Harvesting mouse suprachiasmatic nucleus by vibrating microtome for diurnal transcriptome analysis

The mammalian suprachiasmatic nucleus (SCN) is the principal circadian clock that synchronizes daily behavioral and physiological responses in response to environmental cues. Here, we present a protocol for harvesting mouse SCN by vibrating microtome for diurnal transcriptome analysis. We describe steps for mouse entrainment, isolation of the SCN, tissue preparation, slicing with a vibratome, and handling of the harvested SCN for RNA extraction. This protocol can also be used for harvesting other mammalian brain regions for genomic studies.

Aperiodic neural activity is a biomarker for depression severity

A reliable physiological biomarker for Major Depressive Disorder (MDD) is necessary to improve treatment success rates by shoring up variability in outcome measures. In this study, we establish a passive biomarker that tracks with changes in mood on the order of minutes to hours. We record from intracranial electrodes implanted deep in the brain - a surgical setting providing exquisite temporal and spatial sensitivity to detect this relationship in a difficult-to-measure brain area, the ventromedial prefrontal cortex (VMPFC). The aperiodic slope of the power spectral density captures the balance of activity across all frequency bands and is construed as a putative proxy for excitatory/inhibitory balance in the brain. This study demonstrates how shifts in aperiodic slope correlate with depression severity in a clinical trial of deep brain stimulation for treatment-resistant depression (TRD). The correlation between depression severity scores and aperiodic slope is significant in N=5 subjects, indicating that flatter (less negative) slopes correspond to reduced depression severity, especially in the ventromedial prefrontal cortex. This biomarker offers a new way to track patient response to MDD treatment, facilitating individualized therapies in both intracranial and non-invasive monitoring scenarios.

A missense mutation in zinc finger homeobox-3 (ZFHX3) impedes growth and alters metabolism and hypothalamic gene expression in mice

A protein altering variant in the gene encoding zinc finger homeobox-3 (ZFHX3) has recently been associated with lower BMI in a human genome-wide association study. We investigated metabolic parameters in mice harboring a missense mutation in Zfhx3 (Zfhx3Sci/+ ) and looked for altered in situ expression of transcripts that are associated with energy balance in the hypothalamus to understand how ZFHX3 may influence growth and metabolic effects. One-year-old male and female Zfhx3Sci/+ mice weighed less, had shorter body length, lower fat mass, smaller mesenteric fat depots, and lower circulating insulin, leptin, and insulin-like growth factor-1 (IGF1) concentrations than Zfhx3+/+ littermates. In a second cohort of 9-20-week-old males and females, Zfhx3Sci/+ mice ate less than wildtype controls, in proportion to body weight. In a third cohort of female-only Zfhx3Sci/+ and Zfhx3+/+ mice that underwent metabolic phenotyping from 6 to 14 weeks old, Zfhx3Sci/+ mice weighed less and had lower lean mass and energy expenditure, but fat mass did not differ. We detected increased expression of somatostatin and decreased expression of growth hormone-releasing hormone and growth hormone-receptor mRNAs in the arcuate nucleus (ARC). Similarly, ARC expression of orexigenic neuropeptide Y was decreased and ventricular ependymal expression of orphan G protein-coupled receptor Gpr50 was decreased. We demonstrate for the first time an energy balance effect of the Zfhx3Sci mutation, likely by altering expression of key ARC neuropeptides to alter growth, food intake, and energy expenditure.

Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

DNA methylation networks underlying mammalian traits

Using DNA methylation profiles (n = 15,456) from 348 mammalian species, we constructed phyloepigenetic trees that bear marked similarities to traditional phylogenetic ones. Using unsupervised clustering across all samples, we identified 55 distinct cytosine modules, of which 30 are related to traits such as maximum life span, adult weight, age, sex, and human mortality risk. Maximum life span is associated with methylation levels in HOXL subclass homeobox genes and developmental processes and is potentially regulated by pluripotency transcription factors. The methylation state of some modules responds to perturbations such as caloric restriction, ablation of growth hormone receptors, consumption of high-fat diets, and expression of Yamanaka factors. This study reveals an intertwined evolution of the genome and epigenome that mediates the biological characteristics and traits of different mammalian species.

Dynamic modulation of genomic enhancer elements in the suprachiasmatic nucleus, the site of the mammalian circadian clock

The mammalian suprachiasmatic nucleus (SCN), located in the ventral hypothalamus, synchronises and maintains daily cellular and physiological rhythms across the body, in accordance with environmental and visceral cues. Consequently, the systematic regulation of spatiotemporal gene transcription in the SCN is vital for daily timekeeping. So far, the regulatory elements assisting circadian gene transcription have only been studied in peripheral tissues, lacking the critical neuronal dimension intrinsic to the role of the SCN as central brain pacemaker. By using histone-ChIP-seq, we identified SCN-enriched gene regulatory elements that associated with temporal gene expression. Based on tissue-specific H3K27ac and H3K4me3 marks we successfully produced the first-ever SCN gene-regulatory map. We found that a large majority of SCN enhancers not only exhibit robust 24-hour rhythmic modulation in H3K27ac occupancy, peaking at distinct times-of-day, but also possess canonical E-box (CACGTG) motifs potentially influencing downstream cycling gene expression. To establish enhancer-gene relationships in the SCN, we conducted directional RNA-seq at six distinct times across day and night and studied the association between dynamically changing histone acetylation and gene transcript levels. About 35% of the cycling H3K27ac sites were found adjacent to rhythmic gene transcripts, often preceding the rise in mRNA levels. We also noted that enhancers encompass noncoding actively transcribing enhancer RNAs (eRNAs) in the SCN, which in turn oscillate, along with cyclic histone acetylation, and correlates with rhythmic gene transcription. Taken together, these findings shed light on genome-wide pretranscriptional regulation operative in the central clock that confers its precise and robust oscillation necessary to orchestrate daily timekeeping in mammals.

