Developmental coordination disorder: What can we learn from RI mice using motor learning tasks and QTL analysis

Developmental Coordination Disorder (DCD) is a neurodevelopmental disorder of unknown etiology that affects one in 20 children. There is an indication that DCD has an underlying genetic component due to its high heritability. Therefore, we explored the use of a recombinant inbred family of mice known as the BXD panel to understand the genetic basis of complex traits (i.e., motor learning) through identification of quantitative trait loci (QTLs). The overall aim of this study was to utilize the QTL approach to evaluate the genome-to-phenome correlation in BXD strains of mice in order to better understand the human presentation of DCD. Results of this current study confirm differences in motor learning in selected BXD strains and strains with altered cerebellar volume. Five strains - BXD15, BXD27, BXD28, BXD75, and BXD86 - exhibited the most DCD-like phenotype when compared with other BXD strains of interest. Results indicate that BXD15 and BXD75 struggled primarily with gross motor skills, BXD28 primarily had difficulties with fine motor skills, and BXD27 and BXD86 strains struggled with both fine and gross motor skills. The functional roles of genes within significant QTLs were assessed in relation to DCD-like behavior. Only Rab3a (Ras-related protein Rab-3A) emerged as a high likelihood candidate gene for the horizontal ladder rung task. This gene is associated with brain and skeletal muscle development, but lacked nonsynonymous polymorphisms. This study along with Gill et al. (same issue) is the first studies to specifically examine the genetic linkage of DCD using BXD strains of mice.

Mice deficient in GM1 manifest both motor and non-motor symptoms of Parkinson's disease; successful treatment with synthetic GM1 ganglioside

Parkinson's disease (PD) is a major neurodegenerative disorder characterized by a variety of non-motor symptoms in addition to the well-recognized motor dysfunctions that have commanded primary interest. We previously described a new PD mouse model based on heterozygous disruption of the B4galnt1 gene leading to partial deficiency of the GM1 family of gangliosides that manifested several nigrostriatal neuropathological features of PD as well as movement impairment. We now show this mouse also suffers three non-motor symptoms characteristic of PD involving the gastrointestinal, sympathetic cardiac, and cerebral cognitive systems. Treatment of these animals with a synthetic form of GM1 ganglioside, produced by transfected E. coli, proved ameliorative of these symptoms as well as the motor defect. These findings further suggest subnormal GM1 to be a systemic defect constituting a major risk factor in sporadic PD and indicate the B4galnt1(+/-) (HT) mouse to be a true neuropathological model that recapitulates both motor and non-motor lesions of this condition.

Deleterious Variation in BRSK2 Associates with a Neurodevelopmental Disorder

Developmental delay and intellectual disability (DD and ID) are heterogeneous phenotypes that arise in many rare monogenic disorders. Because of this rarity, developing cohorts with enough individuals to robustly identify disease-associated genes is challenging. Social-media platforms that facilitate data sharing among sequencing labs can help to address this challenge. Through one such tool, GeneMatcher, we identified nine DD- and/or ID-affected probands with a rare, heterozygous variant in the gene encoding the serine/threonine-protein kinase BRSK2. All probands have a speech delay, and most present with intellectual disability, motor delay, behavioral issues, and autism. Six of the nine variants are predicted to result in loss of function, and computational modeling predicts that the remaining three missense variants are damaging to BRSK2 structure and function. All nine variants are absent from large variant databases, and BRSK2 is, in general, relatively intolerant to protein-altering variation among humans. In all six probands for whom parents were available, the mutations were found to have arisen de novo. Five of these de novo variants were from cohorts with at least 400 sequenced probands; collectively, the cohorts span 3,429 probands, and the observed rate of de novo variation in these cohorts is significantly higher than the estimated background-mutation rate (p = 2.46 × 10-6). We also find that exome sequencing provides lower coverage and appears less sensitive to rare variation in BRSK2 than does genome sequencing; this fact most likely reduces BRSK2's visibility in many clinical and research sequencing efforts. Altogether, our results implicate damaging variation in BRSK2 as a source of neurodevelopmental disease.

Astroglial-targeted expression of the fragile X CGG repeat premutation in mice yields RAN translation, motor deficits and possible evidence for cell-to-cell propagation of FXTAS pathology

The fragile X premutation is a CGG trinucleotide repeat expansion between 55 and 200 repeats in the 5'-untranslated region of the fragile X mental retardation 1 (FMR1) gene. Human carriers of the premutation allele are at risk of developing the late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). Characteristic neuropathology associated with FXTAS includes intranuclear inclusions in neurons and astroglia. Previous studies recapitulated these histopathological features in neurons in a knock-in mouse model, but without significant astroglial pathology. To determine the role of astroglia in FXTAS, we generated a transgenic mouse line (Gfa2-CGG99-eGFP) that selectively expresses a 99-CGG repeat expansion linked to an enhanced green fluorescent protein (eGFP) reporter in astroglia throughout the brain, including cerebellar Bergmann glia. Behaviorally these mice displayed impaired motor performance on the ladder-rung test, but paradoxically better performance on the rotarod. Immunocytochemical analysis revealed that CGG99-eGFP co-localized with GFAP and S-100ß, but not with NeuN, Iba1, or MBP, indicating that CGG99-eGFP expression is specific to astroglia. Ubiquitin-positive intranuclear inclusions were found in eGFP-expressing glia throughout the brain. In addition, intracytoplasmic ubiquitin-positive inclusions were found outside the nucleus in distal astrocyte processes. Intriguingly, intranuclear inclusions, in the absence of eGFP mRNA and eGFP fluorescence, were present in neurons of the hypothalamus and neocortex. Furthermore, intranuclear inclusions in both neurons and astrocytes displayed immunofluorescent labeling for the polyglycine peptide FMRpolyG, implicating FMRpolyG in the pathology found in Gfa2-CGG99 mice. Considered together, these results show that Gfa2-CGG99 expression in mice is sufficient to induce key features of FXTAS pathology, including formation of intranuclear inclusions, translation of FMRpolyG, and deficits in motor function.

Identification of a human synaptotagmin-1 mutation that perturbs synaptic vesicle cycling

Synaptotagmin-1 (SYT1) is a calcium-binding synaptic vesicle protein that is required for both exocytosis and endocytosis. Here, we describe a human condition associated with a rare variant in SYT1. The individual harboring this variant presented with an early onset dyskinetic movement disorder, severe motor delay, and profound cognitive impairment. Structural MRI was normal, but EEG showed extensive neurophysiological disturbances that included the unusual features of low-frequency oscillatory bursts and enhanced paired-pulse depression of visual evoked potentials. Trio analysis of whole-exome sequence identified a de novo SYT1 missense variant (I368T). Expression of rat SYT1 containing the equivalent human variant in WT mouse primary hippocampal cultures revealed that the mutant form of SYT1 correctly localizes to nerve terminals and is expressed at levels that are approximately equal to levels of endogenous WT protein. The presence of the mutant SYT1 slowed synaptic vesicle fusion kinetics, a finding that agrees with the previously demonstrated role for I368 in calcium-dependent membrane penetration. Expression of the I368T variant also altered the kinetics of synaptic vesicle endocytosis. Together, the clinical features, electrophysiological phenotype, and in vitro neuronal phenotype associated with this dominant negative SYT1 mutation highlight presynaptic mechanisms that mediate human motor control and cognitive development.

