-13 region cause two distinct neurodevelopmental disorders. Maternally-derived deletions or inactivating mutations of UBE3A, a 15q11-13 gene expressed exclusively from the maternal allele in neurons, cause Angelman syndrome, characterized by intellectual disability, motor deficits, seizures, and a characteristic increased social smiling, laughing, and eye contact. Conversely, maternally-derived triplications of 15q11-13 cause a behavioral disorder on the autism spectrum with clinical features that include decreased sociability that we recently reconstituted in mice with Ube3a alone. Based on the unique sociability features reported in Angelman syndrome and the repressed sociability observed when Ube3a gene dosage is increased, we hypothesized that mice with neuronal UBE3A loss that models Angelman syndrome would display evidence of hypersocial behavior. We report that mice with maternally-inherited Ube3a gene deletion (Ube3a^mKO) have a prolonged preference for, and interaction with, social stimuli in the three chamber social approach task. By contrast, interactions with a novel object are reduced. Further, ultrasonic vocalizations and physical contacts are increased in male and female Ube3a^mKO mice paired with an unfamiliar genotype-matched female. Single housing wild type mice increased these same social behavior parameters to levels observed in Ube3a^mKO mice where this effect was partially occluded. These results indicate sociability is repressed by social experience and the endogenous levels of UBE3A protein and suggest some social behavioral features observed in Angelman syndrome may reflect an increased social motivation.

Autism gene Ube3a and seizures impair sociability by repressing VTA Cbln1

Maternally inherited 15q11-13 chromosomal triplications cause a frequent and highly penetrant autism linked to increased gene dosages of UBE3A, which both possesses ubiquitin-ligase and transcriptional co-regulatory functions. Here, using in vivo mouse genetics, we show that increasing UBE3A in the nucleus down-regulates glutamatergic synapse organizer cerebellin-1 (Cbln1) that is needed for sociability in mice. Epileptic seizures also repress Cbln1 and are found to expose sociability impairments in mice with asymptomatic increases of UBE3A. This Ube3a-seizure synergy maps to glutamate neurons of the midbrain ventral tegmental area (VTA) where Cbln1 deletions impair sociability and weaken glutamatergic transmission. We provide preclinical evidence that viral-vector-based chemogenetic activations of, or Cbln1 restorations in VTA glutamatergic neurons rescues sociability deficits induced by Ube3a and/or seizures. Our results suggest a gene × seizure interaction in VTA glutamatergic neurons that impairs sociability by downregulating Cbln1, a key node in the expanding protein interaction network of autism genes.

JC Virus Infects Neurons and Glial Cells in the Hippocampus

The human polyomavirus JC (JCV) infects glial cells and is the etiologic agent of the CNS demyelinating disease progressive multifocal leukoencephalopathy. JCV can infect granule cell neurons of the cerebellum, causing JCV granule cell neuronopathy and cortical pyramidal neurons in JCV encephalopathy. Whether JCV also infects neurons in other areas of the CNS is unclear. We determined the prevalence and pattern of JCV infection of the hippocampus in archival samples from 28 patients with known JCV infection of the CNS and 66 control subjects. Among 28 patients, 11 (39.3%) had JCV infection of hippocampus structures demonstrated by immunohistochemistry. Those included gray matter (dentate gyrus and cornu ammonis, subiculum) in 11/11 and afferent or efferent white matter tracts (perforant path, alveus, fimbria) in 10/11. In the hippocampus, JCV infected granule cell and pyramidal neurons, astrocytes, and oligodendrocytes. Although glial cells expressed either JCV regulatory T Antigen or JCV VP1 capsid protein, infected neurons expressed JCV T Antigen only, suggesting an abortive/restrictive infection. None of the 66 control subjects had evidence of hippocampal JCV protein expression by immunohistochemistry or JCV DNA by in situ hybridization. These results greatly expand our understanding of JCV pathogenesis in the CNS.