Shift work-like patterns effect on female and male mouse behavior

Shift work (work outside of standard daylight hours) is common throughout the Western world. However, there are notable health consequences to shift work, including increased prevalence of mental health and sleep disorders in shift worker populations. Therefore, the health and wellbeing of shift workers is a public health concern that needs to be addressed. Here we investigate the effects of two separate light induced shift work-like patterns on male and female mouse behaviour (anxiety-like, exploration, marble burying, startle reflex and circadian rhythms). After 6 weeks of shift-like disruptions patterns, animals displayed no behavioral differences in exploration, marble burying and startle reflex. Interestingly however, we identified sex specific and disruption specific effects in light aversion and wheel running activities. Notably, analysis of the activity patterns of animals in disruptive conditions demonstrated that they maintained a degree of rhythmicity through the disruption period, which may explain the lack of behavioral differences in most behavioral tests.

Tissue Proteome of 2-Hydroxyacyl-CoA Lyase Deficient Mice Reveals Peroxisome Proliferation and Activation of ω-Oxidation

Peroxisomal fatty acid α-oxidation is an essential pathway for the degradation of β-carbon methylated fatty acids such as phytanic acid. One enzyme in this pathway is 2-hydroxyacyl CoA lyase (HACL1), which is responsible for the cleavage of 2-hydroxyphytanoyl-CoA into pristanal and formyl-CoA. Hacl1 deficient mice do not present with a severe phenotype, unlike mice deficient in other α-oxidation enzymes such as phytanoyl-CoA hydroxylase deficiency (Refsum disease) in which neuropathy and ataxia are present. Tissues from wild-type and Hacl1^−/− mice fed a high phytol diet were obtained for proteomic and lipidomic analysis. There was no phenotype observed in these mice. Liver, brain, and kidney tissues underwent trypsin digestion for untargeted proteomic liquid chromatography-mass spectrometry analysis, while liver tissues also underwent fatty acid hydrolysis, extraction, and derivatisation for fatty acid gas chromatography-mass spectrometry analysis. The liver fatty acid profile demonstrated an accumulation of phytanic and 2-hydroxyphytanic acid in the Hacl1^−/− liver and significant decrease in heptadecanoic acid. The liver proteome showed a significant decrease in the abundance of Hacl1 and a significant increase in the abundance of proteins involved in PPAR signalling, peroxisome proliferation, and omega oxidation, particularly Cyp4a10 and Cyp4a14. In addition, the pathway associated with arachidonic acid metabolism was affected; Cyp2c55 was upregulated and Cyp4f14 and Cyp2b9 were downregulated. The kidney proteome revealed fewer significantly upregulated peroxisomal proteins and the brain proteome was not significantly different in Hacl1^−/− mice. This study demonstrates the powerful insight brought by proteomic and metabolomic profiling of Hacl1^−/− mice in better understanding disease mechanism in fatty acid α-oxidation disorders.

Zfhx3-mediated genetic ablation of the SCN abolishes light entrainable circadian activity while sparing food anticipatory activity

Circadian rhythms persist in almost all organisms and are crucial for maintaining appropriate timing in physiology and behaviour. Here, we describe a mouse mutant where the central mammalian pacemaker, the suprachiasmatic nucleus (SCN), has been genetically ablated by conditional deletion of the transcription factor Zfhx3 in the developing hypothalamus. Mutants were arrhythmic over the light-dark cycle and in constant darkness. Moreover, rhythms of metabolic parameters were ablated in vivo although molecular oscillations in the liver maintained some rhythmicity. Despite disruptions to SCN cell identity and circuitry, mutants could still anticipate food availability, yet other zeitgebers - including social cues from cage-mates - were ineffective in restoring rhythmicity although activity levels in mutants were altered. This work highlights a critical role for Zfhx3 in the development of a functional SCN, while its genetic ablation further defines the contribution of SCN circuitry in orchestrating physiological and behavioral responses to environmental signals.

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Deletion of Zfhx3 in developing hypothalamus leads to behavioral arrhythmicity

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SCN cell identity is absent while other retinal targets and visual functions remain

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Rhythms in metabolic functions are lost while some molecular rhythms in liver persist

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Conditional mutants can respond to food availability and other environmental cues

Zfhx3 modulates retinal sensitivity and circadian responses to light

Mutations in transcription factors often exhibit pleiotropic effects related to their complex expression patterns and multiple regulatory targets. One such mutation in the zinc finger homeobox 3 (ZFHX3) transcription factor, short circuit (Sci, Zfhx3^Sci/+ ), is associated with significant circadian deficits in mice. However, given evidence of its retinal expression, we set out to establish the effects of the mutation on retinal function using molecular, cellular, behavioral and electrophysiological measures. Immunohistochemistry confirms the expression of ZFHX3 in multiple retinal cell types, including GABAergic amacrine cells and retinal ganglion cells including intrinsically photosensitive retinal ganglion cells (ipRGCs). Zfhx3^Sci/+ mutants display reduced light responsiveness in locomotor activity and circadian entrainment, relatively normal electroretinogram and optomotor responses but exhibit an unexpected pupillary reflex phenotype with markedly increased sensitivity. Furthermore, multiple electrode array recordings of Zfhx3^Sci/+ retina show an increased sensitivity of ipRGC light responses.