PRRT2 mutations: exploring the phenotypical boundaries

BACKGROUND

Mutations in the proline-rich transmembrane protein 2 (PRRT2) gene have been identified in patients with benign (familial) infantile convulsions (B(F)IC), infantile convulsions with choreoathetosis (ICCA) and paroxysmal dyskinesias (PDs). However it remains unknown whether PRRT2 mutations are causal in other epilepsy syndromes. After we discovered a PRRT2 mutation in a large family with ICCA containing one individual with febrile seizures (FS) and one individual with West syndrome, we analysed PRRT2 in a heterogeneous cohort of patients with different types of infantile epilepsy.

METHODS

We screened a cohort of 460 patients with B(F)IC or ICCA, fever related seizures or infantile epileptic encephalopathies. All patients were tested for point mutations using direct sequencing.

RESULTS

We identified heterozygous mutations in 16 individuals: 10 familial and 6 sporadic cases. All patients were diagnosed with B(F)IC, ICCA or PD. We were not able to detect mutations in any of the other epilepsy syndromes. Several mutation carriers had learning disabilities and/or impaired fine motor skills later in life.

CONCLUSIONS

PRRT2 mutations do not seem to be involved in the aetiology of FS or infantile epileptic encephalopathies. Therefore B(F)IC, ICCA and PD remain the core phenotypes associated with PRRT2 mutations. The presence of learning disabilities or neuropsychiatric problems in several mutation carriers calls for additional clinical studies addressing this developmental aspect in more detail.

Cognitive and motor function in long-duration PARKIN-associated Parkinson disease

IMPORTANCE

Data on the long-term cognitive outcomes of patients with PARKIN-associated Parkinson disease (PD) are unknown but may be useful when counseling these patients.

OBJECTIVE

Among patients with early-onset PD of long duration, we assessed cognitive and motor performances, comparing homozygotes and compound heterozygotes who carry 2 PARKIN mutations with noncarriers.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of 44 participants at 17 different movement disorder centers who were in the Consortium on Risk for Early-Onset PD study with a duration of PD greater than the median duration (>14 years): 4 homozygotes and 17 compound heterozygotes (hereafter referred to as carriers) and 23 noncarriers.

MAIN OUTCOMES AND MEASURES

Unified Parkinson Disease Rating Scale Part III (UPDRS-III) and Clinical Dementia Rating scores and neuropsychological performance. Linear regression models were applied to assess the association between PARKIN mutation status and cognitive domain scores and UPDRS-III scores. Models were adjusted for age, education, disease duration, language, and levodopa equivalent daily dose.

RESULTS

Carriers had an earlier age at onset of PD (P < .001) and were younger (P = .004) at time of examination than noncarriers. They performed better than noncarriers on the Mini-Mental State Examination (P = .010) and were more likely to receive lower scores on the Clinical Dementia Rating (P = .003). In multivariate analyses, carriers performed better than noncarriers on the UPDRS-III (P = .02) and on tests of attention (P = .03), memory (P = .03), and visuospatial (P = .02) cognitive domains.

CONCLUSIONS AND RELEVANCE

In cross-sectional analyses, carriers demonstrated better cognitive and motor performance than did noncarriers with long disease duration, suggesting slower disease progression. A longitudinal follow-up study is required to confirm these findings.

[Intellectual disability - a frequent reason for referral to medical genetics]

Mental retardation affects about 2-3% of the population and is often associated with comorbidities. So far, more than 450 different medical conditions are known with mental retardation as a sign and it is assumed that there are many more yet to be defined. The diagnosis of the underlying entity allows for a few specific optimization of cognitive function, but usually improves the treatment of comorbidities. Furthermore, the detection of the underlying genetic defect allows the specification of the risk of recurrence and enables prenatal diagnosis for future pregnancies of persons at risk in the family. Recent findings suggest that especially in diseases that are associated with defective synaptic signal transduction may be targeted by specific drugs for improvement of cognitive performance in the near future.

Impaired motor coordination and disrupted cerebellar architecture in Fgfr1 and Fgfr2 double knockout mice

Fibroblast growth factor receptor (FGFR) signaling determines the size of the cerebral cortex by regulating the amplification of radial glial stem cells, and participates in the formation of midline glial structures. We show that Fgfr1 and Fgfr2 double knockouts (FGFR DKO) generated by Cre-mediated recombination driven by the human GFAP promoter (hGFAP) have reduced cerebellar size due to reduced proliferation of radial glia and other glial precursors in late embryonic and neonatal FGFR DKO mice. The proliferation of granule cell progenitors (GCPs) in the EGL was also reduced, leading to reduced granule cell numbers. Furthermore, both inward migration of granule cells into the inner granule cell layer (IGL) and outward migration of GABA interneurons into the molecular layer (ML) were arrested, disrupting layer and lobular morphology. Purkinje neurons and their dendrites, which were not targeted by Cre-mediated recombination of Fgf receptors, were also misplaced in FGFR DKO mice, possibly as a consequence of altered Bergmann glia orientation or reduced granule cell number. Our findings indicate a dual role for FGFR signaling in cerebellar morphogenesis. The first role is to amplify the number of granule neuron precursors in the external granular layer and glial precursor cells throughout the cerebellum. The second is to establish the correct Bergmann glia morphology, which is crucial for granule cell migration. The disrupted cerebellar size and laminar architecture resulting from loss of FGFR signaling impair motor learning and coordination in FGFR DKO mice.

Intelligence and visual motor integration in 5-year-old children with 22q11-deletion syndrome

The purpose of this study was to explore the relationship between intelligence and visual motor integration skills in 5-year-old children with 22q11-deletion syndrome (22q11DS) (N = 65, 43 females, 22 males; mean age 5.6 years (SD 0.2), range 5.23-5.99 years). Sufficient VMI skills seem a prerequisite for IQ testing. Since problems related to these skills are reported in children with 22q11DS, weak VMI skills may contribute to the lower than average IQ scores commonly reported. To investigate if the correlation of VMI and IQ score was mainly influenced by problems with visual perception skills (VP), motor coordination skills (MC) or difficulties with the integration of both skills (VMI), a subgroup (n = 28) was also administered the Beery VMI supplemental developmental tests. Due to the narrow age range of this study, we were also able to provide an insight into the neurocognitive phenotype of 5-year olds with 22q11DS and the influence of gender, heart disease and origin of deletion on this phenotype. Results show a mean full scale IQ (FSIQ) = 73.0 (SD 10.4) and mean VMI = 86.2 (SD 8.4). A significant correlation between FSIQ and VMI was found (r = .45, p = .000), with most variation (26%) explained in the performance IQ score ((PIQ), r = .51, p = .000). VP correlated significantly with FSIQ (r = .44, p = .01) and PIQ (r = .49, p = .004). MC was not significantly correlated with IQ (FSIQ, r = .21, p = .15; PIQ, r = .28, p = .07), suggesting that problems with motor coordination do not influence results on IQ-tests in a significant way at this age. Girls scored significantly higher on FSIQ and PIQ than boys; cardiac anomalies were not predictive of FSIQ or VMI scores. The results of this study suggest a characteristic neurocognitive phenotype for 5-year olds with 22q11DS. Deficiencies in visual perception and/or processing are negatively correlated with IQ scores, whereas deficiencies in motor skills do not have a relevant negative impact at this age. These findings provide further insight into 22q11DS specific neurocognitive deficiencies.

