Altered chromatin condensation of heat-stressed spermatozoa perturbs the dynamics of DNA methylation reprogramming in the paternal genome after in vitro fertilisation in cattle
Mohammad Bozlur Rahman A D , Md. Mostofa Kamal A , Tom Rijsselaere A , Leen Vandaele B , Mohammed Shamsuddin C and Ann Van Soom A
+ Author Affiliations
- Author Affiliations
A Department of Reproduction, Obstetrics and Herd Health, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
B Department of Animal Science, Institute for Agricultural and Fisheries Research, Scheldeweg 68, 9090 Melle, Belgium.
C Department of Surgery and Obstetrics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
D Corresponding author. Email: mohammadbozlur.rahman@ugent.be
Reproduction, Fertility and Development 26(8) 1107-1116 https://doi.org/10.1071/RD13218
Submitted: 11 July 2013 Accepted: 7 August 2013 Published: 17 September 2013
Abstract
Shortly after penetration of the oocyte, sperm DNA is actively demethylated, which is required for totipotent zygotic development. Aberrant DNA methylation is thought to be associated with altered chromatin condensation of spermatozoa. The objectives of this study were to investigate the dynamics of DNA methylation reprogramming in the paternal pronucleus and subsequent fertilisation potential of heat-stressed bull spermatozoa having altered chromatin condensation. Hence, bovine zygotes (n = 1239) were collected at three different time points (12, 18 and 24 h post insemination, hpi), and stained with an antibody against 5-methylcytosine. Fluorescence intensities of paternal and maternal pronuclei were measured by ImageJ. DNA methylation patterns in paternal pronuclei derived from heat-stressed spermatozoa did not differ between time points (P > 0.05), whereas control zygotes clearly showed demethylation and de novo methylation at 18 and 24 hpi, respectively. Moreover, heat-stressed spermatozoa showed a highly reduced (P < 0.01) fertilisation rate compared with non-heat-stressed or normal control spermatozoa (53.7% vs 70.2% or 81.5%, respectively). Our data show that the normal pattern of active DNA demethylation followed by de novo methylation in the paternal pronucleus is perturbed when oocytes are fertilised with heat-stressed spermatozoa, which may be responsible for decreased fertilisation potential.
Additional keywords: demethylation, de novo methylation, fluorescence intensity, maternal pronucleus, paternal pronucleus.
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