Delta-amino-levulinic acid dehydratase gene and essential tremor.

BACKGROUND: Several reports found a relationship between increased serum lead levels and the risk for essential tremor (ET), especially in carriers of the minor allele of the single nucleotide polymorphism (SNP) rs1800435 in the aminolevulinate dehydratase (ALAD) gene, which is involved in the synthesis of haem groups. Our group reported decreased risk for ET in carriers of the minor alleles of the rs2071746 and rs1051308 SNPs in the haem-oxygenases 1 and 2 (HMOX1 and HMOX2), respectively, involved in haem metabolism. We analysed whether ALAD rs1800435 alone and their interactions with the four common SNPs in the HMOX1 and HMOX2 genes are associated with the risk for ET. MATERIALS AND METHODS: We analysed the genotype and allele variants frequencies of ALAD rs1800435 in 202 patients with familial ET and 218 healthy controls using a TaqMan method. We also analysed the role of the interaction between ALAD rs1800435 and the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363 and HMOX2 rs1051308 with the risk of developing ET. RESULTS: The frequencies of genotype and allelic variants of ALAD rs1800435 did not differ significantly between patients with ET and controls, and were not influenced by gender. Subjects carrying the ALAD rs1800435CC genotype (wild-type) and the HMOX2 rs1051308GG genotype or the HMOX2 rs1051308G allele had significantly decreased risk for ET. CONCLUSIONS: These results suggest that the ALAD rs1800435 SNP is not related with the risk for ET, but its interaction with the HMOX2 rs1051308 SNP could be weakly associated with the risk for this disease.

No association of the SLC1A2 rs3794087 allele with risk for essential tremor in the Spanish population.

BACKGROUND/AIMS: A recent genome-wide association study and other replication studies have suggested that the rs3794087 single nucleotide polymorphism in the solute carrier family 1 - glial affinity glutamate transporter-member 2 (SLC1A2) gene is associated with an increased risk for essential tremor (ET), and a replication study in an Asian cohort has shown a decreased risk for ET associated with the rs3794087T allele. We tried to replicate this association in a White Spanish population. MATERIALS AND METHODS: We analyzed the distribution of allelic and genotypic frequencies of rs3794087 in 202 patients with familial ET and 308 healthy controls using a TaqMan-based quantitative PCR assay. RESULTS: Genotypic and allelic frequencies of rs3794087 did not differ significantly between patients with ET and controls and were unrelated with the age at onset of tremor or sex. CONCLUSION: Our study suggests that SLC1A2 rs3794087 is not associated with the risk for developing familial ET in the Spanish population, thus subtracting relevance to SLC1A2 rs3794087 as a risk biomarker for ET.

Vitamin D Receptor and Binding Protein Gene Variants in Patients with Essential Tremor.

Several studies have shown an association between some variants in the vitamin D receptor (VDR) and the GC vitamin D binding protein (GC) genes with the risk for Parkinson's disease or other neurological disorders. VDR rs2228570 has shown an association with essential tremor (ET) in a previous study. The aim of this study is to look for the association between several common variants in these genes and the risk for ET. We genotyped 272 patients diagnosed with familial ET and 272 age-matched controls using specific TaqMan assays for VDR rs2228570, VDR rs731236, VDR rs7975232, VDR rs739837, VDR rs78783628, GC rs7041, and GC rs4588 single nucleotide variants (SNVs). We found an association between GC rs7041 SNV and ET using recessive, codominant, and allelic models. Despite our results did not find an association between VDR rs2228570 and ET, the pooled data with those by a previous report suggest this association under recessive, codominant, and allelic models. None of the SNVs studied was related to the age at onset of tremor in ET patients. Data from the current study suggest an association between GC rs7041 and VDR rs2228570 SNVs and ET risk.

Gamma-aminobutyric acid GABRA4, GABRE, and GABRQ receptor polymorphisms and risk for essential tremor.

