Mutations of the thyroid hormone transporter MCT8 cause prenatal brain damage and persistent hypomyelination

CONTEXT

Mutations in the MCT8 (SLC16A2) gene, encoding a specific thyroid hormone transporter, cause an X-linked disease with profound psychomotor retardation, neurological impairment, and abnormal serum thyroid hormone levels. The nature of the central nervous system damage is unknown.

OBJECTIVE

The objective of the study was to define the neuropathology of the syndrome by analyzing brain tissue sections from MCT8-deficient subjects.

DESIGN

We analyzed brain sections from a 30th gestational week male fetus and an 11-year-old boy and as controls, brain tissue from a 30th and 28th gestational week male and female fetuses, respectively, and a 10-year-old girl and a 12-year-old boy.

METHODS

Staining with hematoxylin-eosin and immunostaining for myelin basic protein, 70-kDa neurofilament, parvalbumin, calbindin-D28k, and synaptophysin were performed. Thyroid hormone determinations and quantitative PCR for deiodinases were also performed.

RESULTS

The MCT8-deficient fetus showed a delay in cortical and cerebellar development and myelination, loss of parvalbumin expression, abnormal calbindin-D28k content, impaired axonal maturation, and diminished biochemical differentiation of Purkinje cells. The 11-year-old boy showed altered cerebellar structure, deficient myelination, deficient synaptophysin and parvalbumin expression, and abnormal calbindin-D28k expression. The MCT8-deficient fetal cerebral cortex showed 50% reduction of thyroid hormones and increased type 2 deiodinase and decreased type 3 deiodinase mRNAs.

CONCLUSIONS

The following conclusions were reached: 1) brain damage in MCT8 deficiency is diffuse, without evidence of focal lesions, and present from fetal stages despite apparent normality at birth; 2) deficient hypomyelination persists up to 11 years of age; and 3) the findings are compatible with the deficient action of thyroid hormones in the developing brain caused by impaired transport to the target neural cells.

Common genetic variants and risk of brain injury after preterm birth

BACKGROUND

The role of heritable factors in determining the common neurologic deficits seen after preterm birth is unknown, but the characteristic phenotype of neurocognitive, neuroanatomical, and growth abnormalities allows principled selection of candidate genes to test the hypothesis that common genetic variation modulates the risk for brain injury.

METHODS

We collected an MRI-linked genomic DNA library from 83 preterm infants and genotyped tag single nucleotide polymorphisms in 13 relevant candidate genes. We used tract-based spatial statistics and deformation-based morphometry to examine the risks conferred by carriage of particular alleles at tag single nucleotide polymorphisms in a restricted number of genes and related these to the preterm cerebral endophenotype.

RESULTS

Carriage of the minor allele at rs2518824 in the armadillo repeat gene deleted in velocardiofacial syndrome (ARVCF) gene, which has been linked to neuronal migration and schizophrenia, and rs174576 in the fatty acid desaturase 2 gene, which encodes a rate-limiting enzyme for endogenous long chain polyunsaturated fatty acid synthesis and has been linked to intelligence, was associated with white matter abnormality measured in vivo using diffusion tensor imaging (P = .0009 and P = .0019, respectively).

CONCLUSIONS

These results suggest that genetic variants modulate white matter injury after preterm birth, and known susceptibilities to neurologic status in later life may be exposed by the stress of premature exposure to the extrauterine environment.

Systemic autoimmunity in TAM triple knockout mice causes inflammatory brain damage and cell death

The Tyro3, Axl and Mertk (TAM) triply knockout (TKO) mice exhibit systemic autoimmune diseases, with characteristics of increased proinflammatory cytokine production, autoantibody deposition and autoreactive lymphocyte infiltration into a variety of tissues. Here we show that TKO mice produce high level of serum TNF-α and specific autoantibodies deposited onto brain blood vessels. The brain-blood barrier (BBB) in mutant brains exhibited increased permeability for Evans blue and fluorescent-dextran, suggesting a breakdown of the BBB in the mutant brains. Impaired BBB integrity facilitated autoreactive T cells infiltrating into all regions of the mutant brains. Brain autoimmune disorder caused accumulation of the ubiquitin-reactive aggregates in the mutant hippocampus, and early formation of autofluorescent lipofuscins in the neurons throughout the entire brains. Chronic neuroinflammation caused damage of the hippocampal mossy fibers and neuronal apoptotic death. This study shows that chronic systemic inflammation and autoimmune disorders in the TKO mice cause neuronal damage and death.

Revisiting the legal standards that govern requests to sterilize profoundly incompetent children: in light of the "Ashley Treatment," is a new standard appropriate?

This Note discusses the recent controversy surrounding a six-year-old girl named Ashley, whose parents chose to purposefully stunt her growth and remove her reproductive organs for nonmedical reasons. A federal investigation determined that Ashley's rights had been violated because doctors performed the procedure, now referred to as the "Ashley Treatment," without first obtaining a court order. However, the investigation did not make any conclusions regarding whether the "Ashley Treatment" could present a legally permissible treatment option in the future. After discussing the constitutional rights that the "Ashley Treatment" implicates and the current legal standards in place, this Note examines how courts have applied these legal standards to cases involving extreme requests. Drawing upon legal commentators, this Note concludes that a court could approve a request for the "Ashley Treatment" in appropriate and limited cases where the parents have presented clear and convincing evidence before a court that the benefits that the "Ashley Treatment" would provide to the child and her family outweigh the risks associated with the procedure. This Note argues that those benefits may include extrinsic considerations, but courts should remain cautious when considering such evidence and be sure that the evidence as a whole supports their conclusions.