Low-Voltage-Activated CaV3.1 Calcium Channels Shape T Helper Cell Cytokine Profiles

Activation of T cells is mediated by the engagement of T cell receptors (TCRs) followed by calcium entry via store-operated calcium channels. Here we have shown an additional route for calcium entry into T cells-through the low-voltage-activated T-type CaV3.1 calcium channel. CaV3.1 mediated a substantial current at resting membrane potentials, and its deficiency had no effect on TCR-initiated calcium entry. Mice deficient for CaV3.1 were resistant to the induction of experimental autoimmune encephalomyelitis and had reduced productions of the granulocyte-macrophage colony-stimulating factor (GM-CSF) by central nervous system (CNS)-infiltrating T helper 1 (Th1) and Th17 cells. CaV3.1 deficiency led to decreased secretion of GM-CSF from in vitro polarized Th1 and Th17 cells. Nuclear translocation of the nuclear factor of activated T cell (NFAT) was also reduced in CaV3.1-deficient T cells. These data provide evidence for T-type channels in immune cells and their potential role in shaping the autoimmune response.

α-Synuclein pathology accumulates in sacral spinal visceral sensory pathways

Urinary urgency and frequency are common in α-synucleinopathies such as Parkinson disease, Lewy body dementia, and multiple system atrophy. These symptoms cannot be managed with dopamine therapy, and their underlying pathophysiology is unclear. We show that in individuals with Parkinson disease, Lewy body dementia, or multiple system atrophy, α-synuclein pathology accumulates in the lateral collateral pathway, a region of the sacral spinal dorsal horn important for the relay of pelvic visceral afferents. Deposition of α-synuclein in this region may contribute to impaired micturition and/or constipation in Parkinson disease and other α-synucleinopathies.

Self-regulation of adult thalamocortical neurons

The thalamus acts as a conduit for sensory and other information traveling to the cortex. In response to continuous sensory stimulation in vivo, the firing rate of thalamocortical neurons initially increases, but then within a minute firing rate decreases and T-type Ca(2+) channel-dependent action potential burst firing emerges. While neuromodulatory systems could play a role in this inhibitory response, we instead report a novel and cell-autonomous inhibitory mechanism intrinsic to the thalamic relay neuron. Direct intracellular stimulation of thalamocortical neuron firing initially triggered a continuous and high rate of action potential discharge, but within a minute membrane potential (Vm) was hyperpolarized and firing rate to the same stimulus was decreased. This self-inhibition was observed across a wide variety of thalamic nuclei, and in a subset firing mode switched from tonic to bursting. The self-inhibition resisted blockers of intracellular Ca(2+) signaling, Na(+)-K(+)-ATPases, and G protein-regulated inward rectifier (GIRK) channels as implicated in other neuron subtypes, but instead was in part inhibited by an ATP-sensitive K(+) channel blocker. The results identify a new homeostatic mechanism within the thalamus capable of gating excitatory signals at the single-cell level.

A comparison of sonography and radiography student scores in a cadaver anatomy class before and after the implementation of synchronous distance education

Distance education is a solution to expand medical imaging education to students who might not otherwise be able to obtain the education. It can be a mechanism to reduce the health care worker shortage in underserved areas. In some cases, distance education may be a disruptive technology, and might lower student performance. This study compares student scores in a cadaver anatomy course in the four cohorts preceding the implementation of distance education to the first three cohorts that took the course using a multiple campus design. The means and medians of the lecture exam average, the laboratory component score, and the final course score of the nondistance education cohorts were compared with those of the distance education cohorts using nonparametric statistical analysis. Scores in an anatomy course were compared by campus placement among the distance education cohorts, and the independent effect of distance education on the laboratory component, lecture examination average, and final course scores, while controlling for cumulative grade point average and site (originating/distant), was assessed. Students receiving the course in a nondistance education environment scored higher in the anatomy course than the students who took the course in a distance education environment. Students on the distant campus scored lower than students on the originating site. Distance education technology creates new opportunities for learning, but can be a disruptive technology. Programs seeking to implement distance education into their curriculum should do so with knowledge of the advantages and disadvantages.

