Circulating miR-323-3p is a biomarker for cardiomyopathy and an indicator of phenotypic variability in Friedreich's ataxia patients.

MicroRNAs (miRNAs) are noncoding RNAs that contribute to gene expression modulation by regulating important cellular pathways. In this study, we used small RNA sequencing to identify a series of circulating miRNAs in blood samples taken from Friedreich's ataxia patients. We were thus able to develop a miRNA biomarker signature to differentiate Friedreich's ataxia (FRDA) patients from healthy people. Most research on FDRA has focused on understanding the role of frataxin in the mitochondria, and a whole molecular view of pathological pathways underlying FRDA therefore remains to be elucidated. We found seven differentially expressed miRNAs, and we propose that these miRNAs represent key mechanisms in the modulation of several signalling pathways that regulate the physiopathology of FRDA. If this is the case, miRNAs can be used to characterize phenotypic variation in FRDA and stratify patients' risk of cardiomyopathy. In this study, we identify miR-323-3p as a candidate marker for phenotypic differentiation in FRDA patients suffering from cardiomyopathy. We propose the use of dynamic miRNAs as biomarkers for phenotypic characterization and prognosis of FRDA.

Ataxias cerebelosas autosómicas recesivas. Clasificación, aspectos genéticos y fisiopatología / Autosomal recessive cerebellar ataxias. Their classification, genetic features and pathophysiology

Introducción y desarrollo. Las ataxias cerebelosas autosómicas recesivas (ARCA) son un grupo heterogéneo de trastornos neurológicos raros que afectan a los sistemas nerviosos central y periférico y, en algunos casos, a otros sistemas y órganos. Estos trastornos suelen tener una edad de inicio antes de los 20 años de edad. En base a criterios patogénicos se pueden distinguir cinco grupos de ARCA: ataxias congénitas (trastorno del desarrollo), ataxias mitocondriales, ataxias asociadas a defectos metabólicos, ataxias asociadas a defectos en la reparación del ADN y ataxias degenerativas de mecanismo patogénico desconocido. Las formas más frecuentes en la población caucásica son la ataxia de Friefreich y la ataxia-telangiectasia. Otras formas más raras son la abetalipoproteinemia, la ataxia con deficiencia de vitamina E (AVED), la ataxia con apraxia oculomotora tipos 1 (AOA1) y 2 (AOA2), la ataxia precoz con reflejos conservados, la ataxia espástica de Charlevoix-Saguenay y el síndrome de Joubert. La prevalencia de las ARCA se estima en siete casos por 100.000 habitantes. Estas enfermedades se deben a mutaciones en genes específicos, algunos de los cuales y sus proteínas se han identificado, como FRDA (frataxina) en la ataxia de Friedreich, APTX (aprataxina) en la AOA1, aTTP (proteína transferidora de a-tocoferol) en la AVED y STX (senataxina) en la AOA2. Como se trata de trastornos autonómicos recesivos, no suele haber antecedentes en la familia de los enfermos y ambos progenitores están sanos. Conclusiones. La mayoría de las ataxias cerebelosas no tienen tratamiento específico, excepto algunas debidas a déficit de coenzima Q10 y la abetalipoproteinemia. El diagnóstico clínico debe confirmarse mediante las pruebas complementarias de neuroimagen (tomografía axial computarizada, resonancia magnética), el examen electrofisiológico y el análisis de mutaciones del gen causante si éste se ha identificado. El diagnóstico clínico y genético correcto son muy importantes para ofrecer un pronóstico y un consejo genético apropiados y, en ocasiones, un tratamiento farmacológico (AU)