[Epigenetic regulation in alcohol-related brain damage]

Ethanol is a deleterious agent that causes various kinds of neuronal damage to both the developing and adult brain. Recent research on alcoholism implicates impaired function of neural stem cell (NSC) in the pathogenesis of ethanol-induced brain dysfunction. We previously reported that the differentiation of NSCs into neurons was significantly influenced by ethanol. We also found that neuron-restrictive silencer factor/repressor element 1-silencing transcription factor (NRSF/ REST) binding activity potentiated by ethanol underlies the mechanism of ethanol inhibition of neuronal differentiation. Epigenetics refers to post-translational modifications of DNA and nuclear proteins that produce lasting alterations in patterns of gene expression. Epigenetic mechanism plays a critical role of neuronal plasticity and there is clear evidence that dysfunction of epigenetic mechanism also contributes to neurological and psychiatric illness. We will review epigenetic regulation in pathogenesis of psychiatric illness including alcoholism. We also demonstrated that trichostatin A, histone deacetylase inhibitor, reduced the ethanol-induced suppression of neuronal differentiation of NSCs. We suggest that ethanol alters the function of neural differentiation through the mechanism of potentiation of NRSF/REST binding and histone modifications.

Oxidative stress after subarachnoid hemorrhage in gp91phox knockout mice

BACKGROUND

Oxidative stress largely contributes to early brain injury after subarachnoid hemorrhage (SAH). One of the major sources of reactive oxygen species is NADPH oxidase, upregulated after SAH. We hypothesized that NADPH oxidase-induced oxidative stress plays a major causative role in early brain injury after SAH.

METHODS

Using gp91phox knockout (ko) and wild-type (wt) mice, we studied early brain injury in the endovascular perforation model of SAH. Mortality rate, cerebral edema, oxidative stress, and superoxide production were measured at 24 h after SAH. Neurological evaluation was done at 23 h after SAH surgery.

RESULTS

Genotyping confirmed the existence of a nonfunctional gp91phox gene in the ko mice. CBF measurements did not show differences in SAH-induced acute ischemia between ko and wt mice. SAH caused a significant increase of water content in the ipsilateral hemisphere as well as an increase of Malondialdehyde (MDA) levels and superoxide production. There were no significant differences in post-SAH mortality rate, brain water content and the intensity of the oxidative stress between knockout and wild type groups of mice.

CONCLUSIONS

Our results suggest that gp91phox is not critically important to the early brain injury after SAH. An adaptive compensatory mechanism for free radical production in knockout mice is discussed.

Spontaneously hypertensive rats are highly vulnerable to AMPA-induced brain lesions

BACKGROUND AND PURPOSE

Whereas the effects of chronic arterial hypertension on the cerebral vasculature have been widely studied, its effects on brain tissue have been studied less so. Here we examined if spontaneously hypertensive rats (SHRs) or the normotensive control Wistar Kyoto rats (WKYs) made hypertensive by renal artery stenosis (R-WKYs) are vulnerable to an excitotoxic brain lesion provoked by an overactivation of glutamate receptors.

METHODS

Lesion volumes were quantified by histology in WKYs and SHRs subjected to striatal administration of N-methyl-d-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA). The expression of AMPA receptors subunits and calcium/calmodulin kinase-II alpha was analyzed by real-time polymerase chain reaction and Western blot.

RESULTS

NMDA (50 and 75 nmol) induced similar lesions in both SHRs (10+/-2 mm(3) and 16+/-4 mm(3), respectively) and WKYs (11+/-2 mm(3) and 19+/-7 mm(3), respectively). However, AMPA-induced (2.5 and 5 nmol) lesions were significantly greater in 14-week-old SHRs (14+/-3 mm(3) and 20+/-5 mm(3), respectively) than WKYs (4+/-2 mm(3), P<0.05 and 7+/-4 mm(3), P<0.001, respectively). Furthermore, normotensive 7-week-old SHRs also displayed an aggravated AMPA-induced lesion compared with age-matched WKYs (10+/-3 mm(3) vs 6+/-3 mm(3); P<0.05). Neither NMDA nor AMPA produced increased lesion volumes in R-WKYs (12+/-3 mm(3) and 5+/-4 mm(3), respectively) compared with WKYs. Striatal levels of AMPA receptors subunits, GluR1 and GluR2, were not different between SHRs and WKYs. However, SHRs displayed an increase in phosphorylated form of GluR1 at Ser-831 (P<0.05), as well as in calcium/calmodulin kinase-II alpha (P<0.002). Selective inhibition of this kinase by KN-93 reduced AMPA-induced damage in SHRs (P<0.01 vs vehicle).

CONCLUSIONS

These findings show that an increase in phosphorylated GluR1, which increases AMPA receptor conductance, may be involved in the vulnerability of SHRs to AMPA.

Activation of the galanin receptor 2 (GalR2) protects the hippocampus from neuronal damage

Expression of the neuropeptide galanin is up-regulated in many brain regions following nerve injury and in the basal forebrain of patients with Alzheimer's disease. We have previously demonstrated that galanin modulates hippocampal neuronal survival, although it was unclear which receptor subtype(s) mediates this effect. Here we report that the protective role played by galanin in hippocampal cultures is abolished in animals carrying a loss-of-function mutation in the second galanin receptor subtype (GalR2-MUT). Exogenous galanin stimulates the phosphorylation of the serine/threonine kinase Akt and extracellular signal-regulated kinase (ERK) in wild-type (WT) cultures by 435 +/- 5% and 278 +/- 2%, respectively. The glutamate-induced activation of Akt was abolished in cultures from galanin knockout animals, and was markedly attenuated in GalR2-MUT animals, compared with WT controls. In contrast, similar levels of glutamate-induced ERK activation were observed in both loss-of-function mutants, but were further increased in galanin over-expressing animals. Using specific inhibitors of either ERK or Akt confirms that a GalR2-dependent modulation in the activation of the Akt and ERK signalling pathways contributes to the protective effects of galanin. These findings imply that the rise in endogenous galanin observed either after brain injury or in various disease states is an adaptive response that reduces apoptosis by the activation of GalR2, and hence Akt and ERK.