Loss of Frrs1l disrupts synaptic AMPA receptor function, and results in neurodevelopmental, motor, cognitive and electrographical abnormalities

Loss-of-function mutations in a human AMPA receptor-associated protein, ferric chelate reductase 1-like (FRRS1L), are associated with a devastating neurological condition incorporating choreoathetosis, cognitive deficits and epileptic encephalopathies. Furthermore, evidence from overexpression and ex vivo studies has implicated FRRS1L in AMPA receptor biogenesis, suggesting that changes in glutamatergic signalling might underlie the disorder. Here, we investigated the neurological and neurobehavioural correlates of the disorder using a mouse Frrs1l null mutant. The study revealed several neurological defects that mirrored those seen in human patients. We established that mice lacking Frrs1l suffered from a broad spectrum of early-onset motor deficits with no progressive, age-related deterioration. Moreover, Frrs1l^−/− mice were hyperactive, irrespective of test environment, exhibited working memory deficits and displayed significant sleep fragmentation. Longitudinal electroencephalographic (EEG) recordings also revealed abnormal EEG results in Frrs1l^−/− mice. Parallel investigations into disease aetiology identified a specific deficiency in AMPA receptor levels in the brain of Frrs1l^−/− mice, while the general levels of several other synaptic components remained unchanged, with no obvious alterations in the number of synapses. Furthermore, we established that Frrsl1 deletion results in an increased proportion of immature AMPA receptors, indicated by incomplete glycosylation of GLUA2 (also known as GRIA2) and GLUA4 (also known as GRIA4) AMPA receptor proteins. This incomplete maturation leads to cytoplasmic retention and a reduction of those specific AMPA receptor levels in the postsynaptic membrane. Overall, this study determines, for the first time in vivo, how loss of FRRS1L function can affect glutamatergic signalling, and provides mechanistic insight into the development and progression of a human hyperkinetic disorder.

This article has an associated First Person interview with the first author of the paper.

Summary: Loss of the epilepsy-related gene Frrs1l in mice causes a dramatic reduction in AMPA receptor levels at the synapse, eliciting severe motor and coordination disabilities, hyperactivity and cognitive defects, with some evidence of behavioural seizures.

Modelling physical resilience in ageing mice

Geroprotectors, a class of drugs targeting multiple deficits occurring with age, necessitate the development of new animal models to test their efficacy. The COST Action MouseAGE is a European network whose aim is to reach consensus on the translational path required for geroprotectors, interventions targeting the biology of ageing. In our previous work we identified frailty and loss of resilience as a potential target for geroprotectors. Frailty is the result of an accumulation of deficits, which occurs with age and reduces the ability to respond to adverse events (physical resilience). Modelling frailty and physical resilience in mice is challenging for many reasons. There is no consensus on the precise definition of frailty and resilience in patients or on how best to measure it. This makes it difficult to evaluate available mouse models. In addition, the characterization of those models is poor. Here we review potential models of physical resilience, focusing on those where there is some evidence that the administration of acute stressors requires integrative responses involving multiple tissues and where aged mice showed a delayed recovery or a worse outcome then young mice in response to the stressor. These models include sepsis, trauma, drug- and radiation exposure, kidney and brain ischemia, exposure to noise, heat and cold shock.

Disruption of the homeodomain transcription factor orthopedia homeobox (Otp) is associated with obesity and anxiety

Objective

Genetic studies in obese rodents and humans can provide novel insights into the mechanisms involved in energy homeostasis.

Methods

In this study, we genetically mapped the chromosomal region underlying the development of severe obesity in a mouse line identified as part of a dominant N-ethyl-N-nitrosourea (ENU) mutagenesis screen. We characterized the metabolic and behavioral phenotype of obese mutant mice and examined changes in hypothalamic gene expression. In humans, we examined genetic data from people with severe early onset obesity.

Results

We identified an obese mouse heterozygous for a missense mutation (pR108W) in orthopedia homeobox (Otp), a homeodomain containing transcription factor required for the development of neuroendocrine cell lineages in the hypothalamus, a region of the brain important in the regulation of energy homeostasis. Otp^R108W/+ mice exhibit increased food intake, weight gain, and anxiety when in novel environments or singly housed, phenotypes that may be partially explained by reduced hypothalamic expression of oxytocin and arginine vasopressin. R108W affects the highly conserved homeodomain, impairs DNA binding, and alters transcriptional activity in cells. We sequenced OTP in 2548 people with severe early-onset obesity and found a rare heterozygous loss of function variant in the homeodomain (Q153R) in a patient who also had features of attention deficit disorder.

Conclusions

OTP is involved in mammalian energy homeostasis and behavior and appears to be necessary for the development of hypothalamic neural circuits. Further studies will be needed to investigate the contribution of rare variants in OTP to human energy homeostasis.

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A mouse Otp mutation alters hypothalamic neuropeptide expression leading to increased food intake, obesity and anxiety.

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In severe early onset obesity, we found a heterozygous LOF variant in a patient with attention deficit disorder features.

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These studies show for the first time that mutations in the Otp/OTP gene cause obesity.

Inducible Knockout of Mouse Zfhx3 Emphasizes Its Key Role in Setting the Pace and Amplitude of the Adult Circadian Clock

The transcription factor zinc finger homeobox 3 (ZFHX3) plays a key role in coupling intracellular transcriptional-translational oscillations with intercellular synchrony in mouse suprachiasmatic nucleus (SCN). However, like many key players in central nervous system function, ZFHX3 serves an important role in neurulation and neuronal terminal differentiation while retaining discrete additional functions in the adult SCN. Recently, using a dominant missense mutation in mouse Zfhx3, we established that this gene can modify circadian period and sleep in adult animals. Nevertheless, we were still concerned that the neurodevelopmental consequences of ZFHX3 dysfunction in this mutant may interfere with, or confound, its critical adult-specific roles in SCN circadian function. To circumvent the developmental consequences of Zfhx3 deletion, we crossed a conditional null Zfhx3 mutant to an inducible, ubiquitously expressed Cre line (B6.Cg-Tg(UBC-cre/ERT2)1Ejb/J). This enabled us to assess circadian behavior in the same adult animals both before and after Cre-mediated excision of the critical Zfhx3 exons using tamoxifen treatment. Remarkably, we found a strong and significant alteration in circadian behavior in tamoxifen-treated homozygous animals with no phenotypic changes in heterozygous or control animals. Cre-mediated excision of Zfhx3 critical exons in adult animals resulted in shortening of the period of wheel-running in constant darkness by more than 1 h in the majority of homozygotes while, in 30% of animals, excision resulted in complete behavioral arrhythmicity. In addition, we found that homozygous animals reentrain almost immediately to 6-h phase advances in the light-dark cycle. No additional overt phenotypic changes were evident in treated homozygous animals. These findings confirm a sustained and significant role for ZFHX3 in maintaining rhythmicity in the adult mammalian circadian system.

