Biomedical subjects

Imke Puls

Publications and source records attributed to Imke Puls.

11 recordsLinked to original sources

PubMed2006

A motor neuron disease-associated mutation in p150Glued perturbs dynactin function and induces protein aggregation.

The microtubule motor cytoplasmic dynein and its activator dynactin drive vesicular transport and mitotic spindle organization. Dynactin is ubiquitously expressed in eukaryotes, but a G59S mutation in the p150Glued subunit of dynactin results in the specific degeneration of motor neurons. This mutation in the conserved cytoskeleton-associated protein, glycine-rich (CAP-Gly) domain lowers the affinity of p150Glued for microtubules and EB1. Cell lines from patients are morphologically normal but show delayed recovery after nocodazole treatment, consistent with a subtle disruption of dynein/dynactin function. The G59S mutation disrupts the folding of the CAP-Gly domain, resulting in aggregation of the p150Glued protein both in vitro and in vivo, which is accompanied by an increase in cell death in a motor neuron cell line. Overexpression of the chaperone Hsp70 inhibits aggregate formation and prevents cell death. These data support a model in which a point mutation in p150Glued causes both loss of dynein/dynactin function and gain of toxic function, which together lead to motor neuron cell death.

Animals↗

PubMed2006

Serotonergic dysfunction: brain imaging and behavioral correlates.

Identification of gene-environment and gene-gene interactions has become increasingly important in understanding psychiatric disorders. Dysfunction of central serotonergic neurotransmission has been implicated in alcoholism, depression, and anxiety. We review the literature on nonhuman primates that assesses the interaction between the genetic constitution of the regulatory region ofthe serotonin transporter (5-HTT) and environmental factors. Prospective studies in nonhuman primates that underwent social stress found a reduction of theserotonin turnover rate among carriers of one or two short alleles in a functional polymorphism of the 5-HTT promoter. In these primates, brain imaging studies showed a relative increase in the availability of raphe serotonin transporters. A low serotonin turnover rate and a high availability of serotonin transporters were associated with reduced response to excessive alcohol intake, anxiety, and impulsive aggression. Animal experiments point to a relationship between serotonergic dysfunction, negative mood states, and excessive alcohol intake, which may in part be mediated by reduced alcohol-induced sedation.

Aggression↗

PubMed2005

Phenotypic spectrum of disorders associated with glycyl-tRNA synthetase mutations.

We describe clinical, electrophysiological, histopathological and molecular features of a unique disease caused by mutations in the glycyl-tRNA synthetase (GARS) gene. Sixty patients from five multigenerational families have been evaluated. The disease is characterized by adolescent onset of weakness, and atrophy of thenar and first dorsal interosseus muscles progressing to involve foot and peroneal muscles in most but not all cases. Mild to moderate sensory deficits develop in a minority of patients. Neurophysiologically confirmed chronic denervation in distal muscles with reduced compound motor action potentials were features consistent with both motor neuronal and axonal pathology. Sural nerve biopsy showed mild to moderate selective loss of small- and medium-sized myelinated and small unmyelinated axons, although sensory nerve action potentials were not significantly decreased. Based on the presence or absence of sensory changes, the disease phenotype was initially defined as distal spinal muscular atrophy type V (dSMA-V) in three families, Charcot-Marie-Tooth disease type 2D (CMT2D) in a single family, and as either dSMA-V or CMT2D in patients of another large family. Linkage to chromosome 7p15 and the presence of disease-associated heterozygous GARS mutations have been identified in patients from each of the five studied families. We conclude that patients with GARS mutations present a clinical continuum of predominantly motor distal neuronopathy/axonopathy with mild to moderate sensory involvement that varies between the families and between members of the same family. Awareness of these overlapping clinical phenotypes associated with mutations in GARS will facilitate identification of this disorder in additional families and direct future research toward better understanding of its pathogenesis.

Adolescent↗

PubMed2005

Distal spinal and bulbar muscular atrophy caused by dynactin mutation.