Effect of kainic acid treatment on insulin-like growth factor-2 receptors in the IGF2-deficient adult mouse brain

Insulin-like growth factor-2 (IGF2) is a member of the insulin gene family with known neurotrophic properties. The actions of IGF2 are mediated via the IGF type 1 and type 2 receptors as well as through the insulin receptors, all of which are widely expressed throughout the brain. Since IGF2 is up-regulated in the brain after injury, we wanted to determine whether the absence of IGF2 can lead to any alteration on brain morphology and/or in the response of its receptor binding sites following a neurotoxic insult. No morphological differences were observed between the brains of IGF2 knockout (IGF2(-/-)) and wild-type control (IGF2(+/+)) mice. However, our in vitro receptor autoradiography results indicate that IGF2(-/-) mice had lower endogenous levels of [(125)I]IGF1 and [(125)I]insulin receptor binding sites in the hippocampus and cerebellum as compared to IGF2(+/+) mice, while endogenous [(125)I]IGF2 receptor binding showed a decrease only in the cerebellum. Seven days after kainic acid administration, the [(125)I]insulin receptor binding sites were significantly decreased in all brain regions of the IGF2(+/+) mice, while the levels of [(125)I]IGF1 and [(125)I]IGF2 binding sites were decreased only in select brain areas. The IGF2(-/-) mice, on the other hand, showed increased [(125)I]IGF1 and [(125)I]IGF2 and [(125)I]insulin receptor binding sites in selected regions such as the hippocampus and cerebellum. These results, taken together, suggest that deletion of IGF2 gene does not affect gross morphology of the brain but does selectively alter endogenous [(125)I]IGF1, [(125)I]IGF2 and [(125)I]insulin receptor binding sites and their response to neurotoxicity.

Precursors and prodromata of schizophrenia: findings from the Edinburgh High Risk Study and their literature context

BACKGROUND

In schizophrenia research, 'high risk' traditionally referred to studies of the offspring of schizophrenic parents at genetically enhanced risk of illness development. Sixteen major high-risk studies have been undertaken although only six followed through to formal illness so data on prediction remain weak. Recently, 'high risk' has widened to encompass individuals considered 'at risk' by having 'high risk mental states', regardless of family history, in whom initiation of early treatment is postulated to improve outcome.

METHOD

The major familial high-risk studies are reviewed from the perspective of the Edinburgh High Risk Study of Schizophrenia (EHRS), with emphasis on prediction.

RESULTS

Familial high-risk studies have established multiple biological markers, the most reproducible of which relate to neuromotor development and cognition, especially aspects of memory/learning. Although most are probably not specific, they support a neurodevelopmental hypothesis. Family and environmental variables point largely to secondary or indirect associations. Pre-illness, non-specific affective symptomatology may be of greater predictive power than most psychotic phenomena.

CONCLUSIONS

Traditional high-risk designs embody many problems but are able to distinguish non-specific markers from illness predictors, and are ideally suited to exploring the evolution of schizophrenia both clinically and biologically (especially with imaging techniques). The EHRS supports the view that greater specificity may accrue to cognitive domains as precursors of predictive utility.

Long-QT-Syndrom als Differenzialdiagnose einer Grand-Mal-Epilepsie

A 24-year-old female with a history of epileptic seizures was admitted after prolonged cardiac resuscitation. The clinical course together with additional examinations led to the diagnosis of severe hypoxic cerebral damage, with poor prognosis for neurological outcome. In her initial ECG, as in the ECGs of several family members, QT prolongation was diagnosed. Meticulous history taking and ensuing genetic analysis led to the diagnosis of familial long QT syndrome (LQTS) with a mutation in the LQT-2 gene (HERG). In retrospect, the previous seizure episodes have to be considered cardiac syncopes. Two family members had previously died suddenly, and ECG and genetic analysis revealed that a total of eight family members were affected. These relatives were prophylactically treated with beta blockers or supplied with automated implantable cardioverter defibrillating devices. The literature concerning LQTS, diagnosis and prognosis of cerebral hypoxic damage, and differentiation between seizures and cardiac syncopes is discussed.

Mouse brains deficient in neuronal PDGF receptor-beta develop normally but are vulnerable to injury

Platelet-derived growth factors (PDGFs) and PDGF receptors (PDGFRs) are widely expressed in the mammalian CNS, though their functional significance remains unclear. The corresponding null-knockout mutations are lethal. Here, we developed novel mutant mice in which the gene encoding the beta subunit of PDGFR (PDGFR-beta) was genetically deleted in CNS neurons to elucidate the role of PDGFR-beta, particularly in the post-natal stage. Our mutant mice reached adulthood without apparent anatomical defects. In the mutant brain, immunohistochemical analyses showed that PDGFR-beta detected in neurons and in the cells in the subventricular zone of the lateral ventricle in wild-type mice was depleted, but PDGFR-beta detected in blood vessels remained unaffected. The cerebral damage after cryogenic injury was severely exacerbated in the mutants compared with controls. Furthermore, TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive neuronal cell death and lesion formation in the cerebral hemisphere were extensively exacerbated in our mutant mice after direct injection of NMDA without altered NMDA receptor expression. Our results clearly demonstrate that PDGFR-beta expressed in neurons protects them from cryogenic injury and NMDA-induced excitotoxicity.

Purinergic receptors modulate MAP kinases and transcription factors that control microglial inflammatory gene expression

Following many types of brain injury, microglial cell hyperactivation, and the subsequent release of neurotoxic mediators into the CNS contributes to inflammation and neuronal death. Among the proteins important for modulating the inflammatory function of microglia are the P2 purinergic receptors for which extracellular adenine nucleotides, such as ATP, are ligands. Because adenine nucleotides are abundant in the extracellular fluid following brain injury, ATP may represent an important component of the inflammatory microenvironment controlling microglial cell function. Although much work has been done examining the mechanisms whereby adenine nucleotides stimulate inflammatory mediator production, little is known concerning their complementary inhibitory effects. In this review we will focus on what is currently known about the microglial inhibitory effects of adenine nucleotides in the context of inflammation and summarize the current knowledge of their effects via purinergic receptors on microglial signal transduction pathways including transcription factors important for controlling inflammatory gene expression. The relevance of these mechanisms to microglial inflammatory function and physiology will be discussed. Further, we present data here illustrating that MAP kinase signal transduction pathways are altered in activated microglia that have been primed with or co-exposed to adenine nucleotides; effects that are stimulus- and MAPK pathway-specific. We also demonstrate the ability of P2X7 receptors to stimulate the phosphorylation of CREB, a putative inhibitory transcription factor in microglia. Together, these data indicate that ATP may be an endogenous inhibitor or neuroprotective molecule decreasing the inflammatory capacity of microglia.