Some clinical and experimental data suggest a possible role of γ-aminobutyrate (GABA)-ergic mechanisms in the pathophysiology of essential tremor (ET). We studied the allelic and genotype frequencies of the single nucleotide polymorphisms, such as GABRA4-L26M (Leu26Met, rs2229940), GABRE-S102A (Ser26Ala, rs1139916), and GABRQ-I478F (Ile26Phe, rs3810651), in 200 patients with familial ET and 250 healthy controls using TaqMan genotyping. GABRA4-L26M, GABRE-S102A, and GABRQ-I478F genotype and allelic frequencies did not differ significantly between patients with ET and controls, and were unrelated to the age at onset of tremor or sex. The GABRQ-478F allele seemed to be related to improvement of tremor with ethanol use among men (odds ratio=2.32, 95% confidence interval=0.26-4.3, P=0.007, Pc=0.021). The results of this study suggest that the single nucleotide polymorphisms studied in the GABRA4, GABRE, and GABRQ genes are not related to the risk for familial ET.

Dopamine receptor D3 (DRD3) genotype and allelic variants and risk for essential tremor.

To investigate the possible association between dopamine receptor D3 genotype (DRD3) and allelic variants and the risk for developing essential tremor (ET). Leukocytary DNA from 201 patients with ET and 282 healthy controls was studied for the genotype DRD3 and the occurrence of DRD3 allelic variants by using allele-specific PCR amplification and MslI-RFLP's analyses. A meta-analysis of previous studies was performed. The frequencies of the DRD3Ser/Gly genotype and of the allelic variant DRDGly were significantly higher in patients with ET than in controls (P < 0.017 and <0.005, respectively), These findings were especially relevant in women (OR = 1.73, 95% CI: 1.15-2.59, P = 0.008), and in patients with earlier onset of the disease with (P = 0.014). The frequencies of the DRD3Ser/Gly and DRD3Gly/Gly genotypes and of the allelic variant DRD3Gly in patients were significantly higher in patients with voice tremor, but not with head, tongue, or chin tremor, than in controls. The meta-analysis indicated association of variant genotypes with ET risk (OR = 1.18, 95% CI 1.01-1.38). These results suggest that DRD3 genotype and the variant DRD3Gly allelic variant is associated with the risk for and age at onset of ET, and with the risk for voice tremor, in Caucasian Spanish people.

Relations between Sensorimotor Integration and Speech Disorders in Parkinson's Disease.

BACKGROUND: Sensorimotor integration mechanisms can be affected by many factors, among which are those involving neuromuscular disorders. Parkinson's disease (PD) is characterized by well-known motor symptoms, among which lately have been included motor speech deficits. Measurement of the acoustic startle reflex (ASR) and its modulations (prepulse inhibition and prepulse facilitation, PPI and PPF respectively) represent a simple and quantifiable tool to assess sensorimotor function. However, it remains unknown whether measures of the PPI and PPF are associated with motor speech deficits in PD. METHODS: A total of 88 subjects participated in this study, 52 diagnosed with PD and 36 control subjects. After obtaining written informed consent, participants were assessed with PPI at several interstimulus intervals, and PPF at 1000 ms using the SRH-Lab system (San Diego, CA). Percentage of change in the amplitude and latency of the ASR was analyzed between groups. Voice recordings were register of a specific text given to the subjects with a professional recorder and temporal patterns of speech were analyzed. RESULTS: Statistical analysis conducted in this study showed differences in PPI and PPF in subjects with PD compared to controls. In addition, discriminative parameters of voice abnormalities were observed in PD subjects related to control subjects showing a reduction in phonation time, vowel pulses, breaks, breakage and voice speech periods. CONCLUSIONS: PD presents a disruption in sensorimotor filter mechanisms and speech disorders, and there is a relationship between these alterations. The correlation between the PPI and PPF with an alteration of the voice in PD subjects contributes toward understanding mechanism underlying the neurophysiological alterations in both processes. Overall, easy and non-invasive tests such as PPI, PPF together with voice analysis may be useful to identify early stages of PD.