Impaired axonal transport has been postulated to play a role in the pathophysiology of multiple neurodegenerative disorders. In this report, we describe the results of clinical and neuropathological studies in a family with an inherited form of motor neuron disease caused by mutation in the p150Glued subunit of dynactin, a microtubule motor protein essential for retrograde axonal transport. Affected family members had a distinct clinical phenotype characterized by early bilateral vocal fold paralysis affecting the adductor and abductor laryngeal muscles. They later experienced weakness and atrophy in the face, hands, and distal legs. The extremity involvement was greater in the hands than in the legs, and it had a particular predilection for the thenar muscles. No clinical or electrophysiological sensory abnormality existed; however, skin biopsy results showed morphological abnormalities of epidermal nerve fibers. An autopsy study of one patient showed motor neuron degeneration and axonal loss in the ventral horn of the spinal cord and hypoglossal nucleus of the medulla. Immunohistochemistry showed abnormal inclusions of dynactin and dynein in motor neurons. This mutation of dynactin, a ubiquitously expressed protein, causes a unique pattern of motor neuron degeneration that is associated with the accumulation of dynein and dynactin in neuronal inclusions.

Action Potentials↗

PubMed2004

Amygdala-prefrontal coupling depends on a genetic variation of the serotonin transporter.

Major depression is conditionally linked to a polymorphism of the human serotonin transporter gene (SLC6A4). During the presentation of aversive, but not pleasant, pictures, healthy carriers of the SLC6A4 short (s) allele showed stronger activation of the amygdala on functional magnetic resonance imaging. s carriers also showed greater coupling between the amygdala and the ventromedial prefrontal cortex, which may contribute to the abnormally high activity in the amygdala and medial prefrontal cortex seen in major depression.

Aged↗

PubMed2004

Pharmacogenetic insights to monoaminergic dysfunction in alcohol dependence.

RATIONALE: Alcohol dependence is characterized by the development of tolerance, withdrawal symptoms, and craving for alcohol. Chronic alcohol consumption causes neuroadaptive changes in the central dopaminergic and serotonergic system, which are partially reversible after detoxification. The severity and time-course of recovery of these neuroadaptive changes may depend on the genetic constitution of monoamine transporters and receptors and contribute to the relapse risk of alcoholics. OBJECTIVES: To assess the interaction between the genetic constitution and the in vivo availability of dopamine and serotonin transporters and receptors, chronic alcohol intake, alcohol craving and withdrawal. METHODS: Review of brain imaging studies that assess the genotype and availability of dopamine and serotonin transporters in detoxified alcoholics and healthy control subjects. RESULTS: Chronic alcohol intake induced neuroadaptive reductions in striatal dopamine transporter (DAT) availability, which were reversible during early abstinence. A polymorphism of the DAT gene (SLC6A3) was associated with the in vivo transporter availability and with the severity of alcohol withdrawal. Neurotoxic reductions in 5-HTT protein expression were limited to homozygous carriers of the long allele in the 5-HTT gene (SCL6A4) regulatory region and correlated with negative mood states. CONCLUSION: Genetic constitution interacts with the in vivo availability of central dopamine and serotonin transporters during alcohol detoxification and may affect the severity of alcohol withdrawal and clinical depression.

Alcoholism↗

PubMed2004

DNA/RNA helicase gene mutations in a form of juvenile amyotrophic lateral sclerosis (ALS4).

Juvenile amyotrophic lateral sclerosis (ALS4) is a rare autosomal dominant form of juvenile amyotrophic lateral sclerosis (ALS) characterized by distal muscle weakness and atrophy, normal sensation, and pyramidal signs. Individuals affected with ALS4 usually have an onset of symptoms at age <25 years, a slow rate of progression, and a normal life span. The ALS4 locus maps to a 1.7-Mb interval on chromosome 9q34 flanked by D9S64 and D9S1198. To identify the molecular basis of ALS4, we tested 19 genes within the ALS4 interval and detected missense mutations (T3I, L389S, and R2136H) in the Senataxin gene (SETX). The SETX gene encodes a novel 302.8-kD protein. Although its function remains unknown, SETX contains a DNA/RNA helicase domain with strong homology to human RENT1 and IGHMBP2, two genes encoding proteins known to have roles in RNA processing. These observations of ALS4 suggest that mutations in SETX may cause neuronal degeneration through dysfunction of the helicase activity or other steps in RNA processing.