Glutamatergic neuron-targeted loss of LGI1 epilepsy gene results in seizures

Leucin-rich, glioma inactivated 1 (LGI1) is a secreted protein linked to human seizures of both genetic and autoimmune aetiology. Mutations in the LGI1 gene are responsible for autosomal dominant temporal lobe epilepsy with auditory features, whereas LGI1 autoantibodies are involved in limbic encephalitis, an acquired epileptic disorder associated with cognitive impairment. We and others previously reported that Lgi1-deficient mice have early-onset spontaneous seizures leading to premature death at 2-3 weeks of age. Yet, where and when Lgi1 deficiency causes epilepsy remains unknown. To address these questions, we generated Lgi1 conditional knockout (cKO) mice using a set of universal Cre-driver mouse lines. Selective deletion of Lgi1 was achieved in glutamatergic pyramidal neurons during embryonic (Emx1-Lgi1cKO) or late postnatal (CaMKIIα-Lgi1cKO) developmental stages, or in gamma amino butyric acidergic (GABAergic) parvalbumin interneurons (PV-Lgi1cKO). Emx1-Lgi1cKO mice displayed early-onset and lethal seizures, whereas CaMKIIα-Lgi1cKO mice presented late-onset occasional seizures associated with variable reduced lifespan. In contrast, neither spontaneous seizures nor increased seizure susceptibility to convulsant were observed when Lgi1 was deleted in parvalbumin interneurons. Together, these data showed that LGI1 depletion restricted to pyramidal cells is sufficient to generate seizures, whereas seizure thresholds were unchanged after depletion in gamma amino butyric acidergic parvalbumin interneurons. We suggest that LGI1 secreted from excitatory neurons, but not parvalbumin inhibitory neurons, makes a major contribution to the pathogenesis of LGI1-related epilepsies. Our data further indicate that LGI1 is required from embryogenesis to adulthood to achieve proper circuit functioning.

Safe moving and handling of patients: an interprofessional approach

A gap in the medical undergraduate curriculum on safe moving and handling of patients was identified, and a project to enhance moving and handling education for undergraduates in various healthcare disciplines was undertaken. A team of nurses, doctors, physiotherapists and e-learning professionals developed a cross-discipline e-learning resource, piloted with medical and nursing students at Queen's University Belfast. One outcome of the project was the development of a deeper recognition of the common curriculum across healthcare disciplines.

Hyperintense cortical signal on magnetic resonance imaging reflects focal leukocortical encephalitis and seizure risk in progressive multifocal leukoencephalopathy

OBJECTIVE

To determine the frequency of hyperintense cortical signal (HCS) on T1-weighted precontrast magnetic resonance (MR) images in progressive multifocal leukoencephalopathy (PML) patients, its association with seizure risk and immune reconstitution inflammatory syndrome (IRIS), and its pathologic correlate.

METHODS

We reviewed clinical data including seizure history, presence of IRIS, and MR imaging scans from PML patients evaluated at our institution between 2003 and 2012. Cases that were diagnosed either using cerebrospinal fluid JC virus (JCV) polymerase chain reaction, brain biopsy, or autopsy, and who had MR images available were included in the analysis (n=49). We characterized pathologic findings in areas of the brain that displayed HCS in 2 patients and compared them with isointense cortex in the same individuals.

RESULTS

Of 49 patients, 17 (34.7%) had seizures and 30 (61.2%) had HCS adjacent to subcortical PML lesions on MR images. Of the 17 PML patients with seizures, 15 (88.2%) had HCS compared with 15 of 32 (46.9%) patients without seizures (p=0.006). HCS was associated with seizure development with a relative risk of 4.75 (95% confidence interval=1.2-18.5, p=0.006). Of the 20 patients with IRIS, 16 (80.0%) had HCS compared with 14 of 29 (49.3%) patients without IRIS (p=0.04). On histological examination, HCS areas were associated with striking JCV-associated demyelination of cortical and subcortical U fibers, significant macrophage infiltration, and a pronounced reactive gliosis in the deep cortical layers.

INTERPRETATION

Seizures are a frequent complication in PML. HCS is associated with seizures and IRIS, and correlates histologically with JCV focal leukocortical encephalitis.

A common functional promoter variant links CNR1 gene expression to HDL cholesterol level

CB₁ receptor blockers increase HDL-C levels. Although genetic variation in the CB₁ receptor – encoded by the CNR1 gene – is known to influence HDL-C level as well, human studies conducted to date have been limited to genetic markers such as haplotype tagging SNPs. Here we identify rs806371 in the CNR1 promoter as the causal variant. We resequenced the CNR1 gene and genotype all variants in a DNA biobank linked to comprehensive electronic medical records. By testing each variant for association with HDL-C level in a clinical practice-based setting, we localize a putative functional allele to a 100bp window in the 5′-flanking region. Assessment of variants in this window for functional impact on electrophoretic mobility shift assay identified rs806371 as a novel regulatory binding element. Reporter gene assays confirm that rs806371 reduces HDL-C gene expression, thereby linking CNR1 gene variation to HDL-C level in humans.