Changes at the CYP2C locus and disruption of CYP2C8/9 linkage disequilibrium in patients with essential tremor.

To identify low-penetrance genes related to sporadic essential tremor (ET) at the CYP2C locus, located in chromosome 10 q23.33. Leukocytary DNA from 200 ET patients and a control group of 300 unrelated healthy individuals with known CYP2C19 genotypes was studied for common CYP2C8 and CYP2C9 allelic variants by using amplification-restriction analyses. Patients with ET showed the following differences compared with healthy subjects: a 1.6-fold reduction in the frequency for CYP2C8*3 (p=0.006), a 1.35-fold reduction of CYP2C9*2 (p=0.05) and a 1.52-fold reduction in the frequency for CYP2C9*3 (p=0.07). The frequency for patients with ET carrying at least one defective allele was 1.33-fold reduced as compared with healthy subjects (p=0.002). In addition, a disruption of the CYP2C8*3/CYP2C9*2 linkage disequilibrium was observed in ET patients, with a 2.1-fold reduction in the percentage for carriers of the haplotype CYP2C8*3 plus CYP2C9*2 in ET patients (p=0.0001). These findings were independent of gender, age, age of onset, or clinical symptoms. These results suggest that alterations at the CYP2C gene locus are associated with the risk for ET.

Alcohol dehydrogenase 2 genotype and allelic variants are not associated with the risk for essential tremor.

OBJECTIVE: To investigate the possible association between alcohol dehydrogenase 1B, beta-polypeptide (ADH2) genotype and allelic variants and the risk for developing essential tremor (ET). METHODS: Leukocytary DNA from 204 ET patients and 200 healthy controls was studied for the genotype ADH2 and the occurrence of ADH2 allelic variants using allele-specific polymerase chain reaction amplification and MslI-restriction fragment length polymorphism's analyses. RESULTS: The frequencies of the ADH2*1/ADH2*2 genotype and of the allelic variant ADH2*2 did not differ significantly in ET patients when compared with those of the controls. The mean age at onset of ET did not differ significantly between patients with genotypes ADH2*1/ADH2*2 and ADH2*1/ADH2*1. The frequencies of the genotype ADH2*1/ADH2*2 and of the allelic variant ADH2*2 in patients with voice, tongue, and chin tremors did not differ from those of the controls, whereas patients with voice tremor showed lower frequencies of mutated genotypes and ADH2*2 alleles. The frequencies of ADH2 genotypes and ADH2 alleles did not differ significantly between patients who did not drink ethanol and those who reported improvement, no improvement, or unknown response of tremor to ethanol. CONCLUSIONS: These results suggest that ADH2 genotype and allelic variants are not associated with the risk for ET in white Spanish people.

NEFL N98S mutation: another cause of dominant intermediate Charcot-Marie-Tooth disease with heterogeneous early-onset phenotype.

The purpose of this study was to describe a pedigree with NEFL N98S mutation associated with a dominant intermediate Charcot-Marie-Tooth disease (DI-CMT) and heterogeneous early-onset phenotype. The pedigree comprised two patients, the proband and her son, aged 38 and 5 years. The proband, evaluated at age 31, showed delayed motor milestones that, as of the second decade, evolved into severe phenotype consisting of sensorimotor neuropathy, pes cavus, clawing hands, gait and kinetic cerebellar ataxia, nystagmus and dysarthria, she being wheelchair bound. By then, a working diagnosis of sporadic early onset cerebellar ataxia with peripheral neuropathy was established. Screening of mutations associated with SCA and autosomal recessive cerebellar ataxias was negative. Her son showed a mild phenotype characterized by delayed motor milestones, and lower-limb hypotonia and areflexia. Electrophysiology in both patients showed nerve conduction slowing in the intermediate range, both in proximal and distal nerve segments, but where compound muscle action potentials exhibited severe attenuation there was conduction slowing down to the demyelinating range. In the proband, cranial magnetic resonance imaging (MRI) showed cerebellar atrophy, electromyography disclosed active denervation in tibialis anterior, and MRI of lower-limb musculature demonstrated widespread and distally accentuated muscle fatty atrophy; furthermore, on water sensitive MRI sequences there was edema of calf muscles. We conclude that the NEFL N98S mutation is associated with a DI-CMT phenotype characterized by early-onset sensorimotor neuropathy delaying motor milestones, which may evolve into a severe and complex clinical picture including cerebellar ataxia.

