Spinocerebellar ataxia subtypes 1, 3, and 6 (SCA1, MJD/SCA3, and SCA6) are among the most prevalent autosomal dominant cerebellar ataxias worldwide, but their relative frequencies in Peru are low. Frequency of large normal (LN) alleles at spinocerebellar ataxia-causative genes has been proposed to be associated with disease prevalence. To investigate the allelic distribution of the CAG repeat in ATXN1, ATXN3, and CACNA1A genes in a Peruvian mestizo population and examine their association with the relative frequency of SCA1, MJD/SCA3, and SCA6 across populations. We genotyped 213 healthy mestizo individuals from Northern Lima, Peru, for ATXN1, ATXN3, and CACNA1A using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE). We compared the frequency of LN alleles and relative disease frequency between populations. We also tested 40 samples for CAT repeat interruptions within the CAG tract of ATXN1. We found no association between disease frequency and population frequency of LN alleles at ATXN1 and ATXN3. All 40 ATXN1 samples tested for CAT interruptions were positive. Frequency of LN alleles at CACNA1A correlates with SCA6 frequency across several populations, but this effect was largely driven by data from a single population. Low frequency of SCA1 and MJD/SCA3 in Peru is not explained by frequency of LN alleles at ATXN1 and ATXN3, respectively. The observed correlation between CACNA1A LN alleles and SCA6 frequency requires further assessment.
Bibliographical noteFunding Information:
CGS and CCR contributed equally to this study, and are both to be considered first authors. Results of this study are derived from CGS and CCR Master’s thesis’ work. We are very grateful to the participants of the community of Huaura, Santa María, Hualmay, and Huacho for contributing samples for this study. We kindly thank the Universidad de Huacho for the logistical support on the recruitment of participants. We thank Saul Lindo Samanamud for his cooperation in the recruitment of participants. We thank Kevin Boehnke, Miguel Inca Martínez, Hugo Sarapura Castro, and Erick Figueroa Ildefonso for their contribution on critical review and genotyping.
Research reported in this publication was supported by the Fogarty International Center (FIC) of the National Institutes of Health and the National Institute of Neurological Disorders and Stroke (NINDS) under grant #D43TW009345 awarded to the Northern Pacific Global Health Fellows Program and grant #D43TW009137 awarded to the Interdisciplinary Cerebrovascular Diseases Training Program in South America. Acknowledgments
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- Large normal alleles
- Spinocerebellar ataxias
- Triplet repeats