Expansion of the phenotypic profile of the young child with XXY

XXY is a common chromosomal abnormality which remains under diagnosed and not well understood, although it was first described more than 50 years ago. In the last ten years, with advancement in neuroimaging technology and the greater understanding of behavioral neurogenetics, there has been a resurgence of interest in children and adults with XXY. This homogenous population provides insight into the interaction between learning dysfunction, brain development and behavioral performance that may be investigated from birth onward. The unique attributes of the child from birth to 6 years of age with XXY is discussed in this paper. This paper postulates a novel reconceptualization of the phenotypic presentation of the boys with XXY. The neurodevelopmental profile of XXY is actually quite consistent over time with the common thread of speech and language deficits, motor dysfunction and frontal lobe deficits including attention, planning and organization. The early motor and speech disturbances are not random developmental delays, but rather the early presentation of the central nervous system dysfunction associated with XXY. Muscle tonus abnormalities are present in trunk, upper extremities and oral facial musculature in more than 80% of the infants with XXY.Androgen deficiency may be an integral part of the delays observed in boys with XXY, since androgen is influential in brain organization, neurobehavioral development, temperament and mood in humans. It is plausible that the earliest biomarker for androgen deficiency in XXY may be the decreased muscle tonus. Androgen deficiency may not be the only causative factor in the neurodevelopmental disturbance in individuals with XXY, but may promote a restorative function if timing and dosage is appropriate. The study of children with XXY offers an opportunity to observe the impact of the genetic and chromosomal influence on learning and behavior in a population with great homogeneity. XXY is a multifaceted spectrum disorder which demonstrates the complexity of the relationship between brain, behavior, genes and the environment.

Kinematic movement strategies in primary school children with 22q11.2 Deletion Syndrome compared to age- and IQ-matched controls during visuo-manual tracking

The present study focused on the mechanism subserving the production of kinematic patterns in 21 children with 22q11.2DS (mean age=9.6+/-1.9; mean FSIQ=73.05+/-10.2) and 21 age- and IQ-matched control children (mean age=9.6+/-1.9; mean FSIQ=73.38+/-12.0) when performing a visuo-manual tracking task in which they had to track a cursor rhythmically between 2 target zones. Children with 22q11.2DS moved faster (overall) and reached their maximum velocity sooner when compared to controls. However, the number of corrective submovements to attain the target did not differ. Children with 22q11.2DS seem to adopt a young ballistic movement strategy, with a fast ballistic first movement phase, followed by a second movement phase with very little online corrections to attain the target. Children with 22q11.2DS are not able to process the incoming feedback during the second movement phase to maximize the accuracy of the ongoing movement and use this phase to prepare the following. The fact that the parietal cortex and cerebellum are involved in action prediction and internal representation and are implicated in children with 22q11.2DS provides a possible neurological basis for their problems with prospective control and tracking behavior.

Genotype differences in cognitive functioning in Noonan syndrome

Noonan syndrome (NS) is an autosomal-dominant genetic disorder associated with highly variable features, including heart disease, short stature, minor facial anomalies and learning disabilities. Recent gene discoveries have laid the groundwork for exploring whether variability in the NS phenotype is related to differences at the genetic level. In this study, we examine the influence of both genotype and nongenotypic factors on cognitive functioning. Data are presented from 65 individuals with NS (ages 4-18) who were evaluated using standardized measures of intellectual functioning. The cohort included 33 individuals with PTPN11 mutations, 6 individuals with SOS1 mutations, 1 individual with a BRAF mutation and 25 participants with negative, incomplete or no genetic testing. Results indicate that genotype differences may account for some of the variation in cognitive ability in NS. Whereas cognitive impairments were common among individuals with PTPN11 mutations and those with unknown mutations, all of the individuals with SOS1 mutations exhibited verbal and nonverbal cognitive skills in the average range or higher. Participants with N308D and N308S mutations in PTPN11 also showed no (or mild) cognitive delays. Additional influences such as hearing loss, motor dexterity and parental education levels accounted for significant variability in cognitive outcomes. Severity of cardiac disease was not related to cognitive functioning. Our results suggest that some NS-causing mutations have a more marked impact on cognitive skills than others.

Alpha-synuclein A30P point-mutation generates age-dependent nigrostriatal deficiency in mice

Lewy bodies are mainly composed of alpha-synuclein (SNCA) and specific mutations in SNCA gene are related to familial forms of Parkinson's disease (PD). The purpose of our study was to generate a mouse line with A30P knock-in point mutation in SNCA gene and to test if a single point-mutation is able to turn otherwise normal SNCA into a toxic form. The behavioral profile of SNCA A30P mice was followed for 16 months. Generally, these mice are healthy and viable without any obvious abnormalities. Starting from the age of 13 months mice developed a significant deficit in motor performance tests related to nigrostriatal function (ink-test and beam walk). In other tests (motility boxes, rotarod) mice continuously performed normally. Moreover, SNCA A30P mice expressed the altered sensitivity to VMAT2 inhibitor reserpine, possibly reflecting a functional deficiency of dopamine. Indeed, mice at 15 months of age had significantly reduced levels of dopamine and its major metabolite DOPAC in the striatum, and reduced levels of dopamine in the mesolimbic system. The present study confirms that SNCA plays an important role in the development of PD and an insertion of a single point mutation is sufficient to generate age-related decline in specific motor performance. The generated mouse line has a potential to become a model for PD with comparable time course and phenotype.

Locomotor deficiencies and aberrant development of subtype-specific GABAergic interneurons caused by an unliganded thyroid hormone receptor alpha1

Thyroid hormone (TH) deficiency during development causes severe and permanent neuronal damage, but the primary insult at the tissue level has remained unsolved. We have defined locomotor deficiencies in mice caused by a mutant thyroid hormone receptor alpha1 (TR alpha1) with potent aporeceptor activity attributable to reduced affinity to TH. This allowed identification of distinct functions that required either maternal supply of TH during early embryonic development or sufficient innate levels of hormone during late fetal development. In both instances, continued exposure to high levels of TH after birth and throughout life was needed. The hormonal dependencies correlated with severely delayed appearance of parvalbumin-immunoreactive GABAergic interneurons and increased numbers of calretinin-immunoreactive cells in the neocortex. This resulted in reduced numbers of fast spiking interneurons and defects in cortical network activity. The identification of locomotor deficiencies caused by insufficient supply of TH during fetal/perinatal development and their correlation with subtype-specific interneurons suggest a previously unknown basis for the neuronal consequences of endemic cretinism and untreated congenital hypothyroidism, and specifies TR alpha1 as the receptor isoform mediating these effects.

Depressive symptomatology in child and adolescent twins with attention-deficit hyperactivity disorder and/or developmental coordination disorder

Previous research has demonstrated a link between attention-deficit/hyperactivity disorder (ADHD), developmental coordination disorder (DCD), and depression. The present study utilized a monozygotic (MZ) differences design to investigate differences in depressive symptomatology between MZ twins discordant for ADHD or DCD. This extends previous research as it controls for genetic effects and shared environmental influences and enables the investigation of nonshared environmental influences. In addition, children and adolescents with comorbid ADHD and DCD were compared on their level of depressive symptomatology to those with ADHD only, DCD only, and no ADHD or DCD. The parent-rated Strengths and Weaknesses of ADHD Symptoms and Normal Behavior, Developmental Coordination Disorder Questionnaire, and Sad Affect Scale were used to assess ADHD, DCD, and depressive symptomatology respectively. The results revealed higher levels of depressive symptomatology in MZ twins with ADHD or DCD compared to their nonaffected co-twins. In addition, children and adolescents with comorbid ADHD and DCD demonstrated higher levels of depressive symptomatology compared to those with ADHD only, DCD only, and no ADHD or DCD. The implications of these findings are discussed with emphasis on understanding and recognizing the relationship between ADHD, DCD, and depression in the assessment and intervention for children and adolescents with these disorders.