Rapid diagnosis of glycine encephalopathy by13C-glycine breath test

OBJECTIVE

It is currently problematic to confirm the clinical diagnosis of glycine encephalopathy, requiring either invasive liver biopsy for enzymatic analysis of the glycine cleavage system or exhaustive mutation analysis. Because the glycine cleavage system breaks down glycine generating carbon dioxide, we suppose that the glycine cleavage system activity could be evaluated in vivo by measuring exhaled (13)CO(2) after administration of [1-(13)C]glycine.

METHODS

The [1-(13)C]glycine breath test was performed in 10 control subjects and 5 glycine encephalopathy patients with GLDC mutation, including 1 patient with mild glycine encephalopathy.

RESULTS

All the patients showed lower (13)CO(2) excretion than any control subject.

INTERPRETATION

Not only typical GE but also atypical GE can be reliably diagnosed by the (13)C-glycine breath test. Because it is rapid, non-invasive, and requires little expertise, the breath test could be useful as a standard test for diagnosing GE.

Stroke injury in rats causes an increase in activin A gene expression which is unaffected by oestradiol treatment

Activins are members of the transforming growth factor-beta superfamily that exert neurotrophic and neuroprotective effects on various neuronal populations. To determine the possible function of activin in stroke injury, we assessed which components of the activin signalling pathway were modulated in response to middle cerebral artery occlusion (MCAO). Furthermore, because oestradiol replacement protects against MCAO-induced cell death, we explored whether oestradiol replacement influences activin gene expression. Female Sprague-Dawley rats underwent permanent MCAO and the expression of activins and their corresponding receptors was determined by semiquantitative reverse transcriptase-polymerase chain reaction at 24 h after onset of ischaemia. We observed up-regulation of activin betaA and activin type I receptor A mRNA in response to injury. Dual-label immunocytochemistry followed by confocal z-stack analysis showed that the activin A expressing cells comprised neurones. Next, we monitored the time course of activin betaA mRNA expression in oestradiol- or vehicle-treated rats at 4, 8, 16 and 24 h after MCAO via in situ hybridisation. Starting at 4 h after injury, activin betaA mRNA was up-regulated in cortical and striatal areas in the ipsilateral hemisphere. Activin betaA mRNA levels in the cortex increased dramatically with time and were highest at 24 h after the insult, and oestradiol replacement did not influence this increase.

Dementia, pyramidal system involvement, and leukoencephalopathy with a presenilin 1 mutation

The authors describe four members of a family with a novel P284S presenilin 1 mutation presenting a clinical phenotype characterized by early-onset dementia, paratetraparesis, dysarthria, dysphagia, and marked involvement of brain white matter. The distinctive clinical and MRI findings in the family studied extend the phenotypic spectrum of dementia associated with mutation of the PS1 gene.

Maternal mutation 677C > T in the methylenetetrahydrofolate reductase gene associated with severe brain injury in offspring

A frequent polymorphism in the gene coding for 5,10-methylenetetrahydrofolate reductase is the substitution 677C > T which produces a thermolabile and inefficient enzyme. Homozygosity for the 677C > T allele is the most important determinant of hyperhomocys-teinemia, when folic acid intake is reduced. Most studies on the relationship between the 677C > T variant in the mother and defects in the offspring have focused on neural-tube defects. This study is a retrospective case-control investigation of hypoxic-ischemic encephalopathy of the newborn (HIEN) with reference to the 677C > T polymorphism as a genetic risk for this condition. The prevalence of the 677C > T allele was studied in 11 children with HIEN, their respective mothers, and 85 healthy individuals. Plasma homocysteine levels after fasting and methionine loading were determined in both mothers and controls. Ten of 11 patients were evaluated using magnetic resonance (MR) imaging, and all showed multicystic encephalomalacia and severe brain vasculopathy. Seven mothers were homozygous and four heterozygous for the 677C > T allele. Five of the children were homozygous and six heterozygous for this polymorphism. The variant allele frequency was higher in the group of mothers with affected children than in the controls and was associated with an increase in plasma homocysteine after methionine loading, in the group of mothers than in controls. The 677C > T mutation in mothers, either in a homozygous or heterozygous state, together with poor nutritional status (probable folate deficiency) may represent a risk factor for irreversible HIEN in the offspring.

Association between interleukin-1 beta (IL-1beta) gene polymorphism and outcome after head injury: an early report

BACKGROUND

Recent studies focusing on the genetic influences on outcome after head injury (HI) have suggested that different alleles of certain genes are associated with different outcomes. Interleukin-1 beta (IL-1beta) gene, especially beta2 polymorphism, is frequently observed in Alzheimer's disease, a remarkable degenerative state in which HI is among the known risk factors. Therefore, the aim of this paper was to search for the possible association between the outcome and IL-1beta gene polymorphism in human HI.

METHODS

The study group was composed of the 69 patients admitted to the neurosurgery department after HI. The severity of the initial injury was evaluated by means of the Glasgow Coma Scale and outcome six months later was assessed by means of the Glasgow Outcome Scale. IL-1beta genotypes were determined from blood samples by standard methods.

FINDINGS

Fourteen of 25 (56%) patients with IL-1beta +3953 allele 2 had an unfavourable outcome (dead, vegetative state or severe disability) compared with eight of 44 (18.1%) patients without IL-1beta +3953 (p = 0.0004). Similarly, 20 of 28 (71.4%) patients with IL-1beta -511 allele 2 had an unfavourable outcome compared with two of 41 (4.8%) patients without IL-1beta -511 (p = 0.005). Patients who had a composite of IL-1beta 2/2 or 1/2 genotype from both -511 and +3953 region of the chromosome 2 were more prone to have bad prognosis.

CONCLUSION

Results of our study demonstrated that there might be a significant association between IL-1beta gene polymorphism and outcome after HI, supporting the hypothesis of a genetically determined influence.

