Mitochondrial tRNALeu/Lys and ATPase 6/8 gene variations in spinocerebellar ataxias.

BACKGROUND: The spinocerebellar ataxias (SCA) comprise a heterogeneous group of severe late-onset neurodegenerative diseases that are promoted by the expansion of a tandem-arrayed DNA sequence that modifies the primary structure of the protein. METHODS: Genomic DNA of 20 patients affected with SCAs was extracted from peripheral blood and screened for deletions in mitochondrial DNA (mtDNA). Sequencing of tRNA(Leu), tRNA(Lys), cytochrome oxidase II, ATPase 6/8 and NADH dehydrogenase I (NDI) genes belonging to mtDNA from patients with SCAs was also carried out to detect the presence of variations. RESULTS: We identified cytosine-adenine-guanine (CAG) trinucleotide repeat expansions in 20 patients. Seven of these patients had at least one nucleotide change in mtDNA. In such cases, 5 nucleotide variations resulted in amino acid changes with two novel variations T8256G and G9010A. CONCLUSION: SCA patients showed high levels of mtDNA variations in lymphocytes. It can be proposed that the SCA gene proteins (Ataxins) are involved in the complicated intracellular mechanisms that affect cellular organelles and their components, such as the mitochondrial genome. The instability of CAG repeats in polyglutamine diseases such as SCAs and Huntington's disease might be a causative factor in mtDNA variation or possible damage.

Identification and sizing of GAA trinucleotide repeat expansion, investigation for D-loop variations and mitochondrial deletions in Iranian patients with Friedreich's ataxia.

Friedreich's Ataxia (FA) is the commonest genetic cause of ataxia and is associated with the expansion of a GAA repeat in intron 1 of the frataxin gene. Iron accumulation in the mitochondria of patients with FA would result in hypersensitivity to oxidative stress. Mitochondrial DNA (mtDNA) could be considered a candidate modifier factor for FA disease, since mitochondrial oxidative stress is thought to be involved in the pathogenesis of this disease. We studied 25 Iranian patients (16 females and 9 males) from 12 unrelated families. DNA from each patient was extracted and frequency and length of (GAA)(n) repeat was analyzed using a long-range polymerase chain reaction (PCR) test. Also we investigated impact of GAA size on neurological findings, age of onset and disease development. In order to identify polymorphic sites and genetic background, the sequence of two hypervariable regions (HVR-I and HVR-II) of mtDNA was obtained from FA patients harbouring GAA trinucletide expansions. Alignment was made with the revised cambridge reference sequence (rCRS) and any differences recorded as single base substitution (SBS), insertions and deletions. Homozygous GAA expansion was found in 21 (84%) of all cases. In four cases (16%), no expansion was observed, ruling out the diagnosis of Friedreich's ataxia. In cases with GAA expansions, ataxia, scoliosis and pes cavus, cardiac abnormalities and some neurological findings occurred more frequently than in our patients without GAA expansion. Molecular analysis was imperative for diagnosis of Friedreich's ataxia, not only for typical cases, but also for atypical ones. Diagnosis bases only on clinical findings is limited, however, it aids in better screening for suspected cases that should be tested. Our results showed that the rate of D-loop variations was higher in FA patients than control (P<0.05). mtDNA deletions were present in 76% of our patients representing mtDNA damage, which may be due to iron accumulation in mitochondria.

Vestibular evoked myogenic potential for diagnoses of multiple sclerosis: is it beneficial?

AIM: To determine the sensitivity of the vestibular evoked myogenic potential (VEMP) in multiple sclerosis (MS) patients as well as its relation to clinical signs and symptoms, course of the disease and other evoked potentials. METHODS: This case-control study was conducted on 40 subjects (20 MS patients and 20 healthy participants). Participants were selected from Imam Khomeini Hospital, Tehran, Iran. Two hundred stimuli (clicks of 0.1 ms of duration and 2 Hz frequency) were applied to each ear. These stimuli were repeated in two consecutive cycles. In order to evaluate the reproducibility the stimulation intensity of 95dBNHL was applied. During the test, individuals were requested to be seated on a chair and rotate their head to the opposite side of the stimulated ear to activate the ipsilateral sternocleidomastoid muscle (SCM). RESULTS: A biphasic, initially positive, p13-n23 wave pattern was found in all patients. All of the parameters, including latencies and amplitudes fit the normal Kolmogorov-Smirnov (KS) distribution. Fourteen (70%) patients reported abnormal results, and VEMP abnormality was significantly related to disease duration also. In addition, there was a significant correlation between abnormality of VEMP and abnormality of visual evoked potential (VEP) as well as the abnormality of VEMP and brainstem auditory evoked potential (BAEP). CONCLUSION: Vestibular evoked myogenic potential has a high sensitivity (70%) in MS patients, and VEMP could be recommended as a useful complementary neurophysiological method to evaluate the MS patients.

Antigliadin antibody in sporadic adult ataxia.

BACKGROUND: The most common neurologic manifestation of gluten sensitivity is ataxia, which accounts for up to 40% of idiopathic sporadic ataxia. Timing of diagnosis of gluten ataxia is vital as it is one of the very few treatable causes of sporadic ataxia and causes irreversible loss of Purkinje cells. Antigliadin antibody (AGA) of the IgG type is the best marker for neurological manifestations of gluten sensitivity. This study was conducted to measure the prevalence of gluten ataxia in a group of Iranian patients with idiopathic ataxia. METHODS: For 30 patients with idiopathic cerebellar ataxia, a questionnaire about clinical and demographic data was completed. Serum AGA (IgA and IgG) and antiendomysial antibody (AEA) were assessed. Gluten ataxic patients underwent duodenal biopsy. Magnetic resonance imaging was done for all patients to see if cerebellar atrophy is present. RESULTS: Only 2 patients had a positive IgG AGA (6.7%) who both had a positive AEA while none of them showed changes of celiac disease in their duodenal biopsies. Only presence of gastrointestinal symptoms and pursuit eye movement disorders were higher in patients with gluten ataxia. CONCLUSION: Prevalence of gluten ataxia in Iranian patients with idiopathic ataxia seems to be lower than most of other regions. This could be explained by small sample size, differences in genetics and nutritional habits and also effect of serologic tests in clinical versus research setting. Further researches with larger sample size are recommended.