Deletion of the Bax gene disrupts sexual behavior and modestly impairs motor function in mice

Cell death is a nearly ubiquitous feature of the developing nervous system, and differential death in males and females contributes to several well studied sex differences in neuron number. Nonetheless, the functional importance of neuronal cell death has been subjected to few direct tests. Bax, a pro-apoptotic protein, is required for cell death in many neural regions. Deletion of the Bax gene in mice increases neuron number in several areas and eliminates sex differences in cell number in the brain and spinal cord. Here, sexual and motor behaviors were examined in Bax-/- mice and their wild-type siblings to test the functional consequences of preventing Bax-dependent cell death. Animals were gonadectomized in adulthood and provided with ovarian hormones or with testosterone for tests of feminine and masculine sexual behaviors, respectively. Wild-type mice exhibited a sex difference in feminine sexual behavior, with high lordosis scores in females and low scores in males. This sex difference was eliminated by Bax deletion, with very low receptivity exhibited by both male and female Bax-/- mice. Masculine sexual behavior was not sexually dimorphic among wild-type mice, but mounts and pelvic thrusts were nearly eliminated in Bax-/- mice of both sexes. Motor strength and performance at low speeds on a RotaRod apparatus did not differ by sex or Bax gene status. However, Bax-/- animals exhibited impairments on the RotaRod at higher speeds. Thus, developmental cell death may be required for masculine and feminine sexual behaviors and the fine tuning of motor coordination.

Genetic analysis of SCA 2 and 3 repeat expansions in essential tremor and atypical Parkinsonism

Anecdotal reports suggest that patients with spinocerebellar ataxia (SCA 2) patients can present with postural tremor with ataxia. We determined the prevalence of SCA2 and SCA3 mutations in a cohort of ET and atypical Parkinsonism patients. A total of 277 subjects comprising of 177 ET and 100 atypical Parkinsonism were examined. We identified one positive case of SCA3 among those who were diagnosed with ET, yielding a prevalence of 0.5%, but a zero prevalence among our atypical Parkinsonism patients. No study subjects carried an abnormal SCA2 repeat expansion. Our study highlights that SCA3 can present initially with ET symptoms, expanding the spectrum of genetic diseases that can be associated with ET-like phenotype. Routine screening for SCA2 and SCA3 in ET and atypical Parkinsonism patients may not be cost effective. However, in the long-term follow-up of patients who present with an ET phenotype, clinicians should be vigilant for other neurological signs, which may be point to an alternate diagnosis.

Motor discoordination of transgenic mice overexpressing a microtubule destabilizer, stathmin, specifically in Purkinje cells

The proper regulation of microtubule (MT) structure is important for dendritic and neural circuit development. However, the relationship between the regulation of the MTs in dendrites and the formation of neural function is still unclear. Stathmin is a MT destabilizer, and we have previously reported that the expression and the activity of stathmin is downregulated during cerebellar Purkinje cell (PC) development. In this study, we generated transgenic mice that specifically overexpress the constitutively active form of stathmin in the PCs. These mutant mice did not show any obvious morphological or excitatory transmission abnormalities in the cerebellum. In contrast, we observed a decline in the expression of MAP2 and KIF5 signal in the PC dendrites and a discoordination of motor function in the mutant mice, although they displayed normal general behavior. These data indicate that the overexpression of stathmin disrupts dendritic MT organization, motor protein distribution, and neural function in PCs.

Modified behavioral characteristics following ablation of the voltage-dependent calcium channel beta3 subunit

Voltage-dependent calcium channels are important for calcium influx and the ensuing intracellular calcium signal in various excitable membranes. The beta subunits of these channels modify calcium currents through pore-forming alpha1 subunits of the high-voltage- activated calcium channels. In the present study, beta3 subunit-null mice were used to investigate the importance of the beta3 subunit of the voltage-dependent calcium channel, which couples with the CaV2.2 (alpha1B) subunit to form the major component of neuronal N-type calcium channels in the brain. Western blot analysis revealed a significant decrease in N-type calcium channels in beta3 subunit-null mice, while protein levels of other high-voltage-activated calcium channel alpha1 subunits were unchanged. Immunoprecipitation analysis with an anti-CaV2.2 antibody showed that reshuffling of the assembly of N-type channels had occurred in the beta3 subunit-null mice. Ablation of this subunit resulted in modified nociception, decreased anxiety, and increased aggression. The beta3 subunit-null mice also showed impaired learning ability. These results suggest the importance of voltage-dependent calcium channels and the key role of the beta3 subunit in memory formation, nociceptive sensory transduction, and various neurological signal transduction pathways.

Impaired motor functions in mice lacking the RNA-binding protein Hzf

Local protein synthesis in dendrites plays an important role in some aspects of neuronal development and synaptic plasticity. Neuronal RNA-binding proteins regulate the transport and/or translation of the localized mRNAs. Previously, we reported that hematopoietic zinc finger (Hzf) is one of the neuronal RNA-binding proteins that regulate these processes. The Hzf protein is highly expressed in neuronal cells including hippocampal pyramidal neurons and cerebellar Purkinje cells, and plays essential roles in the dendritic mRNA localization and translation. In the present study we demonstrated that mice lacking Hzf (Hzf(-/-) mice) exhibited severe impairments of motor coordination and cerebellum-dependent motor learning. These findings raise the possibility that the post-transcriptional regulation by Hzf may contribute to some aspects of synaptic plasticity and motor learning in the cerebellum.

Multimodal imaging of striatal degeneration in Amish patients with glutaryl-CoA dehydrogenase deficiency

Despite early diagnosis, one-third of Amish infants with glutaryl-CoA dehydrogenase deficiency (GA1) develop striatal lesions that leave them permanently disabled. To better understand mechanisms of striatal degeneration, we retrospectively studied imaging results from 25 Amish GA1 patients homozygous for 1296C>T mutations in GCDH. Asymptomatic infants had reduced glucose tracer uptake and increased blood volume throughout gray matter, which may signify a predisposition to brain injury. Nine children (36%) developed striatal lesions: three had sudden motor regression during infancy whereas six had insidious motor delay associated with striatal lesions of undetermined onset. Acute striatal necrosis consisted of three stages: (1) an acute stage, within 24 h of motor regression, characterized by cytotoxic oedema within the basal ganglia, cerebral oligemia, and rapid transit of blood throughout gray matter; (2) a sub-acute stage, 4-5 days after the onset of clinical signs, characterized by reduced striatal perfusion and glucose uptake, and supervening vasogenic oedema; and (3) a chronic stage of striatal atrophy. Apparent diffusion coefficient maps revealed that at least two of the six patients with insidious motor delay suffered striatal injuries before or shortly after birth, followed by latent periods of several months before disability was apparent. Thus, acute and insidious presentations may occur by similar mechanisms, and differ only with regard to the timing of injury. Intravenous fluid and dextrose therapy for illnesses during the first 2 years of life was the only intervention that was clearly neuroprotective in this cohort (odds ratio for brain injury = 0.04, 95% confidence interval = 0.01-0.34; P < 0.001).

