CCDC79 and SUN1 co-localize with telomeres during the first meiotic prophase. CCDC79, SYCP3, TRF1 and SUN1 were detected by IF on nuclear surface spreads of spermatocytes obtained from 15 dpp testis. A) CCDC79 co-localizes with both TRF1 and SUN1, as shown in the two overlay images (SYCP3-TRF1-CCDC79 and SYCP3-SUN1-CCDC79) of the same pachytene stage spermatocyte. (B) Quantification shows the fraction of all telomeres that are marked by only CCDC79 (CCDC79+ SUN1-), only SUN1 (CCDC79- SUN1+), both CCDC79 and SUN1 (CCDC79+ SUN1+), or neither CCDC79 nor SUN1 (CCDC79- SUN1-) in early leptotene stage spermatocytes. Telomeres were detected by TRF1 staining. Scale bars 10 μm.