High temperatures cause several reproductive losses in @entity291 . Under in vitro conditions, @entity1457 decreases oocyte developmental competence and influences embryonic gene expression (Gendelman and Roth 2012 Anim. Reprod. Sci. 134, 125-134). This preliminary study aimed to evaluate whether @entity1457 during oocyte in vitro maturation (IVM) could have any further effect on chromatin remodelling of fertilized embryos at 4- and 8-cell stages, once such modifications are required for the gene activation in @entity291 embryos. We evaluated the distribution of heterochromatin 1 ( @entity27661 ) and of histone H3 trimethylated at @entity376 9 (H3K9me3), both reportedly correlated with heterochromatin formation, in 4- and 8-cell stage embryos derived from control (C) and heat-shocked (HS) @entity291 oocytes. Immature cumulus-oocyte complexes (COC) collected from crossbred @entity291 in Brazil were exposed for 12h to 38.8  C (C group) or 41.0  C (HS group) followed by 12h at 38.8  C, totalizing 24h of IVM at 5% @entity515 in air. Oocytes were @entity52 ( @entity52 ) with non-sexed sperm and denuded zygotes were in vitro cultured in CR2aa medium at 38.8  C and 5% @entity515 , 5% O2 and 90% N2. Four- and 8-cell embryos at 44h post- @entity52 were fixed in 4% @entity1604 and stained with anti-mouse @entity27661 and anti-rabbit H3K9me3 first antibodies. Immunofluorescence was evaluated by confocal microscopy (Zeiss LSM 700, MIMA platform, INRA) and 3D images processed by ZEN Lite software (Zeiss, Jena, Germany). Three different distribution patterns of fluorescence were identified based on morphological criteria: diffuse, little clusters, and big clusters. Proportions of embryos in every distribution pattern were compared between C and HS groups by Chi-squared test. No difference (P>0.05) on cleavage rate was found between C and HS groups until 44h post-fertilization. Embryos at the 4-cell stage from HS group displayed an increased (P<0.01) proportion of nuclei with H3K9m3 big clusters (44%, n=7/16 embryos), whereas embryos from C group displayed only few nuclei with this pattern (5%, n=1/18). At the 8-cell stage, distribution of H3K9m3 was similar (P>0.05) between C and HS groups. For @entity27661 , embryos at the 4-cell stage from HS group displayed an increased (P<0.05) proportion of nuclei with little clusters (81%, n=13/16 embryos), whereas embryos from C group had low proportion of nuclei with this same pattern (40%, n=7/18). Mostly 4-cell stage embryos from C group presented the diffuse pattern (61%, n=11/18 v.18%, n=3/16 in the HS group; P<0.05). At the 8-cell stage, some embryos from the C group (31%, n=5/16) still showed nuclei with diffuse distribution of @entity27661 , whereas no nucleus with this pattern was found for the HS group. These preliminary data suggest that @entity291 embryos derived from heat-shocked oocytes can display precocious heterochromatin compaction, represented by the accumulation of H3K9 @entity19 and @entity27661 at the 4-cell stage, compared with embryos derived from non-heat-shocked oocytes, which may affect embryonic genome activation with consequences for further gene expression.

77 effect of XXXX during in vitro maturation on heterochromatin compaction in @entity291 embryos at 4- and 8-cell stages: preliminary study.

@entity19 :: ('10090', 'Species') :: ['me3'] @entity1457 :: ('MESH:D012769', 'Disease') :: ['heat shock'] @entity515 :: ('CHEBI:29334', 'Chemical') :: ['CO2'] @entity376 :: ('CHEBI:25094', 'Chemical') :: ['lysine'] @entity27661 :: ('12412(Tax:10090)', 'Gene') :: ['HP1b'] @entity52 :: ('MESH:C566179', 'Disease') :: ['in vitro fertilized', 'IVF'] @entity1604 :: ('MESH:C003043', 'Chemical') :: ['paraformaldehyde'] @entity291 :: ('9913', 'Species') :: ['cows', 'cattle', 'bovine']
@entity1457 :: (MESH:D012769,Disease) :: ['heat shock']
