Age-related instability in spermatogenic cell nuclear and mitochondrial DNA obtained from Apex1 heterozygous mice

Authors

  • Kristine S. Vogel,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Marissa Perez,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Jamila R. Momand,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Karina Acevedo-Torres,

    1. Department of Physiology, University of Puerto Rico, San Juan, Puerto Rico
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  • Kim Hildreth,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Rebecca A. Garcia,

    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Carlos A. Torres-Ramos,

    1. Department of Physiology, University of Puerto Rico, San Juan, Puerto Rico
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  • Sylvette Ayala-Torres,

    1. Department of Pharmacology, University of Puerto Rico, San Juan, Puerto Rico
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  • Thomas J. Prihoda,

    1. Department of Pathology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • C. Alex McMahan,

    1. Department of Pathology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
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  • Christi A. Walter

    Corresponding author
    1. Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
    2. Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
    3. South Texas Veteran's Health Care System, San Antonio, Texas
    • Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900.
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Abstract

The prevalence of spontaneous mutations increases with age in the male germline; consequently, older men have an increased risk of siring children with genetic disease due to de novo mutations. The lacI transgenic mouse can be used to study paternal age effects, and in this system, the prevalence of de novo mutations increases in the male germline at old ages. Mutagenesis is linked with DNA repair capacity, and base excision repair (BER), which can ameliorate spontaneous DNA damage, decreases in nuclear extracts of spermatogenic cells from old mice. Mice heterozygous for a null allele of the Apex1 gene, which encodes apurinic/apyrimidinic endonuclease I (APEN), an essential BER enzyme, display an accelerated increase in spontaneous germline mutagenesis early in life. Here, the consequences of lifelong reduction of APEN on genetic instability in the male germline were examined, for the first time, at middle and old ages. Mutant frequency increased earlier in spermatogenic cells from Apex1+/− mice (by 6 months of age). Nuclear DNA damage increased with age in the spermatogenic lineage for both wild-type and Apex1+/− mice. By old age, mutant frequencies were similar for wild-type and APEN-deficient mice. Mitochondrial genome repair also depends on APEN, and novel analysis of mitochondrial DNA (mtDNA) damage revealed an increase in the Apex1+/− spermatogenic cells by middle age. Thus, Apex1 heterozygosity results in accelerated damage to mtDNA and spontaneous mutagenesis, consistent with an essential role for APEN in maintaining nuclear and mtDNA integrity in spermatogenic cells throughout life. Mol. Reprod. Dev. 78:906–919, 2011. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

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