Transplanted hypothalamic neurons restore leptin signaling and ameliorate obesity in db/db mice

Evolutionarily old and conserved homeostatic systems in the brain, including the hypothalamus, are organized into nuclear structures of heterogeneous and diverse neuron populations. To investigate whether such circuits can be functionally reconstituted by synaptic integration of similarly diverse populations of neurons, we generated physically chimeric hypothalami by microtransplanting small numbers of embryonic enhanced green fluorescent protein-expressing, leptin-responsive hypothalamic cells into hypothalami of postnatal leptin receptor-deficient (db/db) mice that develop morbid obesity. Donor neurons differentiated and integrated as four distinct hypothalamic neuron subtypes, formed functional excitatory and inhibitory synapses, partially restored leptin responsiveness, and ameliorated hyperglycemia and obesity in db/db mice. These experiments serve as a proof of concept that transplanted neurons can functionally reconstitute complex neuronal circuitry in the mammalian brain.

Mutant LGI1 inhibits seizure-induced trafficking of Kv4.2 potassium channels

Activity-dependent redistribution of ion channels mediates neuronal circuit plasticity and homeostasis, and could provide pro-epileptic or compensatory anti-epileptic responses to a seizure. Thalamocortical neurons transmit sensory information to the cerebral cortex and through reciprocal corticothalamic connections are intensely activated during a seizure. Therefore, we assessed whether a seizure alters ion channel surface expression and consequent neurophysiologic function of thalamocortical neurons. We report a seizure triggers a rapid (<2h) decrease of excitatory postsynaptic current (EPSC)-like current-induced phasic firing associated with increased transient A-type K(+) current. Seizures also rapidly redistributed the A-type K(+) channel subunit Kv4.2 to the neuronal surface implicating a molecular substrate for the increased K(+) current. Glutamate applied in vitro mimicked the effect, suggesting a direct effect of glutamatergic transmission. Importantly, leucine-rich glioma-inactivated-1 (LGI1), a secreted synaptic protein mutated to cause human partial epilepsy, regulated this seizure-induced circuit response. Human epilepsy-associated dominant-negative-truncated mutant LGI1 inhibited the seizure-induced suppression of phasic firing, increase of A-type K(+) current, and recruitment of Kv4.2 surface expression (in vivo and in vitro). The results identify a response of thalamocortical neurons to seizures involving Kv4.2 surface recruitment associated with dampened phasic firing. The results also identify impaired seizure-induced increases of A-type K(+) current as an additional defect produced by the autosomal dominant lateral temporal lobe epilepsy gene mutant that might contribute to the seizure disorder.

Increased gene dosage of Ube3a results in autism traits and decreased glutamate synaptic transmission in mice

People with autism spectrum disorder are characterized by impaired social interaction, reduced communication, and increased repetitive behaviors. The disorder has a substantial genetic component, and recent studies have revealed frequent genome copy number variations (CNVs) in some individuals. A common CNV that occurs in 1 to 3% of those with autism--maternal 15q11-13 duplication (dup15) and triplication (isodicentric extranumerary chromosome, idic15)--affects several genes that have been suggested to underlie autism behavioral traits. To test this, we tripled the dosage of one of these genes, the ubiquitin protein ligase Ube3a, which is expressed solely from the maternal allele in mature neurons, and reconstituted the three core autism traits in mice: defective social interaction, impaired communication, and increased repetitive stereotypic behavior. The penetrance of these autism traits depended on Ube3a gene copy number. In animals with increased Ube3a gene dosage, glutamatergic, but not GABAergic, synaptic transmission was suppressed as a result of reduced presynaptic release probability, synaptic glutamate concentration, and postsynaptic action potential coupling. These results suggest that Ube3a gene dosage may contribute to the autism traits of individuals with maternal 15q11-13 duplication and support the idea that increased E3A ubiquitin ligase gene dosage results in reduced excitatory synaptic transmission.