Brain and bone damage in KARAP/DAP12 loss-of-function mice correlate with alterations in microglia and osteoclast lineages

Human polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy, also known as Nasu-Hakola disease, has been described to be associated with mutations affecting the immunoreceptor tyrosine-based activation motif-bearing KARAP/DAP12 immunoreceptor gene. Patients present bone fragilities and severe neurological alterations leading to presenile dementia. Here we investigated whether the absence of KARAP/DAP12-mediated signals in loss-of-function (KDelta75) mice also leads to bone and central nervous system pathological features. Histological analysis of adult KDelta75 mice brains revealed a diffuse hypomyelination predominating in anterior brain regions. As this was not accompanied by oligodendrocyte degeneration or microglial cell activation it suggests a developmental defect of myelin formation. Interestingly, in postnatal KDelta75 mice, we observed a dramatic reduction in microglial cell numbers similar to in vitro microglial cell differentiation impairment. Our results raise the intriguing possibility that defective microglial cell differentiation might be responsible for abnormal myelin development. Histomorphometry revealed that bone remodeling is also altered, because of a resorption defect, associated with a severe block of in vitro osteoclast differentiation. In addition, we show that, among monocytic lineages, KARAP/DAP12 specifically controls microglial and osteoclast differentiation. Our results confirm that KARAP/DAP12-mediated signals play an important role in the regulation of both brain and bone homeostasis. Yet, important differences exist between the symptoms observed in Nasu-Hakola patients and KDelta75 mice.

Human Attentional Networks

In recent years it has been possible to treat attention as an organ system with its own anatomy, circuitry and set of functions. We view attention in terms of three interrelated neural networks in the human brain. These networks carry out the specific functions of developing and maintaining the alert state, orienting to sensory input, and executive control. Damage to these networks or their chemical neuromodulators can produce specific neurological and psychiatric deficits. We have conducted behavioral, developmental, and patient studies using functional magnetic resonance imaging (fMRI), event related potentials (ERP), genetics, and computational modeling to investigate the anatomy, circuitry, pathology, and development of attentional networks. The Attentional Network Test (ANT) is developed to measure the efficiency of each of the attention networks. The ANT can also serve as an endophenotype for genetic studies on attentional networks. This paper reviews our work with the ANT in studies of normal performance and various forms of psychopathology.

Cholesterol Efflux as a Critical Component of Alzheimer's Disease Pathogenesis

The risk of Alzheimer's disease and the levels of amyloid deposition are altered by factors associated with high cholesterol levels. When cells have high levels of cholesterol, they induce an efflux system of to maintain a proper cholesterol equilibrium. In the brain, cholesterol is converted to 24S hydroxycholesterol by the enzyme Cyp46. 24S hydroxycholesterol promotes gene transcription through interactions with LXR. We have found that in cells derived from the brain, two proteins important for cholesterol efflux, ABCA1 and apoE, are induced by this system. Furthermore, we have found that pharmacologic induction of LXR also induced secreted Abeta levels, particularly levels of Abeta42. We suggest that the risk of amyloid deposition associated with high cholesterol may be through induction of the LXR system.

Pyridoxine-dependent seizures: magnetic resonance spectroscopy findings

Pyridoxine-dependent seizures are an extremely rare genetic disorder. Early diagnosis and treatment are important for the prevention of permanent brain damage. Elevated levels of glutamate and decreased levels of gamma-aminobutyric acid (GABA) in the frontal and parietal cortices are among the characteristic features of this disorder. These metabolic abnormalities eventually lead to seizures and neuronal loss. In this case report, we present magnetic resonance spectroscopy findings of a 9-year-old girl with pyridoxine-dependent seizures with mental retardation. The N-acetylaspartate-to-creatine ratio was found to be decreased in the frontal and parieto-occipital cortices, which could indicate neuronal loss. Magnetic resonance spectroscopy could be a useful tool in the neuroimaging evaluation for assessment of parenchymal changes despite a normal-appearing brain magnetic resonance image in patients with pyridoxine-dependent seizures.

Do women possess a unique susceptibility to the neurotoxic effects of alcohol?

Neurodegeneration and neurological impairment associated with alcohol dependence have been observed predominantly in alcohol-dependent men. Thus little research has examined the neuropathological consequences of alcoholism in women. Recent evidence obtained from both human and animal studies, however, suggests that women may well be at greater risk of alcohol-induced brain injury than men are. Further, researchers have used animal models to identify molecular events that may contribute to this putative sex difference. Such data are likely of significance in both understanding women's unique susceptibility to neurotoxic effects of alcohol and addressing the possibility that the medical management of alcoholism in women and men may require distinct approaches. As a whole, these findings clearly indicate the need for a significant expansion of both clinical and basic science research of this topic.

Prenatal contributions to epilepsy: lessons from the bedside

While epilepsy can present at any age, this condition often occurs because of adverse events early in life. Pathogenetic mechanisms also cause deleterious consequences to the brain during prenatal life. For the epileptologist to fully appreciate developmental epileptogenesis, one must apply an ontogenetic approach (i.e. "nature-nurture-niche") in order to study the epileptic condition from a fetal neurology perspective. Genetic susceptibility can involve pre-fertilization and post-fertilization mechanisms that dictate the timing and form of major malformations associated with specific epileptic syndromes. Maternal, fetal, and placental disease conditions also contribute to either brain malformations or injuries, depending on events during the first or second half of pregnancy. Sequential stages during prenatal brain development, from embryonic through perinatal periods, specify which gray and white matter structures may be adversely altered, with later expression of seizures in the context of motor, cognitive and behavioral deficits. Translational research from bench to bedside should consider the acquired causes of pediatric and adult epilepsies in the context of the patient's genetic environment.

The yield of the medical evaluation of children with pervasive developmental disorders

Little information is available regarding the yield of the medical evaluation of children diagnosed with pervasive developmental disorder-not otherwise specified (PDD-NOS) compared to children diagnosed with autistic disorder. Medical records were reviewed for 182 patients less than 18 years of age with either PDD-NOS or autistic disorder evaluated between 1994 and 1998 at Mayo Clinic. A condition likely to be etiologically relevant was identified in 6/117 (5.1%) patients diagnosed with PDD-NOS and 2/65 (3.1%) patients diagnosed with autistic disorder. Genetic disorders, both chromosomal and single-gene, were the most commonly identified conditions. Seizure disorders, electroencephalogram abnormalities, and anomalies on brain imaging were common in both groups. The likelihood of uncovering an etiologically relevant condition in children diagnosed with either PDD-NOS or autistic disorder may be equivalent. The scope of the etiological search in an individual patient with an autistic spectrum disorder should not be limited by the specific diagnostic category.

