Age dependent accumulation of mtDNA mutations in subcutaneous fat tissue of Csb^m/m and Csa^−/− mice. (A) Subcutaneous fat tissue from WT mice and mice lacking a functional Csb or the Xpa gene were assessed for a frequent mouse-mtDNA deletion (D17). Three age groups (13, 5, and 130 wk, 4 mice per group) of each genotype were investigated. Aged Csb^m/m mice show a strong increase of D17 in subcutaneous fat compared with WT or Xpa^−/− controls (Student's t test, P < 0.01). Each PCR experiment was repeated independently two times. (B) Hematoxylin and eosin–stained cross sections with reduced subcutaneous fat tissue in old Csb^m/m mice aged for 130 wk. Bar, 200 µm. (C) Measurement of D17 deletion in subcutaneous fat of WT, Csa^−/− and Xpd^TTD/TTD mice similar to A. Each PCR experiment was repeated independently two times. (D) Restriction digest of PCR product of deletion D17 with EcoRV. (left) Undigested fragment of 850 bp. (right) EcoRV digest leading to fragments of 570 and 280 bp. Data are given as representative of at least three independent experiments.