Arrested glutamatergic synapse development in human partial epilepsy

While studying the brain function of the human partial epilepsy gene, leucine-rich glioma-inactivated 1 (LGI1), a new mechanism of human epileptogenesis was revealed-persistent immaturity of glutamatergic circuitries. LGI1, a novel secreted protein, was found to be increased during the postnatal period; when glutamatergic synapses both downregulate their presynaptic vesicular release probability and reduce their postsynaptic NMDA-receptor subunit NR2B. During this same period, the dendritic arbor and spines are pruned and remodeled. Using bacterial artificial chromosome transgenic mouse techniques, excess wild-type LGI1 was shown to magnify these critical brain developmental events in the hippocampal dentate gyrus; while an epilepsy-associated, truncated, dominant-negative form of LGI1 blocked them. By contrast, the hippocampal dentate granule neuron GABAergic synapses and intrinsic excitability were unaltered. A role for LGI1 in downregulating glutamate synapse function was confirmed by germline gene deletion; this intervention also revealed a selective increase of glutamatergic synaptic transmission with unaltered GABAergic synapses and intrinsic excitability of hippocampal CA1 pyramidal neurons. Interestingly, the role of LGI1 in neurological disease was further expanded when a subset of patients with limbic encephalitis (an autoimmune disorder with memory loss in 100% and seizures in 80% of individuals) were discovered to carry autoantibodies to LGI1.

Fulminant JC virus encephalopathy with productive infection of cortical pyramidal neurons

The polyomavirus JC (JCV) is the causative agent of progressive multifocal leukoencephalopathy and of JCV granule cell neuronopathy. We present a human immunodeficiency virus-negative patient who experienced development of multiple cortical lesions, aphasia, and progressive cognitive decline after chemotherapy for non-small-cell lung cancer. Brain biopsy and cerebrospinal fluid polymerase chain reaction demonstrated JCV, and she had a rapidly fatal outcome. Postmortem analysis showed diffuse cortical lesions and areas of necrosis at the gray-white junction. Immunostaining showed a productive JCV infection of cortical pyramidal neurons, confirmed by electron microscopy, with limited demyelination. This novel gray matter syndrome expands the scope of JCV clinical presentation and pathogenesis.

Differential regulation of action potential firing in adult murine thalamocortical neurons by Kv3.2, Kv1, and SK potassium and N-type calcium channels

Sensory signals of widely differing dynamic range and intensity are transformed into a common firing rate code by thalamocortical neurons. While a great deal is known about the ionic currents, far less is known about the specific channel subtypes regulating thalamic firing rates. We hypothesized that different K(+) and Ca(2+) channel subtypes control different stimulus-response curve properties. To define the channels, we measured firing rate while pharmacologically or genetically modulating specific channel subtypes. Inhibiting Kv3.2 K(+) channels strongly suppressed maximum firing rate by impairing membrane potential repolarization, while playing no role in the firing response to threshold stimuli. By contrast, inhibiting Kv1 channels with alpha-dendrotoxin or maurotoxin strongly increased firing rates to threshold stimuli by reducing the membrane potential where action potentials fire (V(th)). Inhibiting SK Ca(2+)-activated K(+) channels with apamin robustly increased gain (slope of the stimulus-response curve) and maximum firing rate, with minimum effects on threshold responses. Inhibiting N-type Ca(2+) channels with omega-conotoxin GVIA or omega-conotoxin MVIIC partially mimicked apamin, while inhibiting L-type and P/Q-type Ca(2+) channels had small or no effects. EPSC-like current injections closely mimicked the results from tonic currents. Our results show that Kv3.2, Kv1, SK potassium and N-type calcium channels strongly regulate thalamic relay neuron sensory transmission and that each channel subtype controls a different stimulus-response curve property. Differential regulation of threshold, gain and maximum firing rate may help vary the stimulus-response properties across and within thalamic nuclei, normalize responses to diverse sensory inputs, and underlie sensory perception disorders.

