Telomeres and human reproduction Keri Horan Kalmbach, M.S., Danielle Mota Fontes Antunes, M.S., Roberta Caetano Dracxler, M.D., Taylor Warner Knier, B.A., Michelle Louise Seth-Smith, B.S., Fang Wang, Ph.D., Lin Liu, Ph.D., David Lawrence Keefe, M.D.  Fertility and Sterility  Volume 99, Issue 1, Pages 23-29 (January 2013) DOI: 10.1016/j.fertnstert.2012.11.039 Copyright © 2013 Terms and Conditions

Figure 1 Schematic diagram of telomere loop (T loop) and shelterin proteins. Telomere repeat-binding factor 1 and 2 (TRF1, TRF2) associate with double-stranded DNA and serve as binding substrate for TIN2, TPP1, and Rap1. A third DNA-binding protein, Pot1, associates with the single-stranded DNA of the displacement loop (D loop). Fertility and Sterility 2013 99, 23-29DOI: (10.1016/j.fertnstert.2012.11.039) Copyright © 2013 Terms and Conditions

Figure 2 Schematic representation of telomere length relationships over mammalian development. Preimplantation development is associated with the greatest increase in telomere length in the course of development, owing to the telomerase-independent alternative lengthening of telomeres (ALT) pathway. Embryonic development follows with a period of telomere reserve maintained by telomerase activity in virtually every embryonic tissue. Through adulthood, telomerase expression is limited to stem cells, the male germ line, and cancer. Paradoxically, oocytes exhibit marked loss of telomere reserve that fails to recover over a mammalian life span. Fertility and Sterility 2013 99, 23-29DOI: (10.1016/j.fertnstert.2012.11.039) Copyright © 2013 Terms and Conditions

Figure 3 Representative metaphase spread from preimplantation murine blastomere. Double-stranded DNA (blue) is bound by nonspecific DNA-binding dye, and telomeres are bound by a PNA probe specific to telomere DNA repeats. Fertility and Sterility 2013 99, 23-29DOI: (10.1016/j.fertnstert.2012.11.039) Copyright © 2013 Terms and Conditions