[Molecular analysis of the CAG repeat among patients with Type-2 spinocerebellar ataxia in the Mexican population].
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.
Magaña
Jonathan J
JJ
Departamento de Genética y Biología Molecular, Cinvestav-IPN, México D.F., Mexico.
Vergara
María Dolores
MD
Sierra-Martínez
Mónica
M
García-Jiménez
Elvia
E
Rodríguez-Antonio
Facundo
F
Gómez
María del Rocío
Mdel R
Valdés-Flores
Margarita
M
Cisneros
Bulmaro
B
D000293:Adolescent; D000328:Adult; D000067528:Ataxins; D006801:Humans; D008800:Mexico; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010375:Pedigree; D020754:Spinocerebellar Ataxias / Q000235:genetics*; D018911:Trinucleotide Repeats; D055815:Young Adult
D000067528:Ataxins; D009419:Nerve Tissue Proteins