ABSTRACT
Antecedentes: La ataxia espinocerebelosa tipo 2 es causada por la expansión del repetido CAG presente en el exón 1 del gen de la ataxina-2, lo cual origina la incorporación de un segmento de poliglutaminas en la proteína mutante. Métodos: Mediante reacción en cadena de la polimerasa y electroforesis capilar se determinó el número de repetidos CAG del gen de la ataxina-2 en 66 individuos pertenecientes a tres familias mexicanas diagnosticadas clínicamente con ataxia espinocerebelosa tipo 2, y en 400 individuos de una muestra de población mestiza mexicana. Resultados: Se identificó la expansión del repetido CAG en 11 sujetos con sintomatología de ataxia espinocerebelosa tipo 2 y en cuatro individuos asintomáticos, lo que confirmó el diagnóstico en dos de las tres familias analizadas. Se determinó que los pacientes con mayor número de repetidos desarrollaron la sintomatología de la enfermedad a una edad más temprana, fenómeno conocido como anticipación. Los alelos silvestres presentaron un rango entre 13 y 30 repetidos CAG, siendo el alelo de 22 repetidos el más frecuente, mientras que los alelos mutados mostraron un rango de 36 a 54 repetidos. Conclusiones: La identificación de la expansión del repetido CAG del gen de la ataxina-2 confirmó el diagnóstico clínico de ataxia espinocerebelosa tipo 2.
BACKGROUND: Spinocerebellar ataxia type 2 (SCA2) results from the expansion of a CAG triplet located within the coding sequence of the ataxin-2 gene, which ultimately provokes the incorporation of a stretch of polyglutamines in the mutant protein. METHODS: We determined by PCR and capillary electrophoresis the number of ataxin2 gene CAG repeats in 66 individuals belonging to 3 families, clinically diagnosed with SCA2, and 400 subjects from a sample of the mestizo Mexican population. RESULTS: The CAG repeat expansion was found in 11 symptomatic subjects and four asymptomatic individuals, confirming the SCA2 clinical diagnosis in two out of the three families studied. We noted that patients with longer CAG repeat numbers have an early disease onset, a phenomenon known as anticipation. Wild-type alleles showed a CAG repeat range between 13 and 30, and the allele carrying 22 CAG repeats was the most common among our sample. Mutant alleles also displayed a range between 36 and 54 CAG repeats. CONCLUSIONS: The identification of the CAG repeat expansion facilitates an accurate SCA2 diagnosis.
Subject(s)
Humans , Adolescent , Young Adult , Spinocerebellar Ataxias/genetics , Nerve Tissue Proteins/genetics , Trinucleotide Repeats , Mexico , PedigreeABSTRACT
In order to improve carrier detection of Duchenne and Becker muscular dystrophy, denucleotide sequences repeats (CA) of introns 44, 45, 49 and 50 were used as well as two markers located at the 5' and 3' ends of the dystrophin gene. Haplotypes of the unaffected and affected persons of ten DMD/BMD Mexican families were determined. Fifty eight females were studied, 30 of whom were at-risk STR haplotypes. Furthermore, it was possible to identify a recombination event in the dystrophin gene in one family, and a gonadal mosaicism was found in another family
Subject(s)
DNA/isolation & purification , Dystrophin/isolation & purification , Electrophoresis , Genetic Carrier Screening , Genetic Markers/physiology , Muscular Dystrophies/diagnosis , Nucleotides , Polymorphism, Genetic/physiologyABSTRACT
Forty unrelated Mexican patients with Duchenne/Backer muscular dystrophy were analyzed for intragenic DMD gene deletions, using the multiplex amplification of 15 deletion-prone oxons described by Chamberlain et al. and beggs et al. The percentage of deletions was 52.5 percent, and the majority of them (86.3 percent) were located at the hot spot deletion region which encompasses exons 44 - 55. This frequency is higher than that found in American and European populations. There were no correlations between deletion size, location and clinical severity