Assessing mouse behaviour throughout the light/dark cycle using automated in-cage analysis tools

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Automated assessment of mouse home-cage behaviour is robust and reliable.

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Analysis over multiple light/dark cycles improves ability to classify behaviours.

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Combined RFID and video analysis enables home-cage analysis in group housed animals.

An important factor in reducing variability in mouse test outcomes has been to develop assays that can be used for continuous automated home cage assessment. Our experience has shown that this has been most evidenced in long-term assessment of wheel-running activity in mice. Historically, wheel-running in mice and other rodents have been used as a robust assay to determine, with precision, the inherent period of circadian rhythms in mice. Furthermore, this assay has been instrumental in dissecting the molecular genetic basis of mammalian circadian rhythms. In teasing out the elements of this test that have determined its robustness – automated assessment of an unforced behaviour in the home cage over long time intervals – we and others have been investigating whether similar test apparatus could be used to accurately discriminate differences in distinct behavioural parameters in mice. Firstly, using these systems, we explored behaviours in a number of mouse inbred strains to determine whether we could extract biologically meaningful differences. Secondly, we tested a number of relevant mutant lines to determine how discriminative these parameters were. Our findings show that, when compared to conventional out-of-cage phenotyping, a far deeper understanding of mouse mutant phenotype can be established by monitoring behaviour in the home cage over one or more light:dark cycles.

Novel gene function revealed by mouse mutagenesis screens for models of age-related disease

Determining the genetic bases of age-related disease remains a major challenge requiring a spectrum of approaches from human and clinical genetics to the utilization of model organism studies. Here we report a large-scale genetic screen in mice employing a phenotype-driven discovery platform to identify mutations resulting in age-related disease, both late-onset and progressive. We have utilized N-ethyl-N-nitrosourea mutagenesis to generate pedigrees of mutagenized mice that were subject to recurrent screens for mutant phenotypes as the mice aged. In total, we identify 105 distinct mutant lines from 157 pedigrees analysed, out of which 27 are late-onset phenotypes across a range of physiological systems. Using whole-genome sequencing we uncover the underlying genes for 44 of these mutant phenotypes, including 12 late-onset phenotypes. These genes reveal a number of novel pathways involved with age-related disease. We illustrate our findings by the recovery and characterization of a novel mouse model of age-related hearing loss.

Random mutagenesis can uncover novel genes involved in phenotypic traits. Here the authors perform a large-scale phenotypic screen on over 100 mouse strains generated by ENU mutagenesis to identify mice with age-related diseases, which they attribute to specific mutations revealed by whole-genome sequencing.

Genetic background influences age-related decline in visual and nonvisual retinal responses, circadian rhythms, and sleep

The circadian system is entrained to the environmental light/dark cycle via retinal photoreceptors and regulates numerous aspects of physiology and behavior, including sleep. These processes are all key factors in healthy aging showing a gradual decline with age. Despite their importance, the exact mechanisms underlying this decline are yet to be fully understood. One of the most effective tools we have to understand the genetic factors underlying these processes are genetically inbred mouse strains. The most commonly used reference mouse strain is C57BL/6J, but recently, resources such as the International Knockout Mouse Consortium have started producing large numbers of mouse mutant lines on a pure genetic background, C57BL/6N. Considering the substantial genetic diversity between mouse strains we expect there to be phenotypic differences, including differential effects of aging, in these and other strains. Such differences need to be characterized not only to establish how different mouse strains may model the aging process but also to understand how genetic background might modify age-related phenotypes. To ascertain the effects of aging on sleep/wake behavior, circadian rhythms, and light input and whether these effects are mouse strain-dependent, we have screened C57BL/6J, C57BL/6N, C3H-HeH, and C3H-Pde6b+ mouse strains at 5 ages throughout their life span. Our data show that sleep, circadian, and light input parameters are all disrupted by the aging process. Moreover, we have cataloged a number of strain-specific aging effects, including the rate of cataract development, decline in the pupillary light response, and changes in sleep fragmentation and the proportion of time spent asleep.

Neurodegenerative mutation in cytoplasmic dynein alters its organization and dynein-dynactin and dynein-kinesin interactions

A single amino acid change, F580Y (Legs at odd angles (Loa), Dync1h1^Loa), in the highly conserved and overlapping homodimerization, intermediate chain, and light intermediate chain binding domain of the cytoplasmic dynein heavy chain can cause severe motor and sensory neuron loss in mice. The mechanism by which the Loa mutation impairs the neuron-specific functions of dynein is not understood. To elucidate the underlying molecular mechanisms of neurodegeneration arising from this mutation, we applied a cohort of biochemical methods combined with in vivo assays to systemically study the effects of the mutation on the assembly of dynein and its interaction with dynactin. We found that the Loa mutation in the heavy chain leads to increased affinity of this subunit of cytoplasmic dynein to light intermediate and a population of intermediate chains and a suppressed association of dynactin to dynein. These data suggest that the Loa mutation drives the assembly of cytoplasmic dynein toward a complex with lower affinity to dynactin and thus impairing transport of cargos that tether to the complex via dynactin. In addition, we detected up-regulation of kinesin light chain 1 (KLC1) and its increased association with dynein but reduced microtubule-associated KLC1 in the Loa samples. We provide a model describing how up-regulation of KLC1 and its interaction with cytoplasmic dynein in Loa could play a regulatory role in restoring the retrograde and anterograde transport in the Loa neurons.