Reduced hippocampal neurogenesis and skill reaching performance in adult Emx1 mutant mice

Mammalian homeobox gene Emx family is involved in the development of the rostral brain. Loss-of-function studies suggest that, despite the agenesis of corpus callosum, the Emx1 mutants display relatively modest defects compared to the Emx2 mutants. However, the role of the Emx1 in neurogenesis and brain function has never been explored. We used unbiased stereology to determine the number of proliferating progenitors and immature neurons in the adult neurogenic zones. Although previous studies have established that the formation of the dentate gyrus (DG) requires Emx2, we found that the adult Emx1 mutants also exhibited a smaller DG, reduced number of proliferating progenitor cells and immature neurons in the DG, in contrast to the indistinguishable level of neurogenesis in the subventricular zone when compared to the wild type mice. In view of the involvement of callosal projection neurons in mediating interhemispheric crosstalk and spatial coupling between the limbs, and the importance of DG in hippocampus-dependent function in learning and memory, we assessed motor and cognitive functions. Emx1 deletion impaired performance on a forelimb skill reaching task and attenuated training induced hippocampal neurogenesis, but it did not affect motor activity or basic motor function as evaluated in the open field, wire hanging and rotor rod tests. Unexpectedly, the adult Emx1 mutant mice did not exhibit impairment in spatial learning and memory in the Barnes maze test. Our data suggest that deletion of the Emx1 gene reduces hippocampal neurogenesis and affects higher motor function that requires extensive learning.

Motor development in school-aged children with 22q11 deletion (velocardiofacial/DiGeorge syndrome)

The aim of this study was to compare the motor development of primary school children (age 5-14y) with a 22q11 deletion (del22q11) group and a control group. The effects of a congenital heart defect (CHD) and IQ on motor development were additionally studied within the del22q11 group. Motor development of 37 children with a del22q11 (20 males, 17 females; mean age 9y 4mo, range 5y 9mo-13y 3mo) and 34 controls (23 males, 11 females; mean age 9y 1mo, range 4y 8mo-13y 6mo) was assessed with the Bruininks-Oseretsky Test of Motor Proficiency. The del22q11 group showed a significant deficit in motor functioning compared with the control group (p < 0.01). Within the del22q11 group there was a significant effect of IQ on motor performance, but no effect of CHD was found. To conclude, primary school children with a del22q11 syndrome showed a significant deficit in motor performance compared with a control group. A significant effect of IQ on motor performance in del22q11 was found.

Altered MAP kinase phosphorylation and impaired motor coordination in PTPRR deficient mice

The neuronal protein tyrosine phosphatases encoded by mouse gene Ptprr (PTPBR7, PTP-SL, PTPPBSgamma-42 and PTPPBSgamma-37) have been implicated in mitogen-activated protein (MAP) kinase deactivation on the basis of transfection experiments. To determine their physiological role in vivo, we generated mice that lack all PTPRR isoforms. Ptprr-/- mice were viable and fertile, and not different from wildtype littermates regarding general physiology or explorative behaviour. Highest PTPRR protein levels are in cerebellum Purkinje cells, but no overt effects of PTPRR deficiency on brain morphology, Purkinje cell number or dendritic branching were detected. However, MAP kinase phosphorylation levels were significantly altered in the PTPRR-deficient cerebellum and cerebrum homogenates. Most notably, increased phospho-ERK1/2 immunostaining density was observed in the basal portion and axon hillock of Ptprr-/- Purkinje cells. Concomitantly, Ptprr-/- mice displayed ataxia characterized by defects in fine motor coordination and balance skills. Collectively, these results establish the PTPRR proteins as physiological regulators of MAP kinase signalling cascades in neuronal tissue and demonstrate their involvement in cerebellum motor function.

Brief Report: Visual-Spatial Deficit in a 16-year-old Girl with Maternally Derived Duplication of Proximal 15q

Duplications of chromosome 15 may be one of the most common single genetic causes of autism spectrum disorders (ASD), aside from fragile X. Most of the cases are associated with maternally derived interstitial duplication involving 15q11-13. This case report describes a female proband with a maternally derived interstitial duplication of proximal 15q. She did not exhibit any symptoms of ASD apart from some developmental delay. By adolescence, she showed mild dysmorphism, a discrepant profile on the Wechsler Intelligence Scale for Children (Verbal IQ = 87; Performance IQ = 65) and a major deficit in visual-spatial abilities affecting fine motor skills, mathematical reasoning, visual memory and some global reading tasks. This is one of the first reports of a child with a maternal duplication who exhibits a visual-spatial deficit without ASD.

Modifying the subunit composition of TASK channels alters the modulation of a leak conductance in cerebellar granule neurons

Two-pore domain potassium (K2P) channel expression is believed to underlie the developmental emergence of a potassium leak conductance [IK(SO)] in cerebellar granule neurons (CGNs), suggesting that K2P function is an important determinant of the input conductance and resting membrane potential. To investigate the role that different K2P channels may play in the regulation of CGN excitability, we generated a mouse lacking TASK-1, a K2P channel known to have high expression levels in CGNs. In situ hybridization and real-time PCR studies in wild-type and TASK-1 knock-outs (KOs) demonstrated that the expression of other K2P channels was unaltered in CGNs. TASK-1 knock-out mice were healthy and bred normally but exhibited compromised motor performance consistent with altered cerebellar function. Whole-cell recordings from adult cerebellar slice preparations revealed that the resting excitability of mature CGNs was no different in TASK-1 KO and littermate controls. However, the modulation of IK(SO) by extracellular Zn2+, ruthenium red, and H+ was altered. The IK(SO) recorded from TASK-1 knock-out CGNs was no longer sensitive to alkalization and was blocked by Zn2+ and ruthenium red. These results suggest that a TASK-1-containing channel population has been replaced by a homodimeric TASK-3 population in the TASK-1 knock-out. These data directly demonstrate that TASK-1 channels contribute to the properties of IK(SO) in adult CGNs. However, TASK channel subunit composition does not alter the resting excitability of CGNs but does influence sensitivity to endogenous modulators such as Zn2+ and H+.

DCD and ADHD: a genetic study of their shared aetiology

Previous studies have found that rates of attention deficit hyperactivity disorder (ADHD) and developmental coordination disorder (DCD) are very similar, both being approximately 7% in sample populations [Kadesjö, B., & Gillberg, C. (1999). Developmental coordination disorder in Swedish 7-year-old children. Journal of the American Academy of Child and Adolescent Psychiatry, 38, 820-828; Milberger, S., Faraone, S., Biederman, J., Testa, M., & Tsuang, M. (1996). New phenotype definition of attention deficit hyperactivity disorder in relatives for genetic analyses. American Journal of Medical Genetics, 67, 369-377]. The rate of comorbidity between the two has been found to be close to 50% [Barkley, R. (1990). Attention deficit hyperactivity disorder: A handbook for diagnosis and treatment. New York: Guilford Press]. Investigations into the comorbidity of the disorders points to a shared aetiology between them. The aim of the present investigation was to examine the extent to which the shared aetiology is due to common genetic factors to both disorders. We also investigated whether particular subtypes of each disorder were more linked than others. Mailed questionnaires were completed by parents (predominantly mothers) of 1285 twin pairs aged 5 and 16 years from the volunteer Australian Twin Registry (ATR). Included were a DSM-IV-based ADHD form, the alternative SWAN (Strengths and Weaknesses of ADHD Symptoms and Normal Behaviour scale) and the Developmental Coordination Disorder Questionnaire (DCDQ). Statistical analyses including structural equation modelling were carried out to explore the genetic factors of both disorders. The modelling showed a strong shared additive genetic component between most subtypes of ADHD and DCD to the subtypes of the other disorder. Analyses comparing the two ADHD measures showed an overlap of the symptoms captured by each measure but also significant differences. The DCD-fine motor and ADHD-Inattentive were most strongly linked using the DSM-IV based scale. On the SWAN scale the results were similar but the general coordination scale was also very strongly linked. Implications for the use of different assessment tools are discussed.

Syndromic craniosynostosis with elbow joint contracture

This paper reports a new type of syndromic craniosynostosis that was diagnosed by DNA analysis of the patient's fibroblast growth factor receptor (FGFR) genes. At birth, a male infant had ocular proptosis, a pseudotail, and obstructed respiration. He developed craniosynostosis, craniofacial dysmorphism, hydrocephalus, and bilateral contracture of his elbow joints. His treatment included fronto-orbital advancements and a ventriculoperitoneal shunt. Genetic analysis revealed that he was heterozygous for a missense mutation in exon 9 of the FGFR2 gene that resulted in an amino acid substitution of cysteine for serine at residue 351 (Ser351Cys). Seven cases with this mutation had previously been reported. All had severe craniosynostosis with midface hypoplasia, elbow joint contracture, developmental retardation, and early death.

Neurological soft signs in first-episode schizophrenia: a follow-up study

OBJECTIVE

Neurological soft signs are frequently found in schizophrenia. They are indicators of both genetic liability and psychopathological symptoms. To further differentiate "trait" and "state" relations the authors compared the 1-year course of neurological soft signs in schizophrenia patients and comparison subjects.

METHOD

Thirty-nine patients with first-episode schizophrenia spectrum disorders were examined after remission of acute symptoms and 14 months later. Established instruments assessed diagnoses, psychopathological symptoms, predictors of outcome, handedness, and neurological soft signs. Twenty-two age- and gender-matched comparison subjects were also examined twice.

RESULTS

Neurological soft sign scores in patients were significantly elevated relative to comparison subjects at both measurement points. Whereas neurological soft signs remained stable in comparison subjects (time 1: mean=4.8, SD=3.3; time 2: mean=4.6, SD=3.9), they significantly decreased in patients (time 1: mean=15.7, SD=7.1; time 2: mean=10.1, SD=7.9). This effect was more pronounced in patients with a favorable versus a chronic course and was mainly accounted for by motor signs. Predictors of follow-up neurological soft sign scores were neurological soft sign levels at remission and compliance with treatment.

CONCLUSIONS

Although neurological soft signs are intrinsic to schizophrenia, their level varies with the clinical course. Thus, neurological soft signs may correspond to both genetic liability and the activity of the disease process and may be considered as potential predictors of outcome.

Motor flexibility problems as a marker for genetic susceptibility to attention-deficit/hyperactivity disorder

BACKGROUND

Since many children with attention-deficit/hyperactivity disorder (ADHD) have fine visuomotor problems that are already evident at a young age, motor dysfunctioning is investigated in family-genetic perspective. We hypothesized that if fine motor problems may be a marker for genetic susceptibility to ADHD, nonaffected siblings of ADHD probands would experience motor problems similar to those of their ADHD siblings.

METHODS

Twenty-five carefully phenotyped ADHD probands with a family history of ADHD, their nonaffected siblings (n = 25), and 48 normal control subjects (aged 6 to 17) completed a motor fluency task and a motor flexibility task. The motor fluency task involved completion of a familiar, automatized trajectory, whereas the motor flexibility task required continuous adjustment of movement to complete an unpredictable random trajectory.

RESULTS

On the motor fluency task, the performance of the nonaffected children was significantly better than that of the ADHD probands; strikingly, on the motor flexibility task, they performed as well as their ADHD siblings.

CONCLUSIONS

Nonaffected siblings experience complex motor problems similar to their ADHD siblings but only in nonautomatized movements that require controlled processing. The results suggest that higher-order controlled motor deficits in ADHD may be associated with genetic susceptibility for ADHD.

Hereditary sensory autonomic neuropathy Type IV

Hereditary sensory autonomic neuropathy Type IV is an autosomal recessive disorder due to lack of maturation of small myelinated and unmyelinated fibers of peripheral nerves, which convey sensation of pain and temperature, therefore, resulting in self mutilation. There is anhidrosis due to lack of innervation of normal sweat glands resulting in recurrent episodes of hyperpyrexia. The clinical presentation of two children with this rare disease is described.

Impaired motor performance and learning in glia maturation factor-knockout mice

Glia maturation factor (GMF) is a unique brain protein localized in astrocytes and some neuronal populations. Studies with overexpression of GMF using adenovirus vector have uncovered its regulatory role in intracellular signal transduction and downstream induction of biologically active molecules, including the neurotrophins and cytokines. The current paper deals with the behavior of mice devoid of GMF protein (knockout). GMF-null mice developed normally without gross abnormality. When tested for simple position discrimination using a T-maze and for spatial memory using a Morris water maze, the knockout mice performed as well as the wild-type, showing no defect in maze learning. However, with beam walking, GMF-knockout mice performed poorly and failed to learn. Knockout mice were also defective in learning the eyeblink classical conditioning. Histologically, the knockout mice showed a loss of neurons in the inferior olive, which is a component of the circuitry of eyeblink conditioning, and is also essential for motor performance. The structural abnormality in GMF-null mice explained their impaired ability for both motor performance and motor learning.

Locomotor and oculomotor impairment associated with cerebellar dysgenesis in Zic3-deficient (Bent tail) mutant mice

We examined the adult neural phenotypes of the Bent tail mutant mouse. The Bent tail mutant mouse was recently shown to lack a submicroscopic part of the X chromosome containing the Zic3 gene, which encodes a zinc-finger protein controlling vertebrate neural development. While nearly one-fourth of hemizygous Bent tail (Bn/Y, Zic3-deficient) mice developed neural tube defects in their midbrain and hindbrain region, the other Bn/Y mice showed apparently normal behaviour in a C57BL/6 genetic background. A battery of behavioural and eye movement tests revealed impaired spontaneous locomotor activity, reduction of muscle tone and impairments of vestibuloocular and optokinetic eye movements in these mice. Morphological examination of the mutant brain showed a significant reduction in the cell numbers in the cerebellar anterior lobe and paraflocculus-flocculus complex. Our results indicate that the cerebellar dysgenesis characterized by subregional hypoplasia affects the locomotor activity, muscle tone and eye movement control of the mice. These findings may have some clinical implications in relation to disorders characterized by cerebellar dysgenesis, such as Joubert syndrome.

Spermidine/spermine N1-acetyltransferase overexpression in mice induces hypoactivity and spatial learning impairment

The present work addresses the role of polyamines in learning and general behavior by subjecting transgenic mice overexpressing polyamine catabolic enzyme, spermidine/spermine N(1)-acetyltransferase (SSAT) and their syngenic littermates to neurobehavioral profiling assessment (SHIRPA) and to radial eight-arm maze. The general health and physiological conditions as well as the entire behavioral battery comprising of 34 parameters were recorded. The eight-arm radial maze (8-RAM) task included an initial acquisition task for 9 days followed by a 2-day retention test after a 2-week break. In addition, blood samples were taken for hormone analysis. Transgenic mice, which showed reduced motor activity, aggression and muscle tone, spent more time in the radial maze during initial acquisition and retention tasks as compared with syngenic mice. Moreover, the learning performance of transgenic females was significantly inferior to syngenic females. Interestingly, the levels of several hormones were significantly altered in SSAT transgenic mice; circulating adrenocorticotropic hormone (ACTH) and corticosterone levels were markedly increased while testosterone and thyroidal hormone levels were decreased. These changes may be related to the dramatic increase in brain putrescine levels in SSAT-overexpressing (SSAT-OE) mice, but it is likewise possible that the behavioral changes and learning impairment are attributable to more peripheral mechanisms (such as alterations in steroid hormone metabolism), which in turn, could be a consequence of the disturbed polyamine homeostasis.

Characterization of the first supernumerary tricentric ring chromosome 1 mosaicism by conventional and molecular cytogenetic techniques

We report on the conventional cytogenetic and fluorescence in situ hybridization (FISH) results obtained for a 3.5-year-old girl with developmental and language delay and a supernumerary ring chromosome mosaicism in 8% of T-lymphocytes analyzed. Using different conventional and molecular cytogenetic techniques as YAC hybridization and comparative genomic hybridization, we could show that the extra tricentric ring chromosome consists of three heterochromatic blocks with inserted euchromatic material. Additionally, chromosome microdissection followed by FISH analysis demonstrated that the small tricentric ring chromosome consisted of material from the pericentromeric region of chromosome 1q21. Thus, the patient has a mosaic of normal cells and cells with partial pentasomy of the pericentromeric region of chromosome 1. So far, 19 cases with single supernumerary marker chromosome 1 have been published, but no tricentric ring chromosome 1 is, to our knowledge, reviewed in the literature. In this study, we compare the clinical features of our patient with cytogenetically comparable cases described in the literature. We introduce a hypothesis for the formation of a tricentric ring chromosome: starting with a monocentric ring, sister chromatid exchange leading to the formation of a tetracentric ring, which underwent intrastrand recombination generating the tricentric ring.

Transgenic mice expressing F3/contactin from the transient axonal glycoprotein promoter undergo developmentally regulated deficits of the cerebellar function

We have shown that transgenic transient axonal glycoprotein (TAG)/F3 mice, in which the mouse axonal glycoprotein F3/contactin was misexpressed from a regulatory region of the gene encoding the transient axonal glycoprotein TAG-1, exhibit a transient disruption of cerebellar granule and Purkinje cell development [Development 130 (2003) 29]. In the present study we explore the neurobehavioural consequences of this mutation. We report on assays of reproductive parameters (gestation length, litter size and offspring viability) and on somatic and neurobehavioural end-points (sensorimotor development, homing performance, motor activity, motor coordination and motor learning). Compared with wild-type littermates, TAG/F3 mice display delayed sensorimotor development, reduced exploratory activity and impaired motor activity, motor coordination and motor learning. The latter parameters, in particular, were affected also in adult mice, despite the apparent recovery of cerebellar morphology, suggesting that subtle changes of neuronal circuitry persist in these animals after development is complete. These behavioural deficits indicate that the finely coordinated expression of immunoglobulin-like cell adhesion molecules such as TAG-1 and F3/contactin is of key relevance to the functional, as well as morphological maturation of the cerebellum.

Increased intensity of physical therapy for a child with gross motor developmental delay: a case report

BACKGROUND AND PURPOSE

The intensity of physical therapy provided for children in early intervention (EI) programs may be influenced by a number of factors. In an individualized program, however, some children and families may benefit from an increased frequency of services. The purpose of this case report was to systematically document and describe an increase in physical therapy frequency over a 4-week time frame for a child receiving EI physical therapy services.

CASE DESCRIPTION

The child was a 31-month-old girl with a diagnosis of 18p-, a chromosomal abnormality of the short arm of the 18th chromosome. Physical therapy services were increased from once every two weeks to four times a week for four weeks.

OUTCOMES

Improvement was noted on the Gross Motor Function Measure And Goal Attainment Scaling. Her age-equivalent scores on the Peabody Gross Motor Scales did not change.

DISCUSSION

A targeted increase in physical therapy frequency may be appropriate for some children receiving El services. Careful consideration of the readiness of a child, along with use of appropriate measure- ment tools, may be important for determining whether an increase is appropriate and successful.

A review of neuropsychological and motor studies in Turner Syndrome

We reviewed the literature on Turner Syndrome (TS) from 1962 until March 2003 with respect to the following questions: Is there a consistent pattern of cognitive and/or motor dysfunction in TS girls and if so, is there an explanation for the disturbance? Many studies indicate that girls with TS have a disharmonic IQ profile: a verbal IQ that seems to be at a (nearly) normal level and a decreased PIQ. This profile remains into adulthood. Visual-spatial problems are mentioned most frequently and there is some evidence for a relationship to particular neuro-anatomical structures, hormonal dysfunction, and genotype. Although much less research has been done on motor performance in TS, there is clear evidence that it is disturbed too in TS. Many authors emphasize the interaction between somatic, psychological and social factors, but we did not find a clear theoretical framework explaining this relationship. We argue that there may be two independent problems: a visuospatial and a motor deficit possible related to specific genotypes and both have implications for functioning in daily life.

Motor behaviour deficits and their histopathological and functional correlates in the nigrostriatal system of dopamine transporter knockout mice

Chronic dysregulation of dopamine homeostasis has been shown to induce behavioural impairment in dopamine transporter knockout mutant mice arising from the dysfunction of the mesolimbic and hypothalamo-infundibular system. Here, we assessed whether there are also any motor consequences of a chronic and constitutive hyperdopaminergia in the nigrostriatal system in dopamine transporter knockout mutant mice. For this, we analysed motor performances using tests assessing balance, coordinated motor skills (rotarod, pole test), stride lengths and locomotor activity. Dopamine transporter knockout mutant mice were markedly hyperactive in the open field with central compartment avoidance, as previously shown. However, sensorimotor integration was also found to be altered in dopamine transporter knockout mutant mice which displayed a reduced fore- and hind-limb mean stride length, impaired motor coordination on the pole test and reduced rearings in the open field. Moreover, dopamine transporter knockout mutant mice showed a slower task acquisition on the rotarod. Six-week-old dopamine transporter knockout wild type mice having the same femur size as adult dopamine transporter knockout mutant mice ruled out a possible size-effect bias. Whilst there was no significant difference in the striatal volume, we found a slight but significant reduction in neuronal density in the striatum but not in the nucleus accumbens of dopamine transporter knockout mutant mice. There was a reduced binding in the striatum and nucleus accumbens of dopamine(1) receptors ([(3)H]SCH 23390) and dopamine(2) receptors ([(3)H]YM-09151-2). There was no significant difference in the number of dopaminergic neurons in the substantia nigra between dopamine transporter knockout mutant mice and dopamine transporter knockout wild type mice. These results suggest an impaired functioning of the nigrostriatal system in dopamine transporter knockout mutant hyperdopaminergic mice, as illustrated by motor and sensorimotor integration deficits, despite their apparent hyperactivity. These dysfunctions may arise from combined striatal cell loss and/or functional changes of dopaminergic neurotransmission.

Somatostatin receptor 2 knockout/lacZ knockin mice show impaired motor coordination and reveal sites of somatostatin action within the striatum

The peptide somatostatin can modulate the functional output of the basal ganglia. The exact sites and mechanisms of this action, however, are poorly understood, and the physiological context in which somatostatin acts is unknown. Somatostatin acts as a neuromodulator via a family of five 7-transmembrane G protein-coupled receptors, SSTR1-5, one of which, SSTR2, is known to be functional in the striatum. We have investigated the role of SSTR2 in basal ganglia function using mice in which Sstr2 has been inactivated and replaced by the lacZ reporter gene. Analysis of Sstr2lacZ expression in the brain by beta-galactosidase histochemistry demonstrated a widespread pattern of expression. By comparison to previously published in situ hybridization and immunohistochemical data, Sstr2lacZ expression was shown to accurately recapitulate that of Sstr2 and thus provided a highly sensitive model to investigate cell-type-specific expression of Sstr2. In the striatum, Sstr2 expression was identified in medium spiny projection neurons restricted to the matrix compartment and in cholinergic interneurons. Sstr2 expression was not detected in any other nuclei of the basal ganglia except for a sparse number of nondopaminergic neurons in the substantia nigra. Microdialysis in the striatum showed Sstr2-null mice were selectively refractory to somatostatin-induced dopamine and glutamate release. In behavioural tests, Sstr2-null mice showed normal levels of locomotor activity and normal coordination in undemanding tasks. However, in beam-walking, a test of fine motor control, Sstr2-null mice were severely impaired. Together these data implicate an important neuromodulatory role for SSTR2 in the striatum.

