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Expansion of CAG repeats in the spinocerebellar ataxia type 1 (SCA1) gene in idiopathic oligozoospermia patients.

ABSTRACT: The lengths of CAG repeats in two spinocerebellar ataxia genes, SCA1 and SCA3, were analyzed to determine whether such repeats exist in higher numbers in infertile males.Blood samples were collected from healthy controls, oligozoospermia patients, and azoospermia patients. DNA fragments containing target CAG repeats were amplified by PCR with template DNA purified from the blood samples. CAG repeats in PCR fragments were determined, using ABI PRISM 310 Gene Analyzer.In SCA1, the distribution of CAG repeats in oligozoospermic males was different from that of the control group: More alleles had a repeat number that exceeded 32. Conversely, for SCA3, the examined oligozoospermia and azoospermia patients exhibited no differences in distribution of CAG repeats in comparison with the control group.SCA1 in a subset of oligozoospermia patients has an increased number of CAG repeats.

SUBMITTER: Lai YC

PROVIDER: S-EPMC2719072 | biostudies-other | 2009 May

REPOSITORIES: biostudies-other

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Project description:ImportanceRepeats of CAG in the ataxin 2 gene (ATXN2) in the long-normal range (sometimes referred to as intermediate) have been identified as modifiers of amyotrophic lateral sclerosis (ALS) risk. Prior studies have used thresholding considering various cutoffs for ATXN2 repeat length.ObjectiveTo calculate association between ATXN2 CAG repeat alleles and increased risk of ALS across multiple ethnic groups.Data sourcesThe MEDLINE database was searched for studies published by December 29, 2013, reporting ATXN2 CAG repeat length in patients with ALS and controls.Study selectionStudies were included if they reported original data on relative risks or odds ratios (ORs) from ALS and control populations for individual ATXN2 alleles. Review articles that reported no new data were not included in the analysis.Data extraction and synthesisAnalysis of allele distribution was performed to ensure that all studies followed identical allele sizing. The ORs, 95% confidence intervals, and population attributable risk percentages were calculated according to standard procedures.Main outcomes and measuresOccurrence of ALS associated with ATXN2 repeat alleles, expressed as ORs.ResultsNine studies were analyzed, including 7505 controls and 6151 sporadic ALS cases. The ALS and control cohorts were recruited from different geographical and ethnic regions including the United States, French Canada/Canada, Belgium and the Netherlands, Germany, Italy, mainland China, Turkey, and Flanders-Belgium. The ATXN2 CAG repeat lengths ranged from 13 to 39 in patients with ALS and from 13 to 34 in controls. The ORs were less than 1.00 for alleles with 25 to 28 repeats. The OR was 1.55 for 30 repeats, but this elevation was not statistically significant (95% CI, 0.88-2.73). The ORs were 2.70 (95% CI, 1.47-4.93) for 31 CAG repeats, 11.09 (95% CI, 4.16-29.57) for 32 repeats, and 5.76 (95% CI, 1.79-18.57) for 33 repeats.Conclusions and relevanceIn contrast to prior studies with smaller numbers, risk for ALS associated with long-normal alleles is complex. Alleles with 27 and 28 repeats lower ALS risk slightly. The risk for ALS increases beginning with 29 repeats and reaches a maximum at 32 and 33 repeats. Of note, alleles with repeats of these lengths are known to be predisposed to meiotic expansion to full-penetrance mutant alleles. In patients with ALS, alleles with 31 to 33 repeats may have undergone preferential expansion in motor neurons during mitosis or DNA repair. Our meta-analysis provides a framework for counseling individuals with long-normal ATXN2 repeats.

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Expansion of CAG repeats in the spinocerebellar ataxia type 1 (SCA1) gene in idiopathic oligozoospermia patients.

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