Adolescent↗

PubMed2004

[Genetic and pharmacological effects on prefrontal cortical function in schizophrenia].

Brain imaging studies with PET, SPECT, functional magnetic resonance imaging, and spectroscopy provide evidence of prefrontal dysfunction in schizophrenia. Dysfunction of the prefrontal cortex is associated with cognitive impairment and negative symptoms. Combined multimodal imaging shows that a developmentally early disturbance of frontotemporal-limbic neuronal networks is associated with a disinhibition of subcortical dopaminergic neurotransmission. Current studies imply genetic factors in the regulation of dopaminergic neurotransmission and their effects on prefrontal cortex function. Some studies also indicate that atypical neuroleptics may at least partially improve frontal cortex function. We review the literature and discuss genotype and medication effects on frontal dysfunction in schizophrenia. Molecular brain imaging combines imaging techniques with the assessment of genotype effects and represents a powerful tool for the understanding of neuropsychiatric disorders.

Antipsychotic Agents↗

PubMed2003

Glycyl tRNA synthetase mutations in Charcot-Marie-Tooth disease type 2D and distal spinal muscular atrophy type V.

Charcot-Marie-Tooth disease type 2D (CMT2D) and distal spinal muscular atrophy type V (dSMA-V) are axonal peripheral neuropathies inherited in an autosomal dominant fashion. Our previous genetic and physical mapping efforts localized the responsible gene(s) to a well-defined region on human chromosome 7p. Here, we report the identification of four disease-associated missense mutations in the glycyl tRNA synthetase gene in families with CMT2D and dSMA-V. This is the first example of an aminoacyl tRNA synthetase being implicated in a human genetic disease, which makes genes that encode these enzymes relevant candidates for other inherited neuropathies and motor neuron diseases.

Amino Acid Sequence↗

PubMed2003

Mutant dynactin in motor neuron disease.

Impaired axonal transport in motor neurons has been proposed as a mechanism for neuronal degeneration in motor neuron disease. Here we show linkage of a lower motor neuron disease to a region of 4 Mb at chromosome 2p13. Mutation analysis of a gene in this interval that encodes the largest subunit of the axonal transport protein dynactin showed a single base-pair change resulting in an amino-acid substitution that is predicted to distort the folding of dynactin's microtubule-binding domain. Binding assays show decreased binding of the mutant protein to microtubules. Our results show that dysfunction of dynactin-mediated transport can lead to human motor neuron disease.

Amino Acid Motifs↗

PubMedDate not supplied

Prognostic and diagnostic value of global cerebral blood flow volume and cerebral transit time in acute stroke.

Conventional duplex sonography is a well-established method for the assessment of the brain-supplying arteries in acute stroke. However, ultrasound (US) remains inconclusive in a significant number of stroke patients. Recently, two new US parameters, the cerebral transit time (cTT) and the global cerebral blood flow volume (CBF), have been introduced. In the present study, we investigated the diagnostic and prognostic value of both parameters in stroke patients. Conventional duplex examinations of the extra- and intracranial brain-supplying arteries and measurement of cTT and CBF were performed in 50 consecutive stroke patients within 24 h after symptom onset and compared with US findings in 22 age-matched healthy controls. Neurological deficits and the degree of disability were graded using several stroke scores, and were re-evaluated for outcome measure after 1 year. CBF and cTT were not assessable in 26% and 20% of the patients, respectively. Compared with the healthy control group, stroke patients showed a significant reduction of CBF and prolongation of cTT. More than 50% of patients with otherwise normal routine duplex examination had abnormal CBF or cTT findings. Furthermore, there was a strong correlation between the reduction of global CBF and the outcome after 1 year. Sonographic assessment of the CBF and cTT are additional parameters that might increase the diagnostic sensitivity of US in stroke patients, and may have prognostic relevance.

Acute Disease↗