Clinical and molecular study in congenital muscular dystrophy with partial laminin alpha 2 (LAMA2) deficiency

Complete laminin alpha2 (LAMA2) deficiency causes approximately half of congenital muscular dystrophy (CMD) cases. Many loss-of-function mutations have been reported in these severe, neonatal-onset patients, but only single missense mutations have been found in milder CMD with partial laminin alpha2 deficiency. Here, we studied nine patients diagnosed with CMD who showed abnormal white-matter signal at brain MRI and partial deficiency of laminin alpha2 on immunofluorescence of muscle biopsy. We screened the entire 9.5 kb laminin alpha2 mRNA from patient muscle biopsy by direct capillary automated sequencing, single strand conformational polymorphism (SSCP), or denaturing high performance liquid chromatography (DHPLC) of overlapping RT-PCR products followed by direct sequencing of heteroduplexes. We identified laminin alpha2 sequence changes in six of nine CMD patients. Each of the gene changes identified, except one, was novel, including three missense changes and two splice-site mutations. The finding of partial laminin alpha2 deficiency by immunostaining is not specific for laminin alpha2 gene mutation carriers, with only two patients (22%) showing clear causative mutations, and an additional three patients (33%) showing possible mutations. The clinical presentation and disease progression was homogeneous in the laminin alpha2-mutation positive and negative CMD patients.

Runx3 controls the axonal projection of proprioceptive dorsal root ganglion neurons

Dorsal root ganglion (DRG) neurons specifically project axons to central and peripheral targets according to their sensory modality. The Runt-related genes Runx1 and Runx3 are expressed in DRG neuronal subpopulations, suggesting that they may regulate the trajectories of specific axons. Here we report that Runx3-deficient (Runx3(-/-)) mice displayed severe motor uncoordination and that few DRG neurons synthesized the proprioceptive neuronal marker parvalbumin. Proprioceptive afferent axons failed to project to their targets in the spinal cord as well as those in the muscle. NT-3-responsive Runx3(-/-) DRG neurons showed less neurite outgrowth in vitro. However, we found no changes in the fate specification of Runx3(-/-) DRG neurons or in the number of DRG neurons that expressed trkC. Our data demonstrate that Runx3 is critical in regulating the axonal projections of a specific subpopulation of DRG neurons.

Early development and unstable genes in schizophrenia: preliminary results

BACKGROUND

Trinucleotide repeats have been associated with schizophrenia, but the evidence, based on cross-sectional clinical information, is equivocal.

AIMS

To examine the relationship between genomic CAG/CTG repeat size and premorbid development in schizophrenia.

METHOD

Early development and premorbid functioning of 22 patients with DSM-IV diagnosis of schizophrenia were assessed by parental interviews. Repeat expansion detection (RED) technique was used to measure genomic CAG/CTG repeat size, and PCR for CAG repeat size at the ERDA-1 and CTG 18.1 loci.

RESULTS

There was an inverse association between CAG/CTG size and perinatal complications. Patients with speech and motor developmental delay had larger repeats. The results were not due to expansion in the ERDA-1 and CTG 18.1 genes.

CONCLUSIONS

CAG/CTG repeat expansion is associated with speech and motor developmental delay in schizophrenia. We propose that the developmental model may be useful for research into the genetics of schizophrenia.

Novel disease-causing mutations in the dihydropyrimidine dehydrogenase gene interpreted by analysis of the three-dimensional protein structure

Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterized by thymine-uraciluria in homozygous deficient patients. Cancer patients with a partial deficiency of DPD are at risk of developing severe life-threatening toxicities after the administration of 5-fluorouracil. Thus, identification of novel disease-causing mutations is of the utmost importance to allow screening of patients at risk. In eight patients presenting with a complete DPD deficiency, a considerable variation in the clinical presentation was noted. Whereas motor retardation was observed in all patients, no patients presented with convulsive disorders. In this group of patients, nine novel mutations were identified including one deletion of two nucleotides [1039-1042delTG] and eight missense mutations. Analysis of the crystal structure of pig DPD suggested that five out of eight amino acid exchanges present in these patients with a complete DPD deficiency, Pro86Leu, Ser201Arg, Ser492Leu, Asp949Val and His978Arg, interfered directly or indirectly with cofactor binding or electron transport. Furthermore, the mutations Ile560Ser and Tyr211Cys most likely affected the structural integrity of the DPD protein. Only the effect of the Ile370Val and a previously identified Cys29Arg mutation could not be readily explained by analysis of the three-dimensional structure of the DPD enzyme, suggesting that at least the latter might be a common polymorphism. Our data demonstrate for the first time the possible consequences of missense mutations in the DPD gene on the function and stability of the DPD enzyme.

To die or not to die, does it change the function? Behavior of transgenic mice reveals a role for developmental cell death

In humans, perturbations in the developmental neuronal death leading to an excess of neurons could be associated with developmental neuropsychiatric disorders. Hu-bcl-2 transgenic mice appear to be a valuable tool to study the functional role of developmental programmed cell death. Indeed, the over-expression of the anti-apoptotic gene bcl-2 decreases developmental neuronal death and Hu-bcl-2 mice present supernumerary neurons in several brain regions. A detailed behavioral analysis of these mice revealed selective deficits. Hu-bcl-2 mice have normal vision, general activity and motor skills. Only the most complex behavior like anxiety and learning abilities are impaired in these mice.

Hyperactivity, neuromotor defects, and impaired learning and memory in a mouse model for metachromatic leukodystrophy

Deficiency of arylsulfatase A (ASA) causes the autosomal recessive lipidosis, metachromatic leukodystrophy (MLD). Performance on tests of activity, motor ability and learning/memory was assessed in ASA-deficient mice and normal controls at 3, 6 and 12 months-of-age. ASA-deficient mice showed consistently increased cage activity in all age groups, whereas open field activity was increased only in the 3-month-old group. Motor coordination and equilibrium, as tested in the rotarod test, was impaired in 12-month-old ASA-deficient mice. Passive avoidance learning was tested in the step-through box. Performance on this test was impaired in the 12-month-old group only. Spatial learning and memory abilities were tested in the Morris water maze. Six-month-old ASA-deficient mice displayed slightly impaired hidden-platform acquisition performance. Three-month-old animals, on the other hand, did not show any acquisition or retention defect on this task, notwithstanding significantly reduced swimming velocity. Acquisition training, both in the hidden- and visible-platform conditions of the Morris water maze, and retention performance during the probe trials were impaired in 12-month-old ASA-deficient mice. The hyperactivity, motor incoordination and slowing, and the age-related learning/memory defects, reported here in ASA-deficient mice, may relate to the decline of neuromotor and cognitive functions in MLD patients, and could be used as correlative or outcome measures in the study of MLD pathophysiology and treatment.