Chronic exposure to a low concentration of bisphenol A during follicle culture affects the epigenetic status of germinal vesicles and metaphase II oocytes  Tom Trapphoff, M.Sc., Martyna Heiligentag, M.Sc., Nady El Hajj, Ph.D., Thomas Haaf, M.D., Ursula Eichenlaub-Ritter, Ph.D.  Fertility and Sterility  Volume 100, Issue 6, Pages 1758-1767.e1 (December 2013) DOI: 10.1016/j.fertnstert.2013.08.021 Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions

Figure 1 Follicle developmental stages through in vitro follicle culture (A–A′′′′), kinetics of in vitro follicle culture (B–C), and oocyte diameter (D). (A) Follicular stage with spherical conformation and some outgrowing theca and granulosa cells. (A′) Loss of spherical structure within diffused stage with strongly proliferating granulosa cells. Differentiation of granulosa cells into mural and cumulus granulosa cells at antral stage and formation of antral-like-cavities in controls (A′′) and in 3 nM (A′′′) and 300 nM (A′′′′) BPA-treated follicles . Scale bars A–A′′′′: 50 μm. (B) The survival rates of follicles from day 0 (n = 307, 308, and 303, for control, 3 nM BPA, 300 nM BPA, respectively) to day 4 (left) and day 4 (n = 292, 302, and 295, for control, 3 nM BPA, 300 nM BPA, respectively) to day 12 (right) of culture. (C) Percentages of follicles in the follicular, diffused and antral stage at days 4, 8, and 12 of culture. (D) Oocyte diameter at day 12 of culture at germinal vesicle stage. (n = 103, 151, and 132, for control, 3 nM BPA, and 300 nM BPA, respectively; *P<.05 and **P<.01). Fertility and Sterility 2013 100, 1758-1767.e1DOI: (10.1016/j.fertnstert.2013.08.021) Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions

Figure 2 Lollipop diagram of maternal imprinting profile. Each row represents a single allele. Filled circles represent methylated CpGs and empty circles unmethylated CpGs. Gaps indicate missing data. Alleles with at least 50% unmethylated CpG sites were classified as abnormal alleles or imprinting mutations, whereas all other unmethylated CpG sites were defined as stochastic single CpGs errors. Abnormally unmethylated alleles of the maternally imprinted genes Snrpn, Igf2r, and Mest occurred exclusively in oocyte pools exposed to 3 nM BPA. Fertility and Sterility 2013 100, 1758-1767.e1DOI: (10.1016/j.fertnstert.2013.08.021) Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions

Figure 3 Histone modification (A–G), interkinetochore distance (H–I), and scheme of heterochromatin formation/stabilization (J). (A–E) Trimethylated H3K9 (A–C′′) and H4K12 acetylation (D–E′′) profile in metaphase II (MII) oocytes with fully aligned chromosomes (A–B′′; D–E′′) or with some congression failure (C–C′′) after in vitro follicle culture. Metaphase II chromosomes were double labeled with 4,6-diamindino-2-phenylindole (DAPI) (A–E) and antitrimethylated H3K9 antibody (A′–C′) or antiacetylated H4K12 antibody (D′–E′) in the in vitro control (A–A′′ and D–D′′) and 3 nM BPA-treated (B–B′′ and C–C′′ or E–E′′) follicles, respectively. Fluorescence intensity was measured with ImageJ software inside the marked area (A′′–E′′) as arbitrary units [a.u. ± SD]. Scale bars in A–E′′: 5 μm. (F, G) Analysis of control and 3 nM BPA-treated MII oocytes (Student's t-test: statistically significant difference with control; *P<.001). (H) Interkinetochore distance in monastrol-treated MII oocytes (H–H′′′). Images from z-axis series for the solvent (H–H′) and 3 nM BPA group (H′′–H′′′). Interkinetochore distance between sister chromatids was measured from the outer lateral CREST-signal (red) between the corresponding sister chromatids (white arrows in H′). (I) Relative frequency of distance in z-axis sections of solvent controls (blue line) and 3 nM BPA group (red line) is between 0.5 and 2.5 μm. Statistical analysis was with Jarque-Bera and Mann-Whitney U test (P<.001; I). (J) Scheme of DNA methylation and H3K9 posttranslational modifications affecting heterochromatin formation/stabilization and regulation of chromatin at maturation. Histone deacetylase (HDAC) deactylation of H3K9 before methylation by G9a recruitment, and activation of de novo methylase Dnmt3 (49, 61); trimethylated H3K9 in recruitment of HP1 and ATRX and Aurora Kinase (AurK) involved in H3S10 phosphorylation that are critical for chromosome attachment, checkpoint control, and chromosome congression in oocytes (59). Fertility and Sterility 2013 100, 1758-1767.e1DOI: (10.1016/j.fertnstert.2013.08.021) Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions