A Common Copy Number Variation (CNV) Polymorphism in the CNTNAP4 Gene: Association with Aging in Females

Background: Aging is a biological process strongly determined by genetics. However, only a few single nucleotide polymorphisms (SNPs) have been reported to be consistently associated with aging. While investigating whether copy number variations (CNVs) could fill this gap, we focused on CNVs that have not been studied in previous SNP-based searches via tagging SNPs. Methods: TaqMan qPCR assays were developed to quantify 20 common CNVs in 222 senior American Caucasians in order to reveal possible association with longevity. The replication study was comprised of 1283 community-dwelling senior European Caucasians. Replicated CNVs were further investigated for association with healthy aging and aging-related diseases, while association with longevity was additionally tested in Caenorhabditis elegans. Results: In the discovery study of >= 80 vs. <80 years old seniors, a homozygous intronic CNV deletion in the CNTNAP4 gene was inversely associated with survival to the age of 80 (OR=0.51, 95% CI 0.29-0.87, p=0.015 before correction for multiple testing). After stratification by sex, association remained significant in females (OR=0.41, 95% CI 0.21-0.77, p=0.007), but not in males (OR=0.97, 95% CI 0.33-2.79, p=1). The finding was validated in a replication study (OR=0.66, 95% CI 0.48-0.90, p=0.011 for females). CNTNAP4 association with longevity was supported by a marked 25% lifespan change in C. elegans after knocking down the ortholog gene. An inverse association of the CNV del/del variant with female healthy aging was observed (OR=0.39, 95% CI 0.19-0.76, p=0.006). A corresponding positive association with aging-related diseases was revealed for cognitive impairment (OR=2.17, 95% CI 1.11-4.22, p=0.024) and, in independent studies, for Alzheimer's (OR=4.07, 95% CI 1.17-14.14, p=0.036) and Parkinson's (OR=1.59, 95% CI 1.03-2.42, p=0.041) diseases. Conclusion: This is the first demonstration for association of the CNTNAP4 gene and one of its intronic CNV polymorphisms with aging. Association with particular aging-related diseases awaits replication and independent validation.