Introduction and development. Autosomal recessive cerebellar ataxias (ARCA) are a heterogeneous group of rare neurological disorders involving both central and peripheral nervous system, and in some case other systems and organs. They use to have early onset before the age of 20. Based on pathogenic mechanisms five main types may be distinguished: congenital (developmental disorder), mitochondrial ataxias, ataxias associated with metabolic disorders, ataxias with a DNA repair defect, and degenerative ataxia with unknown pathogenesis. The most frequent in Caucasian population are Friedreich ataxia and ataxia-telangiectasia. Other forms are much less common, and include abetaliproteinemia, ataxia with vitamin E deficiency (AVED), ataxia with oculomotor apraxia types 1 (AOA1) and 2 (AOA2), early onset cerebellar ataxia with retained reflexes, Charlevoix-Saguenay spastic ataxia, and Joubert syndrome. The prevalence of ARCA has been estimated to 7 in 100,000 inhabitants. These diseases are due to mutations in specific genes, some of which and its encoded proteins have been identified, such as FRDA (frataxin) in Friedreich ataxia, APTX (aprataxin) in AOA1, αTTP (α-tocopherol transfer protein) in AVED, and STX (senataxin) in AOA2. Due to autosomal recessive inheritance, previous familial history of affected individuals unlikely. Conclusions. Most of these cerebellar ataxias have no specific treatment with exception of the ataxia associated with deficiency coenzyme Q10 and abetalipoproteinemia. Clinical diagnosis must be confirmed by ancillary tests such as neuroimaging (magnetic resonance, scanning), electrophysiological examination, and mutation analysis when the causative gene has been identified. Correct clinical and genetic diagnosis is important for appropriate prognosis and genetic counseling and, in some instances, pharmacological treatment (AU)

[Autosomal recessive cerebellar ataxias. Their classification, genetic features and pathophysiology]. / Ataxias cerebelosas autosómicas recesivas. Clasificación, aspectos genéticos y fisiopatología.

INTRODUCTION AND DEVELOPMENT: Autosomal recessive cerebellar ataxias (ARCA) are a heterogeneous group of rare neurological disorders involving both central and peripheral nervous system, and in some case other systems and organs. They use to have early onset before the age of 20. Based on pathogenic mechanisms five main types may be distinguished: congenital (developmental disorder), mitochondrial ataxias, ataxias associated with metabolic disorders, ataxias with a DNA repair defect, and degenerative ataxia with unknown pathogenesis. The most frequent in Caucasian population are Friedreich ataxia and ataxia-telangiectasia. Other forms are much less common, and include abetaliproteinemia, ataxia with vitamin E deficiency (AVED), ataxia with oculomotor apraxia types 1 (AOA1) and 2 (AOA2), early onset cerebellar ataxia with retained reflexes, Charlevoix-Saguenay spastic ataxia, and Joubert syndrome. The prevalence of ARCA has been estimated to 7 in 100,000 inhabitants. These diseases are due to mutations in specific genes, some of which and its encoded proteins have been identified, such as FRDA (frataxin) in Friedreich ataxia, APTX (aprataxin) in AOA1, alphaTTP (alpha-tocopherol transfer protein) in AVED, and STX (senataxin) in AOA2. Due to autosomal recessive inheritance, previous familial history of affected individuals unlikely. CONCLUSIONS: Most of these cerebellar ataxias have no specific treatment with exception of the ataxia associated with deficiency coenzyme Q10 and abetalipoproteinemia. Clinical diagnosis must be confirmed by ancillary tests such as neuroimaging (magnetic resonance, scanning), electrophysiological examination, and mutation analysis when the causative gene has been identified. Correct clinical and genetic diagnosis is important for appropriate prognosis and genetic counseling and, in some instances, pharmacological treatment.

Prevalence of 2314delG mutation in Spanish patients with Usher syndrome type II (USH2).

The Usher syndrome (USH) is a group of autosomal recessive diseases characterized by congenital sensorineural hearing loss and retinitis pigmentosa. Three clinically distinct forms of Usher syndrome have so far been recognized and can be distinguished from one another by assessing auditory and vestibular function. Usher syndrome type II (USH2) patients have congenital moderate-to-severe nonprogressive hearing loss, retinitis pigmentosa, and normal vestibular function. Genetic linkage studies have revealed genetic heterogeneity among the three types of USH, with the majority of USH2 families showing linkage to the USH2A locus in 1q41. The USH2A gene (MIM 276901) has been identified: three mutations, 2314delG, 2913delG, and 4353-54delC, were initially reported in USH2A patients, the most frequent of which is the 2314delG mutation. It has been reported that this mutation can give rise to typical and atypical USH2 phenotypes. USH2 cases represent 62% of all USH cases in the Spanish population, and 95% of these cases have provided evidence of linkage to the USH2A locus. In the present study, the three reported mutations were analyzed in 59 Spanish families with a diagnosis of USH type II. The 2314delG was the only mutation identified in our population: it was detected in 25% of families and 16% of USH2 chromosomes analyzed. This study attempts to estimate the prevalence of this common mutation in a homogeneous Spanish population.