Heme Oxygenase 1 and 2 Common Genetic Variants and Risk for Essential Tremor.

Several reports suggested a role of heme oxygenase genes 1 and 2 (HMOX1 and HMOX2) in modifying the risk to develop Parkinson disease (PD). Because essential tremor (ET) and PD share phenotypical and, probably, etiologic factors of the similarities, we analyzed whether such genes are related with the risk to develop ET. We analyzed the distribution of allelic and genotype frequencies of the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363, and HMOX2 rs1051308 single nucleotide polymorphisms, as well as the presence of copy number variations of these genes in 202 subjects with familial ET and 747 healthy controls. Allelic frequencies of rs2071746T and rs1051308G were significantly lower in ET patients than in controls. None of the studied polymorphisms influenced the disease onset. The present study suggests a weak association between HMOX1 rs2071746 and HMOX2 rs1051308 polymorphisms and the risk to develop ET in the Spanish population.

EEG characterization of audiogenic seizures in the hamster strain GASH:Sal.

The study was performed to characterize GASH:SAL audiogenic seizures as true epileptic activity based on electroencephalographic markers acquired with a wireless implanted radiotelemetry system. We analyzed cortical EEG patterns synchronized with video recordings of convulsive behavior of the GASH:Sal hamster following an acoustic stimulus. All GASH:Sal presented archetypal motor symptoms comparable to current animal models of generalized tonic-clonic epilepsy. Seizures consisted of an initial bout of wild running, followed by opisthotonus, tonic-clonic convulsions, tonic limb extension, and terminated in postictal depression. EEG patterns correlated with behavior and displayed phase appropriate spike-wave complexes, low-amplitude desynchronized activity, and high frequency large-amplitude peaks. Our results confirm that electroencephalographic profiles of the audiogenic seizures of the hamster GASH:Sal are parallel to EEG patterns of other animal models of generalized tonic-clonic seizures. Therefore, this animal may serve as an appropriate model for epilepsy research.

H1-MAPT and the risk for familial essential tremor.

The most frequent MAPT H1 haplotype is associated with the risk for developing progressive supranuclear palsy and other neurodegenerative diseases such as Parkinson's disease. A recent report suggests that the MAPT H1 is associated with the risk for developing essential tremor. We wanted to confirm this association in a different population. We analyzed the distribution of allelic and genotype frequencies of rs1052553, which is an H1/H2 SNP, in 200 subjects with familial ET and 291 healthy controls. rs1052553 genotype and allelic frequencies did not differ significantly between subjects with ET and controls and were unrelated with the age at onset of tremor or gender, and with the presence of head, voice, chin, and tongue tremor. Our study suggests that the MAPT H1 rs1052553 is not associated with the risk for developing familial ET in the Spanish population.

Gamma-aminobutyric acid (GABA) receptor rho (GABRR) polymorphisms and risk for essential tremor.

Some clinical and experimental data suggest a possible role of gamma-aminobutyrate (GABA)-ergic mechanisms in the pathophysiology of essential tremor (ET), such as the improvement of ET with some GABAergic drugs and the development of an experimental model of ET in GABA A receptor alpha-1 knockout mice (postural and kinetic tremor and motor incoordination similar to human ET). To investigate the possible association between the GABA receptor subtype rho1, rho2, and rho3 (GABRR1, GABRR2, and GABRR3) genotypes and allelic variants of the single nucleotide polymorphisms GABRR1-M26V (Met26Val, rs12200969), GABRR1-H27R (His26Arg, rs1186902), GABRR2-T455M (Thr55Met, rs282129), and GABRR3-Y205X (Tyr205X, rs832032), and the risk for ET, we studied the frequency of the previously mentioned GABRR genotypes and allelic variants in 200 patients with ET and 250 healthy controls using TaqMan genotyping. The frequencies of the GABBR1 genotypes and allelic variants of the studied polymorphisms did not differ significantly between patients with ET and controls, and were unrelated with the age at onset of tremor, gender, localization of tremor, and response of tremor to ethanol. These data suggest that the single nucleotide polymorphisms studied in the GABBR genes are not related to the risk for ET.

Tremor associated with chronic inflammatory demyelinating peripheral neuropathy: treatment with pregabalin.

OBJECTIVE: To report a case of a patient with tremor associated with chronic inflammatory demyelinating neuropathy (CIDP) that improved after treatment with pregabalin. CASE REPORT: A 68-year-old man diagnosed as having CIDP at age 63 years developed postural and kinetic tremor in both hands at age 64 years. Tremor did not improve with propranolol, primidone, phenobarbital, clonazepam, alprazolam, gabapentin, and topiramate, but improved markedly with pregabalin. Tremor worsened after pregabalin withdrawal and improved again after its reintroduction. CONCLUSIONS: Pregabalin could be useful in the treatment of postural tremor associated with CIDP resistant to other therapies.

The nonsynonymous Thr105Ile polymorphism of the histamine N-methyltransferase is associated to the risk of developing essential tremor.

OBJECTIVE: We analyzed in patients with essential tremor (ET) the Thr105Ile polymorphism of the Histamine N-methyltransferase (HNMT) enzyme that is associated to Parkinson's disease (PD) risk. METHODS: Leukocytary DNA from 204 ET patients and a control group of 295 unrelated healthy individuals was studied for the nonsynonymous HNMT Thr105Ile polymorphism by using amplification-restriction analyses. RESULTS: Patients with ET showed a higher frequency of homozygous HNMT 105Thr genotypes leading to high metabolic activity (p < 0.015) with a statistically significant gene-dose effect, as compared to healthy subjects. These findings were independent of gender, and of tremor localization, but the association of the HNMT polymorphism is more prominent among patients with late-onset ET (p < 0.007). CONCLUSION: These results, combined with previous findings indicating alterations in the frequency for the HNMT Thr105Ile polymorphism in patients with PD, suggest that alterations of histamine homeostasis in the SNC are associated with the risk of movement disorders.

CYP2C19 polymorphism and risk for essential tremor.

Many patients with essential tremor (ET) develop acute adverse effects to primidone. We investigated the association between CYP2C19 polymorphism (possibly related to primidone metabolism) and the risk for developing essential ET and acute adverse effects to primidone. Leukocytary DNA from 200 ET patients and 300 healthy controls was studied for the genotype CYP2C19 and the occurrence of CYP2C19 allelic variants by using allele-specific PCR amplification and Sma I and BamH I RFLP analyses. The frequencies of the genotype CYP2C19*1/CYP2C19*2 and of the allelic variant CYP2C19*2 were significantly higher in ET patients than in controls. The mean age at onset of ET did not differ significantly between patients with genotypes CYP2C19*1/CYP2C19*2andCYP2C19*1/CYP2C19*1. The frequencies of the genotype CYP2C19*1/CYP2C19*2 and the allelic variant CYP2C19*2 were similar in ET patients who developed acute adverse effects to primidone, in those who tolerated primidone and in controls; the frequencies were also similar in patients with head, voice, tongue and chin tremor compared with controls. These results suggest that heterozygosis CYP2C19*1/CYP2C19*2 is associated with the risk for ET, but not with the age at onset of ET, the presentation of acute side effects of primidone, or the existence of head, voice, tongue or chin tremor.