Individual susceptibility to Wernicke-Korsakoff syndrome and alcoholism-induced cognitive deficit: impaired thiamine utilization found in alcoholics and alcohol abusers

To investigate mechanisms predisposing to alcoholic brain damage, thiamine (vitamin B1 ), riboflavin (vitamin B2 ) and pyridoxine (vitamin B6 ) status was compared in persistent alcohol misusers (PAM) admitted for detoxification without evidence of significant brain damage, in alcoholics known to have severe chronic brain damage (BDAM), and in age, gender and ethnicity matched controls. Thus, activities of thiamine-dependent transketolase (ETK), riboflavin-dependent glutathione reductase, and pyridoxine-dependent aspartate amino transferase were assayed, together with the enzyme activities following addition of the appropriate co-factor. Twenty per cent of the PAM group had an abnormally low ETK activity and an abnormally high activation ratio, while 45% were abnormal in either one or both parameters. An additional 10% of the PAM group had an abnormally high activation ratio but normal ETK activity, as did 30% of the BDAM group. These subgroups of alcohol misusers may have increased requirements for thiamine secondary to an abnormality of the transketolase protein that may predispose such patients to alcoholic brain damage. There was no evidence of riboflavin or pyridoxine deficiency in either of the patient groups. We conclude that thiamine deficiency was commonly present in the alcoholic patients, and that a subgroup of patients may be predisposed to more severe brain damage as a consequence of abnormalities in the transketolase protein.

Disrupted synaptic development in the hypoxic newborn brain

Infants born prematurely risk significant life-long cognitive disability, representing a major pediatric health crisis. The neuropathology of this cohort is accurately modeled in mice subjected to sublethal postnatal hypoxia. Massively parallel transcriptome analysis using cDNA microchips (9,262 genes), combined with immunohistochemical and protein assays, reveals that sublethal hypoxia accentuates genes subserving presynaptic function, and it suppresses genes involved with synaptic maturation, postsynaptic function, and neurotransmission. Other significantly affected pathways include those involved with glial maturation, vasculogenesis, and components of the cortical and microtubular cytoskeleton. These patterns reveal a global dysynchrony in the maturation programs of the hypoxic developing brain, and offer insights into the vulnerabilities of processes that guide early postnatal cerebral maturation.

Neurocognitive impairments in nonpsychotic parents of children with schizophrenia and attention-deficit/hyperactivity disorder: the University of California, Los Angeles Family Study

BACKGROUND

We tested the hypotheses that certain neurocognitive impairments index genetic liability to schizophrenia and that childhood-onset schizophrenia (COS) is a variant of adult-onset schizophrenia (AOS) by determining whether parents of COS probands show the types of neurocognitive impairments found in relatives of AOS probands.

METHODS

Parents of COS probands (n = 79) were compared with parents of attention-deficit/hyperactivity disorder (ADHD; n = 190) and community control (CC; n = 115) probands on 3 neurocognitive tasks shown in previous research to detect impairments in patients with AOS and ADHD and in the relatives of patients with AOS. Parents with a diagnosis of psychosis were excluded from the study.

RESULTS

On the Degraded Stimulus-Continuous Performance Test and the Trail-Making Test B-Adolescent Version, the parents of COS probands performed significantly worse than the parents of CC and ADHD probands, who did not differ significantly from each other. On the Span of Apprehension, we found no significant group differences. Using rigorous cutoffs, a combination of scores on the 3 neurocognitive tests identified 16 (20%) of the mothers and fathers of COS probands compared with 0% of the mothers and fathers of CC probands. There was diagnostic specificity of the neurocognitive impairments. A combination of neurocognitive scores identified 6 (12%) of the mothers of COS probands vs 0% of the mothers of ADHD probands. A cutoff that identified 2 (2%) of the fathers of ADHD probands classified 5 (17%) of the fathers of COS probands. We found no significant differences in neurocognitive functions between the parents of ADHD and CC probands.

CONCLUSIONS

The aggregation of neurocognitive impairments in the parents of COS probands provides further evidence of etiologic continuity between COS and AOS. A substantial subgroup of parents of COS probands had a worse neurocognitive performance than that of any of the parents of ADHD and CC probands. Receiver operating characteristic curves showed that when rigorous cutoffs define neurocognitive impairments, the combination of scores on certain neurocognitive tasks produced a level of diagnostic accuracy in the parents of COS probands that is sufficient for use in genetic linkage studies.

What framework should we use for understanding developmental disorders?

The neuropsychology of dyslexia has made great strides in the last decade. In particular, a consensus views dyslexia as a developmental disorder with a basis in the brain and in the genes, where the interaction of genetic and environmental factors is taken for granted. However, problems in defining the phenotype continue to bedevil research. The main conceptual problems can be expressed in three main questions: (a) Is dyslexia based on a specific brain abnormality or is it merely part of a continuum of atypical brain development? (b) When can we speak of comorbidity? (c) Why does so much individual variability occur? These questions can be tackled in a common framework that takes into account simultaneously three levels: the biological, the cognitive, and the behavioral.

Neurodevelopmental origins of tardivelike dyskinesia in schizophrenia patients and their siblings

The question of whether dyskinesia of the type found in tardive dyskinesia (TD) related to schizophrenia has a neurodevelopmental background was studied in a sample of 60 younger schizophrenia patients (mean age 38 years) and 21 of their non-ill siblings. TD-like dyskinesia was studied in relation to selected risk factors in the patients, and to neurological abnormality and parkinsonism in both patients and siblings. One or more signs of TD-like dyskinesia in patients were predicted by male gender, a history of obstetric complications, shorter illness duration, and shorter neuroleptic exposure. One or more signs of TD-like dyskinesia were found in 28.5 percent of the siblings and tended to be associated with neurological abnormality. Little co-occurrence of TD-like dyskinesia was found in the sibling and the patient in the same family. Patients' TD-like dyskinesia was significantly associated with hard neurological signs (independent of involuntary movements) but not with soft signs or primitive reflexes per se. TD-like dyskinesia showed a significant positive relationship to parkinsonism in patients. TD-like dyskinesia in younger schizophrenia patients appears to have neurodevelopmental antecedents and seems to represent one aspect of the total neurological abnormality associated with schizophrenia.