Estimating recharge rates with analytic element models and parameter estimation

Quantifying the spatial and temporal distribution of recharge is usually a prerequisite for effective ground water flow modeling. In this study, an analytic element (AE) code (GFLOW) was used with a nonlinear parameter estimation code (UCODE) to quantify the spatial and temporal distribution of recharge using measured base flows as calibration targets. The ease and flexibility of AE model construction and evaluation make this approach well suited for recharge estimation. An AE flow model of an undeveloped watershed in northern Wisconsin was optimized to match median annual base flows at four stream gages for 1996 to 2000 to demonstrate the approach. Initial optimizations that assumed a constant distributed recharge rate provided good matches (within 5%) to most of the annual base flow estimates, but discrepancies of >12% at certain gages suggested that a single value of recharge for the entire watershed is inappropriate. Subsequent optimizations that allowed for spatially distributed recharge zones based on the distribution of vegetation types improved the fit and confirmed that vegetation can influence spatial recharge variability in this watershed. Temporally, the annual recharge values varied >2.5-fold between 1996 and 2000 during which there was an observed 1.7-fold difference in annual precipitation, underscoring the influence of nonclimatic factors on interannual recharge variability for regional flow modeling. The final recharge values compared favorably with more labor-intensive field measurements of recharge and results from studies, supporting the utility of using linked AE-parameter estimation codes for recharge estimation.

Thalamic Cav3.1 T-type Ca2+ channel plays a crucial role in stabilizing sleep

It has long been suspected that sensory signal transmission is inhibited in the mammalian brain during sleep. We hypothesized that Cav3.1 T-type Ca2+ channel currents inhibit thalamic sensory transmission to promote sleep. We found that T-type Ca2+ channel activation caused prolonged inhibition (>9 s) of action-potential firing in thalamic projection neurons of WT but not Cav3.1 knockout mice. Inhibition occurred with synaptic transmission blocked and required an increase of intracellular Ca2+. Furthermore, focal deletion of the gene encoding Cav3.1 from the rostral-midline thalamus by using Cre/loxP recombination led to frequent and prolonged arousal, which fragmented and reduced sleep. Interestingly, sleep was not disturbed when Cav3.1 was deleted from cortical pyramidal neurons. These findings support the hypothesis that thalamic T-type Ca2+ channels are required to block transmission of arousal signals through the thalamus and to stabilize sleep.

AFLP analysis of Cynodon dactylon (L.) Pers. var. dactylon genetic variation

Cynodon dactylon (L.) Pers. var. dactylon (common bermudagrass) is geographically widely distributed between about lat 45°N and lat 45°S, penetrating to about lat 53°N in Europe. The extensive variation of morphological and adaptive characteristics of the taxon is substantially documented, but information is lacking on DNA molecular variation in geographically disparate forms. Accordingly, this study was conducted to assess molecular genetic variation and genetic relatedness among 28 C. dactylon var. dactylon accessions originating from 11 countries on 4 continents (Africa, Asia, Australia, and Europe). A fluorescence-labeled amplified fragment length polymorphism (AFLP) DNA profiling method was used to detect the genetic diversity and relatedness. On the basis of 443 polymorphic AFLP fragments from 8 primer combinations, the accessions were grouped into clusters and subclusters associating with their geographic origins. Genetic similarity coefficients (SC) for the 28 accessions ranged from 0.53 to 0.98. Accessions originating from Africa, Australia, Asia, and Europe formed major groupings as indicated by cluster and principal coordinate analysis. Accessions from Australia and Asia, though separately clustered, were relatively closely related and most distantly related to accessions of European origin. African accessions formed two distant clusters and had the greatest variation in genetic relatedness relative to accessions from other geographic regions. Sampling the full extent of genetic variation in C. dactylon var. dactylon would require extensive germplasm collection in the major geographic regions of its distributional range.Key words: common bermudagrass, AFLP marker, genetic relatedness.

Diversity among Cynodon accessions and taxa based on DNA amplification fingerprinting