The legs at odd angles (Loa) mutation in cytoplasmic dynein ameliorates mitochondrial function in SOD1G93A mouse model for motor neuron disease

Amyotrophic lateral sclerosis (ALS) is a debilitating and fatal late-onset neurodegenerative disease. Familial cases of ALS (FALS) constitute ∼10% of all ALS cases, and mutant superoxide dismutase 1 (SOD1) is found in 15–20% of FALS. SOD1 mutations confer a toxic gain of unknown function to the protein that specifically targets the motor neurons in the cortex and the spinal cord. We have previously shown that the autosomal dominant Legs at odd angles (Loa) mutation in cytoplasmic dynein heavy chain (Dync1h1) delays disease onset and extends the life span of transgenic mice harboring human mutant SOD1^G93A. In this study we provide evidence that despite the lack of direct interactions between mutant SOD1 and either mutant or wild-type cytoplasmic dynein, the Loa mutation confers significant reductions in the amount of mutant SOD1 protein in the mitochondrial matrix. Moreover, we show that the Loa mutation ameliorates defects in mitochondrial respiration and membrane potential observed in SOD1^G93A motor neuron mitochondria. These data suggest that the Loa mutation reduces the vulnerability of mitochondria to the toxic effects of mutant SOD1, leading to improved mitochondrial function in SOD1^G93A motor neurons.

Acetylcholine binding protein of mollusks is unlikely to act as a regulator of cholinergic neurotransmission at neurite-neurite synaptic sites in vivo

A population of glial cells in the central nervous system of the gastropod mollusk Lymnaea stagnalis produces a soluble protein that specifically binds acetylcholine. This protein is named the acetylcholine binding protein (AChBP). Experiments performed in vitro indicated that AChBP inactivates released acetylcholine at cholinergic synapses. On the basis of these observations, a similar in vivo role for AChBP was hypothesized. To fulfill this function, AChBP-expressing glia ought to be located in close proximity to cholinergic synapses in vivo. To examine this, we have analyzed the cellular and subcellular expression of AChBP in the intact CNS. Using a variety of molecular techniques, we demonstrate here that AChBP expression is confined to a subpopulation of glial cells located within the peripheral zone of each of the ganglia constituting the CNS. This zone contains the cell bodies of neurons, but few synapses. Conversely, glial cells that do not express the AChBP are predominantly located in the synapse-rich central neuropile zone but are rare in the cell body zone. Thus, our findings are not compatible with the previous conclusions drawn from in vitro studies and suggest that AChBP functions in vivo as a regulator of nonsynaptic cholinergic transmission.

Role of the histidine residue at position 105 in the human alpha 5 containing GABA(A) receptor on the affinity and efficacy of benzodiazepine site ligands

1. A histidine residue in the N-terminal extracellular region of alpha 1,2,3,5 subunits of the human GABA(A) receptor, which is replaced by an arginine in alpha 4 and alpha 6 subunits, is a major determinant for high affinity binding of classical benzodiazepine (BZ)-site ligands. The effect of mutating this histidine at position 105 in the alpha 5 subunit to an arginine (alpha 5H105R) on BZ-site pharmacology has been investigated using radioligand binding on HEK293 and L(tk-) cells and two electrode voltage clamp recording on Xenopus oocytes in which GABA(A) receptors of subtypes alpha 5, alpha 5H105R, alpha 4 and alpha 6 were co-expressed with beta 3 gamma 2s. 2. The classical BZs, diazepam and flunitrazepam (full agonists on the alpha 5 receptor) showed negligible affinity and therefore negligible efficacy on alpha 5H105R receptors. The beta-carbolines DMCM and beta CCE (inverse agonists on the alpha 5 receptor) retained some affinity but did not exhibit inverse agonist efficacy at alpha 5H105R receptors. Therefore, the alpha 5H105R mutation confers an alpha 4/alpha 6-like pharmacology to the classical BZs and beta-carbolines. 3. Ro15-4513, flumazenil, bretazenil and FG8094, which share a common imidazobenzodiazepine core structure, retained high affinity and were higher efficacy agonists on alpha 5H105R receptors than would be predicted from an alpha 4/alpha 6 pharmacological profile. This effect was antagonized by DMCM, which competes for the BZ-site and therefore is likely to be mediated via the BZ-site. 4. These data indicate that the conserved histidine residue in the alpha subunit is not only a key determinant in the affinity of BZ-site ligands on alpha 5 containing GABA(A) receptors, but also influences ligand efficacy.

pH-dependent secretion of SseB, a product of the SPI-2 type III secretion system of Salmonella typhimurium

The type III secretion system of Salmonella pathogenicity island 2 (SPI-2) is required for bacterial replication inside macrophages. SseB has been considered a putative target of the secretion system on the basis of its similarity with EspA, a protein secreted by the type III secretion system of enteropathogenic Escherichia coli (EPEC). EspA forms a filamentous structure on the bacterial cell surface and is involved in translocation of proteins into the eukaryotic cytosol. In this paper, we show that SseB is a secreted protein that associates with the surface of the bacterial cell and might, therefore, also be required for delivery of SPI-2 effector proteins to the eukaryotic cell cytosol. SseB begins to accumulate inside the bacterial cell when the culture enters early stationary phase. However, SseB is only secreted if the bacteria are grown at low pH or if the pH is shifted after growth from 7.0 to below pH 5.0. The secretion occurs within minutes of acidification and is totally dependent on a functional SPI-2 type III secretion system. As the pH of the Salmonella-containing vacuole inside host cells has been shown to acidify to between pH 4.0 and 5.0, and as SPI-2 gene expression occurs inside host cells, low pH might be a physiological stimulus for SPI-2-mediated secretion in vivo.