Clinical and laboratory findings in twins with neonatal epileptic encephalopathy mimicking aromatic L-amino acid decarboxylase deficiency

Aromatic L-amino acid decarboxylase (AADC) is a vitamin B 6 requiring enzyme involved in the biosynthesis of the neurotransmitters dopamine (DA) and serotonin. Lack of AADC leads to a combined deficiency of the catecholamines DA, norepinephrine (NE), epinephrine (E) as well as of serotonin. Here we describe premature twins who presented with severe seizures, myoclonus, rotatory eye movements and sudden clonic contractions. The patients showed an improvement of the clonic contractions under vitamin B 6 supplementation but died in the third week of life. In CSF and urine a biochemical pattern indicative of AADC deficiency was revealed. Concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were decreased, in association with increased concentrations of 3-ortho-methyldopa (3-OMD) in CSF and significantly increased vanillactic acid in urine. The AADC enzyme substrates L-dopa and 5-hydroxytryptophan (5-HTP) were elevated in CSF. Elevated concentrations of threonine as well as of an unidentified compound in CSF rounded off the biochemical pattern. AADC activity was found to be increased in plasma and deficient in the liver. Molecular studies effectively ruled out a genetic defect in the AADC gene. The basis for the epileptic encephalopathy in the twins may be located in the metabolism of vitamin B 6 and remains to be defined.

Psychiatric disorders after childhood stroke

OBJECTIVES

To determine the rate, types, and correlates of psychiatric disorder (PD) following stroke and orthopedic disorders in children and adolescents.

METHOD

Children aged 5 to 19 were assessed. The study used a cross-sectional design that compared 29 stroke subjects with 29 congenital clubfoot or scoliosis subjects. Assessments of psychiatric status; cognitive, adaptive, academic, and family functioning; family psychiatric history; neuroimaging; and neurological status were conducted. The main outcome measure was a current PD not present before the stroke or orthopedic disorder.

RESULTS

Poststroke PD occurred significantly more often than postorthopedic diagnosis PD (17/29 [59%] versus 4/29 [14%], p < or =.001). Subjects with ongoing poststroke PD had significantly more impaired intellectual and adaptive functioning, higher intensity family psychiatric history scores, and tended toward higher neurological severity index scores, but they were not different regarding lesion volume or family functioning compared with stroke subjects without PD. Regression analyses showed that neurological severity and family psychiatric history independently contributed significantly to predicting PD.

CONCLUSIONS

The data suggest that there are significant biopsychosocial correlates of PD in children with focal neurological lesions. These include a relatively abnormal neurological exam, lower IQ, and increased family psychopathology.

Dilated Virchow-Robin spaces in myotonic dystrophy: frequency, extent and significance

To study the frequency, extent and significance of dilated Virchow-Robin spaces (VRSs) in dystrophia myotonica (DM), we evaluated the cranial magnetic resonance imaging (MRI) of 41 patients with the adult form of DM and 41 healthy controls. Dilated VRSs and white matter lesions (WMLs) were rated according to semiquantitative methods. Convexity VRSs were more frequent (68 vs. 34%; p < 0.01) and severer (median scores: 4 vs. 0; p < 0.01) in DM patients than in controls, while lenticulostriate VRSs did not show significant differences in frequency (83 vs. 70%; p > 0.05) and severity (median scores: 4 vs. 3; p > 0.05). WMLs were more frequent (66 vs. 22%; p < 0.01) and severer (median scores: 5 vs. 0; p < 0.01) in patients. Disease duration was negatively correlated with convexity VRSs and positively with lobar (centrum semiovale) WML scores. Dilated convexity VRSs might be one of the initial findings in cranial MRI of DM, preceding the appearance of lobar WMLs.

Aicardi-Goutieres syndrome in siblings

Two siblings with familial encephalopathy, calcification of the basal ganglia, and cerebrospinal fluid lymphocytosis, constituting the triad of Aicardi-Goutieres syndrome, are reported. This syndrome resembles congenital intrauterine infections, which must be meticulously excluded. Aicardi-Goutieres syndrome is extremely rare and is being reported from the Arab world for the first time to our knowledge.

Ring chromosome 20 epilepsy syndrome in children: electroclinical features

Ring chromosome 20 mosaicism is associated with dysmorphic features, mental retardation, and intractable seizures, including recurrent episodes of nonconvulsive status epilepticus. The authors' findings in four children, all without dysmorphic features, indicate that mental deterioration and frequent subtle nocturnal frontal lobe seizures, associated with a characteristic EEG pattern, represent prominent additional clinical features not previously described in this syndrome. This emphasizes the importance of full-night video-EEG in children with frontal lobe seizures and cognitive deterioration.

Developmental dyscalculia

Developmental dyscalculia is a specific learning disability affecting the acquisition of arithmetic skills in an otherwise-normal child. Although poor teaching, environmental deprivation, and low intelligence have been implicated in the etiology of developmental dyscalculia, current data indicate that this learning disability is a brain-based disorder with a familial-genetic predisposition. The neurologic substrate of developmental dyscalculia is thought to involve both hemispheres, particularly the left parietotemporal areas. Developmental dyscalculia is a common cognitive handicap; its prevalence in the school population is about 5-6%, a frequency similar to those of developmental dyslexia and attention-deficit-hyperactivity disorder. Unlike these, however, it is as common in females as in males. Developmental dyscalculia frequently is encountered in neurologic disorders, examples of which include attention-deficit-hyperactivity disorder, developmental language disorder, epilepsy, and fragile X syndrome. The long-term prognosis of developmental dyscalculia is unknown; it appears, however, to persist, at least for the short-term, in about half of affected preteen children. The consequences of developmental dyscalculia and its impact on education, employment, and psychologic well-being of affected individuals are unknown.

Genetics of central nervous system developmental disorders

The construction of the nervous system is regulated by genetic and environmental factors. In this article, we have highlighted some of the important molecules and genes that contribute to early stages of CNS development. Future research in the neurosciences will address how genetic and environmental factors interact with each other during brain development and in the mature nervous system.

