Novel KCNH1 Mutations Associated with Epilepsy: Broadening the Phenotypic Spectrum of KCNH1-Associated Diseases.

Here, we describe four patients suffering from a rather broad spectrum of epilepsy-related disorders, ranging from developmental and epileptic encephalopathy with intellectual disability (DEE) to genetic generalized epilepsy (GGE), which all harbor novel KCNH1 mutations. In one family, we found a weak association of a novel nonsense mutation with epilepsy, suggesting reduced penetrance, and which shows, in agreement with previous findings, that gain-of-function effects rather than haploinsufficiency are important for the pathogenicity of mutations. De novo missense variants in the pore region of the channel result in severe phenotypes presenting usually with DEE with various malformations. The potential pathogenicity of a novel KCNH1 germline mutation located outside of the critical pore domain observed in a GGE patient with a milder phenotype is supported by the fact that the very same amino acid exchange was detected as a somatic mutation in the resected brain tissue of a patient suffering from a focal cortical dysplasia type IIb. Thus, our case series broadens the phenotypic spectrum of KCNH1-associated diseases.

Reduced inflammatory response and accelerated functional recovery following sciatic nerve crush lesion in CXCR3-deficient mice.

Despite the regenerative capacity of the peripheral nerve system (PNS), functional recovery after mechanical nerve trauma is often incomplete, resulting in motor, sensory, and autonomic deficits. The elucidation of key molecules involved in trauma-induced Wallerian degeneration and the ensuing regeneration processes is a prerequisite for the development of disease modifying drugs. The chemokine (C-X-C motif) receptor 3 (CXCR3) has been implicated in the recruitment of macrophages, the major immune cell population during the process of Wallerian degeneration. In this study, we examined whether deletion of CXCR3 affects macrophage recruitment, the expression of the proinflammatory cytokine tumor necrosis factor (TNF)- α and the CXCR3 agonist interferon gamma-induced protein 10 (CXCL10), and functional recovery in the sciatic nerve crush model. CXCR3 mice displayed significantly reduced macrophage counts preceded by diminished expression of CXCL10 and TNF- α. Furthermore, functional recovery of sciatic nerve motor function was significantly accelerated. In summary, these data indicate that the deletion of CXCR3 leads to a diminished inflammatory response and an accelerated functional recovery following sciatic nerve crush injury. Therefore, CXCR3 may be an interesting target for therapeutic interventions after traumatic nerve lesions.

Sonographic assessment of the optic nerve and the central retinal artery in idiopathic intracranial hypertension.

PURPOSE: Transorbital sonography easily detects papilledema and enlarged optic nerve sheath diameters (ONSD) in IIH (idiopathic intracranial hypertension) patients. As the central retinal artery is located within the optic nerve, its hemodynamic properties might be affected by the increased pressure. In this study we assessed the diagnostic usefulness of transorbital sonography in IIH with a special focus on color Doppler imaging of the central retinal artery. IIH patients presented papilledema and enlarged ONSD. ONSD accurately predicted an increased intracranial pressure in IIH (cut-off: 5.8 mm, 81% sensitivity, 80% specificity). 24 h following therapeutic lumbar puncture ONSD diminished significantly, whereas papilledema was not changed. PSV (peak systolic velocity) and Vmean (mean flow velocity) of the central retinal artery were increased in IIH patients compared to controls. PSV accurately predicted an increase of intracranial pressure (cut-off: 11.0 cm/s, 70% sensitivity, 69% specificity). PI (pulsatility index), PSV and Vmean decreased following lumbar puncture. PSV and Vmean decreases were statistically significant for right eyes only in which the values changed to normal. In summary, besides ONSD enlargement and papilledema transbulbar sonography demonstrated an alteration of central retinal artery blood flow in IIH patients. Especially PSV might serve as valuable surrogate marker for intracranial pressure in IIH. Furthermore, the change of intra-individual central retinal arteries PI might be a valuable parameter to demonstrate response to lumbar puncture in IIH patients.

Distinct segregation of the pathogenic m.5667G>A mitochondrial tRNAAsn mutation in extraocular and skeletal muscle in chronic progressive external ophthalmoplegia.