Genes encoding putative effector proteins of the type III secretion system of Salmonella pathogenicity island 2 are required for bacterial virulence and proliferation in macrophages

The type III secretion system of Salmonella pathogenicity island 2 (SPI-2) is required for systemic infection of this pathogen in mice. Cloning and sequencing of a central region of SPI-2 revealed the presence of genes encoding putative chaperones and effector proteins of the secretion system. The predicted products of the sseB, sseC and sseD genes display weak but significant similarity to amino acid sequences of EspA, EspD and EspB, which are secreted by the type III secretion system encoded by the locus of enterocyte effacement of enteropathogenic Escherichia coli. The transcriptional activity of an sseA::luc fusion gene was shown to be dependent on ssrA, which is required for the expression of genes encoding components of the secretion system apparatus. Strains carrying nonpolar mutations in sseA, sseB or sseC were severely attenuated in virulence, strains carrying mutations in sseF or sseG were weakly attenuated, and a strain with a mutation in sseE had no detectable virulence defect. These phenotypes were reflected in the ability of mutant strains to grow within a variety of macrophage cell types: strains carrying mutations in sseA, sseB or sseC failed to accumulate, whereas the growth rates of strains carrying mutations in sseE, sseF or sseG were only modestly reduced. These data suggest that, in vivo, one of the functions of the SPI-2 secretion system is to enable intracellular bacterial proliferation.

Neuropsychological abnormalities among HIV-infected individuals in a community-based sample

The purpose of this study was to determine the nature and extent of neuropsychological abnormalities among HIV-infected individuals and to examine the interrelationships between measures of cognitive functions and the factors that predict neuropsychological abnormalities. The study focused on cross-sectional data gathered in a multidisciplinary research clinic form 200 HIV-infected (HIV +) men and women recruited from primary medical care settings. Composite scores representing six cognitive domains were derived from the neuropsychological test data. Scores of memory, fluency, spatial, and frontal functions could be predicted by independent assessment of participants' verbal and psychomotor speed abilities. Basic verbal ability itself was predicted by education, race, and handedness, whereas speed was predicted by age, CD4+ cell counts, and a lifetime history of major depression. This model of effects is consistent with the hypothesis that psychomotor slowing is central to mild cognitive disorder in HIV infection and that such changes are associated with markers of the severity of systemic infection.

INKBLOT: a neurological diagnostic decision support system integrating causal and anatomical knowledge

As an initial step in the diagnostic process, human neurologists often use anatomical localization to constrain the set of diagnostic hypotheses deserving further consideration. We describe an automated system, INKBLOT-1, which uses anatomical localization in much the same way as human neurologists. Given a set of manifestations, INKBLOT-1 generates a set of hypothetical localizations relative to a coordinate system of nested cubes and then uses these localization(s) to explain the manifestations. We trace the reasoning mechanism utilized by INKBLOT-1 for a particular set of symptoms and show how INKBLOT-1 is able to generate novel hypotheses that explain the observed manifestations. In doing this, INKBLOT-1 demonstrates capabilities not demonstrated by previously described systems.

Prevalence and predictors of depressive, anxiety and substance use disorders in HIV-infected and uninfected men: a longitudinal evaluation

BACKGROUND

There is little agreement on whether the prevalence of psychiatric disorder is elevated in HIV-seropositive (HIV+) populations compared with uninfected persons. However, evaluation of this issue has been limited difficulties of sampling, study design and failure to control for other risk factors for disorder.

METHODS

Prevalence and clinical characteristics of DSM-III-R major depressive disorder (MDD), generalized anxiety disorder, adjustment disorder, and alcohol and substance abuse/dependence were evaluated in a representative sample of HIV+ men attending primary care physicians' offices in a defined geographical area. Lifetime prevalence at baseline and 1-year rates during longitudinal follow-up were determined for the 113 HIV+ men, as well as 57 HIV-men, via standardized interview. Multivariate analyses considered unique and combined effects of HIV serostatus and other risk factors on likelihood of disorder.

RESULTS

Although there were no differences in lifetime rates prior to baseline, HIV+ men were at greater risk for disorders during the prospective study period. For MDD, this effect was maintained even after controlling for other risk factors. Several of these other factors bore their own effects: regardless of HIV serostatus, men were susceptible to psychopathology if at baseline they were younger, had a lifetime psychiatric history, or had poor social supports or a low sense of personal mastery.

CONCLUSIONS

The risk of certain psychiatric disorders appears uniquely elevated in HIV+ men. Since other factors also influence risk, interventions designed to minimize psychopathology during HIV infection should attend to both HIV-related and non-HIV-related risk factors.

Development of subtle neurological signs after systemic illness in HIV-infected individuals

Thirty human immunodeficiency virus (HIV) infected individuals entered a longitudinal study without signs of dysfunction of the central nervous system (CNS). Nine of these individuals developed a systemic illness between study visits, and 7 of these 9 patients (78%) had neurological signs at the next examination (e.g., action-intention tremors, abnormal gait, release signs, abnormal deep tendon reflexes). Only 2/21 (9.5%) of the subjects who did not develop systemic illness showed such signs. These data are consistent with the hypothesis that other factors (e.g. cytokines) as well as the HIV may cause subtle CNS dysfunction.

An intelligent interactive system for delivering individualized information to patients

This paper is a report on the first phase of a long-term, interdisciplinary project whose goal is to increase the overall effectiveness of physicians' time, and thus the quality of health care, by improving the information exchange between physicians and patients in clinical settings. We are focusing on patients with long-term and chronic conditions, initially on migraine patients, who require periodic interaction with their physicians for effective management of their condition. We are using medical informatics to focus on the information needs of patients, as well as of physicians, and to address problems of information exchange. This requires understanding patients' concerns to design an appropriate system, and using state-of-the-art artificial intelligence techniques to build an interactive explanation system. In contrast to many other knowledge-based systems, our system's design is based on empirical data on actual information needs. We used ethnographic techniques to observe explanations actually given in clinic settings, and to conduct interviews with migraine sufferers and physicians. Our system has an extensive knowledge base that contains both general medical terminology and specific knowledge about migraine, such as common trigger factors and symptoms of migraine, the common therapies, and the most common effects and side effects of those therapies. The system consists of two main components: (a) an interactive history-taking module that collects information from patients prior to each visit, builds a patient model, and summarizes the patients' status for their physicians; and (b) an intelligent explanation module that produces an interactive information sheet containing explanations in everyday language that are tailored to individual patients, and responds intelligently to follow-up questions about topics covered in the information sheet.

