title: Transcriptional and epigenetic status of protamine 1 and 2 genes following round spermatids injection into mouse oocytes.
abstract: The use of round spermatids that are fully active at the transcriptional level to create zygotes (i.e. round spermatid injection; ROSI) raises the question regarding the downregulation of all specific genes that are transcribed from the paternal genome at fertilization. In this study, we show that protamine 1 and 2 mRNAs, which are specific to the round spermatid stage, are repressed at the two-pronuclei (6 h) and two-cell (30 h) stages postfertilization, respectively, in ROSI embryos, by distinct mechanisms. Both genes are fully methylated in round spermatids and sperm but unmethylated in oocytes. At 6 h postfertilization, the protamine 1 and 2 genes are actively demethylated, but the demethylation process happens more rapidly in ROSI than in sperm zygotes. Treatment of zygotes with trichostatin A, a histone deacetylase (HDAC) inhibitor, maintained the protamine 2 mRNAs expression up to 30 h postfertilization while the DNA methylation status of the gene is not affected. Thus, HDACs are involved in the clearance of protamine 2 mRNAs in ROSI two-cell embryos independently of the methylation status of the repressed gene. Contrastingly, HDACs are not directly involved in protamine 1 regulation since trichostatin A does not reverse the silencing of the gene in ROSI embryos at 6 h. The protamine 1 CpG island located in the coding region is actively demethylated in ROSI one-cell embryos where the gene is repressed and may contribute to the regulation of protamine 1 gene expression. The comparison with gene reprogramming occurring during nuclear transfer makes ROSI embryos an attractive model to study the mechanisms involved in gene silencing elicited by the oocyte.
authors.affiliation: INSERM U418, Hôpital Debrousse, 29 rue Soeur Bouvier, 69322 Lyon Cedex 05, France.
authors.forename: Nada
authors.initials: N
authors.lastname: Borghol
authors.forename: Thierry
authors.initials: T
authors.lastname: Blachère
authors.forename: Annick
authors.initials: A
authors.lastname: Lefèvre
mesh_terms: D000818:Animals; D019175:DNA Methylation; D004622:Embryo, Mammalian / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005306:Fertilization; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009865:Oocytes / Q000378:metabolism; D011479:Protamines / Q000235:genetics*; D013087:Spermatids / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C513176:Prm1 protein, mouse; D011479:Protamines; C068621:protamine 2; C012589:trichostatin A; D006655:Histone Deacetylases