Genetic analysis of brain imaging abnormalities

A number of child psychiatric disorders have recently been associated with specific structural brain abnormalities. This article discusses the advantages of neuroimaging for genetic studies, such as clarifying etiologic heterogeneity and establishing pathophysiology. The advantages of twin or family designs for neuroimaging investigations are also discussed.

Lower cognitive performance of older football players possessing apolipoprotein E epsilon4

OBJECTIVE

To determine whether the cognitive status of professional football players varies as a function of age and apolipoprotein E (APOE) genotype.

METHODS

Fifty-three active players underwent APOE and neuropsychological assessments. Players were grouped according to age (proxy indicator of high/low exposure to contact) and the presence/absence of at least one copy of the epsilon4 allele. Outcome measures were overall cognitive performance and scores in cognitive domains.

RESULTS

As a group, older players possessing APOE epsilon4 exhibited significantly lower cognitive test scores than did all other players studied, including non-epsilon4-possessing players and younger epsilon4-carriers. Measures of general cognitive functioning, information-processing speed and accuracy, and attention were related to poorer performance among the epsilon4-carrying players. In an analysis of variance model, the interaction between APOE genotype and age was significant (P = 0.004). As determined using linear regression, age accounted for 34% of the variance in the memory index among APOE epsilon4-possessing players but did not contribute significantly to variance among the non-epsilon4-possessing players. Older APOE epsilon4-carriers were significantly overrepresented among players whose scores indicated possible cognitive impairment, with the criterion of performing two or more standard deviations below the general normal values in a summary index of general cognitive functioning.

CONCLUSION

Older professional football players who possessed the APOE epsilon4 allele scored lower on cognitive tests than did players without this allele or less experienced players of any genotype. The cognitive status of professional athletes with repeated exposure to head trauma may therefore be influenced by age, inherited factors such as APOE genotype, and cumulative exposure to contact.

Aicardi-Goutières syndrome displays genetic heterogeneity with one locus (AGS1) on chromosome 3p21

We have studied 23 children from 13 families with a clinical diagnosis of Aicardi-Goutières syndrome. Affected individuals had developed an early-onset progressive encephalopathy that was characterized by a normal head circumference at birth, basal ganglia calcification, negative viral studies, and abnormalities of cerebrospinal fluid comprising either raised white cell counts and/or raised levels of interferon-alpha. By means of genomewide linkage analysis, a maximum-heterogeneity LOD score of 5.28 was reached at marker D3S3563, with alpha=.48, where alpha is the proportion of families showing linkage. Our data suggest the existence of locus heterogeneity in Aicardi-Goutières syndrome and highlight potential difficulties in the differentiation of this condition from pseudo-TORCH (toxoplasmosis, rubella, cytomegalovirus, and herpes simplex virus types 1 and 2) syndrome.

Clinical characteristics of children with cerebral white matter abnormalities

The rapidly expanding use of magnetic resonance imaging (MRI) in children with neurological impairments of unknown aetiology has revealed a large number of children with abnormalities of the cerebral white matter, some with leukodystrophy-like white matter abnormalities on MRI, but non-progressive in clinical presentation and course. The aim of this study was to investigate the clinical and neuroradiological characteristics of 26 children with white matter abnormalities of unknown origin and to find diagnostic clues or indicators of progressive versus nonprogressive disease. The typical child with white matter abnormalities was characterized by onset of symptoms within the first year of life, most often presenting as general developmental delay and hypotonia. Later-appearing signs were spasticity and ataxia and as a rule severe learning and motor disabilities. Serious ophthalmological signs were frequently seen. Perinatal adverse events were rare, infectious aetiologies not indicated but prenatal stigmata relatively common. The clinical course was progressive in 11 children and non-progressive in 15. Late onset presentation was associated with a progressive course whereas prenatal stigmata and asymmetrical white matter lesions only were found in children with a non-progressive disorder. The MRI showed three main patterns: a) a generalized increase of the T2 signal of the white matter in 12 children, b) a bilateral, symmetric but not generalized abnormality in nine and c) asymmetric, focal or multifocal pathology in five. Useful information as to clinical entities and course was obtained from the combined clinical and radiological assessment. A precise nosological diagnosis could be made in six cases. The study showed that white matter abnormalities in children constitute a heterogeneous group of rare and 'anonymous' conditions, motivating collaborative studies for further clarification of background and management.

Gene therapy using viral vectors for acute neurologic insults

Enormous knowledge has emerged concerning the cellular and molecular events underlying necrotic neuron death after seizure, hypoxia-ischemia, or hypoglycemia. This has allowed the design of rational therapies to protect neurons at such times. One of the most exciting arenas of such interventions is the use of viral vectors to deliver neuroprotective genes. This review considers the progress in this nascent discipline. Neuroprotection has been demonstrated against a variety of in vitro and in vivo rodent models of necrotic insults with vectors overexpressing genes that target various facets of injury. These have included the energetic components, calcium excess, accumulation of reactive oxygen species, protein malfolding, inflammation, and triggering of apoptosis (i.e., programmed cell death) in a subset of cells. A number of caveats, subtleties, and pressing questions concerning this literature then are considered. These include whether these gene therapy interventions actually prevent, rather than merely delay, neuron death; the extent to which the effects of such vectors on neuronal cell biology is actually understood; the potential adverse effects of the use of such vectors; and whether sparing a neuron from death with one of these interventions spares function as well. Finally, we consider the likelihood of such gene therapy becoming relevant to clinical neurology in the near future.

Neurological aspects of adult phenylketonuria

Phenylketonuria, an autosomal recessively transmitted disorder of amino acid metabolism, is caused by a deficiency of hepatic phenylalanine hydroxylase converting phenylalanine to tyrosine. Thus, phenylalanine accumulates to plasma levels exceeding 1200 mumol/l. Untreated phenylketonuria is characterized by microcephaly, epilepsy, severe mental retardation and, in some cases, progressive supranuclear motor disturbances. These symptoms can largely be prevented by the early start of a phenylalanine-restricted diet. Neurological investigations of treated patients reveal only minor neurological signs, such as tremor or brisk deep tendon reflexes. Magnetic resonance imaging shows white matter abnormalities. However, in single patients, progressive neurological symptoms occurred. Thus, the long-term prognosis of treated phenylketonuria is still under discussion.