Qualitative features of the memory deficit associated with HIV infection and AIDS: cross-validation of a discriminant function classification scheme

The neuropsychological defects associated with late stage HIV infection and AIDS have been characterized as being similar to those seen in patients with dementia syndromes of subcortical etiologies. The purpose of this paper is to report on the cross-center replication of the classification of HIV-infected subjects' neuropsychological status based on a discriminant function generated from other HIV-related and unrelated cognitively impaired subjects. Of the HIV-control subjects, 42/46 (91.3%) were classified as "Normal", with only two subjects in each of two "dementia" groups: subcortical and cortical. However, similar to other HIV+ samples, a large proportion (36%) of our HIV-infected subjects were classified as "Subcortical", with 61% classified as "Normal", and one (3%) in the "Cortical" group. These data demonstrate that not only does the cognitive performance of some HIV+ subjects have distinct features relative to that of HIV-control subjects, but that the features are consistent with previous suggestions that such patients have a "Subcortical" pattern of impairment.

Methodological considerations in estimating speed of cognitive operations

Individuals infected with Human Immunodeficiency Virus (HIV) and having cognitive impairment have been described as having slow mentation. Data supporting this proposition come from a variety of sources, including Sternberg's (1966) item recognition memory task. The procedure nominally provides an index of speed of mental operations, independent from input/output demands. However, since the original use of this procedure in the 1960s, advances in cognitive psychology have revealed many of its limitations. The purpose of the present study was to examine the psychometric characteristics of this task. Each participant performed the Sternberg item recognition task twice, 6 mo apart. The stability of the estimate of the slope of regression equations and for zero intercept ranged from excellent (r = .87) to poor (r = .30), and the data from many individual subjects could not be reliably modelled using multiple linear regression techniques. These data, as well as those from previous research, demonstrate the limited practical use of this task in clinical samples. Furthermore, as cognitive psychological theory has advanced in the past 30 yr, the conceptual underpinnings of the procedure have essentially evaporated.

Speech motor control disorder after HIV infection

We examined the clinical characteristics of six right-handed patients who developed speech motor control disorders after human immunodeficiency virus (HIV) infection. They exhibited an ataxic dysarthria, characterized by irregular articulatory breakdowns in consonant and vowel timing; were slow in timed decision-making tasks; and had impaired procedural learning. Other aspects of the neurologic examination revealed signs of diffuse CNS involvement including action-intention tremors, ataxic gait, and release signs. None developed HIV-associated dementia during 1 year of follow-up. Motor speech control disorder appears to be related to a cerebellar dysfunction.

The induction and reversal of topoisomerase II cleavable complexes formed by nuclear extract from the CHO DNA repair mutant, xrs1

The gamma-ray sensitive CHO cell mutant xrs1 is hypersensitive to antitumour drugs that stabilise DNA topoisomerase II (topoII) cleavable complexes. Sensitivity appears to result from DNA double-strand breaks (DSBs) that persist in xrs1 cells, but not wild-type CHO-K1 cells, following drug removal. One possible explanation for the persistence of DSBs in xrs1 cells is a defect in topoII which reduces its ability to reseal the DSBs associated with cleavable complexes following drug removal. To address this possibility, cleavable complexes formed in vitro by incubating VP16, plasmid DNA and nuclear extract from either CHO-K1 or xrs1 cells were induced to reverse by adding EDTA or salt to the reaction, or by raising the temperature to 65 degrees C, or by dilution of the drug. The fraction of drug-induced cleavable complexes that reversed in these experiments was dependent on how reversal was induced, and ranged from 55 to 95%. However, the extent of reversal was independent of the source of nuclear extract in all of the experiments, indicating that CHO-KI and xrs1 topoII is equally able to reseal complex-associated DSBs during cleavable complex reversal in vitro.

Involving patients in health care: explanation in the clinical setting

The long-term goal of our research is to improve the overall effectiveness of physicians' time, by improving the information exchange between physicians and chronic-care patients, initially migraine patients. The computer system we are constructing has a partial knowledge base about migraines, common therapies, and common side effects of those therapies. The system consists of two main programs: data collection and explanation. The design of our system is based on empirical data concerning patients' information needs.

DNA double-strand break repair pathways and cellular tolerance to inhibitors of topoisomerase II

The Chinese hamster ovary cell line xrs-1 is hypersensitive to gamma-radiation. This sensitivity has been attributed to an inability of this cell line to efficiently repair gamma-ray induced double-strand breaks (DSBs). We have recently reported that xrs-1 is also sensitive to topoisomerase II inhibitors that stabilize the cleavable complex. In this study, we have investigated the basis of this sensitivity by monitoring cleavable complex formation and loss in xrs-1 and its parent CHO-KI following treatment with the topoisomerase II inhibitors etoposide and 4'-(9-acridinylamino)methanesulfon-m-anisidide. Our studies indicate that xrs and CHO-K1 cells accumulate drug-induced cleavable complexes at equal rates and to an equal extent. However, studies on the loss of cleavable complexes after drug removal suggest that protein-free DSBs arise in cells treated with topoisomerase II inhibitors. Furthermore, a larger number of these DSBs persist in repair-deficient xrs cells than in repair-proficient Chinese hamster ovary-KI cells. The persistence of DSBs appears to account for the cytotoxic effects of topoisomerase II inhibitors that stabilize the cleavable complex. These results suggest that the xrs repair pathway is required for efficient removal of potentially cytotoxic DSBs that arise in cells treated with topoisomerase II inhibitors.

The alien hand syndrome. Clinical and postmortem findings

Two patients had automatonlike movements of their left hands and arms (alien hand syndrome) following damage to the brain. Autopsy findings in one patient demonstrated gunshot wound damage to the medial frontal white matter bilaterally, as well as the corpus callosum, right basal ganglia, internal capsule, and thalamus. The other patient had a ruptured anterior communicating aneurysm, with subsequent resection of the right frontal gyrus rectus. We postulate that this syndrome is due to the combination of a partial callosectomy and mesial frontal lesions.