Chronic progressive external ophthalmoplegia (CPEO) is a frequent clinical manifestation of disorders caused by pathogenic mitochondrial DNA mutations. However, for diagnostic purposes skeletal muscle tissue is used, since extraocular muscle tissue is usually not available for work-up. In the present study we aimed to identify causative factors that are responsible for extraocular muscle to be primarily affected in CPEO. We performed comparative histochemical and molecular genetic analyses of extraocular muscle and skeletal muscle single fibers in a case of isolated CPEO caused by the heteroplasmic m.5667G>A mutation in the mitochondrial tRNAAsn gene (MT-TN). Histochemical analyses revealed higher proportion of cytochrome c oxidase deficient fibers in extraocular muscle (41%) compared to skeletal muscle (10%). However, genetic analyses of single fibers revealed no significant difference either in the mutation loads between extraocular muscle and skeletal muscle cytochrome c oxidase deficient single fibers (extraocular muscle 86% ±â€¯4.6%; skeletal muscle 87.8 %±â€¯5.7%, p = 0.246) nor in the mutation threshold (extraocular muscle 74% ±â€¯3%; skeletal muscle 74% ±â€¯4%). We hypothesize that higher proportion of cytochrome c oxidase deficient fibers in extraocular muscle compared to skeletal muscle might be due to facilitated segregation of the m.5667G>A mutation into extraocular muscle, which may explain the preferential ocular manifestation and clinically isolated CPEO.

Partial sciatic nerve ligation leads to an upregulation of Ni2+-resistant T-type Ca2+ currents in capsaicin-responsive nociceptive dorsal root ganglion neurons.

BACKGROUND: Neuropathic pain resulting from peripheral nerve lesions is a common medical condition, but current analgesics are often insufficient. The identification of key molecules involved in pathological pain processing is a prerequisite for the development of new analgesic drugs. Hyperexcitability of nociceptive DRG-neurons due to regulation of voltage-gated ion-channels is generally assumed to contribute strongly to neuropathic pain. There is increasing evidence, that T-type Ca2+-currents and in particular the Cav3.2 T-type-channel isoform play an important role in neuropathic pain, but experimental results are contradicting. PURPOSE: To clarify the role of T-type Ca2+-channels and in particular the Cav3.2 T-type-channel isoform in neuropathic pain. METHODS: The effect of partial sciatic nerve ligation (PNL) on pain behavior and the properties of T-type-currents in nociceptive DRG-neurons was tested in wild-type and Cav3.2-deficient mice. RESULTS: In wild-type mice, PNL of the sciatic nerve caused neuropathic pain and an increase of T-type Ca2+-currents in capsaicin-responsive neurons, while capsaicin-unresponsive neurons were unaffected. Pharmacological experiments revealed that this upregulation was due to an increase of a Ni2+-resistant Ca2+-current component, inconsistent with Cav3.2 up-regulation. Moreover, following PNL Cav3.2-deficient mice showed neuropathic pain behavior and an increase of T-Type Ca2+-currents indistinguishable to that of PNL treated wild-type mice. CONCLUSION: These data suggest that PNL induces an upregulation of T-Type Ca2+-currents in capsaicin-responsive DRG-neurons mediated by an increase of a Ni2+-insensitive current component (possibly Cav3.1 or Cav3.3). These findings provide relevance for the development of target specific analgesic drugs.

Neuropathic pain in experimental autoimmune neuritis is associated with altered electrophysiological properties of nociceptive DRG neurons.

Guillain-Barré syndrome (GBS) is an acute, immune-mediated polyradiculoneuropathy characterized by rapidly progressive paresis and sensory disturbances. Moderate to severe and often intractable neuropathic pain is a common symptom of GBS, but its underlying mechanisms are unknown. Pathology of GBS is classically attributed to demyelination of large, myelinated peripheral fibers. However, there is increasing evidence that neuropathic pain in GBS is associated with impaired function of small, unmyelinated, nociceptive fibers. We therefore examined the functional properties of small DRG neurons, the somata of nociceptive fibers, in a rat model of GBS (experimental autoimmune neuritis=EAN). EAN rats developed behavioral signs of neuropathic pain. This was accompanied by a significant shortening of action potentials due to a more rapid repolarization and an increase in repetitive firing in a subgroup of capsaicin-responsive DRG neurons. Na+ current measurements revealed a significant increase of the fast TTX-sensitive current and a reduction of the persistent TTX-sensitive current component. These changes of Na+ currents may account for the significant decrease in AP duration leading to an overall increase in excitability and are therefore possibly directly linked to pathological pain behavior. Thus, like in other animal models of neuropathic and inflammatory pain, Na+ channels seem to be crucially involved in the pathology of GBS and may constitute promising targets for pain modulating pharmaceuticals.