The genus Cynodon (Gramineae), comprised of 9 species, is geographically widely distributed and genetically diverse. Information on the amounts of molecular genetic variation among and within Cynodon taxa is needed to enhance understanding of phylogenetic relations and facilitate germplasm management and breeding improvement efforts. Genetic relatedness among 62 Cynodon accessions, representing eight species, was assessed using DNA amplification fingerprinting (DAF). Ten 8-mer oligonucleotides were used to amplify specific Cynodon genomic sequences. The DNA amplification products of individual accessions were scored for presence (1) or absence (0) of bands. Similarity matrices were developed and the accessions were grouped by cluster (UPGMA) and principal coordinate analysis. Analyses were conducted within ploidy level (2x = 18 and 4x = 36) and over ploidy levels. Each primer revealed polymorphic loci among accessions within species. Of 539 loci (bands) scored, 496 (92%) were polymorphic. Cynodon arcuatus was clearly separated from other species by numerous monomorphic bands. The strongest species similarities were between C. aethiopicus and C. arcuatus, C. transvaalensis and C. plectostachyus, and C. incompletus and C. nlemfuensis. Intraspecific variation was least for C. aethiopicus, C. arcuatus, and C. transvaalensis, and greatest for C. dactylon. Accessions of like taxonomic classification were generally clustered, except the cosmopolitan C. dactylon var. dactylon and C. dactylon var. afganicus. Within taxa, accessions differing in chromosome number clustered in all instances indicating the 2x and 4x forms to be closely related. Little, if any, relationship was found between relatedness as indicated by the DAF profiles and previous estimates of hybridization potential between the different taxa.

Dysfunction of CFTR bearing the ΔF508 mutation

The cystic fibrosis transmembrane conductance regulator (CFTR) is mutated in patients with cystic fibrosis (CF). The most common CF-associated mutation is deletion of phenylanine at residue 508, CFTRΔF508. When expressed in heterologous cells, CFTR bearing the ΔF508 mutation fails to progress through the normal biosynthetic pathway and fails to traffic to the plasma membrane. As a result, CFTRΔF508 is mislocalized and is not present in the apical membrane of primary cultures of airway epithelia. Consequently, the apical membrane of CF airway epithelia is Cl−-impermeable, a defect that probably contributes to the pathogenesis of the disease.

Regulation of the cystic fibrosis transmembrane conductance regulator chloride channel by MgATP

These results begin to indicate that nucleoside triphosphates directly regulate CFTR Cl- channels by interacting with the NBDs. Thus, they may begin to explain why some CF-associated mutations in the NBDs may block Cl- channel function in the epithelia of CF patients. These results also suggest that the intracellular ATP/ADP ratio may be more important than the absolute concentration of ATP in regulating CFTR. Thus, changes in the metabolic state of the cell that alter the ATP-ADP ratio may regulate CFTR Cl- channel activity in vivo. These observations suggest that CFTR might be regulated in the physiologic range of nucleotides. Such a mechanism of regulation could provide a mechanism for coupling the metabolic status of the cell and the activity of the Na-K ATPase with the rate of transepithelial Cl- secretion as regulated by apical membrane CFTR Cl- channels.

Correction

In the final preparation of the manuscript of our report "Regulation by ATP and ADP of CFTR chloride channels that contain mutant nucleotide-binding domains" (18 Sept., p. 1701) (1), we inadvertently plotted the data for figure 1C with an incorrect x axis: MgATP was plotted on the x axis instead of P(o). We did not immediately notice the error, which was brought to our attention by Charles Venglarik and Robert Bridges, because the shape of the two curves is similiar. The correct plot is shown in the figure below. In both plots the data do not fit a straight [See figure in the PDF file] line, which supports our interpretation that more than one site may be involved with adenosine triphosphate (ATP) regulation of the cystic fibrosis transmembrane conductance regulator (CFTR). We regret any inconvenience this may have caused.

Regulation by ATP and ADP of CFTR chloride channels that contain mutant nucleotide-binding domains

Regulation of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is unusual in that phosphorylated channels require cytosolic adenosine triphosphate (ATP) to open. The CFTR contains two regions predicted to be nucleotide-binding domains (NBDs); site-directed mutations in each NBD have now been shown to alter the relation between ATP concentration and channel activity, which indicates that ATP stimulates the channel by direct interaction with both NBDs. The two NBDs are not, however, functionally equivalent: adenosine diphosphate (ADP) competitively inhibited the channel by interacting with NBD2 but not by interacting with NBD1. Four cystic fibrosis-associated mutations in the NBDs reduced absolute chloride channel activity, and one mutation also decreased the potency with which ATP stimulates channel activity. Dysfunction of ATP-dependent stimulation through the NBDs may be the basis for defective CFTR chloride channel activity in some cystic fibrosis patients.