Correlation of immunological studies and disease progression in chronic progressive multiple sclerosis

Thirty untreated patients with clinically definite chronic progressive multiple sclerosis were matched with 10 patients with clinically stable definite multiple sclerosis and 16 patients with other neurological diseases. A group of 12 normal control (NC) volunteers was matched to these groups. All patients with chronic progressive multiple sclerosis and normal control subjects were analyzed for the concanavalin A suppressor assay, mitogen stimulation, and phenotyping of peripheral blood mononuclear cells. In addition, serum was analyzed for interleukin-2 levels. Results of mitogen stimulation studies did not distinguish the groups. Concanavalin A-induced suppression was significantly decreased in the patients with chronic progressive multiple sclerosis (p less than 0.01). Phenotyping of fresh cells showed an elevated CD4: CD8 ratio in the patients with chronic progressive multiple sclerosis. Neither phenotyping nor concanavalin A-induced suppression correlated with or predicted the degree of disability, but the serum levels of interleukin-2 correlated inversely with disability (p less than 0.01) and directly with a poor prognosis after 18 months of observation (p less than 0.05). Serum levels of interleukin-2 decreased as the disease progressed.

Ribavirin: a clinical overview

Ribavirin, a broad spectrum, non-interferon-inducing virustatic chemotherapeutic agent, demonstrates activity against a wide range of RNA and DNA viruses, including the retrovirus known to cause the acquired immune deficiency syndrome. The drug's proposed mechanism of action, as well as pharmacokinetics are discussed, and preclinical toxicity, safety and clinical efficacy studies are presented. To date, the best success has occurred in the use of ribavirin to treat respiratory syncytial virus infection in infants and young children and to treat influenza A and B virus infections in young adults. Viral infections, particularly viral pneumonia, are often life-threatening in infants with severe combined immunodeficiency disease (SCID), and ribavirin aerosol has been used successfully to treat respiratory syncytial virus and parainfluenza virus infection of immunodeficient children. Special note is taken of ribavirin's clinical benefit in treating severe and life-threatening infections caused by the Lassa fever virus and the significant improvement over either the use of immune plasma or supportive therapy alone. Indeed, ribavirin thus emerges as the first antiviral drug that is able to reduce mortality in a highly lethal systemic disease by more than 90%. Additional studies demonstrate the drug's efficacy in acute viral hepatitis, herpesvirus infections, and measles. Controlled clinical trials are underway to test the drug in patients infected with the AIDS virus.

Brachial plexus myoclonus

Rhythmic myoclonus in an arm began abruptly following an injury and persisted continuously for six years. Topographical EMG showed abnormal activity confined to muscles innervated by the axillary and radial nerves from the posterior cord of the brachial plexus. Abduction of the arm above horizontal level stopped myoclonus and EMG discharges. EEG was normal. It is suggested that the myoclonus was caused by mechanical irritation of the posterior cord of the brachial plexus.

Symbolic coordinate anatomy for neurology (SCAN)

Our laboratory is responsible for development and maintenance of CADUCEUS (Formerly INTERNIST-1), a computer program to provide expert advice to the clinician in the realm of medical diagnosis. In order to extend its success in internal medicine into neurology, it was necessary to provide a paradigm for neuroanatomic reasoning. In our anatomic knowledge base (SCAN), the nervous system is partitioned into a hierarchical set of nested cubes. In the computer memory, a symbol for each cube has attached to it lists of structures that are wholly or partially within the cube. The structures may be simple (e.g., right locus ceruleus) or complex (e.g., midbrain). Lists of cubes belonging to particular vascular territories as well as systems (e.g., visual) are also maintained. Thus, computation of anatomic localization from a given symptom or finding is facilitated as well as characterization of consequences of vascular lesions or neighborhood effects from mass lesions.

Central nervous system complications of addiction to "T's and Blues"

Thirteen patients displayed neurologic complications of intravenous abuse of "T's and Blues" (pentazocine and tripelennamine). In six, the major presentation was seizures. Three patients had strokes, and three had CNS infections, two fungal and one related to subacute bacterial endocarditis. One patient had hepatic failure and an unusual encephalopathy. Foreign body embolization is common; the materials enter the cerebral circulation because of pulmonary arteriovenous shunts. Emboli may cause seizures, which also occur as a toxic effect of the drugs. Infection is due to unsterile injections. Enzyme elevations and diffuse vasculopathy raise the possibility of immune mechanisms.

Isoelectric focusing of gamma globulins in cerebrospinal fluid from patients with multiple sclerosis

The technique of isoelectric focusing has been adapted for rapid clinical analysis for globulins in cerebrospinal fluid with use of commercially prepared horizontal-slab acrylamide gels. The globulin fraction is concentrated by ammonium sulfate precipitation, which allows more of the relevant protein to be applied, use of a wider range of total protein concentrations, and higher resolution than is true for previously described methods. Critical variables include a constant concentration and volume of IgG, a constant low temperature of the acrylamide gel, and sensitive staining with Coomassie Brilliant Blue G-250. The apparatus used is adaptable for other electrophoretic procedures in the clinical laboratory, and the use of commercially prepared gel slabs is more convenient, more reproducible, and requires less time than other methods.

Isoelectric focusing of gamma globulins in cerebrospinal fluid from patients with multiple sclerosis

The technique of isoelectric focusing has been adapted for rapid clinical analysis for globulins in cerebrospinal fluid with use of commercially prepared horizontal-slab acrylamide gels. The globulin fraction is concentrated by ammonium sulfate precipitation, which allows more of the relevant protein to be applied, use of a wider range of total protein concentrations, and higher resolution than is true for previously described methods. Critical variables include a constant concentration and volume of IgG, a constant low temperature of the acrylamide gel, and sensitive staining with Coomassie Brilliant Blue G-250. The apparatus used is adaptable for other electrophoretic procedures in the clinical laboratory, and the use of commercially prepared gel slabs is more convenient, more reproducible, and requires less time than other methods.