The transcription factor Smad-interacting protein 1 controls pain sensitivity via modulation of DRG neuron excitability.

The perception of pain is initiated by the transduction of noxious stimuli through specialized ion channels and receptors expressed by primary nociceptive neurons. The molecular mechanisms that orchestrate the expression and function of ion channels relevant for pain processing are poorly understood. We demonstrate here a central role of the transcription factor Smad-interacting protein 1 (Sip1/Zfhx1b/Zeb2), a 2-handed zinc finger DNA-binding protein with essential functions in neural crest and forebrain development, in controlling nociceptive neuron excitability and pain sensitivity. Mutant mice lacking 1 Zfhx1b allele displayed decreased thermal pain responses, whereas mechanical pain was unaffected. In parallel, repetitive firing of capsaicin/heat-sensitive nociceptive DRG neurons was markedly impaired. Analysis of the voltage-gated currents underlying repetitive firing revealed a significant increase in persistent sodium currents and a reduction in delayed rectifier potassium currents. Modeling experiments in conjunction with experimental results suggest that these changes cause a depolarization-induced block of action potential propagation past the DRG axon T-junction. These data suggest that Sip1 controls the transduction properties of heat-sensitive primary sensory neurons and thus thermal pain sensitivity in a novel manner via coordinated changes in DRG-neuron voltage-gated ion channels.

Potassium channel dysfunction and depolarized resting membrane potential in a cell model of SCA3.

Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant inherited neurodegenerative disease caused by the expansion of a polyglutamine repeat within the disease protein, ataxin-3. There is growing evidence that neuronal electrophysiological properties are altered in a variety of polyglutamine diseases such as Huntington's disease and SCA1 and that these alterations may contribute to disturbances of neuronal function prior to neurodegeneration. To elucidate possible electrophysiological changes in SCA3, we generated a stable PC12 cell model with inducible expression of normal and mutant human full-length ataxin-3 and analyzed the electrophysiological properties after induction of the recombinant ataxin-3 expression. Neuronally differentiated PC12 cells expressing the expanded form of ataxin-3 showed significantly decreased viabilities and developed ultrastructural changes resembling human SCA3. Prior to neuronal cell death, we found a significant reduction of the resting membrane potential and a hyperpolarizing shift of the activation curve of the delayed rectifier potassium current. These findings indicate that electrophysiological properties are altered in mutant ataxin-3 expressing neuronal cells and may contribute to neuronal dysfunction in SCA3.

Serial MRI of limbic encephalitis.

INTRODUCTION: The aim of the study was to analyze serial magnetic resonance imaging (MRI) scans in patients with various forms of limbic encephalitis (LE) in order to evaluate whether, and at what time point, MRI findings support the diagnosis of LE. METHODS: Serial MRI scans (1 day to 15 years after the onset of symptoms) of 20 patients with LE were retrospectively evaluated. Of these 20 patients, 16 had definite LE (histopathological limbic inflammation, n=6; onconeural antibodies, n=5; voltage-gated potassium channel antibodies, n=3; malignant tumors, n=5), and 4 possible LE because they met the clinical criteria but had no typical antibodies or tumors. RESULTS: Of 13 patients who were studied with MRI within 3 months after the onset of symptoms, 11 had swollen temporomesial structures (unilateral, n=7; bilateral, n=4). After up to 9 months, the swelling had resolved in nine of ten re-evaluated patients. Of seven patients who were initially studied with MRI more than 3 months after disease onset, three had swollen temporomesial structures, one had a hyperintense, normal-sized hippocampus, and three had hyperintense and atrophic temporomesial structures. CONCLUSION: LE starts as an acute disease with uni- or bilateral swollen temporomesial structures that are hyperintense on fluid attenuation inversion recovery and T2-weighted sequences. Swelling and hyperintensity may persist over months to years, but in most cases progressive temporomesial atrophy develops.